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gprice5 · Oct 12, 2009, 02:45 PM

A Lennox Series gas furnace w/ heatpump Model (80 MGF3/4-100, 12HPB036, C26-41) was installed at the time I had the home built. Things appeared correct in the Furnas assembly as to the sequence of operations, but I did concede I was unfamiliar with how the sequence of events of the heating and cooling via the various sources should interact. I did notice in ALL modes the FAN was the first thing to operate... I thought this was somewhat strange because it can produce an uncomfortable environment for a few minutes prior to actually performing the required function. If you need heat, the FAN and Heatpump operate simultaneously and immediately (The Compressor operates in reverse of what it does for the cooling function producing heat in the "A" frame coil (inside) assembly instead of the condenser coil (outside) assy.)... However, this also leads to an uncomfortable environment until the "A" frame coil assy begins producing heat. The older/earlier furnaces have a temp switch that keeps the FAN in the OFF mode until the actual heat source comes too temperature and then the temp switch turns ON the fan. This unit has temp switches but don't appear to be wired to operate the system in this manner. To further complicate matters a NEW heatpump assy was installed after a lightning strike but, ONLY the cooling function operates (TX Valve jammed, long story) of which requires a continual operation in "Emergency Heat(EH)" mode to heat the home. EH consists of natural gas backup of which is more expensive than pulling heat out of the air. And again the FAN is the first and ONLY thing that immediately comes on. It’s a good full minute or two of COLD air before the gas fired heat exchanger begins producing heat. Now the question, (Finally! You say!). IS this Assembly working properly? It seems the FAN should come ON after the heat sources have come to, or near there operational temperature or is this the way they achieve efficiency?

hvac1000 · Oct 13, 2009, 06:53 AM

Usually there is a slight delay for blower activation in the heating mode. Many times this is controlled by the main circuit board itself or a smaller device designed for this purpose. This allows the unit to warm up a bit before blowing the air into the home. Naturally this is done for comfort since blowing cold air around before the heat builds up a bit will be uncomfortable.

brucoll · Oct 13, 2009, 07:24 AM

No

gprice5 · Oct 13, 2009, 12:52 PM

[QUOTE=hvac1000;2028812]Usually there is a slight delay for blower activation in the heating mode. Many times this is controlled by the main circuit board itself or a smaller device designed for this purpose. This allows the unit to warm up a bit before blowing the air into the home. Naturally this is done for comfort since blowing cold air around before the heat builds up a bit will be uncomfortable.[/QUOT

gprice5 · Oct 13, 2009, 12:54 PM

Originally Posted by hvac1000

Usually there is a slight delay for blower activation in the heating mode. Many times this is controlled by the main circuit board itself or a smaller device designed for this purpose. This allows the unit to warm up a bit before blowing the air into the home. Naturally this is done for comfort since blowing cold air around before the heat builds up a bit will be uncomfortable.

Sooo, Why wouldn't the Tech wire the system to operate in that manner? Even after it was brought to their attention several times? Does the Heat Pump present some sort of complicated problem getting it to operate in this manner?

hvac1000 · Oct 13, 2009, 01:30 PM

You will have to talk to the person (Tech) who was there since I have no idea of the surroundings of this job or situation.
What I did was to confirm your feelings on the subject. It is obvious that the person who worked on your equipment does not know what he is doing or the situation he found himself in was unavoidable since you are using emergency heat at this time and in some cases the emergency heat selection can cause the blower to be activated without delay. My suggestion is that if you want your system to perform differently and the person who has worked on it before can not or will not do that for you is to call a different company or person and have them wire it the way you want it to work. This is one major disadvantage of boards like this is the fact that we are not there to see what they did and all we can do is advise steps for taking corrective measures.