Feed for AC Condenser

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Zapdog

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Malibu, California
Hello, I'm bidding a residential job where I'll be upgrading an existing 100 amp service to 200 amps to accommodate a new air conditioning system . The main service sits on the side of the detached garage in the rear of the property ( the panel is an "all in one"). The house is fed by an existing 90 amp underground circuit from the garage to a 30 space sub panel. The 5 ton condenser will sit in the back yard near the rear of the deck off the family room. And I plan to feed it from the new 200 amp main service panel on the garage, but I'm wondering now if there is anything in the code that says I cannot feed equipment servicing one building (house) from another building (garage). And I'm perplexed.... might be losing sleep on this one. Personally, I don't see a problem with this, being that the condenser is essentially electrically isolated from the house except for the 2 conductor control wire from the FAU.

I'll probably try to call the AHJ in the morning, but until then I was hoping someone could share their thoughts on this one.

Thanks, Mike
 
infinity said:
You can feed it from either panel, your choice.
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But don't attach anything to the house if you feed it from the garage panel, unless your inspector is willing to accept that.

It would be supplying more than one feeder to the building to some and really is in a strict sense.
 
kwired said:
But don't attach anything to the house if you feed it from the garage panel, unless your inspector is willing to accept that.

It would be supplying more than one feeder to the building to some and really is in a strict sense.
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Hello, kwired. Could you please clarify "But don't attach anything to the house"

Thanks, Mike
 
Hi, Just got off the phone with Santa Monica Building and Safety. What I've been told is no way. Theoretical chance of fault current going through the copper condensing lines, intermingling of electrical sources with 24 volt control circuit from FAU.

I guess I go with 200 amp meter main on garage, 200 amp sub panel at house that feeds new sub panel on garage ( garage has been transformed into "guest house").

Thoughts anyone? Do I fight this one, or is the inspector right on. ( he sort of making sense here ).

Thanks, Mike
 
Zapdog said:
Hi, Just got off the phone with Santa Monica Building and Safety. What I've been told is no way. Theoretical chance of fault current going through the copper condensing lines, intermingling of electrical sources with 24 volt control circuit from FAU.

I guess I go with 200 amp meter main on garage, 200 amp sub panel at house that feeds new sub panel on garage ( garage has been transformed into "guest house").

Thoughts anyone? Do I fight this one, or is the inspector right on. ( he sort of making sense here ).

Thanks, Mike
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Mike your post does not make sense.

What did you ask to accomplish?
 
Mike, Kwired was saying if you were to mount the A/C disconnect to the house you would then have 2 supplies to a single building. You would need to mount the disconnect to a post or directly on the unit.

I have no idea what your inspector is talking about. How would this create more fault current on the line set or the 24V control circuit. How would it be any different than running the same circuits if the service was mounted on the house?

It sounds like you new plan is to install a 200 amp feeder from the garage to the house then run a 100 amp feeder from the house back to the garage. Is that correct? If so you should just get a meter/main/loadcenter that has 200 amp feed through lugs. It will have space for 8/16 circuits to be used for the garage.
 
Zapdog said:
Hi, Just got off the phone with Santa Monica Building and Safety. What I've been told is no way. Theoretical chance of fault current going through the copper condensing lines, intermingling of electrical sources with 24 volt control circuit from FAU.
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That is just the inspectors way of saying 'I have no clue but I don't allow that in my city'

Did he cite a single code section for this foolishness?
 
iwire said:
That is just the inspectors way of saying 'I have no clue but I don't allow that in my city'

Did he cite a single code section for this foolishness?
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Hello, he did not quote a code section, but I think his rationale comes from not having one or more feeders, or branch circuits to another building. He did elaborate on his theoretical scenario, where the condenser has a fault that travels through the condensing lines to the house, there is a fire, fireman thinks he is turning off power to house when he turns off breaker to house, but alas there is still current on the condenser circuit traveling through the copper condensing lines to the house. Is he smoking something? Is is time to talk to a senior inspector?

Thanks for all your input, Mike
 
If the condenser has a fault the over current device supplying it will trip removing power from the circuit. I think you need to make the decision if its worth fighting this or just supply the feeder from the house panel.
 
Zapdog said:
Is he smoking something? Is is time to talk to a senior inspector?
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I don't know if he is smoking something but I do know how the system works. Inspectors try to cover their ass just like everyone else. He does not know so when in doubt he refuses permission.

I would call the senior inspector which could be a little smarter than the other one. If he does give permission or the OK then the first guy really won't care because it's no longer his call.

If they sick to their position they are the one's screwing the customer and not you, make some money.
 
Zapdog said:
Hello, I'm bidding a residential job where I'll be upgrading an existing 100 amp service to 200 amps to accommodate a new air conditioning system . The main service sits on the side of the detached garage in the rear of the property ( the panel is an "all in one"). The house is fed by an existing 90 amp underground circuit from the garage to a 30 space sub panel. The 5 ton condenser will sit in the back yard near the rear of the deck off the family room. And I plan to feed it from the new 200 amp main service panel on the garage, but I'm wondering now if there is anything in the code that says I cannot feed equipment servicing one building (house) from another building (garage). And I'm perplexed.... might be losing sleep on this one. Personally, I don't see a problem with this, being that the condenser is essentially electrically isolated from the house except for the 2 conductor control wire from the FAU.

I'll probably try to call the AHJ in the morning, but until then I was hoping someone could share their thoughts on this one.

Thanks, Mike
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Hey,

One idea would be to install a WP pushbutton switch to control both the condenser and house panel disconnect switches simultaneously as one. Is the house panel on the outside wall ? Run it pass the inspector, see if he'll accept this. NEC 225.31 and NEC 225.32.

Also see if the inspector would go along with just providing documented switching procedures at both disconnects, NEC 225.30 (E).

Another concern would be the grounding. I would tie both house and condenser grounds together to minimize any potential differences. NEC 250.32 (D).

Too bad the service drop is closer to the garage. Otherwise, I would replace the house panel with that 200A meter/main and backfeed the garage with the existing UG 90A feeder (if it reaches the buss).

Oh by the way, I'm new here.
 
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If the main panel is in a detached garage and the a/c is for the house then IMO, the a/c should be fed from the house as that equipment is servicing the house. Now technically one can argue that the a/c is a separate structure but I can see where the inspector is coming from.
 
Dennis Alwon said:
If the main panel is in a detached garage and the a/c is for the house then IMO, the a/c should be fed from the house as that equipment is servicing the house. Now technically one can argue that the a/c is a separate structure but I can see where the inspector is coming from.
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The inspector/AHJ is a dope. This is taking Art 225 to the extreme. There is absolutely nothing wrong with this. The OP's proposed branch circuit to feed this from the garage panel/service does not extend any circuits into the house (that already has a feeder) in violation of Art 225 rules. What if the condenser was located next to the garage next to the service panel and the refrigerant lines were piped over to it because that's where the owner wanted the condensing unit? Then where would the inspector want it fed from?
If you use this rational, then as in a common commercial setting, a remote package chiller plant fed from a separate feeder and building would not be allowed to feed any AHU in another building by this AHJ either.
This is what happens when you have a little government minion that is clueless. I'd never roll over for this kind of crap just based on principal.
 
What's all in this garage? Could you re-feed the house with a 200 amp sub-service with fusible disconnect and gutter below, then use the tap rule and set two sub-panels, 100 amp for house and a 50 amp for the AC unit.
 
Update

Update

Hello All,

Finally got through to the senior inspector this morning and after my 30 second explanation of what I was planning he said "no problem with that".

Thanks again for all the input.

All the Best.

Mike
 
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