furnace runs when AC is on

Reply

  #1  
Old 03-31-03, 12:12 PM
itsjustme
Visiting Guest
Posts: n/a
Unhappy furnace runs when AC is on

I have a 2 story house with 2 seperate ac/gas furnace units. When I tried to run the AC for the first time this year, I noticed it was blowing out warm air. Upon further inspection, found that the AC unit was running, however, the gas burners were lit also. Tried "resetting" the sytem by turning off the switch and flipping the breaker - no change. Thought it might be the thermostat, so I swapped the upstairs and downstairs thermostats - no change.

Furnace is a Rheem Criterion II installed in 1995.

Any suggestions would be greatly appreciated.
 
Sponsored Links
  #2  
Old 03-31-03, 12:29 PM
GregH's Avatar
Super Moderator
Join Date: Jan 2001
Location: Manitoba
Posts: 9,919
Likes Received: 3
itsjustme:

There are several possibilities for this and you would have to be able to remove wires and also be able to use a volt meter to test the controls.
If this is something you can do we likely could help.
If you are unable to do this, it would be better to call a qualified heating specialist.
 
  #3  
Old 03-31-03, 01:00 PM
itsjustme
Visiting Guest
Posts: n/a
I do have a voltmeter and can get access to the wiring.

Thanks
 
  #4  
Old 04-02-03, 03:59 AM
itsjustme
Visiting Guest
Posts: n/a
More help, PLEASE!

Any more help would be greatly appreciated. Summer is quickly approaching and I need to fix this. Thanks!
 
  #5  
Old 04-02-03, 04:46 AM
GregH's Avatar
Super Moderator
Join Date: Jan 2001
Location: Manitoba
Posts: 9,919
Likes Received: 3
Talking Sorry for the delay.........My darn job is cutting into my personal life!

itsjustme:

If there is any chance that the wires somehow got moved and put on the wrong terminals you should check the connections.'
The terminal ID in the stat should match up to the one's on the furnace. The Y terminalis sometimes not on the furnace and in that case would go to one wire going out to the condensing unit.

If the wires are correct you can remove the wire from the Y terminal at the stat. If it still continues to run then then the problem could be at the furnace.
 
  #6  
Old 04-02-03, 05:55 AM
KField's Avatar
Member
Join Date: Dec 2002
Location: Easton, PA
Posts: 3,245
Were there any changes made to the system since the last time it worked right? Like a new thermostat or any repairs? It sounds like a wiring problem, but not something that usually happens on its own.

Ken
 
  #7  
Old 04-04-03, 05:03 AM
itsjustme
Visiting Guest
Posts: n/a
Thanks for the suggestions, still trying

Thanks for the help, guys.

Ken, can you tell me what you are trying to do by removing the Y connection at the stat. If my understanding of the Y connection is correct, removing this connection would keep my AC from turning on. My problem is that I don't want the gas burners coming on in the AC mode. Are you thinking Y is somehow connected to W as well?

I have not had any work done on my upstairs-zone units. However, I did have a repairman out working on my lower-zone heat last winter.

Would it help to check for resistance between the Y and W, and the G and W at the stat?

Thanks for any advice you can give me.
 
  #8  
Old 04-04-03, 05:28 AM
KField's Avatar
Member
Join Date: Dec 2002
Location: Easton, PA
Posts: 3,245
Let me ask a few more questions.
1. Are we troubleshooting the first floor(one that had service last fall) or second floor unit.
2. What model are the thermostats?
If they are the type that uses a sub-base, did you carefully check all wires for short circuits when you had the thermostat off to change it?
*Now the one that will help the most. .
3. When you run the unit in HEAT mode, does the outdoor unit turn on?

If it DOES, forget the rest of this post and let us know.

If it DOES NOT, I suspect the problem lies in the blower relay, fan control area. To check this, set the thermostat to cool mode and turn the setpoint up above room temp. Is the furnace running? If NOT, turn the fan switch to ON. Is the furnace running now? I suspect it will. Let us know the results of this test and we are getting closer to nailing it.
 
  #9  
Old 04-04-03, 02:46 PM
itsjustme
Visiting Guest
Posts: n/a
the continuing saga....

Ken, Thanks for the response. Sorry for the confusion. The problem I am having is with the upstairs zone. Per your instructions, I turned the stat to auto/cool, with the temp set above room temp. Nothing turned on. I then turned the fan to "on" and the fan came on, but not the furnace. Also, the condenser does not come on when the stat is set to "heat".

My thermostats are Honeywell Chronotherm III.

Checked for shorts between W, Y, and G, and none exist.



More help would be greatly appreciated.
 
  #10  
Old 04-04-03, 03:25 PM
KField's Avatar
Member
Join Date: Dec 2002
Location: Easton, PA
Posts: 3,245
Can you identify the fan relay on the furnace? Maybe we should have a look at that.

What seems to be happening is
R to W is OK
R to Y somehow shorts to W
but R to W does not short to Y (sounds impossible)
R to Y includes R to G
R to W does NOT include R to G
If G was shorting to W furnace should run when fan switch is set to On(but that doesn't happen).

I'm not having much luck at this remotely. I wish I could see it. Let us know about that fan relay.
 
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