How To Set Nest Thermostat To Heat

Using Auxiliary Heat with a Nest Thermostat

If you have a central HVAC (heating / ventilation / air conditioning) system called a "oestrus pump", and live in an area where the temperature in the wintertime goes below almost 50°F (or ten°C) then you probably have something called "emergency heat" or "auxiliary heat". The two different names refer to the aforementioned matter: an electric heating system using resistive heating coils (like in a toaster or hair dryer) located inside the airflow path of the ventilation system.

In normal operation, a heat pump works similar an air conditioner: a compressible vapor with low humid point (like freon) is forced through a cycle that includes a compresser, a cooling heat exchanger (a bunch of radiator fins), a bottleneck valve (serving every bit a pressure-release point), and a warming oestrus exchanger. I heat exchanger is located within the house or apartment, and the other is outside (perhaps on the roof).

In summer, the estrus pump circulates in i direction, causing the refrigerant vapor to exist compressed just earlier travelling through the outdoor rut exchanger, where oestrus is released; then through the bottleneck value (making the refrigerant common cold) and then through the indoor heat exchanger (where the indoor air gets cooled).

In winter, solenoid-actuated valves reverse the circulation pattern, so that the compressed vapor goes immediately to the indoor heat exchanger to release heat into the indoor air, then through the bottleneck valve and the outdoor rut exchanger, where the relatively-colder refrigerant is warmed by the not-quite-so-common cold outdoor air. You're "air workout the outdoors", cooling the air outside in order to warm the house.

When operating in this second "heating" mode, there is a limit to how well it can piece of work when the exterior temperature is very common cold. Typically, if the outside temperature is below about 25°F (or -4°C), a heat pump cannot warm the inide of a house quickly enough to counteract the cooling that happens from oestrus going out through the walls, windows, and roof. For this reason, estrus pump systems installed in climates that become below freezing need another way of providing heat, if only for a short fourth dimension in the morning when your organisation goes from your lower "while comatose" temperature setting to your higher "while I'grand awake" setting. (This process of re-heating the dwelling house every morning is called "recovery".)

The difference in name "emergency rut" vs. "auxiliary heat" results from differences in needs based on your local environs.

If you live in an area when the temperature hardly ever goes below 30 degrees, even at dark during the coldest month of the twelvemonth, then a heat pump should be able to go on you warm all the time. If information technology fails to do so, then it is probably really broken. Thus, the simply time yous'd need to apply the electric heating coils is when the system is broken — thus the name, "emergency heat".

On the other hand, if you lot live somewhere that the temperature frequently stays below freezing all day for many days of the year, and then the use of the electric heat in your organisation will be mutual, even when the heat pump is working perfectly well, and in this case the term "auxiliary heat" is more advisable.

Thermostats rarely make this distinction: it will either say "auxiliary" or "emergency", rarely both. If your HVAC contractor gave y'all a "warm climate" thermostat, or failed to add together a jumper betwixt the E and AUX terminals, you'll take to flip a manual switch to get the auxiliary heat to turn on.

Nest Terminology

The user interface provided past the Nest thermostat differs from the Nest website and iOS/Android apps.

The temperature below which you want to utilise Auxiliary rut (rather than the heat pump compressor) is referred to every bit the "Compressor Lockout" setting in the website and app interfaces. But on the Nest Thermostat itself, the term "Lockout" is not used, instead you lot see "Use the estrus pump compressor when the outdoor temperature is in a higher place". This wording is ambiguous considering information technology sounds like you are telling it that it should "always use the compressor..." above that temperature, or maybe y'all are telling it that it "may sometimes use the compressor" above that temperature. In practce I have establish that the 2d interpretation (may sometimes) is authentic.

The temperature above which you want to always use the compressor is chosen "Auxiliary Heat Lockout" in the website and app. Again, the actual thermostat uses the words "Use the rut pump aux. estrus when the outdoor temperature is below", and over again this diction is ambiguous considering you don't know if yous are giving it permission to sometimes employ aux. rut beneath that temperature, or telling it to always employ aux. heat below that temperature.

Setting the Nest for Emergency or Auxiliary Rut

If your heating organization does not have a fan that blows air through vents, or if you get your heat from oil or gas, then these instructions do not utilise to you.

It is assumed that you have already gone through the consummate setup instructions, which would probably start with Nest's compatibility checker including peculiarly the footstep where you identify what wires your old thermostat has. For more about identifying the functions of thermostat control wires, see Nest's identifying thermostat wires commodity.

One time your thermostat is set up upward and running, here'south how to select emergency vs. auxiliary heat:

Go to SETTINGS > EQUIPMENT. (This setting is about 4 or 5 from the rightmost finish, or about fifteen steps from the left)
You'll run across "Equipment detected" and a diagram of the backplate with the wires that are continued and their labels. In the lower right the "*" connection should say either "emer. heat" or "aux. heat"; or in the upper-correct on "W_two/AUX" you should see "aux. heat". If not, and then these instructions probably don't apply to y'all.
Next screen is "Your System", which should read: "heat pump heating", ("auxiliary heating" or "emergency estrus"), "heat pump cooling", "fan". (If you don't see this, these instructions don't utilise to you lot.) Select Continue.
Next you lot have the screen where yous can actually suit the settings. The choices are "HEAT Blazon", "Estrus PUMP", "SAFETY TEMP", "* WIRE Type", and "PRO SETUP".
If you had a connection to the "*" wire then select "* WIRE TYPE". If you live in an expanse where the outdoor temperature never goes below nearly 20-25°F, select "E: EMERGENCY", because you should never need to use the electric heating coils unless the master oestrus pump is actually broken. Simply if you live in a colder climate, select "AUXILIARY HEAT".
If yous chose "E: EMERGENCY", then you're washed, there is nothing else to set. Otherwise keep:
Now you lot're back at the "Equipment Settings" menu; select "Washed".

Go back into SETTINGS > EQUIPMENT; click through the "Equipment detected" screen to get to "Your Organisation". Get to the bottom and select "TEST". Test the "AUX. Heat" or "EMERGENCY HEAT". It should plow on the fan and after a minute or two you should feel distinctly warm air coming out of the vents. If the fan does non plough on, stop the test immediately. Electric heating coils will overheat, burn down out or cause damage if the fan isn't going. (Your organization might have a fail-safety for this, but it's good to know right away, it may mean your fan wire (maybe the G connection) isn't connected.)

Go to SETTINGS > NEST SENSE (which is the four^th setting from the left). Select "Estrus Pump Rest". Choose "OFF". Y'all must do this first, considering the other settings won't be settable unless you lot turn off this feature (temporarily, merely so you can access the options).

In one case once more get to SETTINGS > EQUIPMENT; click through the "Equipment detected" and "Your System" screens to go back to "Equipment Settings". At present select "Heat PUMP".
It volition ask if you have an "O wire" or a "B wire". You probably already have this set up properly (if information technology were set improperly, your system would be heating the house when it should be cooling, and vice versa), and then just leave this setting every bit-is.
Then yous'll see "Apply the heat pump compressor when the outdoor temperature is above" and the word "Always". Plough the thermostat wheel to the right, and information technology volition let you choose a temperature, starting at about -20°F. I chose 20°F. Your setting volition depend on how efficient your dwelling house is at retaining heat. If you lot have a lot of windows, poor insulation, no southward-facing windows, etc. then y'all lose estrus easily and volition need to set this setting somewhere in the 20-thirty°F area. The way to find out what setting is all-time is past leaving this set to "ALWAYS", and look until a solar day when it is so cold exterior that the heat pump cannot continue up. So you know that the outside temperature is too cold, so yous'll need to set up this setting higher than that temperature. My house has problem when the outside temperature is in the low-20's or lower, so I prepare information technology to 20.
If y'all see "Compressor min. temperature should but exist used if AUX controls an auxiliary heater.", and if your test of Aux. heat was successful (it fan the fan and blew warn air out the vents) then hit Ostend and proceed.
Now you'll get "Use the heat pump aux. rut when the outdoor temperature is below". Hither y'all can select E'er or a temperature from 35 to 90. This is an upper limit for aux. heat: it will not use the aux. heat higher up whatever number you choose (but if you lot pick ALWAYS, Nest is gratis to apply Aux heat whenever it thinks it's a good thought).
Now y'all're back at Equipment Settings; select DONE.

Go to SETTINGS > NEST SENSE. Select "Rut Pump Balance". Choose "MAX SAVINGS", "Counterbalanced", or "MAX. Condolement". I chose "BALANCED" so later a few weeks, when things seemed to be working well, I switched to "MAX. SAVINGS". Notation that if you desire to change the min. and max. temperatures for aux. oestrus, you'll need to turn Heat Pump Balance OFF once again.

Once NEST SENSE > Rut Pump Balance is enabled, if you go dorsum into SETTINGS > EQUIPMENT > Equipment Settings > HEAT PUMP you'll have a setting for the "Use compressor when ... temperature is above" choice which is ignored, followed by a bulletin "Nest Sense Heat Pump Rest is on. Nest will use auxiliary heat as needed.". This indicates that Nest is using its "avoid aux. heat except when really needed" intelligent algorithm.

After making these settings, the Nest "home screen" (showing the electric current temperature and whether it'south heating" will bear witness "AUX. Heat" or "EMERGENCY HEAT" instead of "HEATING" (as appropriate) when it is using the electrical heating coils.

This page was written in the "embarrassingly readable" markup language RHTF, and was last updated on 2022 Mar 25. due south.27