JesseWBryant Posted October 17, 2007 Report Posted October 17, 2007 New home inspection today. The heater was a gas forced air furnace in the attic and the AC was a split system, outdoor condenser and indoor evaporator coil. When there was a call for heat or AC, both units would come on. Is it likely that this is due to an improperly wired thermostat? Just curious.
kurt Posted October 17, 2007 Report Posted October 17, 2007 Are you saying the heat & AC operated simultaneously?
JesseWBryant Posted October 17, 2007 Author Report Posted October 17, 2007 Yes, that is exactly what I am saying. I apologize for the brief and hurried description. I am currently multi-tasking and getting into sloppy mode.
kurt Posted October 17, 2007 Report Posted October 17, 2007 Boy, ya got me. I didn't know a furnace could fire & the AC could function @ the same time.
JesseWBryant Posted October 17, 2007 Author Report Posted October 17, 2007 I didn't either. Thats why I had to post it to see if anyone else has. The funny thing is, my client originally did not want to get an inspection as it is a new home. Her mother-in-law talked her into it by paying the inspection fee for her. As I was describing the HVAC issue to her, she said "I'm really glad I got that inspection!" Converting clients one day at a time.
Jim Katen Posted October 17, 2007 Report Posted October 17, 2007 Originally posted by JesseWBryant . . . Is it likely that this is due to an improperly wired thermostat? Just curious. Yes. There's a problem with the control wiring. Might be in the stat or on the board in the furnace. - Jim Katen, Oregon
Bain Posted October 17, 2007 Report Posted October 17, 2007 Are you certain the system isn't a heat pump, with gas auxiliary heat?
Tim Maxwell Posted October 17, 2007 Report Posted October 17, 2007 Originally posted by Bain Are you certain the system isn't a heat pump, with gas auxiliary heat? I had one like that about a month or so ago. The only difference was that the heat only cycled up to the point of ignition and then started over. The vent fan would start, then the starter would glow, then it would stop, and then start the cylce over again. Weird to see. The technician that came while I was there said it was a board at the furnace as Jim indicated it might be. The unit I saw was in the attic and who knows how long it had been doing that. I knew something was up as soon as I pulled the stairs down because the vent fan started just as I opened the attic.
kurt Posted October 17, 2007 Report Posted October 17, 2007 Originally posted by Bain Are you certain the system isn't a heat pump, with gas auxiliary heat? That was one of my initial thoughts. What brand was the system? Trane has some auxiliary gas fired heat pumps out. I've still never seen a heat pump, ever.
Jim Katen Posted October 17, 2007 Report Posted October 17, 2007 Originally posted by Bain Are you certain the system isn't a heat pump, with gas auxiliary heat? If it were, the gas furnace shouldn't run at the same time as the compressor. Units with gas back-up just use ambient indoor air for the defrost cycle. - Jim Katen, Oregon
Bain Posted October 17, 2007 Report Posted October 17, 2007 But Jim, what if the furnace was supplementing the heat produced by the condenser? The condenser would remain energized even though the burners were ignited. If someone dialed the thermostat to 90 degrees to check the system, the auxiliary heat would likely kick in while the compressor remained on.
Phillip Posted October 18, 2007 Report Posted October 18, 2007 Most of the heat pumps in my area that has gas backup has a set up where the exterior unit will not come on when the gas is being used.
Bain Posted October 18, 2007 Report Posted October 18, 2007 I didn't realize that, Phillip. Around here, 'cause it doesn't get too awfully cold, almost all heat pumps have electrical supplemental heat. Does it get cold enough in Alabama to warrant the installation of gas auxiliary heat?
JesseWBryant Posted October 18, 2007 Author Report Posted October 18, 2007 It was a straight AC system with a gas furnace. Both units are Goodmans (maybe thats the problem). I agree that it is more than likely an issue with the board. However, the status indicator light showed "all systems go."
Bill Kibbel Posted October 18, 2007 Report Posted October 18, 2007 "When there was a call for heat or AC, both units would come on". That's the system my wife must have ordered. When it's in the 90s, she drives around with the windows and sun roof open and the AC blasting.
Jim Katen Posted October 18, 2007 Report Posted October 18, 2007 Originally posted by Bain But Jim, what if the furnace was supplementing the heat produced by the condenser? The condenser would remain energized even though the burners were ignited. If someone dialed the thermostat to 90 degrees to check the system, the auxiliary heat would likely kick in while the compressor remained on. No. Heat pumps with gas back up don't ever run both at the same time. There really isn't an "auxilliary" function with these systems. When it gets too cold out, the heat pump stops and the gas furnace takes over. They're designed like this because the gas heat exchanger is always upstream of the indoor heat pump coil. If you were to run both at the same time, the heat pump's coil would be awash in hot air fresh from the gas heat exchanger. It then wouldn't be able to dump any of its heat and it would develop high head pressures. - Jim Katen, Oregon
russ myers Posted October 26, 2007 Report Posted October 26, 2007 It sounds like you may have encountered a system with a defective relay...........very common problem. or maybe something as simple as thermostat wires making contact with each other somewhere in the system. You did say new installation, correct?
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