Auxiliary heat

[Golfer222]

Anybody know why my heat pump is doing auxiliary heat past couple of days. Seems to blow cool air when say heat is on and if I turn up the thermostat it changes to auxiliary heat

[Altavia]

The auxiliary heater works in conjunction with your HVAC system to keep your home warm when the outside temperature is too cold for the heat pump system to be efficient on its own. The thermostat automatically activates the auxiliary heating when the desired temperature is not met by the heat pump system alone.

After some period of your thermostat not reaching the set temperature, your thermostat automatically activates the auxiliary heat.

The auxiliary heat will only shut off once the thermostat has reached set temperature.

What is Aux Heat? Everything to Know About Auxiliary Heat (https://www.ars.com/blog/what-does-auxiliary-heat-mean)

[Battlebasset]

The auxiliary heater works in conjunction with your HVAC system to keep your home warm when the outside temperature is too cold for the heat pump system to be efficient on its own. The thermostat automatically activates the auxiliary heating when the desired temperature is not met by the heat pump system alone.

After some period of your thermostat not reaching the set temperature, your thermostat automatically activates the auxiliary heat.

The auxiliary heat will only shut off once the thermostat has reached set temperature.

What is Aux Heat? Everything to Know About Auxiliary Heat (https://www.ars.com/blog/what-does-auxiliary-heat-mean)

100% correct. Something else I do when it gets cold like this and the heat pump is struggling is to put a pot of water on our gas stovetop and boil it for a bit. Puts both heat and humidity into the house and gets the house warmer quicker on a cold morning before the sun comes up.

[RICH1]

ALTAVIA is spot on…I also would have your AC/ Heat pump checked for Proper Charge… we got cold but your Heat Pump should have kept up with it..( also depends on your settings)

[retiredguy123]

ALTAVIA is spot on…I also would have your AC/ Heat pump checked for Proper Charge… we got cold but your Heat Pump should have kept up with it..( also depends on your settings)
I agree. It really hasn't been cold enough for the electric heat coil to come on.

[Battlebasset]

I agree. It really hasn't been cold enough for the electric heat coil to come on.

My unit is newer and I just had it serviced, and my electric heat coil came on. Heat pumps, at least the ones the builder installs, struggle once temps go below about 40 degrees. And if you set back your thermostat at night (like I do) and it is having to raise the temp vs just maintain, it will have to work even harder.

[villagetinker]

My unit is newer and I just had it serviced, and my electric heat coil came on. Heat pumps, at least the ones the builder installs, struggle once temps go below about 40 degrees. And if you set back your thermostat at night (like I do) and it is having to raise the temp vs just maintain, it will have to work even harder.

We have had no problems with the builder installed (2013 vintage) Carrier HVAC system, and we have never had the emergency heat come on. I am not an HVAC expert and I do not have any equipment to check the system, so I would suggest having the system checked again.
One other thought, if your temperature change is large enough this may be causing the emergency heat to come on. We keep the temp more or less the same between night and day, and just use a fan if it is too warm at night.

[Babubhat]

Same here. Set to 65 and heat never came on. Benefit of block construction

[ton80]

My unit is newer and I just had it serviced, and my electric heat coil came on. Heat pumps, at least the ones the builder installs, struggle once temps go below about 40 degrees. And if you set back your thermostat at night (like I do) and it is having to raise the temp vs just maintain, it will have to work even harder.

AS VT state,d keeping a constant heat setpoint helps to minimize the need for the aux heating to come on during normal heat mode.

See Altavia post #3 for a link to a good description of auxiliary heating uses in a heat pump system.

IMHO, ALL heat pumps struggle when temperatures are below 40F since the heat pump is using a reverse air conditioning cycle to take heat from the outside air and eject it to the inside air and actually heating it. The cooling occurring at the outside condenser now acting as an evaporator now causes water in the outside air to freeze on the coils. The HVAC system senses this and goes into defrost mode.
1. The system goes back to AC.
2. Warm inside air now goes through the inside heat exchanger and evaporates the refrigerant.
3. The refrigerant vapor gets compressed in the outside compressor and increases in temperature.
4 The hot refrigerant vapor now goes to the condenser and rejects heat to the coil and melts the ice/frost.
5. The auxiliary heater now comes on to avoid cooling the air inside the house.
6. When defrosting complete, the system goes back to the original heating using the heat pump.

[DAVES]

100% correct. Something else I do when it gets cold like this and the heat pump is struggling is to put a pot of water on our gas stovetop and boil it for a bit. Puts both heat and humidity into the house and gets the house warmer quicker on a cold morning before the sun comes up.

A perhaps better idea. Make some soup.

[rsmurano]

These haven’t been cold temperatures that would have caused any aux heating issues. There are multiple variants of furnaces and heat pumps and we in the villages have the simple/less efficient 1’s installed (not talking about the seer rating, I’m talking about single stage vs. multi stage setups). I had a heat pump installed in my home in snow country that was beneficial down to 0 degrees and this setup was a multistage configuration where it operated efficiently at low temps by using more and more of the furnace as the temps dropped (stages) instead of the units coming on all at once say at 30 degrees.

[Toymeister]

Aux heat comes on when then the thermostat is set for three or more degrees increase in heat.

[Golfer222]

Why didn’t you just call the company that makes your model - or would you waste your time hearing from the “experts” on this site?

Why waste your time on this site posting a comment that is of no help and yes, actually there are experts on this site

always the typical "why ask here" response from mkjelenbaas -you can count on it-

[SeaCros]

It’s a shame that some just like to post nonsense instead of actually helping. Hopefully you get a resolution to your question or at least get you going in the right direction.

[jrref]

My unit is newer and I just had it serviced, and my electric heat coil came on. Heat pumps, at least the ones the builder installs, struggle once temps go below about 40 degrees. And if you set back your thermostat at night (like I do) and it is having to raise the temp vs just maintain, it will have to work even harder.

You mentioned you set-back the heat. This is why your Aux-Heat came on. The system is trying to get the house back to the target temperature and the heat pump alone is not generating enough heat to make this happen.

Almost every electronic thermostat i know of has settings to manage when the Aux-Heat comes on. Just google aux heat for your specific thermostat to find out where these settings are.

Also remember when the Aux-Heat comes on the coil in you air handler can draw about 40 amps so if it's on a long time expect a large electric bill.

Normally the Carrier HVAC the builder installed should work fine with the weather here in Central Florida. But it is possible the temperature could drop below the point where the Heat Pump being able to heat your home which is why we have Aux-Heat.

I can tell you 100%, many don't worry about heat because it usually doesn't stay cold (around freezing) for several days here in the Villages. If it ever stayed around freezing for several days the house and the ground underneaith would loose it's heat build up and your heat would be going on a lot.

[pauld315]

Part of why I hate heat pumps. Give me a good old fashioned gas furnace anyday.

[BFISHER54]

Increasing the temperature setting on your thermostat by more than 2 or 3 degrees above the current temperature in the house will cause the auxiliary heat to come on. Auxiliary heat is much more expensive, so they recommend increasing the temperature setting in 2 degree increments to keep it from coming on. Also, heat pumps produce a much cooler air flow than gas and other furnaces, especially when it’s very cold outside.

[MidWestIA]

The thermostats em heat may be that - you want that as a last resort - expensive

[jmaccallum]

Heat Pumps are also “Set It, and Forget It”. In other words, you don’t move the thermostat up and down like you would with a gas or oil furnace.

On the heat side, if the thermostat is raised more than 2 degrees, the Aux heat will come on to satisfy demand. So when raising the thermostat set point, do it in 1 degree increments. Let the unit satisfy that increase and then move it up another 1 degree increment, and so on.

You can get a programmable thermostat for heat pumps, they are the most expensive because they operate as described above.

Heated air coming out of the vents with a heat pump will always feel cool. Most deliver at about 86 degrees which is cooler than your body temp, so it feels cool, but they are still heating. Just not the cozy hotter air you might be used to with a gas or oil furnace.

Just a few more tidbits :spoken:

[mvivanco]

I had my HVAC orientation yesterday. The service guy told me the Aux Heat comes on when its cold outside and there is frost on the unit outside. It puts the Aux heat on to defrost the coils. It is an electric heat source and not as efficient so it isn't really intended to be used or long term heating of your home.

[retiredguy123]

I had my HVAC orientation yesterday. The service guy told me the Aux Heat comes on when its cold outside and there is frost on the unit outside. It puts the Aux heat on to defrost the coils. It is an electric heat source and not as efficient so it isn't really intended to be used or long term heating of your home.
I don't think you understood the technician. The auxiliary heat coil is an electric coil that is location in the inside unit, not the outside unit. It is designed to provide supplemental heat for your house when the heat pump reverse cycle does not keep up with the thermostat setting. Any heating coil located in the outside unit would not be able to provide any heat to your house because all of the supply air comes from the inside fan unit. I am not familiar with a coil designed to remove frost from the outside unit. I have never seen one.

[tuccillo]

Not exactly. When the outside coil (the condenser coil) frosts up (because the condenser coil is cold in heating mode), the unit will sense this and go into defrost mode. When in defrost mode, the system will reverse into cooling mode. The fan on the outside condensing unit will stop. In cooling mode (aka air conditioning), the outside coil will heat up to melt the frost. Since the unit is now in air conditioning mode (the inside evaporator coil is now cold), there will be cold air coming from the vents. The auxiliary heating strips (resistance strips in the air flow that get hot because current is flowing through them) will be turned on to heat the cold air until the defrost cycle is complete - typically a couple of minutes. Once the defrost mode is complete, the system will reverse back to heating mode and the fan on the condensing unit will start again and the auxiliary heating strips will be turned off. It is easy to tell when the unit goes into defrost mode as the outside fan will stop and the auxiliary heating light will be on.

I had my HVAC orientation yesterday. The service guy told me the Aux Heat comes on when its cold outside and there is frost on the unit outside. It puts the Aux heat on to defrost the coils. It is an electric heat source and not as efficient so it isn't really intended to be used or long term heating of your home.

[Vladimir]

During these past very cold days the aux heat will temporarily kick in for a few minutes but it is not normal if it runs continuously. Also sometimes you may hear a loud noise coming from your outside unit for a few seconds but do not get alarmed...its some sort of defrost function.
I have had heat pumps all my life

[Battlebasset]

A perhaps better idea. Make some soup.

That works too. But I generally don't have that ready to go first thing in the morning. Would have to make it up the night before and pull it out of the fridge.

[jrref]

Heat pumps are actually very efficient at around 40 degreees and higher. Much better than an oil or gas furnace. As it get's colder the efficiency goes down but the units we have here in the Villages are fairly efficient. If you have a 15 Seer A/C unit the HSPF (heat pump efficiency) should be 8.7. That's what i have in my 2016 home. The heat pump will continue to work all the way down to 0 degrees but it looses too much efficienty at 20 degrees. All this said for the winters we have here in Central Florida where we get a couple of 26 degree nights, a heat pump is efficient and works well. Newer A/C units will work more efficiently at lower temperatures. Some have a HSPF of 10. The trick though is understanding the Aux Heat and how your thermostat works.

Talking about thermostats, If you have the standard Carrier thermostat that came with the house, some people said the Aux heat comes on when the set point is 2 degrees higher than the indoor temperature. I don't have this thermostat but i don't believe it has any smarts when using the Aux Heat.

If you have a Google Nest Thermostat, you can set the heat pump balance settings from Off to Balanced to Max Savings to Max Comfort. The thermostat will learn how long it takes for the heat pump to raise the temperate in you house given the outside temperature and based on the heat pump balance setting will use the Aux Heat appropriately. So for Max Savings the themostat will use less Aux Heat causing your home to heat up more slowly and for Max Comfort the thermostat will use more Aux Heat, when needed, to heat your house up faster. When turning the Nest thermostat heat pump balance to OFF, you can then set the parameters as to when the Aux Heat is used manually.

Now if you want to get really crazy you can buy the new Echobee Premium thermostat which came out in May of this year. For those who love customization and settings this is the thermostat for you. It works the same as the Google Nest thermostat but there are more options/settings that you can adjust to fine tune how the thermostat works including the Aux Heat. If you don't want to manually make changes there is the default Automatic mode that uses an AI engine to give you the best efficiency. The Ecobee also has a remote sensor that comes with the thermostat that you can place in another room. So for example, in my Ivy house the master bedroom is usually about 2-3 degrees colder than the rest of the house in the winter so i put the remote temperature sensor there. I programmed the Ecobee to use only the master bedroom sensor when we are sleeping so the bedroom is at the thermostat set temperature. When morning comes, I set the Ecobee to only use the main temperature sensor in the thermostat for the rest of the day. This saves money and makes the house more comfortable becasue the thermostat will only use the bedroom temperature to turn on the heat or air conditioning in the summer vs using the thermostat in the living room which might cause the bedroom to be too hot or cold. You can also set it up to use both sensors at the same time and the Ecobee will average the temperature from both sensors. You can also buy more sensors to put in different rooms.

All this said, I've used the standard thermostat that came with the house, the Google Nest and now the Ecobee Premium thermostats. At a high level the thermostats range from "stupid" to very smart. With the Google Nest and the Ecobee they are connected to the internet so you can control them from an app on your phone plus with Google Home or Alexa and with the Ecobee you can use Siri if you are an Apple user.

At the end of the day, the Aux Heat draws about 40 amps when it is on and that will increase your electric bill significantly if used too much. The Google and Ecobee cost about $250 so if you can install it yourself you can probably pay back the cost in one winter season if we get a couple of below freezing nights here in the Villages. For sure pay back in two years.

Hope this helps. This is a very complicated topic.