Lennox furnace problem

[homebuilt burner]

I have a Lennox G32Q3-75-3 furnace in my home. It is @ 15 years old. It has done a good job of keeping us warm for most of those years (not all as I had a corn burning add-on for 7 of those years). Last summer I added a 4 ton A coil into the duct work above the furnace. In the fall when I first started the furnace the combustion fan was making a lot of noise. So, I got the numbers of the fan and found a factory replacement on line and installed it myself. Now, the problem is when the weather outside is near or below zero the furnace does not keep up. It will run non stop and not catch the thermostat. Our house is not well insulated, but this furnace kept us warm in the past. It has two green led lights on the circuit board that blink quickly, on the diagnostic sheet that reads as thermostat calling for heat and furnace running. I looked at the burners (there are three) and they all look to be firing cleanly and correctly. What is the next item on the check list? Is there something that should be cleaned or adjusted??

Also, it is running on Nat. gas.

 

[driftpin]

Sorry I cannot answer your question, as we don't have NG heat at our home in south FL. We have a Lennox AC system which was installed a couple of years ago, it's got a heat strip for the light duty it's required to do in heating. It got to the 40's the last couple of nights. Then yesterday the blower in the airhandler stopped, and the trouble code on the smart thermostat said, #201: air handler not communicating." The guy who I use for service since the original master license holder who originally installed it died in a construction accident (story in itself) said it was the motor. He was out of the country, but he responded to my text, and had his friend who is covering his customers for him until he gets back, come out for the service call. He stopped at the parts jobber warehouse & got a replacement air handler motor, installed it, everything's working well now. He'll bill me when he gets back, I expect it to be a service call but a warrantied motor, as it's supposed to have a 10 year guarantee in residential use. Lennox CBX32MV-060-230-6-06.

I have a Lennox G32Q3-75-3 furnace in my home. It is @ 15 years old. It has done a good job of keeping us warm for most of those years (not all as I had a corn burning add-on for 7 of those years). Last summer I added a 4 ton A coil into the duct work above the furnace. In the fall when I first started the furnace the combustion fan was making a lot of noise. So, I got the numbers of the fan and found a factory replacement on line and installed it myself. Now, the problem is when the weather outside is near or below zero the furnace does not keep up. It will run non stop and not catch the thermostat. Our house is not well insulated, but this furnace kept us warm in the past. It has two green led lights on the circuit board that blink quickly, on the diagnostic sheet that reads as thermostat calling for heat and furnace running. I looked at the burners (there are three) and they all look to be firing cleanly and correctly. What is the next item on the check list? Is there something that should be cleaned or adjusted??

Also, it is running on Nat. gas.

 

[Brian_WK]

I have a Lennox G32Q3-75-3 furnace in my home. It is @ 15 years old. It has done a good job of keeping us warm for most of those years (not all as I had a corn burning add-on for 7 of those years). Last summer I added a 4 ton A coil into the duct work above the furnace. In the fall when I first started the furnace the combustion fan was making a lot of noise. So, I got the numbers of the fan and found a factory replacement on line and installed it myself. Now, the problem is when the weather outside is near or below zero the furnace does not keep up. It will run non stop and not catch the thermostat. Our house is not well insulated, but this furnace kept us warm in the past. It has two green led lights on the circuit board that blink quickly, on the diagnostic sheet that reads as thermostat calling for heat and furnace running. I looked at the burners (there are three) and they all look to be firing cleanly and correctly. What is the next item on the check list? Is there something that should be cleaned or adjusted??

Also, it is running on Nat. gas.

I would start with a temp rise across the furnace at the furnace. Temp probe in the return and supply ducts. 2 Simple meat thermometer would work fine for this.

Brian

 

[cheesehead2]

Filters clean

 

[PWC Repair]

If it has worked fine in the past, AND burner flame looks good, you might do a visual check of duct system. If something has been torn loose, or open by critters, it will cause exactly this issue.

 

[Showkey]

"A" coil installed this Summer is the only major change ? So is it ( the coil) restricting air flow by creating excessive static pressure that the blower can not deal with ????

 

[homebuilt burner]

Duct work looks the same. Filter was replaced in the fall, same as every year. I cleaned the A coil before installation, the filter is in the cold air return so the inside of the A coil and furnace are clean. I have not checked the temp rise, will do so tonight possibly. The air flow coming out of the registers seems normal but the temp seems low.

 

[homebuilt burner]

What temp rise should I look for??

 

[mrpizza]

There should be a label inside the furnace, it will tell you what your temp rise or differential should be.

 

[Showkey]

Single or multi stage furnace ?

 

[brewchief]

That's a two stage furnace, sounds like it is only running on low fire.

Did the thermostat get changed at any point?

 

[Rockhead261]

A/C add on, poor heat? Hmmmm.... what are the chances the installer stole W2 for G??

 

[homebuilt burner]

I bumped my A/C install thread so you folks can check what I went through with my wiring. Brewchief it is the same thermostat and hooked up the way you helped me with last summer. Is there a way to check for high/low fire?

 

[mrpizza]

Turn your thermostat up like 10 degrees or more. It should kick into the second stage of heat to try and quickly make up the difference.

 

[brewchief]

There is a second circuit board in the blower compartment that controls second stage, since I didn't see a W2 wire on the stat in the other thread it should be set to W2 timed on, there is a little jumper on the second board to set this along with one to set the time delay.

When you replaced the induced draft motor did you make sure the proper orifice was installed at the inlet of the motor? There should have been several included the one for a 75k should be red if davenet is correct.

 

[homebuilt burner]

Pics of wiring

 

[homebuilt burner]

Not sure what you mean about the orifice for the inducer motor. I am talking about the fan that is about 12" around.

 

[brewchief]

Not sure what you mean about the orifice for the inducer motor. I am talking about the fan that is about 12" around.

On the back there is a hole that gets an orifice(basically a plastic disc) that changes the size of the hole, each size furnace gets a different size and they are color coded. there should have been a bag included with the motor that had different orifices and a foam gasket.

That is set up for timed second stage, after 8 minutes you should hear the inducer speed up and the gas valve should go to high fire.

 

[zmaxmotorsports]

I don't know who talked you into the 4t coil in there ,but according to the number you posted your furnace only has a 3t drive on it.
What else did,you do to the furnace/duct work besides,adding the coil to make it fit?

 

[Showkey]

I am in central Wisconsin. It has been really cold........-20* at night with high winds. Barely 0* during the day with high winds. While the building does not feel wind chill the cooling effect is accelerated and objects are cooled faster to the actual temperature with wind.

You describ the home as poorly insulated.............and in the past the corn stove was used to supplement the heat. I thinking the furnace might not be broken ???????? If that coil did not change the furnace air flow for the worse ?????

Sounds like it does keep up when temps are 20 to 30* like it is today ?????

 

[homebuilt burner]

I am thinking brewchief is on the right track. I do not remember a red disc. When I get home, I will check on that. Showkey in the past the furnace did a good job on it's own. Zmax nobody talked me into the 4 ton the original installer had it quoted for a 3 1/2 ton and I got the 4 ton for free and did the install myself. I know it is to large but it works and again free. If I have problems down the road I would change it out for the proper size.

 

[homebuilt burner]

The red disk/orifice was in place.

 

[brewchief]

All the wiring looks OK, if you have a multi meter see if you have 24vac at the gas valve C and MV or C and HI.

Can you hear a change in speed in the induced draft motor after 8 minutes or so of run time? It should speed up just before gas vale goes to second stage.

You can try moving the jumper from W2 timed to single stage, if there is a problem in the timer part of the board it might give you high fire.

 

[homebuilt burner]

I get 24 vac at the C and MV when running. At the 8 min. mark, the inducer fan speeds up and I get 24vac at the C and HI the burner flame goes up then after about 30 sec. the voltage drops out and the burner goes down 30 seconds later it tries again, then the inducer fan slow back down. I did not hear the circulation blower speed up.

I moved the jumper to single stage, the furnace fired up on low then went to high for about a minute and the voltage at gas valve dropped out and it did not try to go back to high fire.

 

[Showkey]

Sounds like your on to the cause of poor heat.......it's not going to high fire?

 

[homebuilt burner]

So, after reading up in the service manual, I went down thinking I was going to check continuity on the high heat pressure switch. And the furnace powers up the High side of the gas valve and runs on high fire now. It's working for now. But......