no power on thermostat leads

Reply

  #1  
Old 12-21-13, 02:03 PM
Member
Thread Starter
Join Date: Dec 2013
Location: usa
Posts: 2
Received 0 Votes on 0 Posts
no power on thermostat leads

My thermostat suddenly stopped working. Thus no heat!
I bought a replacement Hon eywell T87K1007 but found there was no power across the leads on the old thermostat. On the boiler I have a Honeywell R845A relay controller.
Is there any way to test the controller?
Is there anything else to test?
Some sellers only have R845A 1030 Is this the same item?
Thank you
 
Sponsored Links
  #2  
Old 12-21-13, 02:16 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 52,676
Received 340 Votes on 318 Posts
Welcome to the forums.

That should be a basic two wire system between the R845A and the thermostat.

Remove the cover from the controller and short the two T connections or test for 24vac there.

If no 24vac there try carefully activating the relay manually. If the boiler fires then the transformer in the controller is shot.
 
  #3  
Old 12-21-13, 03:05 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 2 Votes on 2 Posts
Some sellers only have R845A 1030 Is this the same item?
The 4 digit suffix usually doesn't mean anything... and good luck even trying to find out what it means because Honeywell literature is so durn confusing sometimes. The installation instructions rarely even mention the suffix. Yes, it will work... but before you do that...

In addition to testing as PJ has suggested, it would be wise to know if you've got 120VAC on terminals 1 and 2 of the R845 relay. If you don't have 120VAC on 1 and 2, you won't have 24 VAC on T T either.

For a few bucks less, the R8845U is a 'universal replacement' for the 845 and others...

R8845U1003 - Honeywell R8845U1003 - Universal Switching Relay w/ Internal Transformer
 
  #4  
Old 12-22-13, 06:35 AM
Member
Thread Starter
Join Date: Dec 2013
Location: usa
Posts: 2
Received 0 Votes on 0 Posts
thanks

Thank you so much.
A new relay is on its way and all I have to do is install it correctly
 
  #5  
Old 12-22-13, 09:17 AM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 2 Votes on 2 Posts
Did you do the remainder of the testing and have concluded that the relay is definitely bad?

Please report your findings.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


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