Temperature varies 13 degrees around setpoint on aux heat
When outside temperature drops to the point where the auxillary heating elements come on, the temperature in the room will vary 13 degrees. Foe example, with the thermostat set for 70 degrees, the temperature in the room will vary from 66 degrees to 79 degrees. This is unacceptable for comfort. I had a GE technician come out last December to service the unit and he replaced a number of parts, but the problem still exists.
The problem is only this severe when the unit is on auxillary heat. Even on normal heat pump heating, the temperature variation is about 5 or 6 degrees.
This Zoneline replaced an 8 year old Zoneline AZ51H09DBC the performed just perfect....temperature on all seasons and operating mode controlled temperature within about 2 or 3 degrees.
Since my previous Zoneline worked fine in this room, does anyone have any ideas why this new unit has such a large hysteresis in controlling the temperature around the set point?
Any help will be appreciated. I very disappointed in the unit and in GE's inability to fix it.
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Re: Temperature varies 13 degrees around setpoint on aux...
I don't have the book for this particular unit but, check the sequencers that control the electric heat mode, as the regulator heat pump works good. The part may have a time or temperature delay that is too long for you. Also if it has a remote thermostat, check the heat anticipate setting. You will have to check the installation manuel, but its usually .6 to .8, but I don't think that is the problem.
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It may be getting low on refrigerant due to a small leak. I'd have it serviced soon. When running at less than peak efficiency it will much more often switch on the heat strips and they are not cheap to operate.
Unless you just installed or had the thermostat installed recently, I would not point at the thermostat as the problem. With what you have described I would suggest have your units serviced as it sounds like a loss of charge, or failed defrost control board. The "Aux" comes on when the unit is using secondary heating (electric heat strips). That occurs when the demand temperature (what you set it to) in Heat mode is more than the current room temperature, usually ~2-4 degrees higher. Also happens in defrost mode. Defrost is a heat pump cycle that melts any build up of ice on the condenser unit (outside unit). That process is simply the unit running in cool mode which will heat up the outside unit to melt any ice. Defrost cycles vary with manufacture but usually you can tell if is in defrost by looking at the outside unit, during defrost the unit will be warm or hot sometimes there is steam and the compressor will be running but not the fan. Defrost only happens on heat pumps in "Heat" mode. Rheem has a 10 yr compressor and parts warranty, so call the installer or Rheem authorized service company.
See if it happens only when your temperature of the room is more than 3 degrees of your setpoint temperature. Since you have a heat pump, the auxiliary (electric heat strips) is use for backup of the heat pump when it can't keep up. The heat pump will run by itself if it can maintain temperature within a couple degrees. If it is too cold outside to handle the load or you set the temperature more than 2 degrees past room temperature, the auxiliary will turn on. The thermostat has a memory of how long it takes to reach desired temperature. If it goes into auxiliary mode trying to satisfy setpoint during the last call for heat, it will start the next call for heat in both aux & heat pump mode until the thermostats algorithm (timed program) allows only the heat pump to run. Not sure if you have an air to air, or geothermal heat pump. The outside air temperature will affect only the air to air system ie. when the temps drop outside, the heat coming out of your vents will be cooler...the air to air systems drops efficiency when the outdoor air drops.
If you turn your heat on and the temperature is set 3 degrees above what the actual temperature of the room, the auxillary heat will automatically come on. The auxillary heat is an electric heat strip that provides heat to your home while the heat pump is in defrost cycle or if there are extremely low temperatures outside. Try not to set the temperature more than 2 degrees above the actual temperature of the room. Hope this helps.
If your thermostat has an emergency heat setting this means you have a heat pump system.
Yes you need to set the thermostat to heat for heating the house.
The emergency heat setting should never be used unless your outside unit is not functioning.
The emergency heat setting overides the heat pump (the outside unit will not be energized).
The emergency heat setting will run the auxillary heat (heat strips) only.
When the thermostat is set in the heat position the heat pump will run to heat your house.
If the heat pump can't keep up (extreme cold) then then the auxillary heat will kick in to augment the heat pump until it satisfies the thermostat settings. If your room temperature gets 2 degrees below your thermostat setpoint, your auxillary heat will kick on. Example, say you are going to be gone a couple of days and you turn your heat down to 60 degrees. When you return and it is 60 degrees in your house, you turn the thermostat up to 70 degrees. Since you are turning the temperature up 2 degrees or more (10 degrees in this case) from the 60 degree room temperature then the heat pump will come on and the auxillary heat strips. The unit will continue heating like this until the temperature in the house gets to 69 degrees and the heat strips will turn off and the heat pump will continue to run until the 70 degree setpoint is reached.
Hope this helps.
If it is a heatpump, the outside unit should not turn on below 35degrees or so. Below that temperature, the unit cannot effeciently exchange heat. When the outside temperature is low, the system automatically switches over to auxillary heat which uses the same heating elements as emergency heat.
I believe the unit you are describing is a heat pump. Heat pump are great when the temperature isn't below 30 With low ambient temps. outside it is much more efficient and comfortable to run aux. electric heat from the heat pump.
Perhaps the item you are using to check temperatures is not accurate. I my line of work, I use a digital thermometer which records immediate temperature. Perhaps understanding the process will help you see more accuracy in the way you read the temperature in your oven. Allow me to offer this explanation....First of all, place your thermometer near on the top rack as close to the oven temperature probe as possible. This probe is the focal point for your oven and detects the temperature and opens the electrical circuit to turn off the element when the desired set temperature is attained. Set your electric oven to 300 degrees and hopefully, you have a window in your oven to watch. The bake element will come on and the temperature will rise until it reaches 300 degrees. It is at this point when your oven bake indicator light should go out. When this happens....look inside. The element is still bright orange and emitting heat and will continue to raise the temperature in the oven to approximately 325 - 340 degrees. With this noted, you will see the temperature beginning to drop 315, 310, 300, 295, 290, 285 perhaps even 280 or some even lower to 275 and then the indicator lamp will go on indicating the circuit has closed thus turning on the element, Finally there is a variance and no range GAS or ELECTRIC will ever maintain a even 300 degree temperature. The calibration set point is based on the 300 degrees. If your oven light goes off within 20-25 degrees of three hundred degrees, your oven is already calibrated pretty close and I would not attempt to adjust it at all.
I set the thermostat for 70 degrees. It comes on always in auxillary heat and does not shut off when it reaches 70 degrees. It is a heat pump, I am assuming, it might be the thermostat? But when the air conditioner is on, it turns off when it reaches it's temperature.