Transfer Switch v. Interlocked Breaker

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  #1  
Old 09-08-08, 02:05 PM
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Transfer Switch v. Interlocked Breaker

I have a 5500/8250 watt generator with an L14-30 outlet and I'd like to power my lights, fans and 110 outlets with it.

My uncle is an electrician so I'll have him come out once I decide what I want.

From what I can gather the advantages of the interlock is that I can have the option of flipping on any breaker in the house rather than committing to 6 or 10 or 12 circuits (Depending on the switch). The disadvantage is that I will not be able to see what kind of load I'm pulling on each side of the generator and I would be limited in my ability to balance the loads. Also, I have no room in my panel for another 2 pole breaker without switching out some of my 20 amps with 20 amp tandem breakers (Not even sure my panel supports them).


On the transfer switch I'd be able to divide up the load pretty equally based on what I know will likely be running on each circuit. I'd also know when power returns because the remaining circuits would remain on the grid and would power up immediately. Also, I wouldn't need any more space in the current box. The disadvantages are that, unless I get a big one, I'd be limited on what I could run off of generator power and the higher cost.

I've also noticed that a lot of transfer switches have a built in L14-30 inlet right on the bottom or top of the box. This won't really work for my application and I'd prefer to run wire to an outdoor location for the inlet. Do these "kits" include provisions to set them up this way or are you stuck with running the generator cable back to the box directly?
 
  #2  
Old 09-08-08, 02:11 PM
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It sounds like you have the pros and cons of each solution pretty well understood.

The built-in inlet on the generator panels can usually be removed from the panel and installed in a standard box outside the house with a weatherproof box and in-use cover.
 
  #3  
Old 09-08-08, 08:07 PM
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A couple of options for you with the interlock.

You say that your panel is full, one option is to replace the panel with a new that comes with the transfer switch and watt meters built in. If the panel is older this may be worth it for you.

Another option is to install a separate watt meter box, they sell for around $60 and can be mounted right next the panel with interlock kit

either way you go, a separate inlet called a "remote inlet" can be installed in any location you want to plug the generator in.

I personally don't recommend the 6/10 circuit type switches. They will probably cost you more than an interlock kit and limit your available circuits

Here is some links:

Remote outdoor inlet

http://www.reliancecontrols.com/ProductDetail.aspx?PB30


Watt meter box

http://www.reliancecontrols.com/ProductDetail.aspx?MB75


Panel with built in meters and interlock

http://www.reliancecontrols.com/Prod....aspx?TTV2003C
 
  #4  
Old 09-10-08, 08:38 AM
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I'm leaning towards the interlock.

My panel is only 3 years old cause it's a new house.

They did a real good job of limiting the scope of each circuits but the problem with that is that I'd need a 14-17 circuit transfer switch to power all of the lighting and outlets in a 1900 sq. ft. house. I could eliminate some rooms but then I'd still need a 12 circuit switch which is big $$$.

If you go with the interlock do you just have to move breakers from one side to the other if you're consistently pulling more load on one side or the other? How do you physically balance the load? Should the panel be setup to provide a pretty balanced load to each side already or is that not really an issue on grid power?
 
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Old 09-10-08, 08:58 AM
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Originally Posted by Jeff d View Post
I'm leaning towards the interlock.
I agree that the interlock sounds best for your situation.

If you go with the interlock do you just have to move breakers from one side to the other if you're consistently pulling more load on one side or the other?
Yes that would do it, or plug your appliances into different circuits temporarily if they are portable.

How do you physically balance the load?
You can do a ballpark estimate by re-arranging the breakers based on what you know you'll need on the generator. For example put the fridge and freezer on opposite legs. As you look at the panel, breakers directly across from each other are on the same leg, i.e.:

A A
B B
A A
B B

Should the panel be setup to provide a pretty balanced load to each side already or is that not really an issue on grid power?
It is not really an issue on grid power.
 
  #6  
Old 09-11-08, 01:17 AM
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In General the lighting loads are not worried about since most times even with every light on in your house you will be less than 2000 watts ( unless of course your talking about a 5000 square foot monster house)

What you need to be worried about is the appliances, toasters, coffe pot, window or portable A/C's, microwave, Refrig. You need to also turn off the breakers for anything that comes on automatic.....Central A/C, Water Heater, pumps etc..

Rule of thumb is never have more than 2 appliances on at same time, and make sure those 2 appliances are on opposite legs. This is crucial with a generator less than 10,000 watt. The bigger generators are more forgiving.

Example would be refrig and coffee maker, or refrig and window A/C.

The beauty of the interlocks is that say you have electric water heater, just turn off all your other loads and let water heater run by itself for an hour. Once water is hot turn off water heater and turn back on your other stuff.


What you need to do is find out what outlets in the house you want to use for the heavy stuff and find out which leg they are on.

As IPBOOKS said the panels are not left side/right side but are like this

A A
B B
A A
B B
A A


Be careful not to confuse the twin breakers/tandem breakers, even though there is 2 handles, they are still the same leg since they only take up one full size space.

Definitely run a test or 2 once you get everything set up, you need to get familiar with it, then it will come easy
 
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Old 09-25-08, 10:08 AM
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How to use Interlock

OK, I've been reading and plan on installing a Square D interlock kit. I have a Honda EU2000i generator that will produce 16.6 Amps max. So I assume I need to install a 20 Amp circuit breaker in the 2-4 position. But in reading this post I got confused. I thought all I had to do was then turn all circuit breakers off including the main or utility, back feed breaker on, and then turn on the circuits I deem necessary - of course taking power management and total watts into consideration. What's this AA BB left side right side stuff? I just want to power the fridge & freezer during summer, and furnace blower motor in the winter. Maybe a few lights if I've got some watts left over.

Thank you
 
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Old 09-25-08, 10:29 AM
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The Honda unit you listed can only supply 2000W at 120V, which in my opinion is not an ideal unit for a panel interlock. It has a very small output and cannot supply 240V. You would need to feed both poles of the panels from the one pole of the generator and then be very diligent about load management. Perhaps a long #12 extension cord and single circuit transfer switch on the furnace might be a better solution.
 
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Old 09-25-08, 10:39 AM
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Hum...I understand I only have 2000 watts to play with and have figured out I can do what I want to do even considering start up watts/amps. I don't need 240. Would not the 2 pole breaker feed both poles?
 

Last edited by OhioIOIO; 09-25-08 at 11:20 AM.
  #10  
Old 09-25-08, 12:19 PM
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Yes it could if the hot wire from the generator inlet was wired to both poles of the backfed breaker. This would supply the 120V circuits on both sides of the panelboard.

Have you tried to run the fridge and freezer on the generator? The only reason I ask is that inverter-type generators like yours are not particularly good at dealing with start-up current. Even though the math might work, a live test is best. The furnace shouldn't be a problem. The blower is usually only a couple amps and the ignition is about 8-10 amps for 15 seconds or so.

Just an additional note. The generator/inverter is actually rated at 2,000 VA (volt-amps), which is only equal to watts for resistive loads like light bulbs and heaters. When powering motors, it's something more like 0.8 W = 1 VA depending on the efficiency of the specific motor. So you really may have more like 1600W to work with given the intended loads.
 
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Old 09-26-08, 06:44 AM
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Thank you ibpooks. I used my new generator to power several things but not those two specific appliances yet. I will take your advice and run ext. cords to test them. Worst case would require me to selectively power them.

So what I need to do is use four conductor wire with an insulated neutral and a separate ground to run a circuit from my generator to a 2 pole 20 amp circuit breaker in the 2/4 position with my interlock kit. Then when this is activated, that would provide 120v (instead of 240 as would be normal with a 2 pole breaker) to both poles in my service panel. This would allow me to selectively provide power to limited appliances in my home during the emergency type outage.
 
  #12  
Old 09-26-08, 09:55 AM
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You actually do not need to use four-conductor cable for this generator. You can run regular 12/2g NM-B Romex from a NEMA 5-20 inlet to the main panel. At the main panel, the white and ground wires both go to the shared ground/neutral bus. Wirenut the black wire with two other short black pigtails of wire which then go to the breaker poles.

When you connect the generator to the inlet you can use a standard heavy-duty 20A #12 extension cord from the store, nothing custom required. The 20A inlet and cord will have one side-ways blade instead of the more common parallel blades found on 15A cords.

 
  #13  
Old 09-30-08, 05:34 AM
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ibpooks, you were right all along. I've had this grand plan of a disconnect and the NEMA 5-20 inlet. It would work fine but be a lot of work and then I think...other than last week when I was without power for 8 days, how often does the power go out for more than a day? My other brain said, "not often". And I say if I disconnect myself from the grid, how will I know the power has come back on? Well, to make a long story short, I decided just to use extension cords and the furnace transfer switch (which I still need to order and install). But I wanted to say thank you for allowing me to bounce ideas off you.
 
  #14  
Old 09-30-08, 01:18 PM
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Any idea how to hook up a Reliance 1 curcuit furnace transfer switch? I can't find instructions on line. Model Number: TF151W.
 
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Old 10-13-08, 10:23 AM
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Final Post

I priced out a furnace transfer switch for $90. Then I found a Gen/Tran #15114 (4 - 15 amp curcuits) transfer switch for $70. I went with it and it was easy to install. Now I have a switch for my furnace, frige, freezer and other. check out this link for transfer switch install video.

http://www.reliancecontrols.com/Stre...layer_DSL.aspx

I decided to go with a transfer switch for several reasons, and one I didn't think of at first was had I gone with a box interlock, I would not know when power came back on. Thanks
 
 

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