Fan stays on after heat turned off- fix myself ? Pics included:)


  #1  
Old 03-02-09, 07:49 PM
W
Member
Thread Starter
Join Date: May 2005
Location: Texas
Posts: 86
Upvotes: 0
Received 0 Upvotes on 0 Posts
Fan stays on after heat turned off- fix myself ? Pics included:)

I have a heating unit built by "evcon industries". Model # BGH080 16C. Digital thermostat. Only when I run the heat do I have the following problem- say I set the heat to 72, but once the temp gets there it keep on going (both heating and blowing) up to 80 without and signs of shutting off. Turning it to off on the thermostat will shut the heating part off, but the fan wil continue to run. If I turn the fan on 'auto' when the fan was stuck on, I can tell that the speed increases. The only way I got the fan off was going up into the attic where the unit has some power switch- the first time I turned the switch off the fan stopped, the controller clicked off(relay??), and when I flipped the switch back on the fan stayed off. The second time I had this problem, the fan was on, I flipped the switch it turned off, but there was no click, and when I fliipped the switch on the fan turned on again. I left the switch off for a day and now the fan stays off when I flip the switch on.

Ok so my suspicion is its a relay problem. The question is, should I mess with fixing this thing myself or just get a service guy over to do it for me. I like fixing things myself and saving money and have done some wiring in my time, but a dead me isn't good either...





 
  #2  
Old 03-02-09, 09:00 PM
M
Member
Join Date: Jan 2008
Location: Tennessee
Posts: 438
Upvotes: 0
Received 0 Upvotes on 0 Posts
Too Hot

First picture far left silver rectangle is your fan /limit combination. You will probably have to replace it but try holding the wheel and moving the pointers to a different temperature and sometimes you can get them to act right for a while but it is just a matter of time. Now why the unit is over running the setpoint if it is I don't know but work on the switch and see if it helps.
 
  #3  
Old 03-02-09, 09:21 PM
W
Member
Thread Starter
Join Date: May 2005
Location: Texas
Posts: 86
Upvotes: 0
Received 0 Upvotes on 0 Posts
Mike,
Thanks for the info- how would I determine that that is the problem for sure?
 
  #4  
Old 03-03-09, 04:50 AM
Grady's Avatar
Forum Topic Moderator
Join Date: Jan 2005
Location: Delaware, The First State
Posts: 12,682
Received 41 Upvotes on 39 Posts
Fan Stays On

If you have a volt meter & know how to use it, tracing the cause of the problem should not be difficult.

Once the furnace has cooled & the thermostat fan switch set to 'auto', check for 120 volts between where the black & brown wires connect in the previously mentioned fan/limit control. If you get no voltage but you do get 120v from each wire to ground the fan/limit is the problem.
 
  #5  
Old 03-03-09, 05:25 AM
S
Member
Join Date: Sep 2008
Location: Long Island
Posts: 695
Upvotes: 0
Received 0 Upvotes on 0 Posts
check out item 2E819 in the Grainger Industrial Supply site for an exact replacement for that limit controller.the only thing there that sounded out of sequence is your getting the HI fan in the auto setting on the stat.you should always be in heat/auto setting and that silver covered controller you show is the fan cycle switch,and the burner hi limit in one.check out how long the burner runs before the fan comes on and then when the burner shuts off how long it stays on.....should be close in time of heat ON the exchanger then heat OFF the exchanger!if you shut the 115V power to the furnace right after a heat cycle there still might be heat there with and no fan then it will start up again after you power it back up.the difference between the FAN stat settings "auto fan" and "on fan" is the speed change.why your getting HI is the question in auto the silver covered control controls the fan in the heating mode and nothing else.if their is a relay it is for the cooling side of the system and the supply fan only away from the heating limit controller.easy change out just mark the wires on those push pins coming out and going in.
 
  #6  
Old 03-03-09, 05:48 AM
W
Member
Thread Starter
Join Date: May 2005
Location: Texas
Posts: 86
Upvotes: 0
Received 0 Upvotes on 0 Posts
I did mis-type- the fan gets louder when I turn it to "on". I will have to tinker with it some this weekend to see how long the interval is- roughly I know that when it starts up, I hear the heater run for 15-30 seconds or so before the fan kicks in-I'm not as sure about the turning off interval.

Thanks!
 
  #7  
Old 03-03-09, 07:45 PM
W
Member
Thread Starter
Join Date: May 2005
Location: Texas
Posts: 86
Upvotes: 0
Received 0 Upvotes on 0 Posts
Ok I took the cover off the limit controller- does this still seam like the 2E819- the catalog picture looks a little different?
HVACR > Controls > Fan and Limit Controls > Fan/Limit Control : Grainger Industrial Supply
Should I pull it and take it to grainger (I live in houston so there is one about 10 miles away)? Can I just buy from them like that(do they have the retail option)? Thanks!!!!

 
  #8  
Old 03-03-09, 07:52 PM
W
Member
Thread Starter
Join Date: May 2005
Location: Texas
Posts: 86
Upvotes: 0
Received 0 Upvotes on 0 Posts
also I was at this site
How furnace fan and blower motor controls work and repair wiring

and they said "If you have problems with the blower not shutting off, set the "Off" setting to the bottom then after the burner cycles wait about 3 to 4 minutes and hold the dial and raise the stop until it shuts off. Run the burner several more cycles to make sure it works reliably (use your best judgment)."

Should I try that first? I haven't tinkered with the setting- or do you just think its fried.
 
  #9  
Old 03-03-09, 08:00 PM
Grady's Avatar
Forum Topic Moderator
Join Date: Jan 2005
Location: Delaware, The First State
Posts: 12,682
Received 41 Upvotes on 39 Posts
Fan/Limit

Hold the dial with your thumb & push the bottom (fan off) pointer up about 10. That may cure your problem.

That one from Grainger is not the right one. You need a Honeywell L4064W-xxxx. The last 4 digits will vary depending upon length. 1080=5", 1098=8", & 1106=11".
 
  #10  
Old 03-04-09, 04:55 AM
S
Member
Join Date: Sep 2008
Location: Long Island
Posts: 695
Upvotes: 0
Received 0 Upvotes on 0 Posts
Yes, you can walk in to Graingers and pick it up over the counter no problem they welcome home owners.
 
  #11  
Old 03-13-09, 08:10 AM
W
Member
Thread Starter
Join Date: May 2005
Location: Texas
Posts: 86
Upvotes: 0
Received 0 Upvotes on 0 Posts
Follow-up:
Thanks for all the advice. I ended up waiting until it got cold again (last night - Houston, TX) and bumped up the fan off switch about 10 degrees. I ran the heater 2 times and both the heater and then the fan cycled properly with the fan only staying on for a few minutes after the heater shut off! Thanks for the advice- hopefully I won't have more problems next year- if so I'll be back on this forum!

Beer 4U2
 
  #12  
Old 03-13-09, 03:41 PM
Grady's Avatar
Forum Topic Moderator
Join Date: Jan 2005
Location: Delaware, The First State
Posts: 12,682
Received 41 Upvotes on 39 Posts
Thumbs up Working

Good Job. Glad we were able to help. Come on back anytime.
We are here & will do our best to help you do it yourself.
 
 

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