AUX only with Nest....is this possible?


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Old 11-12-14, 12:17 PM
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AUX only with Nest....is this possible?

My HP has died and I want to continue to use the Nest to operate the furnace. When in regular heat mode it just blows cool air. Once I turn it up four degrees the AUX kicks in and heats my house in no time. I would like to set the Nest to automatically use AUX every time with out having to manually crank it up until it comes on. Is this something that I can do? I can send a picture of the wires if that might help. Is there a way to bypass the blower all together by disconnecting something? Thank you in advance for any insight you can provide.

Read more: http://www.doityourself.com/forum/thermostatic-controls/482797-nest-2-install-heat-pump-w-aux-heat.html#ixzz3It4vPry1
 
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Old 11-12-14, 12:28 PM
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Welcome to the forum!! To better assist much more information is needed. Is your auxiliary heat a gas furnace or is it an air handler with electric heat strips? Please post the model number.

If I understand you correctly, you want your auxiliary heat source to become your primary heat source, Is that correct?
 
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Old 11-12-14, 12:57 PM
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Thank you! Sorry if the questions was long winded, but yes I would like to use the auxiliary heat as my primary heat source. It is an air handler with electric heat strips. I will have to get the model number later, but it is a Luxaire. I will post the model number as soon as I can.
 
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Old 11-12-14, 01:33 PM
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Is there a way to bypass the blower all together by disconnecting something?
The blower has to run while the electric heat strips are on or you will quickly burn up the coils on the strips and the thermal cut-off will open and shut off power.

Operating the electric strips by themselves is an expensive choice as a primary heat source.

When you post the model number of the air handler we will also need to know what heat strips you have installed.
 
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Old 11-12-14, 06:27 PM
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Looks like the model number is IHP36FBA. I am not sure where to find the heat strips so not sure what they are. I will dig deeper into that. It is a split heat pump that was installed in 1979 or so. The outside unit is a replacement that was installed in 1997.

I know it sounds crazy to use the AUX heat as the primary heat but I did a little test last month and by heating the house in AUX mode it heated the house much faster and my bill was actually much much lower. This is why I want to use it this way. I just installed the Nest and was hoping it would work, it does but I have to crank it way up to reach AUX heat.

I can send a picture of the wires as they were connected to my old thermostat and see if that might help show you what I am working with. I am obviously clueless when it comes to all the ins and out of wiring so I really appreciate any input.
 
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Old 11-12-14, 07:47 PM
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Thanks for the model number. I will see if I can find a schematic. It may be difficult since it is a 1979 model. Photos of the inside of the air handler and of the thermostat wiring would be helpful.
 
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Old 11-13-14, 07:46 AM
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Do you currently have a wire connected to * on your Nest? Is the thermostat 2nd generation?
 
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Old 11-13-14, 11:03 AM
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I do not have it connected to the *. I am not sure if it is 2nd Generation or not. I just bought it two days ago so I am guessing yes. It doesn't say 2nd Generation anywhere. Here is how I have it wired. I am wired into...Y1 G OB Rc W2AUX and C. Not sure if that helps
 
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Old 11-13-14, 11:37 AM
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The 2nd generation Nest will support emergency heat whereas the 1st generation doesn't. Here is an option that I believe will work if you have the 2nd generation: Since you will not be using the heat pump you will not need the wires going to Y1 and OB. The wire that is going to W2Aux would be moved to the * terminal. Once the wire is connected the Nest will allow you to control Emergency heat. 2nd generation allows the thermostat to control the emergency heat based on your settings. So basically the auxiliary heat wire becomes your emergency heat wire. Of course, without knowing how many or how many kilowatts of heat strips it is impossible to know if they are all wired together in the air handler. You can look at your installation manual to see how to program the emergency heat settings. Here is a link that might answer some of your questions:

https://nest.com/support/article/Wha...est-support-it

Here is the pro version of the installation guide:

http://support-assets.nest.com/image...ller-Guide.pdf
 

Last edited by firedawgsatx; 11-13-14 at 12:01 PM. Reason: Added links to guides
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Old 11-13-14, 01:03 PM
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Heck I will give it a try. Should I just tape off the OB and Yellow wires? Thanks so much!
 
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Old 11-13-14, 01:15 PM
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Yes, taping them off will be good. I am not sure if the Nest wants to see wires in those spots before it will allow you to get the * programmed. If so, just put them back in there. Hopefully, the emergency heat can be programmed as the linked article stated. If you try it and it doesn't work post back and we'll try plan B.
 
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Old 11-13-14, 01:56 PM
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So I tried this but now for some reason it isn't detecting power at the Rc even though it is connected. Code E23 on the link you sent me. Is there a fuse that I could have blown? Thanks
 

Last edited by seapru; 11-13-14 at 02:50 PM.
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Old 11-13-14, 02:40 PM
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Did you turn power off to the air handler before moving the wiring? If not, you probably blew a low voltage fuse (if installed). You will need to shut off power to the air handler and locate the transformer. Then see if you can locate a 3 or 5 amp automotive type fuse to see if it is blown, I never could find a schematic for your air handler based on the model number provided.

Do you have a voltmeter?
 
 

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