Nest Thermostat Retrofit for 110v wiring


  #1  
Old 11-09-12, 11:47 AM
A
Member
Thread Starter
Join Date: Nov 2012
Posts: 4
Received 0 Votes on 0 Posts
Nest Thermostat Retrofit for 110v wiring

The heating and cooling in my condo is done by an old 110v system that powers a fan only (water based registers). Nest told my that their thermostat is not compatible, but there has to be a way.

I have purchased the parts below. Before connecting them I wanted to ask you all if this will work? Is there anything else that I will need?
 
Attached Images  
  #2  
Old 11-09-12, 02:42 PM
hvactechfw's Avatar
Member
Join Date: Jan 2011
Posts: 6,244
Received 4 Votes on 4 Posts
we need to know more about your system and your current thermostat. It does NOT look like it will work the way you have described.
 
  #3  
Old 11-09-12, 03:25 PM
A
Member
Thread Starter
Join Date: Nov 2012
Posts: 4
Received 0 Votes on 0 Posts
Here is an updated drawing that shows the old system. There's nothing to it really. The old existing thermostat connects the 110v line, which turns on the blower. When the room reaches temp it turns it off.

The blower itself is stand alone -- the water flow and temperature of the pipes is managed by the building, separate from the thermostat. All that the old original thermostat does is turn blower on or turn blower off based on temperature.

What about the drawing will not work. From my basic understanding of electrical circuits, the setup is complete. Can you explain more?
 
Attached Images  
  #4  
Old 11-09-12, 04:48 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Jersey
Posts: 70,130
Received 2,965 Votes on 2,675 Posts
What you've drawn should work. 24 vac transformer and 24 vac relay/contactor required. I'm not real familiar with the Nest yet but it may require the C connection I drew in to charge its battery.
 
Attached Images  
  #5  
Old 11-10-12, 05:25 AM
A
Member
Thread Starter
Join Date: Nov 2012
Posts: 4
Received 0 Votes on 0 Posts
I was basing it on this from their website. I don't know how it charges -- maybe it only charges when the blower is on?
 
Attached Images  
  #6  
Old 11-10-12, 05:30 AM
hvactechfw's Avatar
Member
Join Date: Jan 2011
Posts: 6,244
Received 4 Votes on 4 Posts
If you are running new wire anyway, then run 18-5 so you have enough wires just in case. I have heard of a lot of batteries not charging in the NEST if no C connection is made. Nest claims otherwise, but that is not the case from what I have seen from a few forums.
 
  #7  
Old 12-13-12, 05:41 PM
A
Member
Thread Starter
Join Date: Nov 2012
Posts: 4
Received 0 Votes on 0 Posts
Just in case anyone else wanted to try this, my drawing above does NOT work.

All you need to buy in the end to retrofit a Nest for an old 110v line system in a fan control center. I purchased this one by Honeywell (R8239A1052). It provides all 5 wires for Nest (YGWCR) and it works great.

All four Nest thermostats work perfectly now!



 
 

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