Hey all,

I moved into this house a couple of years ago, and have been fighting the furnace ever since. I have been told by a reputable source that the person who installed it was 'a moron'. So take that into consideration.

I think I'm now starting to get ahead of the problems, but when cleaning it recently I noticed something concerning on the far side of the furnace. You can see in the picture below that some of the foil tape has gotten rather toasty brown:
https://drive.google.com/file/d/0B9h...ew?usp=sharing
In addition, most of the seal had been lost, and I was pushing a decent amount of air into the attic.

The outlet of the furnace is a bit restricted, even before it goes into the AC:
https://drive.google.com/file/d/0B9h...ew?usp=sharing
And, for orientation:
https://drive.google.com/file/d/0B9h...ew?usp=sharing

Should I be concerned? I'm currently running it on single stage mode and it works well enough to keep our place warm. I've kept both heat exchangers relatively clean, at least after the initial discovery of all the dust that had built up.

Any opinions are welcome. I'm going to let it spin up and update with a temperature for that one location.

 

Update:

Using a little non-contact thermometer, the side of the furnace gets to a maximum of 250-300F, centered right around where the dark brown burn mark is. It fades from there to an ambient 65F or so near the corners. So it is pretty hot... Although I'm not sure that's hot enough to be a concern.

Is there something that needs to be done about this, or am I just making something out of nothing?

Thanks again for any opinions.

 

I'd be concerned if I were you.

Whether there is a problem or not I can't say. You might have a serious problem.


You probably need a GOOD repairman to sort out what may be wrong. They can be hard to find.


>


Well, that's probably good enough to limp along during the rest of the heating season. But I'd have this checked out before fall.

And I'd be at the repairman's elbow when he checking out the furnace, asking questions until the repairman satisfies himself and you that any problems are identified and corrected.

The problem is, when some goof horses around with a furnace, ANYTHING can happen. That can be a lot worse than almost any part going bad.

And when someone goofs up with a furnace, the defect put into the system may not be something that can be found with the usual diagnostic methods.


I once found a limit switch in a furnace someone had wired up. Usually, if the furnace overheats, the limit switch shuts off the furnace and the fan runs to cool off the overheated furnace.

The Bozo who worked on the furnace wired the limit switch so that it SHUT OFF THE FAN, while leaving the burners running! When I got there, the sides of the furnace were glowing a dull orange...

 

DIY is one of the VERY few sites that hosts members pictures. Most sites you are required to host them elsewhere and post links. To that end.... there is a picture size restriction in place to keep the pictures from #1 taking over the thread and #2 keeping file storage manageable.
Here's a link that details picture posting. http://www.doityourself.com/forum/el...-pictures.html

I'd be extremely concerned about that. As SP mentioned..... it could be a "customer fixed" high limit switch.

 

PJ:

Thank you for the heads up. My images were 1024x768, which I thought would be ok. It just gave me a generic "Invalid file" error. Thanks for pointing me to that post.

SP and PJ:

I checked the limit switches, and they seem to operate fine. Nothing is near glowing dull orange (thankfully... that's a terrifying story!), and the rest of the system operates at a perfectly normal temperature. It's just that one spot where a bit of... 'creative' duct work was done, almost assuredly by the goof who installed it.

Luckily, temperatures have skyrocketed here, and are likely to remain that way for the summer. I'll take you all's advice and get a real pro to look at it.

Thanks again!

 

The blanked off part of the furnace shouldn't be blanked off - that's the problem.

The high limit switch which prevents overheating is at the front so an airflow restriction at the back won't cause it to trip.

Call someone to correct the installation errors, check the gas pressure and temperature rise, inspect the heat exchanger for damage.

The back of the heat exchanger will get damaged like that even on low fire. This furnace can not be locked on low, just set to run on a timer.

It has a single speed draft inducer as well which messes up the fuel-air ratio on low - ignore the 95% rating.

 

Muggle,

Yeah, I had feared that a bit. It looks like a hack job by someone who realized that the existing duct was an inch short as it was being installed.

I'll get it fixed up sometime soon (while it is still nice out, I figure that's when most A/C and heat techs have time). I did look at the heat exchanger, and didn't see explicit signs of damage. I'm hoping that it's just an airflow issue.

Thanks again all for you help.