Nest for heat pump with aux and emergency heat


  #1  
Old 03-30-17, 10:25 AM
B
Member
Thread Starter
Join Date: Feb 2014
Location: USA
Posts: 10
Received 0 Votes on 0 Posts
Nest for heat pump with aux and emergency heat

I am installing a nest thermostat on my heat pump and air handler system. I am all electric. I have both a W1 white wire and a W2 brown wire. I assume the white is for heat strips in the air handler and brown for heat strips in the compressor. Please correct me if I am wrong. How do I hook them to the nest and get emergency heat as well??
Thanks, Arnold
 
  #2  
Old 03-30-17, 12:55 PM
S
Member
Join Date: Feb 2014
Location: USA
Posts: 2,101
Received 0 Votes on 0 Posts
There are no heat strips in the outside unit ( heat pump ). Heat pump will be W1 and W2 will be heat strips.
 
  #3  
Old 03-30-17, 01:40 PM
Houston204's Avatar
Forum Topic Moderator
Join Date: Oct 2009
Location: Texas
Posts: 7,438
Received 18 Votes on 15 Posts
Name:  nestwithHPwithauxheat.jpg
Views: 45672
Size:  31.9 KB

I would treat white as the Aux wire and brown as the E wire.

Connect the E wire to the * terminal.
Connect Aux wire to the W2/Aux terminal.
 
  #4  
Old 04-01-17, 07:54 AM
B
Member
Thread Starter
Join Date: Feb 2014
Location: USA
Posts: 10
Received 0 Votes on 0 Posts
Red face did this

Hi Houston. My wires are setup the way you indicated. I see on the air handler board that there are 2 white and 2 brown wires hooked into the terminal. I assume the second wire goes to the heat pump.

If the heat strips are only in the air handler, why do I need both W1 and W2?? do they do the same thing?? Why hook them to the heat pump???

I am trying to understand if the Nest is handling my system correctly.

Thank You.
 
  #5  
Old 04-01-17, 09:10 AM
Houston204's Avatar
Forum Topic Moderator
Join Date: Oct 2009
Location: Texas
Posts: 7,438
Received 18 Votes on 15 Posts
Do you have 4 wires on a single terminal? I would be surprised to see brown connected to anything outside.

The Nest thermostat doesn't like jumpers at the stat but you may get away with this bridge at the air handler.

The outdoor unit must be able to also control the heat strips to compensate for the fact that it actually goes into cool mode when it enters defrost mode. The only difference is that it turns off the outdoor fan. Defrost mode energizes the heat strips so you don't notice 55 degree air blowing into the house.
 
  #6  
Old 04-02-17, 11:05 AM
B
Member
Thread Starter
Join Date: Feb 2014
Location: USA
Posts: 10
Received 0 Votes on 0 Posts
W1 and W2

Thank You houston204. We are getting closer. My big question is if W1 and W2 do the same thing on my air handler, to turn on the heat strip. If so, it won't matter which wire goes where.. white or brown, as long as the heat strip is activated.
I don't know why both wires go to the heat pump from the air handler, but I presume only 1 is used for defrost mode.
I have not jumped the nest, and don't need to if W1 and W2 do the same thing.
Arnold
 
  #7  
Old 04-02-17, 02:14 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 62,651
Received 1,611 Votes on 1,483 Posts
White and brown are mostly likely combined at the air handler.
You could open the wiring access cover and confirm it.
 
  #8  
Old 04-03-17, 06:21 AM
B
Member
Thread Starter
Join Date: Feb 2014
Location: USA
Posts: 10
Received 0 Votes on 0 Posts
w1 and w2 combined

Thanks for your reply Pete. The white and brown are not combined at the air handler. White is on W1 and Brown is on W2. Both terminals have a second wire connection going to the heat pump. I assume one is for the defrost from the heat pump. I don't know what the other would be used for.
My big question is if W1 and W2 do the same thing at the air handler. I have an 11 year old 13 seer York system. Ate there multiple levels of heat where W1 and W2 each turn on different levels?? Or do they activate the same thing on the heat strips??
 
  #9  
Old 04-03-17, 02:14 PM
D
Member
Join Date: Dec 2012
Location: United States
Posts: 254
Received 1 Vote on 1 Post
why W1 and W2 from heat pump you ask ?
On my York HP the outdoor unit defrost control board turns W1 and or W2 on when a defrost cycle
or when it receives a signal (on E I think) that emergency mode or third stage heat is entered when it sequences W1 and W2 to control the indoor resistance heaters depending on the outdoor ambient temperature ... turning on various sections of the resistance heat - in my case 5kw or 10 kw or 20 kw according to a York timing scheme.
A long way of saying that for at least one manufacturer the fact that W1, W2 are independently used by the outdoor unit is part of the normal operation.

After writing this I see from your fresh post that you have a York unit - so it all makes sense as described. I'd suggest that you get the York document for your defrost control board that explains how it all works and use that, along with the nest particulars, to wire the thermostat to your taste. Without the documentation it could easily end up a frustrating mess...
 

Last edited by dsomerv; 04-03-17 at 02:29 PM.
  #10  
Old 04-04-17, 12:47 PM
B
Member
Thread Starter
Join Date: Feb 2014
Location: USA
Posts: 10
Received 0 Votes on 0 Posts
Nest with W1 and W2

OK. Now I understand the wires. So it seems that Nest is not a good thermostat for my system.
The W1 white wire goes into the W2/aux on the Nest. The W2 brown wire goes in to * on the Nest which is emergency heat.
Nest only triggers W2/aux when you need auxiliary heat from the power strip. It only triggers * when you manually turn on Emergency heat.

Thus, there is only 1 level of auxiliary heat from the thermostat, turning on 1 or 2 strips. You never get the second level of auxiliary heat.

Does this sound correct???
 
  #11  
Old 04-04-17, 02:01 PM
S
Member
Join Date: Feb 2014
Location: USA
Posts: 2,101
Received 0 Votes on 0 Posts
On most heat strips W2/aux will turn on all the strips.
 
  #12  
Old 04-05-17, 08:20 AM
D
Member
Join Date: Dec 2012
Location: United States
Posts: 254
Received 1 Vote on 1 Post
Do you have documentation for the Nest that specifies which terminals are asserted under what conditions?

What is the model number of your heat pump ( outdoor ) and air handler (indoor ) ?
Do you know the size of the resistance heaters - e.g. 5kw ? 15 kw ? 20 kw ? 25 kw ?

Will you trade economy for comfort or vice versa ? Which is more important ?

There are many ways to connect the three wires (emergency, W1, W2) to/from the outdoor unit ; the two wires (Emergency, Auxiliary) from the thermostat; to the two terminals in the air handler (W1,W2) and it really depends on the capabilities of the thermostat, the defrost control board, the air handler controller and what's important to you.

An important caveat for the Yorks is don't wire it so the E to/at the Heat pump is connected to either W1 or W2 from the heat pump .
 

Last edited by dsomerv; 04-05-17 at 09:56 AM.
  #13  
Old 04-06-17, 06:05 AM
B
Member
Thread Starter
Join Date: Feb 2014
Location: USA
Posts: 10
Received 0 Votes on 0 Posts
York heat pump

Thank you for your reply.

The Nest turns on W2/aux when it wants auxillary heat from the heat strip. This wire is connected to the W1 terminal on the air handler and has a second wire connection which goes to the heat pump.

The Nest turns on Emergency heat ONLY manually when selected on the thermostat. This wire is connected to W2 on the air handler and has a second wire connection which goes to the heat pump.

I did a test and turned on emergency heat. The heat pump did not turn on, but the heat strips did.

I believe the heat strip is either on or off, there are no stages.

This leads me to believe that one of the W1 or W2 wires to the heat pump is not used, probably W1.

Does this sound like I am hooked up correctly with Nest???
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: