ruud not turning off when set point is reached - instead blows COLD air

Reply

  #1  
Old 02-13-18, 09:11 AM
Member
Thread Starter
Join Date: Feb 2018
Location: USA
Posts: 3
ruud not turning off when set point is reached - instead blows COLD air

I have a heat pump that once it reaches set point will continue to run, but the output temperature fluctuates..

Example.. I have the set point at 68 F, it is 40F outside. Heat comes on and blows about 99F until set point is reached, then, until either I manually turn it off, or the program cycles it off, it will continue to run, but the temperature of the output cycles between 55 and 85. It never gets as hot as it was when trying to reach the set point, and it will eventually get to where it is outputting air colder than the set point. Is there something wrong? or do I just not understand how heat pumps work? If there is something wrong, how do I convince the service company ( who has been out twice, once replacing the thermostat another replacing the condenser ) that there IS a problem?
 
Sponsored Links
  #2  
Old 02-13-18, 09:57 AM
Member
Join Date: Feb 2014
Location: USA
Posts: 2,077
Sounds like it's going into defrost mode ? The back up heat should come on in defrost mode. Next time it happens take a look at the outside unit and see if there is frost on the coil.
 

Last edited by skaggsje; 02-13-18 at 10:00 AM. Reason: Added
  #3  
Old 02-13-18, 10:47 AM
Member
Join Date: Oct 2015
Location: usa
Posts: 543
When the t’stat is satisfied the control board should turn off the compressor. The air blower should continue to run for the programmed cool down time on the control board, usually between 1-2 minutes to remove residual heat in the system. The assumption here is the t’stat won’t call for heat during the 1-2 minute cool down time. When the t’stat calls for heat, the cycle repeats. In your problem my guess is the control board is turning off the compressor based on a satisfied t’stat but the air blower control on the control board is not operating, hence eventually allowing air blower to blow cold air until manually shut off. I think you have a defective control board.
I am not sure why the circulating air temp is fluctuating during this problem condition as I think it would just get cooler. Is there supplemental electric heaters in the ducts? If your heat source is ambient air, the heat pump efficiency decreases with decreasing temperature. This type of system has a temperature switch that turns off the heat pump and energizes the secondary heat source at a selected temperature.
 
  #4  
Old 02-13-18, 10:48 AM
Member
Thread Starter
Join Date: Feb 2018
Location: USA
Posts: 3
I thought about that, but couldn't make it work in my head. It will run for days like this, and the aux heat works just fine. I believe I remember that it will cycle like that even when the thermostat is set to "emergency heat" as well, but I would have to run an experiment using that to be sure.
 
  #5  
Old 02-13-18, 10:58 AM
Member
Thread Starter
Join Date: Feb 2018
Location: USA
Posts: 3
What you say makes sense. I've had heat pumps before and they always turned the blower off after just a minute or two. This unit is reliably blowing 65-75 F air for 5-10 minutes before switching back to 85 for a minute or two. The process is maintaining a very even ambient temperature in the house, although if you are near a duct you can feel the rather cool output. I suspected something is not turning off the blower and the aux heat is coming on for short bursts.

This is an odd ball set up the thermostat is placed in a small side room directly under a small vent.

Our current outdoor temps have been running from 30-70F.
 
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
'