Moving and updating and service meter

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  #1  
Old 08-23-01, 09:44 PM
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DavidLila
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Question

O.K. I originally started out just trying to run a new circuit to a detached garage but now I'm thinking about the following and would like some basic advice:

The house is 1600 sq ft (built in 1908). It has a 100 amp panel. I would like to move the servicehead/weatherhead and meter from the house to the garage so the wire is not overhanging the small yard. I have started to download and print WG's article on how to do this but I would still love comments on the plan to do this. Is it worth it? What size wires to I use etc.. Here is the background information. I have calculated the load as follows:

1600 sq ft x 3 watts = 4800 watts
2 kitchen circuits = 3000 watts
landry circuit = 1500 watts
permanent appliances as follows
range - 11,700 watts
dryer - 6,700 watts
dishwasher - 1000 watts
disposal - 768 watts
AC - 4464 watts
water heater - 4500 watts
gas furnace - 0

Detached 20x20 sq ft. garage currently has no electricity but I would like to add the following (watts are estimated)
3 motion light sensors - 900 watts
garage door - ???? watts
appliance circuit outlets (4)- 1500 watts
other lights (inside garage) - 400 watts
possible baseboard heaters - 4500 watts

Other notes: distance from the house to the garage is 45 feet.

I estimated the total gross load at 41,468 watts (since the AC and baseboard heaters will never be running at the same time). Using the first 10,000 watts at 100% and the remaining watts at 40% I get a load of 22,627 or 98.4 amps (which includes the future planned updates to the garage). Finally I plan on removing the electric range in the next year or two and replace it with a gas range and microwave.

So, if I decide to move the weatherhead and meter to the garage I assume it would be best to use a 200 amp panel on the outside of the garage which would ease future updates and house expansions. I'm thinking that the 200 amp meter/panel would act as the main panel and since it is on the garage I could use the circuit spaces inside this panal for the garage circuits. Then I would run the current house panel (which I really don't want to change at this time) as a 100 amp subpanel. So here are my questions:

Is this a viable idea?

Do I need to ground the new 200 amp meter/panel and how would I do this since the garage has no water pipes.

I plan to run the wire from the new 200 amp panel underground to the house 100 amp panel. What size circuit breakers would I use at each end (100 amp?) and what size wire (6/3 or larger?)? Could this wire be place in conduit and be run though the garage walls or ceiling space in the garage (none of which is finished at this time) and exit the garage at the trench for the cable? Again, I want to be able to upgrade the house panel in the future to 125 or 150? amps if needed.

I have already talked to the utility company and they will send an engineer out (for free!) to go over the plans for the weatherhead and meter placement. I've talked with the city inspector too but need to firm up the plans. I already have a trench dug to 24" from the garage to the house and if I don't complete this project soon and resod the yard my wife may kill me! Help! thanks.



 
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  #2  
Old 08-25-01, 10:09 AM
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Wgoodrich
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YOU SAID;
The house is 1600 sq ft (built in 1908). It has a 100 amp panel. Here is the background information. I have calculated the load as follows:
1600 sq ft x 3 watts = 4800 watts
2 kitchen circuits = 3000 watts
landry circuit = 1500 watts
permanent appliances as follows
range - 11,700 watts
dryer - 6,700 watts
dishwasher - 1000 watts
disposal - 768 watts
AC - 4464 watts
water heater - 4500 watts
gas furnace - 0
Detached 20x20 sq ft. garage currently has no electricity but I would like to add the following (watts are estimated)
3 motion light sensors - 900 watts
garage door - ???? watts
appliance circuit outlets (4)- 1500 watts
other lights (inside garage) - 400 watts
possible baseboard heaters - 4500 watts
I estimated the total gross load at 41,468 watts (since the AC and baseboard heaters will never be running at the same time). Using the first 10,000 watts at 100% and the remaining watts at 40% I get a load of 22,627 or 98.4 amps (which includes the future planned updates to the garage). Finally I plan on removing the electric range in the next year or two and replace it with a gas range and microwave.

REPLY;

I ran you data through a calculation and came up with the following demand load on your project. Keep in mind that the garage is calculated in a different manner than the home. You would need to do two calculations one for the home and one for your garage.

Home demand load calculation that I did calls for a minimum service size of 29,339 Va. equalling 123 amps requiring a 125 amp service as per 240-6 rounding up to the nearest normal size overcurrent device. The home by itself should be a minimum of 125 amp service, you may go larger but the NEC says you must not go smaller unless you have an existing service.

The garage calculates a bit funny. It depends on how many people are going to use equipment in that garage. 220-3-A dictates that you use .25 Va per square feet for you garage.
If you have only one person working in that garage you would only have to use the largest motor load in that garage. The receptacles designed for unknown loads such as for convenience outlets you would calculate the number of receptacle at 280 va per outlet allowing about 13 receptacles on a circuit as a minimum. Most people install 8 on a circuit in a garage with an odd even type design allowing two receptacles in a certain area to be on two different circuits. This allows you to go anywhere in your garage and run two appliances or tools and have 30 or 40 amps available without having both tools or appliances running on the same circuit. Thought is that you tend to work in a tight area using receptacles in that certain area.

Calculating as an approximate as discribed above your minimum service size for your garage should be a minimum of 100 Va minimum lighting, 1170 Va GDO, 4500 Va for baseboard heat. This would hit your garage demand load as you discribed at 25 amp main service for this detached garage.

Now you did not mention any motor loads, welders, ranges, etc. that may be used intermittently in this garage. If any of these type loads will be in your garage then add the full load current plus 25% of the largest motor load plus add any more motors at full load current only that will run at the same time to that garage service size. Keep in mind only one person is working in that garage you could have 1000 amps worth of motors but you would calculate only the largest motor and omit the other motors that would not be running at the same time same as you furnace versus A/C unit.

Considering the 25 amp minimum service size and considering cost best buy factor of the feeder serving a garage you should pick either a 60 amp service using a #6 USE copper or use [depending on the ruling of the local inspector three or four #4 THHN in a conduit or #2 URD for a 100 amp service. These are commonly the two service sizes used to feed a detached garage.

YOU SAID;
Other notes: distance from the house to the garage is 45 feet.
So, if I decide to move the weatherhead and meter to the garage I assume it would be best to use a 200 amp panel on the outside of the garage which would ease future updates and house expansions. I'm thinking that the 200 amp meter/panel would act as the main panel and since it is on the garage I could use the circuit spaces inside this panal for the garage circuits. Then I would run the current house panel (which I really don't want to change at this time) as a 100 amp subpanel. So here are my questions:
Is this a viable idea?

REPLY;
Best scenario is to install your service at your location where the most load is used being as close to that most load is located. This would suggest installing your service on the dwelling, not the garage.

YOU SAID;
I would like to move the servicehead/weatherhead and meter from the house to the garage so the wire is not overhanging the small yard. I have started to download and print WG's article on how to do this but I would still love comments on the plan to do this. Is it worth it? What size wires to I use etc..

REPLY;

It is my opinion that it would be best design to locate your main service in the dwelling sub feeding the garage due to the minor load in the garage and the heavier load in the dwelling and the associated desire to locate the main service closest to the heavier loads to limit voltage drop where we pay for electricity that we didn't get to use. Let the Utility company eat any voltage loss incurred. You speak of a concern about overhead wiring going to your house. I suggest that you contact you Utility company and ask a cost factor to install an underground lateral from their transformer to you meter base located at the home. Consider the cost factor of going underground as your main service from your Utility transformer versus the dislike of the overhead service on your dwelling versus the less efficient wiring design of installing the main service in a remote building when the main loads are in the main building before you make a final design dicision.

YOU SAID;
Do I need to ground the new 200 amp meter/panel and how would I do this since the garage has no water pipes.

REPLY;
My personal opinion if you are going to upgrade your service I would upgrade to the 200 amp service also. Yes you will be required to install a grounding electrode system to a main service rated panel.

YOU SAID;
I plan to run the wire from the new 200 amp panel underground to the house 100 amp panel. What size circuit breakers would I use at each end (100 amp?) and what size wire (6/3 or larger?)? Could this wire be place in conduit and be run though the garage walls or ceiling space in the garage (none of which is finished at this time) and exit the garage at the trench for the cable? Again, I want to be able to upgrade the house panel in the future to 125 or 150? amps if needed.

REPLY;
I would read and consider what I have said above and consider any further opinions after I post this reply, then make you final decision on your wiring design. Then tell us what you plan by planning it yourself and discribe in detail. Then we will come back in with further suggestions and details of requirements once we are sure the wiring disign, location of main service, and whether overhead or underground that you have chosen. Also include the distance from the meterbase and the feeders entering the building to where the main service rated panel is located inside that building.

YOU SAID;
I have already talked to the utility company and they will send an engineer out (for free!) to go over the plans for the weatherhead and meter placement. I've talked with the city inspector too but need to firm up the plans. I already have a trench dug to 24" from the garage to the house and if I don't complete this project soon and resod the yard my wife may kill me! Help! thanks.

REPLY;

You made a very good start. You contacted you inspector and your serving Utility Company. I am proud and impressed. You will probably get a varying range of advice as to what you should do from all you talk to. You should listen to what everyone has to say then make your own decision keeping in mind what is said to you that can be enforced by those in authority.

Let us know your final plans then we can help with the details then.

Hope this helps

Wg
 
  #3  
Old 08-25-01, 03:53 PM
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DavidLila
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Wg:

Thank you very, very much for your reply. I didn't realize the garage had to be calculated differently. Anyway, the garage/shop will be mostly a garage and used as a shop occasionally and mostly by one person. It will probably have a table saw and some other basic woodworking equipment but certainly no welders.

But let me pour over your suggestions and your website articles (I printed out the sections on the service and wiring a garage - 75 pgs!) and develop a plan (or a retreat to something less involved) and I post some more questions for you soon. Thanks for your help.

DavidLila
 
  #4  
Old 09-14-01, 06:32 AM
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DavidLila
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After reviewing WG's suggestions, reading a bit and talking with the city inspector here are my current plans - I love to hear comments and reviews:

Starting at the garage I will place a 2" rigid conduit 3 feet above the roof to a weatherhead (this should provide enough clearance for the roof, driveway, road and ally).

I will run 2/0 copper in the conduit down to a 200 amp "all-in-one" service meter and panel on the outside of garage. Now I know you would prefer the main panel on the house but here is the problem: I would have to bury the unfused wire in conduit at least 36" down. Currently I have a trench 24" down and getting down to 36" or more will be a major problem with the huge oak tree I have in the back yard. If I were to get down to 36" I would have to run the unfused cable in the conduit, bury it with 12" of dirt then run wire back to the garage (either direct bury at 24" or in conduit at 18"). This seems like twice the work. I think the real question here is how much voltage will I lose going from the garage to the house panel which is approximately 50 feet? Is it worth all the extra digging and wire?

Anyway, with the current plan I'll have the 200 amp panel on the garage and run the circuits for the garage directly out of that panel (which will be more than big enough). Then I'll run a #1 copper (for a max of 150 amps) in schedule 80 conduit from a 100 amp fuse in the main/garage panel to an outside disconnect (100 amp - the inspector said I needed this) then into the house (which is currently 100 amps). I figure if I use the #1 wire then it will be easy to upgrade the house panel in the future to 125 amps or 150 if needed.

Some other details:

- the garage will be used by one person. Thus only one motor will be running at one time (i.e. a table saw or small drill/planer but no welders however!)

- The distance from the service panel at the garage to the house is 50 feet and then the house panel (which would become a subpanel) is about 6 feet further inside the house.

- As for the grounding, the inspector said I would need 2 grounding rods 6 feet apart at the main panel and the house subpanel. In addition I need to connect the grounding the the water pipe within 5 ft of entering the house (this dose not exist currently).

What do you think? Should I go with these plans or spend the next week digging out the trench to 36 inches? Thanks.

DavidLila
 
  #5  
Old 09-14-01, 10:03 AM
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Wgoodrich
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Where are you getting 36" minimum depth. Most Utility companies run their trenches 30" and supply the trench themselves. Most residential wiring is buried 18", and most commercial settings have a minimum of 24" depth for their trenches. I am confused where you came up with a 36" depth requirment.

Curious

Wg
 
  #6  
Old 09-15-01, 06:23 PM
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DavidLila
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Wg;

I have called the utility company twice and both times been told that unfused direct burial wire must be run at 36". In conduit the minimum depth is 30" to the top of the conduit (schedule 40). This city inspector told me that this unfused wire must be covered by 12" of dirt and then a warning ribbon.

As for fused wire (after the service meter) the city inspector has indicated that underground rated wire must be at 24" and a minimum of 18" if run in conduit. Again it must be a minimum of 12" above any unfused wire - (see above).

I haven't asked the utility about providing the trench. I figured they wouldn't do that since this is a revovation/upgrade and not new construction.

I'll call the utility company again on Monday and double check everything - and I'll make sure I'm talking to the electrical inspector for the company and not just the office folks. I'll get back to you after that. Other than the trench depth problem any comments on the rest of the plan? Thanks for your continued interest.

DavidLila
 
  #7  
Old 09-16-01, 07:03 AM
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Wgoodrich
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You may have misunderstood depth a bit. The Utility company usually require a depth of 30 to 36" depending on the area you are in for utility feeders on the line side of a meter. Once the feeders are on the load side the rules apply to the NEC. The NEC requires 18" on a residential setting and 24" on a commercial setting whether unfused or in PVC or direct buried. There are some different depths such as 12" for GFI protected branch circuits or 6" deep if in rigid metal conduit.

I still strongly suggest the main service being located at your heaviest load [dwelling] and any accessory buildings being fed from that dwelling. However it is you, your utility company, and your AHJ [County electrical inspector]choice in wiring design.

One thing that I picked up that you said I thought that I would clarify is that you mentioned ease in future upgrading power to the dwelling from the garage. Remember that all main breakers, fuses, and disconnects serving a building must be located in that building and those mains must be grouped together in the same location. You won't be able to run a new feeder from that main service rated panel if located on the garage to a new panel in the dwelling that is in a different locaction from where the first main panel is located. Any new panel in a structure must be grouped with the existing main panels. There is a maximum of 6 main disconnects allowed to serve the same structure as long as they are grouped together as required.

Just be sure to keep communicating with your Utility engineer and your County electrical inspector.

Good Luck

Wg
 
  #8  
Old 09-18-01, 12:58 PM
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DavidLila
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Wg:

So here is the lastest update. After calling the utility company again and talking with the electricians it turns out that the feed from the transformer on the telephone pole to the meter must either be above ground (overhead)from the pole to the meter via a weatherhead or underground from the pole to the meter. It cannot, as I was proposing, go from the pole overhead to a weatherhead and then underground to the meter.


Currently the pole for my house is on the other side of the street and thus the only two options are for the power company to put a pole on my side of the street ($1200) or for them to dig under the street (only $5 a foot but with the cost of street repair the total would be up above $1000 again). Anyway being a low-budget house renovator I can't afford either of these options and thus will probably go with the overhead feed to a weatherhead on the garage and then run the house as a subpanel off the combination service meter/panel on the garage. I know it isn't optimal but without spending big bucks it's my only choice for removing the overhead wire from my yard. Is this a terrible choice? That is, is this a dangerous thing to do or just a sub-optimal design that will work though certainly isn't elegant?

DavidLila
 
  #9  
Old 09-18-01, 03:15 PM
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Wgoodrich
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I suspected by the way you were talking that you needed more conversation and to pin down a little closer what your AHJ and Utility wanted. I am glad you caught the construction charges involved allowing you to make an informed decision. I see no Code violations as we have talked. I agree that this design would in my opinion be a second choice but in your situation it may be the best choice you have. Just keep in open contact with your AHJ and Utility company as you go to try and avoid buying and installing material and labor that must then be discarded at the orders of your authorities. Don't look at the picture as a hay loft of hay but as a bunch of bails being put in that loft one at a time. Do your job a little section at a time keeping in mind the whole picture. This way the job won't grow to a monster in you thoughts.

Good Luck and let us know how you come out.

Wg
 
  #10  
Old 10-25-01, 05:28 PM
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DavidLila
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How do I ground this?

Help! I need help planning out how to ground my new service. As detailed above I have put a new 200 amp panel on the garage and run 1/0 Alum. in 2" conduit to the house. (As previously discussed this is clearly a less desirable set up but will bring power to the garage and allow me to remove the overhead cable. I've did discover a draw back to this set-up: the new 200 amp square-D combo meter/service panal is only rated for a maximum 100 amp breaker! Thus I can't get any more than that to the house which is now a subpanel! Oh well, the house has been running on a 100 amp panel for 30 years without problems and once I get rid of the electric range that should free up some extra reserve). Anyway back to the main problem:

1) on the new 200 amp main meter/panel combo on the garage it appears the ground and neutral bar are one in the same. The inspector told me to run grounding wire (#6 copper) from the bar to 2 grounding rods seperated by 6 feet. He also stated I do not need to connect the house and the garage panels with a ground wire. No problems here.

2) The problem I have is at the house. So the 1/0 Alum to the house will run to an outside disconnect and then to the house subpanel inside the house (approx 6 feet away). I have copper plumbing coming into the basement at the front of the house. The copper pipes go into the ground and at some point (probably just 1 - 2 feet into the ground) attaches to PVC (the main water service). Currently the ground wire goes from the panel to the outside disconnect then outside to one ground rod and at some point some of the ground wires attach to the hot and cold water pipes by the house panel (these are expose in the laundry room - is this dangerous?).

My current plan is to do the following:

Start the ground wire at the copper pipe where it enters the house. Run the ground wire in the crawl space attached to the joists and then outside (distance is approx 50 feet). Once outside I'll bury it along side the house about 6" down (does this have to be in PVC?) and run it past the gas meter (but not connected to the gas meter or any gas pipes) about 20 feet to the first grounding rod, then 6 more feet to a second grounding rod and then up in PVC to a new outside disconnect and finally through conduit to the isolated ground in the house sub-panel. Is this o.k. to do?? What else do I have to do? Do I have to connect both hot and cold water pipes? If so, can the ground wires be out in the open or should they be out of harms way?Finally, if I have to put the ground wires to the hot and cold piping by the water heater can I run is down the PVC which is already hooked up to the panel and contains romex 12/2 wire?

Thanks for your help!
 
  #11  
Old 10-26-01, 03:11 PM
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Wgoodrich
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YOU SAID;
As detailed above I have put a new 200 amp panel on the garage and run 1/0 Alum. in 2" conduit to the house. (As previously discussed this is clearly a less desirable set up but will bring power to the garage and allow me to remove the overhead cable.

REPLY;
1/0 aluminum is rated for 125 amps serving your dwelling main panel. You should be fine as long as you don't try to pull more than the ampacity of the conductor.

YOU SAID;
I've did discover a draw back to this set-up: the new 200 amp square-D combo meter/service panal is only rated for a maximum 100 amp breaker! Thus I can't get any more than that to the house which is now a subpanel! Oh well, the house has been running on a 100 amp panel for 30 years without problems and once I get rid of the electric range that should free up some extra reserve). Anyway back to the main problem:

REPLY;

Most panels are rated to accept 125 amp breakers in their panel. You might check with your manufacturer. You also have the option of installing a second 100 amp breaker in that panel and run a second feeder to that main dwelling and installing a second main panel in the main dwelling again 100 amp rated. Check if this would be an approved option for growth with your AHJ. Another option is to increase the size of your meter base to a double lug meter making what is called an unlimited tap feeding your dwelling from your garage without a disconnect or overcurrent device required until you reach the nearest point of entrance of you dwelling. This would allow you to install a 200 amp feeder instead of your 125 amp feeder and upgrading you 200 amp main panel in your dwelling to a 200 amp panel without increasing the load in your garage panel. Look at the link below, then click on the left column on unlimited tap link. While this drawing is designed to serve the garage from a main dwelling you can also serve the main dwelling from the garage in reverse. The unlimited tap rule is found in the NEC in Article 240-21-B-5. Check with both your utilty company and AHJ to confirm that there is no local ordinance forbidding use of this unlimited tap rule.

http://homewiring.tripod.com/detgarage.html

YOU SAID;
1) on the new 200 amp main meter/panel combo on the garage it appears the ground and neutral bar are one in the same. The inspector told me to run grounding wire (#6 copper) from the bar to 2 grounding rods seperated by 6 feet. He also stated I do not need to connect the house and the garage panels with a ground wire. No problems here.

REPLY;
You are fine with that statement.

YOU SAID;
2) The problem I have is at the house. So the 1/0 Alum to the house will run to an outside disconnect and then to the house subpanel inside the house (approx 6 feet away).

REPLY;
The main disconnect outside your dwelling is your main service rated panel. Your grounding electrode system must be connected to this main service rated disconnect and not to the sub panel inside the dwelling.

YOU SAID;
I have copper plumbing coming into the basement at the front of the house. The copper pipes go into the ground and at some point (probably just 1 - 2 feet into the ground) attaches to PVC (the main water service). Currently the ground wire goes from the panel to the outside disconnect then outside to one ground rod and at some point some of the ground wires attach to the hot and cold water pipes by the house panel (these are expose in the laundry room - is this dangerous?).

REPLY;
250-50-A requires that the water pipe must be in direct contact with the earth for a minimum of 10'. You only have a contact with earth for 2'. Do not use this water pipe as a grounding electrode. Bond the water lines as you say you already have and use the grounding rods as your grounding electrode system, not the water pipes. You are to only make the metal water pipes as one entity with the equipment grounding bar of the main disconnect located outside. Do not connect the water pipes to be bonded to the subpanel.

YOU SAID;
My current plan is to do the following:

Start the ground wire at the copper pipe where it enters the house. Run the ground wire in the crawl space attached to the joists and then outside (distance is approx 50 feet). Once outside I'll bury it along side the house about 6" down (does this have to be in PVC?) and run it past the gas meter (but not connected to the gas meter or any gas pipes) about 20 feet to the first grounding rod, then 6 more feet to a second grounding rod and then up in PVC to a new outside disconnect and finally through conduit to the isolated ground in the house sub-panel. Is this o.k. to
do??

REPLY;

Scrape the paragraph you wrote above. Do not use that water pipe as a grounding electrode source. You do not have 10' of direct contact with earth as a minimum as required by the NEC to use this water pipe as a grounding electrode source.

YOU SAID;
What else do I have to do?

You might want to install a phone line from your home to your garage designed for direct burial. Now would be a good time if you want a phone in the garage.

YOU SAID;
Do I have to connect both hot and cold water pipes? If so, can the ground wires be out in the open or should they be out of harms way? Finally, if I have to put the ground wires to the hot and cold piping by the water heater can I run is down the PVC which is already hooked up to the panel and contains romex 12/2 wire?


REPLY;

YOu must disconnect the bonding from the water pipes hot and cold from the existing house panel. This existing house panel is a sub panel the bonding of the cold water pipes with a jumper from that cold to the hot water pipes should come from the main service rated disconnect which is outside. This bonding wire from the water pipes to your main service rated disconnect may be insulated or bare and without protection except if subject to SEVERE physical damage. Do not install this bonding wire inside a conduit with branch circuit wiring.

One last thing, remember that your existing main service rated panel inside has now become a nonservice rated panel. [sub panel] You must separate the neutrals and grounding bars in this subpanel. The neutral bar must not be in contact with the metal box of this sub panel.

Hope this helps

Wg
 
  #12  
Old 10-27-01, 12:06 PM
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DavidLila
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Wg;

Thank you very much for the infomation. Boy was I off base in my design. I going to digest what you said and get back to you later with my final design.

Is there a web site that explains (in very plain/simple english) ground systems and requirments. The whole ground thing still baffles me. For example why is the grounding and neutral connected in the main 200 amp meter/panel combo. Why is the ground and neutral seperated in the main house disconnect? (at least the local electrical store said it should be seperate). Finally, my current house panel already has the ground and neutral seperated but I guess it was always a subpanel since the house has always had an outside disconnect. Anyway, I'll finalize my plan and get back to you. Thanks again.

DavidLila
 
  #13  
Old 10-30-01, 01:12 PM
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DavidLila
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Grounding - plan B!

Wg;

So after reviewing your information and my current set up, it appears that the grounding system won't change much. Currently the set up is as follows:

The service wires are overhead and run down to a meter/outside disconnect (100 amp) outside the house. On the downstream side (after the disconnect) there are 4 wires. Two blacks (hot), one neutral, and one ground. The neutral and ground are on one bar. Once inside the house subpanel (approx. 6 feet away) the neutral runs to one bar and the ground to another (i.e they are isolated). A #6 copper wire is pig-tailed to the ground wire in the outside disconnect and runs down to a single grounding rod and then back inside the house to the cold water pipe and a metal electrial conduit. It is not attached to the nearby (approx. 2" away) hot water pipe.

It seems the new set up would be about the same with the exception of seperating the ground and neutral (for reasons I don't understand yet) in the 100 outside disconnect (which as you said previously is now the main service rated panel). So I assume the following: the 1/0 alum. comes from the main meter/panel 200 amp combo on the garage and connects into the 100 amp outside disconnect on the house with the neutral wire going to an isolated neutral bar. A seperate isolated grounding bar should be installed in the outside disconnect. Would a ground wire run from this to the house subpanel (as it currently does)? Then a wire would also run from the ground bar in the outside disconnect to 2 grounding rods seperated by 6 ft. and another to the hot and cold water pipes inside the house. Does this work?? Thanks for your help!!

DavidLila
 
  #14  
Old 11-03-01, 02:56 PM
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DavidLila
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Help with Grounding plan

Wg and others:

Any possibility on getting any feedback on the above (see the previous post) grounding plan? Thanks.

DavidLila
 
  #15  
Old 11-04-01, 03:46 AM
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Wgoodrich
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YOU SAID;
So after reviewing your information and my current set up, it appears that the grounding system won't change much. Currently the set up is as follows:

The service wires are overhead and run down to a meter/outside disconnect (100 amp) outside the house. On the downstream side (after the disconnect) there are 4 wires. Two blacks (hot), one neutral, and one ground. The neutral and ground are on one bar. Once inside the house subpanel (approx. 6 feet away) the neutral runs to one bar and the ground to another (i.e they are isolated).

REPLY;
You sound fine so far.

YOU SAID;
A #6 copper wire is pig-tailed to the ground wire in the outside disconnect and runs down to a single grounding rod and then back inside the house to the cold water pipe and a metal electrial conduit. It is not attached to the nearby (approx. 2" away) hot water pipe.

REPLY;
You are a bit confusing here. What do you mean by pigtailed to the ground wire in that outside disconnect? This 6 awg wire is a grounding electrode conductor intended to be connected to the neutral bar of you main service disconnect and ran to the ground rod. Is this what you mean, or are you splicing this grounding electrode conductor to the neutral conductor in that main disconnect? The wire ran to the cold water pipe may be connected to the ground rod or come from the grounding bar in the main disconnect, either location is fine. The hot should be jumped to the cold metal water pipes making both hot and cold water pipes as one entity.

YOU SAID;
It seems the new set up would be about the same with the exception of seperating the ground and neutral (for reasons I don't understand yet) in the 100 outside disconnect (which as you said previously is now the main service rated panel).


REPLY;
If the meterbase is on the garage and you run a 4 wire feeder from that garage to the house outside disconnect you must separate the neutrals and the grounding bars in that disconnect outside that house fed from that common service at the garage, with the outside disconnect at the house wired as a sub panel. If you run only three wire feeder from that garage to the house fed from the garage meterbase then you must marry the neutrals and grounding conductors in that house outside disconnect as a main service rated panel.

YOU SAID;
So I assume the following: the 1/0 alum. comes from the main meter/panel 200 amp combo on the garage and connects into the 100 amp outside disconnect on the house with the neutral wire going to an isolated neutral bar. A seperate isolated grounding bar should be installed in the outside disconnect. Would a ground wire run from this to the house subpanel (as it currently does)?

REPLY;
This wiring requirement is discribed in the reply just before this section. Depends on whether you run a 4 wire feeder or a 3 wire feeder from that garage meterbase to the house.

YOU SAID;
Then a wire would also run from the ground bar in the outside disconnect to 2 grounding rods seperated by 6 ft. and another to the hot and cold water pipes inside the house. Does this work?? Thanks for your help!!

REPLY;
This part of your statment sounds fine.


Hope this helps

Wg
 
  #16  
Old 11-05-01, 08:25 AM
D
DavidLila
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Wg:

Thanks again for your help. So if we ignore the current set up then the new set up will be as follows:

As you already know the new 200 amp meter/panel is on the detached garage. The city inspector said I should run 3 wires to the house so I have 1/0 Alum. (3 wires) running to the house outside disconnect. The 2 black (hot) wires will attach to the breaker and the neutral to the neutral bar in the outside disconnect. Now it sounds like the ground will be on the same bar (i.e. neutral and ground will NOT be isolated). The ground will then run down to 2 grounding bars seperated by 6 feet (per the city inspector's instructions). It sounds like another piece of grounding wire should run to the water pipes just inside the house.

So here is the final question (I hope): Do I have to run a seperate ground wire to the inside house subpanel from the outside disconnect or not? Currently such a wire exists in the current set up - should I just leave it there?

In summary it sounds like if I'm running 3 feeder wire to the house then the outside disconnect would have a married (not isolated) ground/neutral bar. Then the subpanel inside the house would have an isolated ground and neutral bar. Is that correct?

Thanks again for you time and patience.

Davidlila
 
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