Need help with new Honeywell Thermostat


  #1  
Old 10-31-14, 10:57 AM
A
Member
Thread Starter
Join Date: Oct 2014
Location: USA
Posts: 2
Received 0 Votes on 0 Posts
Need help with new Honeywell Thermostat

I recently replaced an old mercury-switch RUUD Q674L-1504 thermostat with a Honeywell RTH6580WF but it doesn't seem to be working properly. I'm getting cold air when the heat should be on. My system is an RUUD AC/Heat Pump with a aux heat provided by an oil furnace. Here is the wiring for the old thermostat.

Name:  RUUD Thermostat2.jpg
Views: 7140
Size:  34.0 KB

I was told by Honeywell to wire the new thermostat as follows:

Y to Y
G to G
E to Aux/E
R to R/RC
W2 to W2
X to C
O to O/B
B - Not Used

Having read more about the O & B wires in a Heat Pump system it seems that you need both to tell the unit if the reverse valve should produce heat (B) or cool (O). So if the new thermostat doesn't use B, how does the Heat Pump know to throw the reverse valve into the heat position? Here is the wiring terminal for the Honeywell RTH6580WF thermostat:

Name:  20141031_134559222.jpg
Views: 14803
Size:  22.1 KB

The white wire is not hooked up and it was not hooked up on the old thermostat. Please help, we woke up freezing last night as the temperature dropped into the 40s and the AC kicked on instead of the heat. Thx......Arthur
 
  #2  
Old 10-31-14, 11:49 AM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 61,828
Received 1,473 Votes on 1,361 Posts
Welcome to the forums.

Does this thermostat also control the oil burner ?
If it doesn't..... turn on the oil burner.

You may not be able to use that thermostat as some Ruud heatpumps required both the O and B functions to be used.
 
  #3  
Old 10-31-14, 06:46 PM
Houston204's Avatar
Forum Topic Moderator
Join Date: Oct 2009
Location: Texas
Posts: 7,425
Received 17 Votes on 14 Posts
I would check to see if the orange wire is in use at the furnace or outdoor unit.
Ruud normally uses the blue wire on B not the orange wire on O.

If you are lucky you may get away with connecting blue to the O/B terminal and setting function 1 to 5 and function 2 to 1.

A low ambient control or fossil fuel kit may require separate O and B terminals.

Name:  Ruud heat pump stat.jpg
Views: 2829
Size:  37.6 KB
 
  #4  
Old 10-31-14, 07:19 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 61,828
Received 1,473 Votes on 1,361 Posts
Thanks for the clarification Houston. Looking at the B and O terminals connected on the old thermostat I just assumed that both were required.
 
  #5  
Old 11-01-14, 09:29 AM
A
Member
Thread Starter
Join Date: Oct 2014
Location: USA
Posts: 2
Received 0 Votes on 0 Posts
I will check but I assumed both the B & O were required, B to activate the reverse valve for heat & O to activate the reverse valve for cooling, since they were both connected to the old thermostat.
 
  #6  
Old 11-01-14, 01:21 PM
Houston204's Avatar
Forum Topic Moderator
Join Date: Oct 2009
Location: Texas
Posts: 7,425
Received 17 Votes on 14 Posts
The reversing valve will only have 2 wires, B and 24 volt common with a Ruud heat pump.

24 volts to the reversing valve puts it into the heating position and a lack of 24 volts puts the reversing valve into the cooling position with a Rheem or Ruud heat pump.

The most common use of both O and B that I have seen is old zone control boards.
 
  #7  
Old 10-16-16, 11:51 AM
G
Member
Join Date: Oct 2016
Location: Usa
Posts: 1
Received 0 Votes on 0 Posts
I am having issues as well. I had the same thermostat and Rehm heat pump with gas furnace as emergency heat.. my current system has been in place since 1998. It used terminals Y,G,E,R,B,&X. I have replaced my thermostat with the Honeywell rth6850wf. They have informed me to use terminals E TO AUX/E, G TO G, B TO O/B, X TO C, Y TO Y, AND R TO R. I have done what they said but I no longer have air to air heat pump. When I turn the furnace on all I have is propane heat. Any advice would be greatly appreciated
 
  #8  
Old 10-16-16, 12:00 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 61,828
Received 1,473 Votes on 1,361 Posts
Welcome to the forums.

Did you program the stat for B wire use ? (it comes default set for O)

If you set the thermostat to 3-4 degrees over the room temperature it may bring the gas heat on. Try setting it to just one degree over room temp.

If the set temp gets 3-4 degrees over the actual temp.... the stat thinks the heat pump can't keep up and turns the gas heat on. This is the main reason why a setback is not used on a heat pump system.
 
 

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