Connecting a portable generator for emergency use

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Old 11-24-14, 04:16 PM
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Connecting a portable generator for emergency use

So I bought a 7500 W generator which I want to connect to the house wiring with something better than an illegal suicide cord into the dryer outlet. Based on what I have seen the possible choices are a switch between utility connection and generator before coming into the load center, a subpanel or a backfeed solution via an interlock kit. Cost is a consideration, but don't need to save pennies and make a solution inconvenient, unsafe or otherwise problematic.

We have a lot of branch circuits, many extremely lightly loaded, but necessary. However, we need to drive them to keep things like electronics attached to the furnace which otherwise runs with natural gas, etc.

I am an electronics engineer, so I'm not too worried about coming up with solutions, sizing things, etc. -- but I usually deal with 1.25V-5V DC and very low A, so there's a limit on what I want to do -- in particular, I want to stay away from 200A AC...

In looking on the net, the options discussed here can also be found as a thread on DIY, but without the specific discussion of component choices and pros and cons -- I'll be curious to get additional pointers to other information to compare =>
http://www.doityourself.com/forum/el...generator.html


Transfer switch before main panel

Pro:
the generator can be used to supply all circuits in the house, understanding that a 7500W (~30A) is not going to be able to supply all loads...

Con:
The switches that are available do not seem to be able to carry 200A which is the main feed. Those that may exist are crazily expensive, and I'm also concerned about having to mess with utility power.


Subpanel

Pro:
relatively contained solution
Avoid overdriving generator by selecting circuits to drive statically

Con:
we have many circuits in the house, this may make a solution expensive

There are two ways to do this:
  1. get a normal load center, pick circuits and populate them, then link the new load center into the original load center. to cover the circuits we need a fairly big load center, it may be almost like depopulating and duplicating the main load center. This would look something like this: TRC0602AP9 Panel/Link - Reliance Controls Corporation I expect that this is fairly intrusive, requires a lot of labor, and expense.
  2. there are modular load centers, that have everything fairly prepopulated, and can be attached to the main panel. All that's necessary here is to pick of the branch circuits and attach them to the prepopulated load center. This would look something like this: 31406CRK Pro/Tran - Reliance Controls Corporation This is almost easy enough to do by myself... (note about getting near 200A, though.)

    Alas, the major downside is that I can't find one with enough connections. The Reliance sizer puts me directly into solution (1), if I want to do anything more than keep the heating going (4 circuits) and have a couple of room lights (all CFLs, but 6 circuits).

Interlock kit
Pro:
can drive arbitrary number of branch circuits (subject to total Wattage)

Con:
need to avoid overloading the generator

There are commercial panels that can support an interlock kit, which is basically the mechanically secured variant of the infamous
dryer plug suicide cord backfeed.

On issue is the nature of my panel. I have a GE Panel and GE makes interlcok kits that can be gotten in places like Home Depot. Alas, there
is no interlock kit for my panel - the GE TLM3220CCU /TM3220CCU. Not to despair, there are several companies that make OEM interlock kits.
  1. National RAM: National Ram Electronics - ca. $70
  2. Gen Interlock: General Electric Generator Interlock Kits | GenInterlock.com - Model #GE-200HD- ca. $70
  3. Interlockkit.com Kit K-8310 - ca. $150

The interlock kits fabricated by GE seem to cost about $50, but using any of these is cheaper than ripping out the load center and replacing it with a GE load center for which GE makes interlock kits.

There is a discussion whether interlock kits can pass code, and apparently some installers have run into problems in NJ jurisdictions. The issue becomes particularly contentious when the interlock kit is not made by the same manufacturer as the panel. Alas, it appears that the interlock kit is just a mechanical contraption, so I can't see how a third party vendor could screw something up. It appears that they (some) are considered to be
up to code in NY.

There are at least three vendors - one of which is notably more expensive (interlockkit.com). On the other hand, that supplier also has UL testing information etc. -- so the question is to what extent is that information necessary / useful to pass an inspection and being recognized as being up to code, and in particular with respect to the inspection rules and practices in the state of NY? It would appear that paying $80 more for what is essentially the same face plat would be fiscally irresponsible, but the cost of even a bit of extra time required to get inspector to be happy may swamp any savings possible. Also, any savings possible would be negated if the interlock kit doesn't fit properly, and the necessary drilling in the load center face plate destroys the load
center, requiring to replace the load center.

Does anybody have any opinions on the respective merits of vendors 1, 2, and 3 and how they might fare with respect to an inspection and general operation.


The plan

At present, I am predisposed to go with a solution based on the Interlock kit. I may end up going for kit #3, although paying $80 more under more or less the assumption built into that choice that more expensive is better is somewhat offensive to my belief system.

My load center has 32 branch circuits -- to back feed I need to evacuate 2 circuits, and replace them with a 240V paired two-phase breaker. These then need to be relocated into half-width breakers at the bottom. Overall, this may result in some rearrangement of circuits. While at it, that may also represent cause to reorganize other circuits to balance the load between the two 120V supplies, to ensure balancing of the Wattage across both circuits when running on generator which gives the best efficiency.

Given the constraints of a limited supply, and the desire to balance load, plus the fact that I'm in technology and a geek, I want to monitor actual load on both circuits... I already acquired an Amp Meter box from Reliance MB125 Amazon.com : Reliance Controls MB125 Indoor 50-Amp Meter Box : Generator Accessories : Patio, Lawn & Garden

This box would be in series with the backfeed circuit, then going to an outlet that I would attach outside the house (next to garage door, the generator would sit in the driveway). I would want to run a permanently installed wire in the garage, and put an weather-protected inlet outside next to the garage door door,
rather than having the inlet inside and having to leave the garage open.

Somehow I feel it makes sense to run this through a hard conduit and not just have a high amperage line sit on top of the wall where it could get damaged and
lead to problem down the road.

Final setup considerations

A 7000 W generator can drive approximately 30 Amp, but I want to build in opportunity for growth without redoing everything in case I ever get a 12.5kW generator. It only seems a few dollars more, so even if not likely to happen, it seems to be a move to protect the investment. I already bought the MB125 box following this rationale, rather than an MB 75 box. How far to go? Certainly putting down wire that can comfortably handle 50W seems to make sense. What about the inlet? Do I want to install a 50W inlet as well? What about the breakers for the backfeed? It may be prudent to put circuit breakers at 30W, to protect the generator, but that means touching the load center for any future upgrade and that in and of itself may involve future significant expense and defeat the purpose of it all... (New permit? New inspection? Electrician? Coordinate with utility?) On the other hand, the generator would have a built in breakers, and if not backfeeding we would completely rely on those breakers.

To limit amperage, I would select which circuits I would drive in power outage situation, and shut down other circuits, with enough head room that when kids turn on a TV or computer, the breakers would not drip. Are there limitations on what I can/should run? Are GFI circuits OK to attach? Do I want to attach the generator to a ground pole? (I think what I've seen in diagrams suggests no ground for backfeeding, but ground for subpanel or top of panel solution (i.e., a completely separately derived system with no shared ground...)


Procedural and contracting considerations

I am a weird mix of experiences and clueless. I am an electronics engineer, and so I can pass engineering judgment on a lot of things, but don't do A/C, and did
not grow up in this country (so not internalized as much about local code as I have about the old country). Add to that vocabulary shortfalls in the subject area of high voltage engineering in English.

On the other hand, I don't just want to put this in an electricians hand to do what they think they want to do, which might be a non-scalable solution on one end where I have to go back and redo everything for every change and have an inlet for the power inside, or a Rolls Royce-style solution on the other end of the spectrum. (Esp. since my vocabulary in this domain has some limitations which may lead an electrician to conclude I am clueless... or need to spend countless hours to discuss for which I might get billed...)

I also want to have some handle on the selection of components, and what I want, and/or want to rely on y'all's best judgement. I'm still recovering from the last contractor who just spec'ed the components on the house, contrustcion.. taking the lowest of the good sounding names everywhere and slapping huge markups at which he billed the components. So, the question is -- do I want to get everything myself and just get an electrician to install everything? What is the effect on cost going to be on that?

Should I do some stuff that is easily doable myself - install conduits, pre-run wire etc.? Will an electrician just pump up the price on the estimated labor to make up any margin he would have made on selling equipmen or doing the low-skilled workt... so, that there I'll be the piper one way or the other? There's of course also the question about what grade components they use. I don't begrudge anybody their fair income, but I also don't want to be taken for a ride.

Finally, and that comes down to code and trades customs in this country... how/when do permits, inspections etc., get done and paid for? Who is on the hook for making something pass? presumably if I select and get supplies, an electrician may just park that at my door -- I made the plan and components, there's a problem, you pay, dear customer. On the other hand, in some countries the customer pays for screwups of the contractor anyway, so that shouldn't be a consideration, then?

Anyway, I'll appreciate y'all's thoughts on the options, choices and ideas... and any recommendations and experiences you have.

Thanks
Mike
 
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Old 11-24-14, 06:06 PM
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I'd recommend the interlock if it is approved by your local AHJ.

Whether you do it yourself or not be sure to pull a permit. That will be added to the cost. In some locations the homeowner won't be able to however. Check with your local AHJ. The electrician can always pull it. Usually on something like this the inspection is done at completion.

Nothing you are purchasing is that "special" that an electrician couldn't easily obtain it. IMHO most would rather supply everything as they know what they are dealing with. If there was ever a problem then is clearly on them to remedy it.

What I'm getting at is that say breaker failed a week after the install. You obtained it from a big box store. You call the electrician back to repair it. Does he then bill you for the repair? I would say yes and you'd eat the cost of the bad breaker too. Whereas if the electrician supplies everything I wouldn't expect any cost for the repair or the breaker. We'd just return it to the supply house for credit.

You can certainly tell them that you'd rather go with the 50 amp inlet or whatever and point out where you want them installed. Go through everything with the electrician so you both know what YOU want. It's your money and he works for you.

Is there a markup on parts, yes. Most reputable electricians will not take you for a ride however. What is your time worth? What if you get a wrong/defective part? Remember that you are paying them for their knowledge and skills. It's no different that what you do in your job.

FYI, I have an interlock on my panel and use a 3000 watt generator. It's all in how you manage your loads.
 
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Old 11-24-14, 06:27 PM
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Welcome to the forums! I couldn't read all your thesis (too long), but I would use a Generac switch to separate the generator from your panel and still allow certain circuits to operate. 7500 watts will in no way run your entire house. Remember, you will be in an emergency situation when using the generator, so certain circuits will be abandoned and only the pertinent ones energized during that time.
 
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Old 11-24-14, 09:16 PM
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Not to confuse the issue..... you need to consider the immediate loads. I install a lot of generators. For a fixed auto start generator.... a load calculation is needed. For your portable it is not required.

As far as loads.... heat, hot water, cooking. Are they gas or electric ? City or well water ?
If you are on gas service you are set. If your house is all electric your loads need to be considered carefully.

I run my entire house on a 5kw generator connected thru a manual disconnect in the service line.My house is all gas and city water... no major loads.

If allowed.... a bypass kit is your best way to go.
 
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Old 11-24-14, 09:52 PM
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In my view, the portable generator @ 7.5kW is oversized, but it was on sale and cost less than a smaller elsewhere. I expect urban camping, but in reality we really only need lights, fridge, heat/hot water which is a combined furnace with forced air.

I think 7.5kW is almost like grid power, unless doing something stupid (dryer, washer, range, microwave, dishwasher, vacuum -- actually just back of the envelope, half of this simultaneously is sustainable which is insane - I was in Botswana this summer for work, and people lived on a car battery charged from a solar panel!)

So, my thinking is interlock kit, plus load meter and size for 50A (at 12.5kW I could run all of the above the above craziness, so the more I look at the list, the more I question the need for something bigger... but having reserve capacity frees the mind). I'm curious about efficiency of various generator sizes per generated kWh (not so much to save gas, although that's nice, but because it would save me runs to the gas station and after Sandy there just wasn't gas available for days).

The interlock kit question gets me right to my inexperience with US code and anything related thereto -- how do I find out? Just call town hall? Who do I ask for? Building inspector?

Some details:
  1. city water, natural gas for heating, so no immediate loads for that.
  2. range and dryer are electric, but I think we'll be fine with a hot plate (once we buy one... I'll be curious though whether running one ceramic field of electric range might actually give better efficiency)
  3. I expected microwave to be a no-go, but at 1kW, it's actually not a big deal
  4. lights - almost entire house as CFD
  5. cable modem, wireless, several laptops (2x kids schoolwork and 2x parents work) - I was going to say I don't expect this to be big, but the latest laptops @ 100W are actually pigs when it comes to power use...
  6. refrigerator is interesting -- during defrost they can peak and I don't know that's under my control
    - but total should be less than 1kw
  7. 2 screens - one a plasma (300W), one LED (150)... don't need to run both, or either. We don't have cable except for internet and no aerial reception so it's only for occassional DVD/Netflix anyway. Nobody will miss what we don't use during the year.

The surprise was the laptop wattage rating (but I knew these laptops were drawing current, because on United, the overcurrent protector shuts down my outlet when I plug my machine in)
 
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Old 11-24-14, 10:19 PM
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Generator power actually goes pretty far.

As far as the fridge..... defrost draws less power than the unit running. I believe the defrost heating element is under 100 watts.

You can check with your local electrical inspector about the interlock.

On a 5k generator I ran 3 TV's, washer and dryer, 2 computers, microwave oven, lights. The more balanced your circuits are the more you can run.
 
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Old 11-24-14, 11:01 PM
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Right, I agree. Blancing the load on the two 120V will go a long way to efficiency. I grew up with 220 V, so the whole asymmetric power thing is still weird to me...

Anyway, to see load and load balance, I got myself this watt meter a to include in the setup
Amazon.com : Reliance Controls MB125 Indoor 50-Amp Meter Box : Generator Accessories : Patio, Lawn & Garden

Alas, it produces almost non-operable data. If you find one side is out of balance with the other, all you can do is shut off devices on one side -- or turn on more on the other...

So, while one might swizzle around a few small things (move the laptop to another circuit, move the coffee maker, attach the screen via a long cable elsewhere... ), there's not way to reconfigure the loads at the load center once set on a specific configuration...

So, if one gets the initial estimation of what is actually going to run wrong, there's little one can do.
 
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Old 11-25-14, 12:47 AM
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I have a sub-panel with my critical loads, small appliance branch circuits (includes refrigerator, microwave oven, toaster oven and counter receptacles), gas furnace, Internet modem and routers, computer, television with video recorders and some lighting. All powered through a 60 ampere transfer switch.

My generator is a Yamaha EF3000iSE that I converted to gaseous fuel only, I run it on natural gas. The output is 2800 watts continuously and 3000 watts for 20 minutes but ONLY at 120 volts. I have NO problem with using either the microwave OR the toaster oven along with everything else.

Mike, what you could do, although I am not advocating it, is to run straight 240 from the generator to a 1:1 center-tapped transformer. That way the generator only "sees" a 240 volt load and the transformer absorbs the imbalance between the two legs.
 
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Old 11-25-14, 07:09 AM
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I've always liked the idea of the panel interlock, as long as it passes inspection. It allows you to tailor what you have running based on time of year and how you feel at the time. 7500w could probably even run your A/C in the summer (I've never tried, but it might).

The problem with larger generators is typically the larger they get, the more gas they guzzle and the louder they are. I got a back-of-the-truck 7,500 during Sandy and while it works well, it's LOUD and turned out to be way more than I need. All I need is a few lights, fridge, blower for the natural gas furnace and computer/Internet. I'm actually considering downsizing to a smaller 2000w inverter gen for the power quality and noise as well as the ease of moving it around.

If it were me, I wouldn't even bother with the 50A wire/inlet. If you were going to get that large a gen, I would switch over to a Natural Gas permanently wired auto-start one.
 
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Old 11-25-14, 08:31 AM
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tl;dr

If allowed by your city electrical inspector, the interlock kit will be the least expensive and most flexible method to connect your protable generator to the panel.

You'll be able to run a surprising amount of stuff on a 7kW generator: furnace, microwave, dishwasher, lights, computer gear, etc all will be fine. It is a good idea to run any electronics through a decent UPS with regulated sine wave output as portable generators are not all that stable on voltage and frequency. Don't bother with a hot plate - a single burner of the electric range will work just fine on the generator. Cloths dryer and water heater would be okay if you limited other stuff.
 
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Old 11-25-14, 09:11 AM
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In a 19 hour period..... my Honda 5kw used approximately five gallons of gas. I shut it off several nights for a few hours at night when I went to bed.
 
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Old 11-25-14, 11:35 AM
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"My generator is a Yamaha EF3000iSE that I converted to gaseous fuel only, I run it on natural gas. "

That has sounded intriguing to me, since we have natural gas, and that would avoid avoing to go and transport gas in containers and/or deal with scarcity where natural gas flows constantly. I've seen youtube videos how to do the conversion, but I'm more than just a bit worried about those do it myself. I'm also curious about any modfications to gas service, and whether that combination - a tappable line and a tap that's a self-modifed generator will raise all sports of insurance and code red flags?

Probably not my most urgent worry - but I'd b curious about your experience with those issues, and how you attache a portable generator to natural gas. (We have natural gas, so even with a manual generator, and the reduced efficiency of natural gas over liquid fuel would make this about as good as utility power :-) )
 
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Old 11-25-14, 12:45 PM
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I converted a gasoline generator to natural/propane using one of the conversion kits. It was really pretty easy. I plumbed up a quick change style fitting off the gas meter which is normally used for connecting cooking ranges in commercial kitchens to easily connect and disconnect the gas supply to the generator. I also bought a tank regulator to use the generator with portable propane cylinders so I can use it anywhere. A standard BBQ cylinder seems to be about the same run time as 5 gal of gasoline.
 
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Old 11-26-14, 05:02 AM
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There is no "loss of efficiency" in using natural gas as fuel. However, since natural gas has a significantly lower BTU content than gasoline on a volume basis you will burn more natural gas. That is offset by the much lower cost of natural gas so in the long run the natural gas is actually less expensive than gasoline.

There is nothing special about the conversion and it is done using all industry standard parts, especially when doing a gaseous fuel only conversion. Generally, the manufacturer will still honor the warranty after a conversion as well. The piping at the home is subject to your LOCAL codes and that usually requires a permit be issued for the work and an inspection afterwards. Fairly simple to tap just downstream of the meter. Here is a picture of my installation where I added about five feet of pipe to allow placement of the gennie between the gas meter and the power inlet connection.

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I use regular 45[SUP]0[/SUP] flared fittings on a flexible hose but the quick-connect mentioned by ibpooks is also a good method.

This is the best website I have found to detail the conversion process and they carry all the necessary materials.

Propane and Natural Gas Generator Conversion Kits - Motor Snorkel

I have no interest with US Carburetion other than as a satisfied customer.
 
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Old 11-26-14, 05:53 PM
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I have a Generac 4000EXL, B&S 6KW, and a Generac 7550EXL. I also had a Generac Lp3250 but that grew legs.

I found I can live comfortably off the 4000EXL. It's able to run all of the receptacle and lighting circuits, 2 fridges, deep freezer, microwave or other 120V cooking appliance, tv's, 3 laptops, network and phone systems, ceiling fans, etc. The best thing is it only uses a gallon of gasoline every 3-4 hours.

I won't use the 6KW B&S for back-up because it puts out a really bad sine wave. When used for the light tower, it uses a gallon every 2 hours.

I have my 7550EXL which will run everything above mentioned, plus the washer/dryer on air dry mode, or 1-3 stove burners or the oven. I have a tri-fuel conversion kit on it which lets me run it on gasoline, propane, or natural gas. It goes through about a gallon an hour. I'd be happy to post pictures of the conversion.


Sorry this is probably behind, I got a fire call and then started hanging lights.
 
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Old 12-03-14, 11:58 PM
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Furd, Thanks for posting the image of your setup, and pointer to the conversion kit. The conversion looks like something very worthwhile, and not so problematic as I had feared based on videos I had previously found on youtube. (Where some fearless soul just drilled into the carburator to stick a gas line in.)

You natural gas entry point looks almost like mine... which brings me to a bunch of questions. (Truth in advertising - this is more of a long term project, first I need to get the generator attached. And it has a bearing on where I put the power entrance point.)

So, my drive way is what would be to the right of the picture (corner to driveway entrance almost immediately around the corner from the gas meter) suggesting that the pipe runs away from the driveway... Hmmm. We tend to lose power a lot in/after snow storms, and the path along the house would be inaccessible... also, wouldn't want the warm exhasut sit on snowy/frozen round and melt surrounding snow. So, I was planning on putting the generator in my driveway...

Is your pipe running away from the meter for code reasons -- it there a minimum distance from the meter, house entry point or other such ? (I have absolutely no model of gas as a utility and any associated code). You 5 ft tupe would be literally 5 inches to get me to my driveway, running in the opposite direction. Is that legal?

Also, it would sit more or less right on top of power inlet. Any problems there? I see you have the power attach point quite separated from the gas delivery point.

Finally, how do you secure the gas line from unauthorized opening? (Are there code considerations? Even without code considerations I'd be scared about stupid kids opening the gas pipe, or even trying to see if gas burns...)

Thanks!
 
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Old 12-04-14, 12:35 AM
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I can answer some, but not all of your questions.

Drilling the carburetor is really easy as all you do is follow the hole already there that contained the main gasoline jet. I didn't even use a drill motor, just a few drill bits of increasing size held (poorly) in a T-handle tap wrench and turned by hand. This leaves a goodly amount of the original internal thread and the new fuel tube simply screws in place of the old jet. I did need to shorten the new fuel tube but that is not hard nor critical and the instructions are clear on that point. You also have to remove any adjusting screw that is actually ported into the carburetor body and fill the holes with silicone sealant. Total time on the carburetor was maybe fifteen minutes and letting the silicone harden overnight.

I'm not very good at visualization so your description of your driveway and gas meter is lost on me. A picture would help. I do not know of any code that required me to have the gas connection five feet away, I just did it that way. I've also thought about changing it to a valve right at the meter but I will probably just leave it the way it is.

As for the electrical inlet...again, it is just the way I did it without giving it much thought. It is about fifteen feet from the transfer switch and probably had as much to do with the amount of flexible conduit I had after mounting the transfer switch as anything. I also wanted my generator behind the fence/gate so it was not readily visible from the street. Since making this installation I have often thought that running both the gas piping and the electrical inlet to my back porch would have made far more sense as I could then leave the generator on the porch and start/stop it as needed by just stepping out on the porch rather than traipsing halfway around the house. Plus, it would likely be a little more secure on the porch. I was able to get (for free) a length of 10-4 type SOOW cable to use for the generator-to-house interconnect and that length was probably part of the reason why the gas and electrical connections are where they are as well as any sort of real planning.

You CAN use a relatively long length of hose for the gas connection. I have read of people that use a 75 foot hose without problem BUT you must use a hose of sufficient inside diameter to allow the necessary gas flow; a 3/8 inch barbecue hose won't cut it with a larger engine. Same is true for the electrical interconnect and the same rules of voltage drop apply here as well.

At the gas connection itself I have a flared connection with a cap on it. The cap is tightened enough that it requires a wrench to remove. Many people advocate a quick connect coupler made specifically for gas and these do not allow for a gas flow unless the proper mating plug is used. I used the flared connection because it was significantly less expensive although it does require a wrench to remove the cap and to install the hose.
 
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Old 12-04-14, 02:37 AM
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I decided to review this thread and actually read through your initial post. I'll admit I only skimmed it originally. Here are some answers to your questions.


Transfer switch before main panel
Any such transfer switch between the meter and the service panel will need to be listed as "Suitable for Service Equipment" or else have overcurrent protection (200 ampere circuit breaker) on the utility side. Yes, such a switch IS expensive but it gives you the ability to connect the whole panel to the generator. Your serving utility MIGHT offer the GenerLink solution for a relatively small monthly fee and if it does, this is the easiest and least capital intense answer.

GenerLink.com - About GenerLink - The easy way to connect a home generator

Interlock

I think it has already been pointed out that some jurisdictions will not allow an interlock that can be defeated by simply removing the panel cover. Since all code is local (ask if you do not understand this phrase) you need to check with YOUR local Authority Having Jurisdiction (AHJ), i.e the local electrical inspection agency, to see what, if any, interlocks are acceptable for YOUR panel.
My load center has 32 branch circuits -- to back feed I need to evacuate 2 circuits, and replace them with a 240V paired two-phase breaker.
Terminology problem. There is no such thing as a "240V paired two-phase breaker", what you will need is a two pole circuit breaker. In addition, that two pole CB (for the generator supply) must also be securely attached to the panel with a hold-down kit from the manufacturer of the panel.

A little aside here; there are VERY few installations of two-phase power in the US (and likely the entire world) and ALL of them will be in commercial or industrial facilities built at least eighty years ago. Most electricians and contractors have never even heard of two-phase let alone worked with it.

Final setup considerations

A 7000 W generator can drive approximately 30 Amp, but I want to build in opportunity for growth without redoing everything in case I ever get a 12.5kW generator. It only seems a few dollars more, so even if not likely to happen, it seems to be a move to protect the investment. I already bought the MB125 box following this rationale, rather than an MB 75 box. How far to go? Certainly putting down wire that can comfortably handle 50A seems to make sense. What about the inlet? Do I want to install a 50A inlet as well? What about the breakers for the backfeed? It may be prudent to put circuit breakers at 30A, to protect the generator, but that means touching the load center for any future upgrade and that in and of itself may involve future significant expense and defeat the purpose of it all... (New permit? New inspection? Electrician? Coordinate with utility?) On the other hand, the generator would have a built in breakers, and if not backfeeding we would completely rely on those breakers.

To limit amperage, I would select which circuits I would drive in power outage situation, and shut down other circuits, with enough head room that when kids turn on a TV or computer, the breakers would not drip. Are there limitations on what I can/should run? Are GFI circuits OK to attach? Do I want to attach the generator to a ground pole? (I think what I've seen in diagrams suggests no ground for backfeeding, but ground for subpanel or top of panel solution (i.e., a completely separately derived system with no shared ground...)
Yes, I think it is prudent to upsize all the parts initially for a 12.5 kW generator IF you think there is any chance of upgrading in the future. On the other hand, you might be surprised at how much you can run with the 7.5 kW gennie. Remember, this is for emergency use (I think that has already been mentioned) and not for living a normal life when the utility power goes out. If you do this I would use the 50 ampere inlet along with #6 copper conductors and a 60 ampere circuit breaker. Remember that the CB in the panel is only being used as a switch and it is the generator mounted CB that ultimately protects the generator.

Yes, GFCI circuits are acceptable PROVIDING that the neutral-to-equipment ground bond is in the correct place. (More later if you need it.) Since ALL kitchen counter top receptacles ARE GFCI protected it makes no sense to exclude them from the generator supply.

No, generally speaking you do NOT want to connect the generator to an earth connection BUT there are some other considerations that need to be discussed in detail (and have been touched upon already) before making this an absolute.

So, the question is -- do I want to get everything myself and just get an electrician to install everything?
This is a DIY forum and what you want to do is definitely DIY-able. Several people here can walk you through the steps necessary for a good and code compliant installation PROVIDING that your LOCAL code allows homeowners to do electrical work on their own homes. You might have to take some silly exam to prove that you actually know something about electricity before they will issue you the permit.

Should I do some stuff that is easily doable myself - install conduits, pre-run wire etc.? Will an electrician just pump up the price on the estimated labor to make up any margin he would have made on selling equipmen or doing the low-skilled workt... so, that there I'll be the piper one way or the other?
A large majority of licensed electricians will refuse to do work on a job where some parts are done by the owner as they will need to verify everything the homeowner does in order to not place their license in jeopardy. I see no reason why you cannot do it all based upon what you have written.
Finally, ... how/when do permits, inspections etc., get done and paid for? Who is on the hook for making something pass? presumably if I select and get supplies, an electrician may just park that at my door -- I made the plan and components, there's a problem, you pay, dear customer.
The person taking out the permit is the one who has to make it pass inspection. If you take out the permit then you have to make it right. If an electrical contractor takes out the permit then he or she has to make it right UNLESS you have a contract with different terms. Doing it yourself means applying for the permit, which will usually require a plan including scope of work, materials list and schematic drawing of the job. Inspections are usually done after the "rough-in" and again at finish although in this particular job it is possible that only one inspection will be made at finish. Most inspectors will be quite helpful to a homeowner doing his own work although some can be really harda**ed about following the code to the letter. Whatever, do NOT argue with an inspector. If you feel he/she is incorrectly interpreting the code then write a polite letter to his/her supervisor explaining your position. OR, just do what the inspector wants if it is fairly easy.
 
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Old 12-04-14, 08:51 AM
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Did someone mention a transfer box with several small transfer switches as opposed to one "whole house" transfer switch?

From the outside it vaguely resembles a breaker panel.

Wiring it up is quite easy. One set of lugs or male receptacle is mounted right in the transfer box to connect a cord or feed cable to the generator.

You do not have to add or replace any panels (load centers) and you do not have to relocate any fat feed cables.

But you can and must select a small number of circuits (perhaps twelve) to be eligible to receive generator power.

The transfer box installs next to the existing panel and requires a fairly fat nipple connection through which typically 10 to 25 small (12 or 14 gauge) conductors pass.

Wiring detail: For each small switch in the transfer box, a pair of wires is run to the breaker panel. Disconnect the branch circuit wire from a breaker and connect it to one of the pair. Connect the other of the pair to the breaker terminal. Use pigtails (short lengths) as needed if the wires that came with the transfer box do not reach.

************

There is one thing you might not find out about off brand interlock kits until it is too late. The moving parts may have so much slop so as not to work correctly; the affected breakers might both be able to be forced on.
 

Last edited by AllanJ; 12-04-14 at 09:16 AM.
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Old 12-04-14, 11:56 PM
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"But you can and must select a small number of circuits (perhaps twelve) to be eligible to receive generator power."

right, around here this is usually referred to as subpanel, as described in my house wiring thesis. My short answer is noway, nohow. As per below, we have a ton of branch circuits and almost no load. Just heating uses at least 3 circuits. There is no load on any of them.

I can probably run our entire daily load on a 7k generator without taking any circuits out of service. Yes, it's for an emergency, and it surely would beat the last 3 urban camping episodes of 1 week each with 46 F inside, 2 years ago... But if I do it, I might as well build in that extra flexibility.
 
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Old 01-28-15, 07:17 PM
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I have been procrastinating on the generator connection - this week's storm was an unwelcome reminder that I have to get on this. (It hit while I was/am on the road and my family alone... fortunately it's wasn't as bad as feared.)

At this point, I'm pretty much set on going with the interlock kit... I called the town, inspector seemed to not be concerned but indicated he would follow up and get back to me after checking with his electrical expert.

GE does not make an interlock kit for my panel, the GE TLM3220CCU /TM3220CCU. Not to despair, there are several companies that make OEM interlock kits.
* National RAM: National Ram Electronics - ca. $70
* Gen Interlock: General Electric Generator Interlock Kits | GenInterlock.com - Model #GE-200HD- ca. $70
* Interlockkit.com Kit K-8310 - ca. $150

Is anybody familiar with these choices? One concern I have heard is whether the interlockkit properly prevents mutual lockout of the generator and main line. Is any one of these notably better/worse than others?

All other things being equal I would probably opt for Geninterlock.com - on the other hand intelockkit.com seems to have more documentation/UL testing online? (but all other things being equal I would prefer to spend $70 than $150,if they're both substantially similar).

Also, Geninterlock has 3 models that seem to fit this panel http://geninterlock.com/product_generalelectric.html : #GE-200HD, #GE-200S and #FAC-GE200HD which is described as "Factory Model, Listed" - I am surprised because GE does not produce an interlock kit for this model - or so I thought - and what is "listed" - is that UL? Thoughts?

What else will I need? My panel is fully populated, so I am looking at freeing up two slots by using half-wiidth breakers... THQP-120 and -115 ( Shop GE Q-Line THQP 20-Amp Single-Pole Circuit Breaker at Lowes.com ). It seems most straight forward to push all the breakers down by two slots on the right hand side and just put 4 halfwidth breakers in the bottom 2 slots... except my sense of symmetry is rebelling against it... any thoughts? (Yes, like many an engineer I am sometimes a bit OCD when it comes to symmetry...)

Cable with headroom for 50 Amps would be a 6-3 ? If I understand this correctly, this has 4 conducting wires. (Still getting used to how electricty is done in this country... my instincts acquired with what I grew up with sometimes fail me, because in Europe 240V has no neutral.)
http://www.lowes.com/pd_70166-295-63...3D1&facetInfo=

I'll also need a paired breaker for the generator, and male and female plugs. I was going to go with everything at 50 Amps, but I'm increasingly thinking I might put the breaker @ 30 Amps for extra protection and that that should be a comparatively easy upgrade should I ever want to go to 50 Amps, but size everything else for 50 Amps.

Finally, my generator bonds neutral and ground and I am tempted to just drop the ground connection from the inlet switch. (This keeps neutral and ground bonded in the generator in case I want to run the generator standalone.)

I'll appreciate your guidance and suggestions with this plan - Thanks so much in advance!



Read more: http://www.doityourself.com/forum/el...#ixzz3QAgAN4ly
 
  #22  
Old 01-28-15, 08:06 PM
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Not to despair, there are several companies that make OEM interlock kits.
* National RAM: National Ram Electronics - ca. $70
* Gen Interlock: General Electric Generator Interlock Kits | GenInterlock.com - Model #GE-200HD- ca. $70
* Interlockkit.com Kit K-8310 - ca. $150
Are they U.L. Listed? Will the AHJ accept them?
 
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Old 01-28-15, 10:52 PM
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AHJ's answer was basically they have no special requirements and follow state rules. Now, the Town Engineer who is responsible for permits didn't even seem to understand interlock kit. he did say he was going to talk to his electrical expert and call back, but no call back in over 2 mos... Guess it's time to follow up.

Couldn't find anything about National Ram Electronics..

For Gen Interlock, they list for one of 3 possible parts: "Factory Model, Listed"

Interlock kit has this on their website:
Tested by Meth Laboratories.
Certified File E113647
Complies with UL 67
InterLock Kits meet all NEC requirements for optional standby systems (Article 702)
 
  #24  
Old 01-29-15, 01:24 AM
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Interlock kit has this on their website:
Tested by Meth Laboratories.
Certified File E113647
Complies with UL 67
InterLock Kits meet all NEC requirements for optional standby systems (Article 702)
Is "Meth Laboratories" a Nationally Recognized Testing Laboratory (NRTL)? If not, then their "testing" is meaningless. Are you sure that it isn't MET Labs.? MET Labs | Third Party Electrical Testing for Product Safety, EMC & Environmental Simulation

Who, or what agency "certified" File E113647? What does the file consist of?

Complies with UL 67. Meaningless, the ONLY thing that matters is "Listing" by a NRTL.

Meet all NEC... Also meaningless, see above concerning NRTL listings.


National Ram Electronics home page. National Ram Electronics

You need to contact the state electrical inspection office to see if they will accept the interlock kit of your choice.
 
  #25  
Old 01-29-15, 06:02 AM
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Complies with UL 67
Being in compliance with is not the same as being "Listed by". I agree with Furd.

You need to contact the state electrical inspection office to see if they will accept the interlock kit of your choice.
Interlock kit has this on their website:
Tested by Meth Laboratories.
If I owned that lab I think I'd be changing the name really fast!
 
  #26  
Old 01-29-15, 07:43 AM
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"Con: Risk of overloading the generator."

This risk, and the need to proactively monitor what you turn on at any given time, exists no matter what method you use to connect up the generator. Including exclusive use of extension cords stretched over to the generator's built in duplex receptacle.

The generator should have its own breaker rated for its own output (watts, amperes). This makes it possible for you to construct the inlet and panel connection for a higher amperage to permit, say substituting a larger generator in the future. You can do such things as construct an adapter (If it's more than about 2 feet long, you can call it an extension cord) with a higher amperage, say 50 amps, (female) receptacle and a lower amperage, say, 30 amps, (male) plug. You should not make an adapter with a smaller amperage receptacle and a larger amperage plug.

If the generator has a documented or easily accessible ground-neutral bond, this should be removed if your home electrical system already has a ground neutral bond. But if the generator needs to be pried apart to do such unbonding, I, too, would be tempted to just drop the ground connection from the inlet (unhook the green or bare wire from the back of the male receptacle). This will not affect the generator operation adversely.
 

Last edited by AllanJ; 01-29-15 at 08:57 AM.
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Old 01-29-15, 11:54 PM
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Yeah, typo. Met Laboratories... (Maybe Freudian?)

And indeed, all of the verbiage I quoted was not confidence inspiring (i.e., it sounded like it may be weasel words rather than constitute certification/ UL Listing... the file number listed in conjunction with this is structured to look like an UL file number, but lookup at UL does not return anything )

Now, one of the geninterlockkit parts asserts it is "Listed" and even a "factory model".
http://geninterlock.com/images/panel...200hd_i_lg.jpg

Again, some weasel words... (is Listed UL? What's a "factory model" -- seems to imply that it comes from GE... and some of the shape is indeed reminiscent of GE manufactured facture models... However, GE does not list availability of an interlock kit for this model... And I have some difficult visualizing how this model would work...

In particular, it would appear that when the top main breaker is set to on, the interlock bracket would have to slide down, to open the cavity in the lower arm for the double pole generator breaker... In the process, it seems it would go down far enough to force the next breaker below to be turned off to make space for the metal piece that prevents the generator from being turned on when the main breaker is on...

Humph... this doesn't look like good engineering, and is a bit disturbing.
 
  #28  
Old 01-30-15, 12:42 AM
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The term "Listed" is the official stamp of approval. When a NRTL "Lists" a device it is saying the device meets all of the requirements set down in the model codes and performs as the manufacturer states.

In particular, it would appear that when the top main breaker is set to on, the interlock bracket would have to slide down, to open the cavity in the lower arm for the double pole generator breaker... In the process, it seems it would go down far enough to force the next breaker below to be turned off to make space for the metal piece that prevents the generator from being turned on when the main breaker is on.
Yes, that IS how that particular interlock works. Notice in the picture that the space below the generator CB is vacant. To use that particular interlock the space immediately below the generator CB MUST be vacant.

Now here is the downside. Many jurisdictions prohibit the use of interlocks IF the interlock may be defeated by merely removing the panel cover. It appears that particular interlock would fall into that category.
 
  #29  
Old 01-30-15, 03:32 AM
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I don't remember seeing it but your panel may not accept tandems so another solution like a sub panel would be needed for the additional spaces.

Also multi-wire branch circuits need to have the two hots on opposite legs in the panel. If not the neutral can get overloaded.
 
  #30  
Old 01-31-15, 11:11 AM
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All the interlock kits that I have seen appear to be easily disabled by removing the front cover because they appear all to be attached to the cover...

In any event, to the specific model at hand here, if the model blocks the slot below as it slides down to enable the generator backfeed breaker to be enabled, what's the recommended action for dealing with that slot? (I can't find a manual online for this interlock kit)

The slot is already punched out on the panel, so that limits the options..
1 - Leave it unpopulated? (I assume that would expose the power rail where the breaker usually attached?)
2 - leave a decay breaker unattached to any circuit?
3 - pick a circuit that likely won't be used during a power outage, and accept that the interlock will lock out that circuit when it is switched to enable the generator?
 
  #31  
Old 01-31-15, 12:13 PM
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The are breaker fillers available that plug the unused openings.
 
  #32  
Old 01-31-15, 12:34 PM
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All the interlock kits that I have seen appear to be easily disabled by removing the front cover because they appear all to be attached to the cover.
Yep, most of the aftermarket interlocks are that way. That is why you need to get permission (preferably in writing) from your LOCAL inspection agency.
 
 

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