Minimal/No Heat From Gas Furnace


  #1  
Old 11-30-07, 03:24 PM
D
Member
Thread Starter
Join Date: Nov 2007
Posts: 12
Upvotes: 0
Received 0 Upvotes on 0 Posts
Unhappy Minimal/No Heat From Gas Furnace

I'm hoping there's someone out there can help me diagnose the problem with my furnace.

I have a Frigidaire Gas-fired furnace. The system is igniting correctly (I replaced the ignitor a couple of years back), flames are coming from the burners, the blower motor is running but I'm getting cold or only slightly warm air blowing out of the forced air vents where last year i was getting hot air coming from them. I'm praying its not the heat exchanger as I've heard that once those things break its the end of the furnace..

Thanks...
 
  #2  
Old 11-30-07, 05:22 PM
L
Member
Join Date: Nov 2007
Posts: 36
Upvotes: 0
Received 0 Upvotes on 0 Posts
well if you dont have bad headaches, problems waking up. or dead. i'd say chances are that its not the heat xchangers. if your worried it is call your local gas company they will normally check it for free in most states. as for why its not blowing realy hot....ahhh not sure without being there. most furnaces now adays blow air at just a few degree's below body temp. so the air feels cold but its not. but if your furnace used to be hot and now its not. then if your in a trailer i'd almost say cold air is getting to the ducts cooling off the system. but like i said. without being there and without more information its hard to say
 
  #3  
Old 11-30-07, 06:11 PM
E
Banned. Rule And/Or Policy Violation
Join Date: May 2007
Location: Wisconsin
Posts: 7,826
Upvotes: 0
Received 1 Upvote on 1 Post
I can't recollect the brand furnace, but this woman in this condo complained about feeling drafty cool heat. I went there and found the temp in register at only 96. I went down to look at the furnace and it is of a strange variety where I will call it a SEMI-closed system. The burner compartment is closed with 2 lenses to peek in at burner flame. Yet, on the underside to the burner section it is open, but covered with a finer screen. The screen was getting clogged with dust. I cleaned the screen and the flame height increased and I was able to raise the register temp to 108 F.

Something else to look for is to make sure upstairs cold air returns are clean and that your basement (if that is where furnace is?) is not real cold because air is being drawn more down a gas water heater flue pipe or coming in a stuck open dryer vent, and the furnace is pulling that cold air into the furnace. And make sure you do not have registers in the basement cold air return ducts that are open in cold basement. And if you have a door at top of basement steps, see if the door wants to pull shut toward the basement direction. This test would be of more interest if you have a totally closed burner compartment, as an open burner one may have to pull air down the basement steps to fuel the burner.
 
  #4  
Old 11-30-07, 06:23 PM
D
Member
Thread Starter
Join Date: Nov 2007
Posts: 12
Upvotes: 0
Received 0 Upvotes on 0 Posts
Thanks for the help. I forgot to mention that I did test for Carbon Monoxide. I stuck a carbon monoxide detector (one of the ones with the LCD readouts) right up to a vent and got a reading of zero. I also verified it with another detector (the non-readout variety) and it never triggered. I even took them both down to the basement and placed them right up to the furnace when it was running and got a reading of zero. Will there always be a noticable amount of Carbon Monoxide if the exchanger is broken?

The puzzling thing for me it that the ductwork directly above the furnace is barely getting warm where it used to be really hot to the touch. It also has an AC in-line which works fine in the summer.
 
  #5  
Old 11-30-07, 06:35 PM
E
Banned. Rule And/Or Policy Violation
Join Date: May 2007
Location: Wisconsin
Posts: 7,826
Upvotes: 0
Received 1 Upvote on 1 Post
I'm trying to help but can't if every question is not answered.

How cold is your house when you are trying to bring up the temp? How cold is the basement? For how long does the burner flame run for if say you turn the stat up to 80? (At such a cool operating temp one would have to think it is going to run and run and run - but DOES it? Or is it short-cycling?)
 
  #6  
Old 11-30-07, 06:50 PM
D
Member
Thread Starter
Join Date: Nov 2007
Posts: 12
Upvotes: 0
Received 0 Upvotes on 0 Posts
Sorry, i should have mentioned that it is a two-zone system. I have the same model furnace in the attic & that runs fine. I'm guessing that the hot air from upstairs is making its way downstairs eventually as it is taking the best part of the morning to heat the first floor up to an acceptable level.

This probably makes testing the system difficult unless I turn the upstairs furnace off

I have the temp set to 69 degrees. If I go into any single room & shut the door then the room cools down, even though the return is not blocked.
 
  #7  
Old 11-30-07, 07:06 PM
E
Banned. Rule And/Or Policy Violation
Join Date: May 2007
Location: Wisconsin
Posts: 7,826
Upvotes: 0
Received 1 Upvote on 1 Post
Is there common ducting between the 2 furnaces?

Does the attic furnace primarily, or soley heat the 2nd floor?, and the basement furnace heat just the first floor, and can both be interconnected by sliding any damper control?

IS the attic furnace truly a complete furnace that is gas fired?

Are both furnaces now running at the same time and yet you feel cold air blowing somewhere, or does this happen only when one of the two is running?

When you go in WHAT "any room", upstairs or downstairs, or both, does it actually get COOLER when the furnace is RUNNING?

You have to be as clear as possible about everything because it can get very frustrating and a needlessly drawn out thread otherwise. You have to tell us completely everything you can think of.
 
  #8  
Old 11-30-07, 07:26 PM
D
Member
Thread Starter
Join Date: Nov 2007
Posts: 12
Upvotes: 0
Received 0 Upvotes on 0 Posts
Is there common ducting between the 2 furnaces?

>>> Nope. Completely seperate.

Does the attic furnace primarily, or soley heat the 2nd floor?, and the basement furnace heat just the first floor, and can both be interconnected by sliding any damper control?

>>> the attic services the second floor, although I have a living room & foyer that stretches up to both levels. The two systems are completely seperate.


IS the attic furnace truly a complete furnace that is gas fired?

>>> Yes. It is the same model at that in the basement with the same setup.


Are both furnaces now running at the same time and yet you feel cold air blowing somewhere, or does this happen only when one of the two is running?

>>> There is hot air blowing from the attic vents, and cold (but not freezing) air blowing from the vents downstairs.


When you go in WHAT "any room", upstairs or downstairs, or both, does it actually get COOLER when the furnace is RUNNING?

>>> I can feel cool air from the registers downstairs. I have 3 rooms downstairs that I can close off completely. If I close the door in either of those, its register blows cool air & cools the room down.


You have to be as clear as possible about everything because it can get very frustrating and a needlessly drawn out thread otherwise. You have to tell us completely everything you can think of.

>>> There are no registers in the basement area, nor are there any leaks that I am aware of. The ductwork directly above the furnace is not hot to the touch when running (only warm), although the exhaust flue pipe gets hot when the furnace is running. The basement door is not closing by itself.

There seem to be no flashing error codes on the circuit board.

Is there any other info you think would be useful to know?
 
  #9  
Old 11-30-07, 07:45 PM
E
Banned. Rule And/Or Policy Violation
Join Date: May 2007
Location: Wisconsin
Posts: 7,826
Upvotes: 0
Received 1 Upvote on 1 Post
Thank you. The questions are not just for my benefit but may help anyone else who wants to jump in.

Here are some more:

Have you actually run both furnaces at once and compared the temp (with a thermometer) at a regsiter from attic furnace to that of basement furnace at registers closest to each one?

And is the force of the air blowing out the registers of the same force about? If not, this will raise more questions.

Can you see the burner flame? If so, are all the burners going and how high is the cone of the flame and how tall is the total height of the flame? Or instead is your burner the kind that is propels fire into the chamber like a jet engine?

Is the furnace open or closed combustion? Open has only the exhaust duct, but closed has another duct for letting fresh air into the burner. And are both furnaces identical in THAT aspect, also?
 
  #10  
Old 11-30-07, 08:01 PM
D
Member
Thread Starter
Join Date: Nov 2007
Posts: 12
Upvotes: 0
Received 0 Upvotes on 0 Posts
>>> Thanks. I appreciate your time & knowledge.


Have you actually run both furnaces at once and compared the temp (with a thermometer) at a regsiter from attic furnace to that of basement furnace at registers closest to each one?

>>> Both are running & there is a big difference between the registers closest to the furnace. Cool air from the downstairs register, hot air from the upstairs one.

And is the force of the air blowing out the registers of the same force about? If not, this will raise more questions.

>> The air force seems comparable between the two. In fact, the downstairs register furthest away from the furnace blows with a fiar amount of force.

Can you see the burner flame? If so, are all the burners going and how high is the cone of the flame and how tall is the total height of the flame? Or instead is your burner the kind that is propels fire into the chamber like a jet engine?

>> There are 4 'jet engine style' burners.

Is the furnace open or closed combustion? Open has only the exhaust duct, but closed has another duct for letting fresh air into the burner. And are both furnaces identical in THAT aspect, also?

>> The furnaces are both the same model numbers. They both do not pull air from anywhere other than the return vent.

>>> Like I said, the exhaust flue seems to get real hot, but the rest of the ductwork around the furnace does not.


Thanks again for any comments.
 
  #11  
Old 11-30-07, 09:22 PM
D
Member
Join Date: Aug 2007
Posts: 1,851
Upvotes: 0
Received 0 Upvotes on 0 Posts
Is the a/c on at the same time?
 
  #12  
Old 11-30-07, 10:52 PM
D
Member
Thread Starter
Join Date: Nov 2007
Posts: 12
Upvotes: 0
Received 0 Upvotes on 0 Posts
Is the a/c on at the same time?

Alas, nothing's ever that simple....
 
  #13  
Old 12-01-07, 10:52 AM
L
Member
Join Date: Nov 2007
Posts: 36
Upvotes: 0
Received 0 Upvotes on 0 Posts
weird, only thing i can think of at this time is maybe the fan speed was somehow set too high (black Cool line now at heat?) not allowing the chamber to heat up enouph and causeing cool down on you.....i have to admit. as long as ive done this and all the fields i'm in i'm at a bit of a loss
 
  #14  
Old 12-01-07, 10:55 AM
L
Member
Join Date: Nov 2007
Posts: 36
Upvotes: 0
Received 0 Upvotes on 0 Posts
Is it possible that the filter is dirty causing the furnace to overheat and shut down early? have you watched the fire up for a while...at least 10 min to see what its doing?
 
  #15  
Old 12-02-07, 04:52 PM
D
Member
Thread Starter
Join Date: Nov 2007
Posts: 12
Upvotes: 0
Received 0 Upvotes on 0 Posts
Originally Posted by LaBait
Is it possible that the filter is dirty causing the furnace to overheat and shut down early? have you watched the fire up for a while...at least 10 min to see what its doing?
I'm pretty good at changing the filters on a regular basis (and I use the regular fiberglass $0.50 ones as they seemd to circulate the air better.). As for the fan speed, that may be a possibility. Is there any way to vary it? I replaced the blower moter and cap a while back as the bearings on the thing were starting to sound like a tortured mouse.

The only other thing I can think of (and its a really long shot) is that a year back at Christmas time I bought one of those inflatable snow globes. The little foam balls that were in it got wet and i empyied them out on my carpet to dry. I'm wondering whether a small amount of the balls got sucked into the the return & melted somewhere in the system as i DID notice a very small amount ot them on the floor of the motor housing when I replaced it... is this possible or am i clutching at straws? It would probably be difficult for a lot of them to work their way round the filter at the edges I would have thought...

Thanks!
 
  #16  
Old 12-03-07, 06:26 PM
E
Banned. Rule And/Or Policy Violation
Join Date: May 2007
Location: Wisconsin
Posts: 7,826
Upvotes: 0
Received 1 Upvote on 1 Post
We have to solve this.

What is the actual temperature coming out a register where you think you have no heat. You may be actually surprised. The windchill effect can be a fooler. Please let us know.
 
  #17  
Old 12-03-07, 06:37 PM
D
Member
Thread Starter
Join Date: Nov 2007
Posts: 12
Upvotes: 0
Received 0 Upvotes on 0 Posts
Right now the registers are blowing semi-warm air out of them. It is the evening and I have the ceiling fan in the living room set to suck the air from the (working) upstairs furnace. Seems like by the evening the temperature stabilizes throughout the house (having had all day to do so). I was thinking of pulling out the blower motor assembly tomorrow morning and poking my head in to see if I can see any obvious damage to the exchanger.

One question I have is, will a cracked or broken exchanger cause the system to produce cold air? Even if no Carbon Monoxide is registering?

The ductwork directly above the furnace used to be really hot to the touch, but now its barely warm...

Thanks!
 
  #18  
Old 12-03-07, 06:45 PM
E
Banned. Rule And/Or Policy Violation
Join Date: May 2007
Location: Wisconsin
Posts: 7,826
Upvotes: 0
Received 1 Upvote on 1 Post
I think you'd need a chunk out of the exchanger to cause enough cold air to mix in with that of the firebox to actually produce cool air. And if it was that bad, I'd think the flame would get snuffed, and/or send safety devices into a frenzie.

I'd still like to know the actual temperature, and also the temp put out by your good upstairs furnace.

And is the fire going during the whole time?
 
  #19  
Old 12-03-07, 06:47 PM
D
Member
Join Date: Aug 2007
Posts: 1,851
Upvotes: 0
Received 0 Upvotes on 0 Posts
Whoa- time out! You replaced the blower motor? What speed are you using for heat?
 
  #20  
Old 12-03-07, 06:57 PM
E
Banned. Rule And/Or Policy Violation
Join Date: May 2007
Location: Wisconsin
Posts: 7,826
Upvotes: 0
Received 1 Upvote on 1 Post
[QUOTE=DIYGuvnor;1268578>>> Both are running & there is a big difference between the registers closest to the furnace. Cool air from the downstairs register, hot air from the upstairs one.

ecman51` question:
And is the force of the air blowing out the registers of the same force about? If not, this will raise more questions.

>> The air force seems comparable between the two. In fact, the downstairs register furthest away from the furnace blows with a fiar amount of force.[/QUOTE]

If the one farthest from the furnace blows with such force, what about a closer one?
 
  #21  
Old 12-03-07, 07:07 PM
D
Member
Thread Starter
Join Date: Nov 2007
Posts: 12
Upvotes: 0
Received 0 Upvotes on 0 Posts
Originally Posted by daddyjohn
Whoa- time out! You replaced the blower motor? What speed are you using for heat?
I'm not sure. I just picked up a working used blower (same GE model that was originally in the furnace) from an HVAC dealer on eBay. Just plugged it in the socket. Also got a replacement capacitor as this was causing problems on the original.

Do I need to vary the speed somehow?
 
  #22  
Old 12-03-07, 07:10 PM
D
Member
Thread Starter
Join Date: Nov 2007
Posts: 12
Upvotes: 0
Received 0 Upvotes on 0 Posts
Originally Posted by ecman51`
If the one farthest from the furnace blows with such force, what about a closer one?
I just took a few sheets of paper & measured the deflection as I put them up to the vents. The vent nearest to the furnace seems to deflect the paper about the same amount as the one furthest away from the furnace.
 
  #23  
Old 12-03-07, 07:14 PM
D
Member
Thread Starter
Join Date: Nov 2007
Posts: 12
Upvotes: 0
Received 0 Upvotes on 0 Posts
Now this is getting weirder. The temperature at the vents seems to be going down by a few degrees over the period of 20 minutes or so... I'm at a loss.
 
  #24  
Old 12-03-07, 07:28 PM
D
Member
Thread Starter
Join Date: Nov 2007
Posts: 12
Upvotes: 0
Received 0 Upvotes on 0 Posts
One thing I will say is that during the summer, the AC that shares the ductwork produces a hell of a lot of condensation. So much so that there's rusting on some of the ductwork. I just went down & took out the slot for the humidifier & theres rust on the roof of the duct directly above the AC condenser.
 
  #25  
Old 12-04-07, 10:21 AM
E
Banned. Rule And/Or Policy Violation
Join Date: May 2007
Location: Wisconsin
Posts: 7,826
Upvotes: 0
Received 1 Upvote on 1 Post
Originally Posted by DIYGuvnor
Now this is getting weirder. The temperature at the vents seems to be going down by a few degrees over the period of 20 minutes or so... I'm at a loss.
Actually it is not weird at all if Daddyjohn's assertion is correct. What happens is the furnace fires up and comes up to temperature where the fan will come on. But then if you have a blower motor that is turning the squirrel cage faster than what the heating part of the furnace was designed for, you could actually start cooling down the heat exchanger from the extra amount of cold air return air being sucked thru the heat exchanger per given amount of time.
 
  #26  
Old 10-12-09, 12:13 PM
javidmar's Avatar
Member
Join Date: Oct 2009
Location: Colorado
Posts: 2
Upvotes: 0
Received 0 Upvotes on 0 Posts
Furnace blowing cold air no heat

I am having the same issue. Up until this weekend the furnace was working great blowing heat and the all of a sudden Saturday it was cold air, and the fan never shut off until i shut the furnace off. I have the same setup with a furnace for upstairs and one for downstairs and I replace the filters thinking it might be that but that did not help either. The temp gage was reading 60 when taken as the other was in the 70's. Because the furnace working heats the upstairs the downstairs never warmed up. Thank god I still have a wood fireplace to huddle up to.
 
  #27  
Old 10-12-09, 05:02 PM
E
Banned. Rule And/Or Policy Violation
Join Date: May 2007
Location: Wisconsin
Posts: 7,826
Upvotes: 0
Received 1 Upvote on 1 Post
So the downstairs furnace only, does not work, and the upstairs one does? Are they identical units? If so, compare what fails in what part of the sequence. You can remove the big furnace cover that has the burner and the small fan motor that vents the burned gas to the outside. Then post what you see. Time every part of the sequence of when you hear teh venting fan start up, until it tries to ignite, if then any flame goes out and how long it took for it to go out, etc.
 
 

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