Go Back  DoItYourself.com Community Forums > Heating, Cooling, Air Conditioning, Ventilation and T-Stat Controls > Heat Pumps and Electric Home Heating
Reload this Page >

Heat comming out after replacing old Lennox 21J7201 thermostat with Honeywell RTH7400

Heat comming out after replacing old Lennox 21J7201 thermostat with Honeywell RTH7400

Reply

  #1  
Old 07-04-06, 02:07 PM
Member
Thread Starter
Join Date: Jul 2006
Posts: 4
Red face Heat comming out after replacing old Lennox 21J7201 thermostat with Honeywell RTH7400

Hello,

I am trying to replace my old Lennox thermostat (21J7201) with a new programmable one, Honeywell RTH7400. After I followed the wiring instructions in the manual my A/C system was blowing hot air.

I have a Lennox CB30M-41-1P multistage heatpump system with auxilary heat pump (there is an emergency heat light).

The original wiring configuration is set up as:
G - green wire
O - orange wire
Y1 - Yellow wire
W1 - white wire
C - blue wire
R - red wire

I don't know where to look for or where these wires connect to in the heatpump system. I labeled these wires as they were connected to the terminals in the Lennox thermostat.

The connection to the Honeywell RTH7400 was the following:
Honeywell - Lenoxx
C - C
G - G
Y - Y1
O/B - O
Rc and R are jumped together - R into Rc
Aux - W1
E
L

Connections E and L were not connected to anything. I've tried also jumping Aux and E together with W1 going into Aux. But all tentatives resulted in hot air comming out.

Please, help me if possible. If you need more info please let me know.

Thanks for your attention!
 
Sponsored Links
  #2  
Old 07-05-06, 03:47 AM
Member
Join Date: Dec 2005
Posts: 190
Did you program the thermostat for your system? Just recently I installed a Honeywell 3311 (?) and once fired up produced heat instead of cooling. Upon investigation, I discovered I had neglected to go through the system set-up programming. One of the steps asked if a reversing valve is used on this system (O wire). I performed the set-up and all was well afterwards.
 
  #3  
Old 07-05-06, 09:47 AM
Member
Thread Starter
Join Date: Jul 2006
Posts: 4
Thanks for your reply!

I have programmed the thermostat for my system. It was set up to cool, the temperature inside room was over 80 and I set it at 74. But once the thermostat turned on the system, only hot air would come out.

I have an O wire (I don't have a B wire), and I connected it to the O/B connector on the new thermostat (Honeywell). Would you recommend to connect at a different connector?

Thanks again!
 
  #4  
Old 07-05-06, 12:29 PM
Ed Imeduc's Avatar
Member
Join Date: Aug 2002
Location: Mountain Williams Missouri
Posts: 18,389
Wink

Dont know the stat you have but for sure keep O on O. is there a wire lay out on the blower door you can look at?


ED
 
  #5  
Old 07-05-06, 12:55 PM
Ed Imeduc's Avatar
Member
Join Date: Aug 2002
Location: Mountain Williams Missouri
Posts: 18,389
Wink

Try http://customer.honeywell.com/Techli...0s/69-1726.pdf
Check page 30
Or call 1 800 468 1502

ED
 
  #6  
Old 07-06-06, 03:24 AM
Member
Join Date: Dec 2005
Posts: 190
On the Honeywell t/stat I installed it had two different wiring designations for the t/stat wiring blocks....one for HEAT PUMP and one for CONVENTIONAL....very similar but different. This could make a difference. When your system is blowing hot air is the outside unit running? If the "O" wire is not connected (or the wire is bad etc) the outside unit will be in heat mode as the fail-safe mode will dictate and the reversing valve, without being energized, will default to "heat". Hope this helps!
 
  #7  
Old 07-06-06, 06:33 AM
Member
Thread Starter
Join Date: Jul 2006
Posts: 4
Smile

Thanks for all your posts and help!
I still can't make the system blow cold air.. The link for the RTH7400 manual is very good and much more detailed than the ne that came with the thermostat. But I have followed those instructions and nothing changes.

The heat comes out when the outside unit starts.. when I turn on the system to cool it takes a while (2 to 3 minutes) until the outside unit is turned on. When it turns on, hot air starts to come out. While the outside unit is not turned on, I think that only the fan is working, it is not cold air that comes out, but room temperature air.

This Honeywell thermostat has two type of connection settings, conventional and heat pump. I have a heat pump in my system, so I'm using the heat pump configuration.

By the way, how can I check if I have a heat pump? I've bought this house for a month now, and I am still figuring out how the electrical appliances are wired and working.

Hey, thanks very much for all your input! I'm still trying to figure out what the problem is here..
 
  #8  
Old 07-06-06, 12:12 PM
Member
Join Date: Dec 2005
Posts: 190
If all wiring is connected to the proper connections at the t/stat and the outside unit is running but producing heat, then it sounds as if the reversing valve may be stuck....as I said in my earlier post, the reversing valve, on newer heat pumps, will default to the heat mode if not energized. The reversing valve looks like a horizontal cylindrical tube approx 6" long and is usually right next to the compressor....sometimes, while the t/stat is calling for cooling, a light tap (or two or three!) on the valve will allow it to reverse and begin cooling....an indication the valve is going bad. Be careful if you choose to open up the unit however as there is high voltage present. Another possibility could be a bad circuit board that is normally located at the outside unit behind the electrical panel....again, be careful and mindfull of the high voltage present. The circuit board, among other functions also controls the heat pump defrost cycle that controls the reversing function (during heat operation, the defrost cycle reverses the heat pump and works as an ac unit to defrost the unit during colder weather). I am assuming the unit cooled and heated before the t/stat was replaced? It may prove beneficial to re-mount the old t/stat and see if all works well....could also be a defective t/stat but I doubt it as Honeywell is, IMO, the best. Hope this helps and good luck.
 
  #9  
Old 07-07-06, 04:17 AM
Member
Join Date: Dec 2005
Posts: 190
Are you handy enough with a multimeter to check the voltages at your outside unit? When the t/stat is on "cool", you should see 24v at the "Y" wire and the "O" wire, as well as the "R" wire. Remember to be careful inside the unit as high voltages are present and the capacitor(s) can still bite even when the power is disconnected. I'm betting the circuit board is bad and not allowing the reversing valve ("O" wire) to shift to cooling. As I said earlier, newer units will default to heat if the reversing valve/circuit fails...older units normally default to cool. As you are probably aware, a heat pump works by reversing the refrigerant flow, I.E. in heat mode the inside coil acts as the condensor and the outside coil the evaporator and in cool mode exactly the opposite, thus the reason for the reversing valve...the reversing valve reverses the refrigerant flow. Circuit boards are fairly inexpensive and are easily replaced by a DIY'er...just remember to disconnect all power, including the circuit for the air handler where the transformer is normally located.
 
  #10  
Old 07-07-06, 06:32 AM
Member
Thread Starter
Join Date: Jul 2006
Posts: 4
Thanks a lot for your help lhewitt. I finally got it working! It was a really stupid thing, I am kind of embarassed to say this.. I should have read the operations manual more carefully. I forgot to adjust the settings as EdImeduc pointed out. That's what happens when you start things without looking at the manual.. it's a man's thing.. hehe.

Everything is working good now, it is cooling when it is set to cool, and heating when it needs to heat.

Thanks very much everyone for your help!
 
  #11  
Old 07-07-06, 11:36 AM
Member
Join Date: Dec 2005
Posts: 190
Excellent! Glad to hear it and thank you for letting us know.
 
  #12  
Old 07-08-07, 01:38 PM
Member
Join Date: Jul 2007
Posts: 1
System Programming?

Like rotoskowsky, I have installed this t-stat and have hot air coming out. I have C, Y, G, R, O, and W (connected to W2/AUX). I have a heat pump.

I have gone through all 10 of the settings on this to program it, but all either blow hot air or don't work at all. rotoskowsky - what setting finally worked for you? Any help is GREATLY appreciated.

Scott
 
  #13  
Old 11-28-07, 02:06 PM
Member
Join Date: Nov 2007
Posts: 3
change the settings

sounds like the settings aren't correct. if you get into the setup mode you should be able to switch the reversing valve. some manufacturers will have the valve normally on heat and won't switch over until it's energized by the t-stat during a call for cooling. that way if the valve fails at least the customer will still have heat. other manufacturers do the opposite. once you change the settings you should be all set.
 
  #14  
Old 11-28-07, 03:44 PM
Member
Join Date: Apr 2007
Location: Vagrant
Posts: 220
Have seen that happen several times. Careful review of the installation manual will most likely solve your problem move the setting on the reversing valve option to the opposite of where it is and you should be good. As others have stated there is no manufacturers industry standard on if the heat pump reversing valve energizes in heat or cool mode. Rheem?Ruud is one manufacturer that energizes for heat, Lennox I think energizes for cool. Try that first and make sure that you do have the other settings correct to match your system. The new electronic t-stats are great but do take some time to properly program. If that does not work for you we will need to do some further checks, come back either way and let everyone know the outcome if you dont mind.
 
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