Hello everyone,

New to the community here, and I'm looking at getting some advice on my furnace.

As stated in the title, my ComfortMaker N9MSB is failing to ignite the gas when the temperatures drop down below 32 degrees. I'm in Oklahoma and the house is a 1400 sq ft starter home that was built in 2014. The furnace is up in the attic, and there are vents all around the side of the house that lead up into the attic. Due to these vents, it gets pretty cold up there in the winter.

I thought maybe this problem had to do with water freezing in the condensate drain line (would make sense since this problem only happens in cold weather). I got an error of 3 blinks, which is a pressure switch error, but in the manual it says it can be many other things. Upon further inspection, it looks like the main drain line has heat cable/tape wrapped all the way down to the water heater closet where it then drains to the sewer. I have a hard time believing that the water could somehow freeze in that pipe because the heat cable being installed.

I did some further inspection by taking both doors off of the furnace, turning the thermostat up a bit higher to initiate the startup of the furnace, and held down the RH wire button. I think the inducer starts up first, and after about a minute or so, the glow starts on the igniter. I noticed that the glow igniter went on and off 4 times before it finally lit the gas on fire. I then released the RH wire button to shut everything off, waited a minute or two, and then held the button down again. This time the igniter did one glow and shut off, and then it started the gas on fire on the second glow. This was all testing while it was warm out, probably around 50 degrees in the attic.

What do you guys and gals think this could be? It's weird to me that it only happens in extreme colder weather. I am leaning towards maybe the igniter being old/bad and doesn't function well enough in the cold, or the gas sensor might be dirty with carbon. As soon as the outside temperature rises back up to ~34 degrees or so, everything functions normally or at least well enough to not notice any issues. Hopefully this makes sense enough so that I can get some advice and replace the part that's causing the issue.

Thanks for any help you can offer!

 

Have you verified the heat tape is actually working? Why people install condensing furnaces in areas where theyi can freeze is beyond me.

 

Hi Grady,

I did grab ahold of the heat tape and the wire that runs through it seemed to be emanating some heat. It wasn't super warm or anything, but I would imagine all it takes is just a little warmth to keep things flowing. We have some cold nights coming up so I'll have to go up in the attic and check again.

I have no idea why they would do this without insulating it in a box of some sort. I'm pretty sure in the manual it said to place the furnace in an area that does not get below 50 degrees. I could be wrong though since that seems kinda high.

 

Some manufacturers won't honor a warranty if the furnace is installed in an area which can drop below freezing. Others have very specific instructions for such installations.
Some heat tapes/cables say to insulate over the tape/cable on certain kinds of pipe & no insulation on other kinds of pipe.

 

From what I can tell they knew what they were doing when they installed it all since that heat tape is there. If they really didn't care, they would have just left it bare. The warranty is already expired since I'm the 2nd owner of the home and the warranty is only 5 years. I'm probably about a year or year and a half out of warranty.

I will just keep an eye on things on the next couple of below-freezing nights and see what the pipes feel like.

One other thing I thought was interesting was that when I looked at the blower compartment, there was a whole page of the installation manual sitting on top of the fins. It was folded in a couple of places, I honestly can't believe it didn't get sucked in a nook and be torn apart. The company that installed the unit is really something else. How could you not notice something like that when installing the unit?

 

You wouldn't believe the number of installation manuals, or parts thereof, I've found in blowers & elsewhere where they shouldn't have been. Most of the time it's obvious they've never been opened, let alone read.

 

Grady,

They must've had two manuals or something because they left two on top of the furnace and they are in immaculate condition, no pages missing or anything like that.

I'm really stumped as to why the issue was happening in the first place. The past couple of days were below freezing at night and the furnace is not having an issue at all in the mornings. This happened last year too, but seems to go away after a while. Not really sure what to think, but if it ain't broken, don't fix it!

 

Gremlins.....Grrrrr They seem to come & go. Sooner or later one will decide to stay. At that point, we can find & evict it.

 

Ok, so I came back here to update everyone on what seemed to fix this issue. I started experiencing it again this year when temps got to freezing at night. Again, this problem only happening in mornings around 5am-8am. If you want the short answer, skip all the way to the last two sentences at the bottom of this post.

The installers did not install the flue pipe properly. I found this out due to the inducer motor turning on and a large gurgling noise coming from the flue. Upon further inspection, I saw the flue pipe was drooping AWAY from the furnace when it should be slanted TOWARDS the furnace in order to properly drain. Being that I live in Oklahoma, there's lots of humidity in the air, and when things get hot or possibly when it would rain, the pipe was getting a lot of condensate in it. This explains why the problem only happens when it is cold out. The water is most likely getting very close to completely freezing in that pipe, thus creating a pressure issue.

I thought it was the pressure switch, so I even ordered one after I bypassed the current pressure switch and everything fired right up, but after 30 seconds to a minute it would still shut off. This indicated to me that the problem was elsewhere. I put my ear up to the flue pipe and I could just hear massive amounts of water in there. I then shut the unit off, reached over the furnace, and pushed upwards on the flue pipe so that it would push up further out of the roof. I found there was about 6 inches of play on the pipe where it can move up and down. Once it was pushed upwards, you could hear the massive amounts of water draining back down to the furnace unit and then you could hear it flush down the proper drain pipe which goes to a drain in my water heater closet.

Now you may ask... How did this happen? Well, the installers didn't install a pipe strap on the pipe, so there is nothing but the rubber boot on the roof keeping it in place. Idiots!

So in short, the rise over run was going in the wrong direction and clogging the flue up, thus creating a pressure issue in cold temps. I will fix this by buying a (probably $2) pipe strap. Amazing how simple this issue was.

 

Installing a high efficiency condensing furnace in an a cold attic is a bad ideas to start but all the more reason for a better installation. Obviously in your case.... that didn't happen.

Glad you finally got the issue resolved.

 

bclark, Thanks for stopping by & letting us know what you found. Maybe we'll remember this thread & be able to pass it along to someone else.

 

Grady and PJmax, thanks! Always have to give back on forums or else we don't learn from each other! Hoping this thread helps a couple people out in the future!