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1 members (Scott35),
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Joined: Apr 2002
Posts: 7,382 Likes: 7
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Steve:
17K sq ft is a huge house, no doubt about that. Yes, NEC calcs are how services are sized. No, you should not install a 10 amp service & ATS/MTS. (LMAO)
POCO records were mentioned by me, as it is a reliable record of consumption on existing loads, and is used frequently. I did NOT see the OP's 17k Sq ft data in his reply posts until now.
My point was & is...the original (#1) post was regarding the CT & ATS/MTS placement.
No mention was made as to the loads to be connected to the gen and if a gen panel was being installed. Perhaps an engineer may be needed?
John
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Joined: Jul 2002
Posts: 8,443 Likes: 3
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800A into a residential installation??!!
I'd like to see the service wires on that.
Big house or not, no way are you going to need capacity like that.
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Joined: Apr 2002
Posts: 7,382 Likes: 7
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Mike:
600 amp, single phase is 'normal' on the BIG >10k Sq Ft McMansions here; 800 for 17k Sq ft may be overkill, may not.
Depending on the toys; pool; sauna; jacuzzi's, steamers, etc. the 5 to 10k sq ft range from 300 to 400 amps
One EC has a 21k sq ft maxi-McMansion coming soon....800 amp, 3 phase, 4 wire, 120/208 volt.
Now....don't ask about the bills...or the actual loads! LOL
John
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Joined: Jul 2004
Posts: 9,931 Likes: 34
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The only problem with the electric bill method is a steady load of just 30a could be a $700-800 electric bill.
Greg Fretwell
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Joined: Apr 2002
Posts: 7,382 Likes: 7
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Greg:
We get a KW reading record going back xxmonths or years, not dollars
John
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Joined: Sep 2004
Posts: 174
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We have begun this installation and yes the transfer switch is rated and wired for 800 amps. We are installing a fused disconnect for the generator to insure it doesn't pull more than it can handle.
This house also has Geothermal heating and cooling which seems to draw less electricity then convential cooling anyways. I have checked the ampacity and it hasn't gone over 120 amps as of yet.
Now on grounding. As I understand(haven't checked with the AHJ yet)this is now the mpd and should be grounded/bonded as such. Also are you required to drive a ground rod and bond the generator?
Jesus may have been a capenter,but God was an electrician.Genesis1:3
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Joined: Jan 2005
Posts: 5,445 Likes: 3
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Driving a groud rod for the generator will accomplish nothing ... though, I suppose, you might consider it a 'detached structure.'
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Joined: Dec 2005
Posts: 152
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Bonding generator may create a parallel current path with the neutral and EGC depending on how your transfer switch is set up. Should generator frame be grounded - most manuf. require it. Check out the following reference for your scenario: http://members.rennlist.org/warren/Gen_Panels_Appl_Note_EN.pdf
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Joined: Mar 2005
Posts: 1,213
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We have begun this installation and yes the transfer switch is rated and wired for 800 amps. We are installing a fused disconnect for the generator to insure it doesn't pull more than it can handle.
This house also has Geothermal heating and cooling which seems to draw less electricity then convential cooling anyways. I have checked the ampacity and it hasn't gone over 120 amps as of yet.
Now on grounding. As I understand(haven't checked with the AHJ yet)this is now the mpd and should be grounded/bonded as such. Also are you required to drive a ground rod and bond the generator? The generator frame must be bonded and grounded, but HOW it's bonded/grounded is up to you. Driving a supplemental rod is never a bad thing, but it's probably not required. The neutral grounding depends on whether you have a 3-pole or 4-pole ATS, and where the present neutral-ground bond is. It will most likely be floated at the generator.
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Joined: Jan 2005
Posts: 5,445 Likes: 3
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Don't make more of this than it is.
The transfer switch is probably arranged to make your installation nearly mistake proof. That is, it will have sets of lugs, grouped together and clearly identified as to main power, generator power, and load. From that point on, it's just "connect the dots."
Likewise, the generator likely has a big ground lug for you to use.
As for the "parallel path" issue ... at this size there ought to be no doubt about breaking the neutral, and having a separately derived system. When the generator is running, there is no reason to remain connected to the PoCo wiring in any manner.
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