Originally Posted By: dbowers
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Back when I was a Factory Rep for a HVAC Manufacturer, I’ve seen Technicians and have done it myself - start and run an HVAC unit when the o/S temp was 45 - 50 degrees. We were in the Trade, we had a big truck at the curb, and we had access to the parts we would need if we screwed something up (so it was relatively cheap to fix if we blew it).
I'd guess that 95% of all HI's don't fit that description. Therefore why be stupid and do something like turning an HVAC on just to make a few Brownie Points with the Realtor or Client.
I don't walk roofs in lightning storms or when its raining - If the electrical disconnect is off, it stays turned off - I don't feel that lucky.
We've got industry standards - use them.
As far as the same day operation of heat & cooling. If its 65 degrees O/S I would normally run both my gas fired furnace and later my HVAC - or vice versa. If it was 95 degrees O/S, and the house had a Boiler and separate HVAC unit, I personally would probably not fire the boiler.
The furnace and A/C are both 28 years old and so dirty as to be almost clogged. Its 88 degrees O/S. The A/C is running when you arrive but cooling with only a 10 degrees TD. You hold off on running the furnace until the end so as to not make everyone uncomfortable. It works but is "NASTY". You tell everyone both units work but need cleaning, servicing and a full check-up - you also tell them the OLDER units are at or near the end of their useful lifespans, with replacement emminent. YOU LEAVE!!
That night you get a call from the Realtor telling you that shortly after you left the A/C quit and would not come back on and cool. The sellers are angry and have called Uncle Charlies Service Co. He tells them the HI must have done something to damage the unit and they need a new one.
By the time you get hold of themn tomorrow to explain the compressor has just kicked out on its internal overload - and to get out a garden hose to run over the compressor and get it to reset - Uncle Charlie has already put in the new unit. WHO DO YOU THINK THEY WANT TO PAY FOR THIS??
Some of this is not ground in stone rules as much as common sense.
Dan Bowers, CRI