The ASHI standards require identification of the fuel source for the AC. I'm confused. I know this is probably a really stupid question, but, here goes anyway. On a shared system, the AC only shares the supply ducts. Right?
The AC unit doesn't rely on the fuel source of the furnace. Right? Wouldn't the fuel source for an AC always be electric? I told you it was a dumb question but if you don't ask, you don't learn. Please be gentle.

You are right about the a/c using the duct system. And most or at least 99 out of 100 times the unit is ran on electric but there are units out there that run on GAS either LP or natural. I have seen one that was ran off LP gas, after over 20 years in the HVAC business.

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Well thats my 2 cents.
Brian Kelly
Kelly Home Inspections

After posting the last one I just realized that there is different voltages that a residential A/C unit can be, and either 1 phase or 3 phase. Just a FYI

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Well thats my 2 cents.
Brian Kelly
Kelly Home Inspections

Thanks Brian.

Jim D., I am not familiar with the SOP you refer to, but if it says energy source rather than fuel, that might allude to the possibility of a ground source heat pump which is still uncommon but still much more common than the absorption systems that use gas as a fuel source.
Technically the ground source heat pump does not get energy from the earth but rather releases energy to the earth during the cooling cycle, but that is at least something to consider.
My state SOP requires the "type and energy source" be reported and I always state "central - electric" and then go on to further describe any peculiarities that might be present such as a ground source heat pump, etc. in my comments should the need arise. I have often questioned the need to state the obvious also, but I just report it and leave it at that.
I think it is just in there because it is listed that way in the section above which is heat... but that is just my opinion.
Jim L.

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Jim Luttrall
www.MrInspector.net
Allen, Texas 75002

Thanks for the good info Jim.

To me, Jim L is describing the 'heat transfer medium' and not the 'energy source'.

The 'energy source' would be the source of energy which runs the system.

For a gas furnace, with the old octopus gravity feed systems, the energy source would be 'gas', but as soon as you introduce a blower, then it would (technically) be gas/electric.

Or, just to include the entire scope of the 'energy source' for heat transfer medium and operating power, the energy source would be the 'Sun'.

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Jerry Peck, Construction / Litigation Consultant
Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
www.AskCodeMan.com