dual services in a house???

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I just installed a new sevice in a house for a storage boiler that allready hads a 200 amp general sevice. so now there are two sevices in the house. both panels are bonded and both have a ground running to the water lines and the heat panel's grounding electrod conductor is ran into the general sevice. there is a 4/0 from the transformer to the general sevice and 250mcm from the same tranformer to the heat sevice. both are connected to the same lugs on the transformer. Now wouldn't there be current from one sevice running back to the transformer on the other service's neutral. and current running on the grounding electrod jumper between sevices and the bonding jumpers that bond the water lines. now granted the heat panel is only 240v loads but if they weren't couldn't there be 240v difference between the panels. it all just donesn't seem right to me. tell me what you think or if i am wrong.
thanks luke
 

mdshunk

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Location
Right here.
Two services with the same characteristics is a violation in and of itself. I'm surprised they let that fly. Should rightfully have been a 400 amp upgrade.
 

cowboyjwc

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I started to agree with Marc, until I read your response to him. We have sort of the same thing for electric cars here, but it's more dual metering feeding a timeclock controled outlet. Sorry Marc I tried.

And I belive that 230.40 ex.3 might allow it.

Now if I understand you question and I may not. How would this be any different than you and your neighbors houses all being fed off of the same transformer?
 
i am guessing your talking about current traveling on metal water lines inbetween houses? i agree with you, it would be the same. i guess my question was, is it dangerous? or is the likelyness of anyone getting hurt or anything damaged very unlikely?, and just to clear up some more it is two separate runs from the same transformer. there is 4/0 from trans. through the meter to the general panel. and there is 250mcm from the same trans. through the second meter to the heat panel.
 

cowboyjwc

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And no I wasn't talking about the water piping, though that is a good point, I was more talking about the fact that all the houses are being fed with the same grounded conductor so the potential for unbalance loading is the same as it would be in you situation I guess.

I was once told by an engineer that if you removed the grounding (rod and cw) from your panel, you would still be grounded at your next door neighbors house.

Are we on the same page?
 
i don't know if we are yet or not. i'll talk some more. the two panels are about 2 feet apart. for the existing general sevice panel there is a #6 going out to a ground rod and a #4 bonding on to the house metal water lines(plastic into the building). the heat sevice panel grounding electrod is a #4 from the Heat panel to the General panel. and the heat panel also has a number 4# to the water lines. now for example, during the summer the heat panel wouldn't be used but the general would and any unbalanced current from the general panel would travel through the #4 used to ground the heat panel, current would also travel though the 4# used to Bond the interior water lines. if just seams wrong that current is running through grounding wires and useing a different neutral.
 
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Dennis Alwon

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Location
Chapel Hill, NC
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Retired Electrical Contractor
electricdrill said:
the heat sevice panel grounding electrod is a #4 from the Heat panel to the General panel. and the heat panel also has a number 6# to the water lines.

Deleted because electricdrill fixed the error.
 
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dbuckley

Senior Member
The bottom line is that you have a parallel neutral path through the ground wiring and plumbing at the house, and the 'rouge' path will have a lower impedence than they typical impedence between adjacent residences, so there could be significant current flowing, the magnitude depending mostly on the length of the wiring; this is one of those situations where fractions of an ohm make a difference. The #4 between panels is the most likely place to see current, so thats where to put the clamp meter first.
 

tallguy

Senior Member
cowboyjwc said:
I was once told by an engineer that if you removed the grounding (rod and cw) from your panel, you would still be grounded at your next door neighbors house.
I've heard others post the same thought here as well. Don't know if it's true or not, but I would point out that it is much like rationalizing that "I don't need to get vaccinated for polio since everyone else is vaccinated anyway".
 

cowboyjwc

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Location
Simi Valley, CA
tallguy said:
I've heard others post the same thought here as well. Don't know if it's true or not, but I would point out that it is much like rationalizing that "I don't need to get vaccinated for polio since everyone else is vaccinated anyway".

Don't really know if I agree or disagree, just what I heard. :D
 
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