Heat temperature issues with Goodman GMP 100-4 furnace
The problem that i am having is that the furnace blows around 92 degree air. It cycling and getting my thermostat to temperature. I have extra thermometers sitting all around my house and i have confirmed that i have about a 3 degree temperature drop from shoulder level thermostat to floor. When i raise the temp on the thermostat the furnace will blow much warmer air(around 130 or so) until it gets the thermostat there and then cycle off. Then the cycling from there on to hold that temperature goes back to the cooler air unless i raise the temperature so more. When that cooler air i can never get from about waist down to heat up. It always does heat up when that warmer air is blowing, but it doesn't do it everytime the furnace comes on, only when i raise the temp. Hope this makes sense to someone. I have only been told by a professional that my unit is undersized. They said it is 69,000 btu's. My house is 2000 square feet of conditioned space. I use propane and propane alone is costing $300 per month and i am still not comfortable. Thanks so much for your time.
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Re: heat temperature issues with Goodman GMP 100-4...
69,000 btuh is adequate for a 12-1400 square foot house.
Otherwise, your thermostat simply tells the furnace to cycle on/off.
If it calls for heat and does not come on, the problem is with switches and relays within the furnace.
Your setting the temp higher only causes the other parts to keep trying until they finally light and heat.
This is based on your information saying it will cycle on and blow cool air--not hot air.
You will have several temperature variations from floor to ceiling.
You probably have ceiling vents as well.
You need a technician to verify the rollout switches, fan relay, inducer fan etc. if the furnace is not firing everytime you call for heat.
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A heat pump on the optimal heating day (about 50 degrees ambient) will only deliver approximately 85 degree air as compared to 125 degree air from a fossil fueled furnace. The colder the outdoor air is the less heat there is available to be transferred to the living space. At 30 degrees, the heat transfer capability is getting close to negligible meaning the run cycles will be approaching continuous and eventually as the heat pump along cannot maintain setpoint, the outdoor stat or stats will bring on auxilliary heat in the air handler.
If your ambient temp is below the 'balance point' of the heat pump, the house temp will drop a little lower and most times energize the heat strips through the outdoor t-stat. Your outdoor stat could be set too low for the heat pump to carry the structure all the way down to the balance point so when you turn it off and back on, the lower indoor temp automatically brings on the heat pump plus a heat strip or two, thus the warmer air. Second stage on the stat satisfies due to the heat strip, drops them out of the circuit and the heat pump is left running on first stage heat delivering the perceived cold air.
Your outdoor stat could also be not functioning correctly and not allowing the heaters to come on until the system is turned back on reestablishing the two stage call for heat.
Tons of possibilities and not enough room to list....
The fan switch is set to turn on at approximately 125 degrees and run until the heat exchanger temp drops to around 105 degrees. With age the sensitivity of this switch varies and summer heat can cause the switch to turn on if the outside temp is over 100 degrees. Only the fan is running, not the burner but you can shut off the power to the unit if this is an issue.
Sounds like the fan switch on the furnace is set to low. Turn power off to furnace, take door off of furnace look for a fan switch, it may be a fan - limit together. The limit settings should be approximately 160° to 200°, and the fan settings should be about 100° to 140° set it to 120° it it's already set there then you probably need to replace it.
Yes. The defrost cycle of a heat pump is actually turning on your airconditioning to heat up the condenser to thaw it out. During this cycle your electric strip heaters "should" be adequate enough to compensate for the a/c being on. At about 30 - 34 degrees outdoor temp there is not enough heat in the air to to adequately heat your home with the heat pump only. Some technitions will use an outdoor thermostat to turn off the heat pump when it is under 34 degrees outside. If you are to cold when its under 34 degrees intall more electric strip heaters.. But if you do this your electric bill may go up significantly.
Welcome to the wonderful world of electric heat pumps (lol).
blowing cold air on this furnace usualy caused by high limit trip, or flame roll out. the first one, (high limit) is from insf. air flow. (blocked filter,bad zone damper?
The second,(flame roll out) caused by bad heat exchanger,blocked vent.ect.
check out the fan switch on the unit and make sure that its the correct one. it should cycloe on @ 120 degrees and cycle off around 100 degrees. Someone may have put in a different one and that is not the approve one.
I am confident the technician(s) have done this but check anyway.
Gas pressure 4-7 inches W.C for natural, 10 - 11 for Propane.
Air filter clean and unrestricted.
Temperature over supply plenum 140 degrees F.
All registers open and unrestricted.
Vent and intake unrestricted and not blocked.
Condensate hoses free of debris and draining.
OK now lets check to see if the furnace is staying on long enough.When it runs for a heat cycle, is the flame staying on until about 2 minutes prior to achieving the set temperature or is it cycling everyfew seconds and never reaching temp? To check you will need to view the flame through a small viewing port of thru the fins in the front door. Watch them for 10 to 15 minutes.
If they are staying on a long time, we will need to see if the room blower is working properly. If they are going out quickly and or cycling. Get the technician on the pone to talk it over. It could be a safety sensor.
If the blower stays on and the burners are on as well, you have a door open somewhere. Just kidding. Remove the thermostst documenting which wires go where. Take the white wire and cross it with the red wire. This will (or should) turn on the furnace. Clamp them together untill the either the house gets warm or you are confident it is not going to reach temperature. If it did get close to the temperature you wanted, it is a thermostat issue. If not, you got me!
And they say we have an easy job! Get beck to us with your results.
I don't know where you are located, but there is a Goodman distributor in Sacramento, CA. Also in Ontario CA. They are a distributor so they may be able to help you or tell where to find someone who will help. Goodman is also known as GMC or Janitrol.