Heat exchanger split after 4 years, misadjusted burner the cause?

fprintf

We've just been notified by our furnace repair company (who is also our oil dealer) that our heat exchanger in our 17 year old Heil forced warm air furnace needs replacement. We replaced the heat exchanger, at our cost, 4 years ago since there was only a 10 year warranty on the original at the time.



The furnace has been fine all season long. No fumes in the house, nothing. Somehow, however, that changed when they came to do the annual furnace cleaning. After the service person left the furnace stopped working some hours later. 3 service calls later, waking up at 3 a.m. to a house full of oily smelly fumes, a number of additional cleanings and adjustments of the nozzles, we find out that the heat exchanger has split along the seam where it is bolted together.



Is it possible that a poorly adjusted furnace can overheat or otherwise cause the exchanger to split? We are perplexed that our heat exchanger should break after only 4 years, and suspicious that a poor servicing has damaged our property.



Thanks in advance,

fprintf

earl burnermann

Air flow

A major cause of heat exchanger failure is the air flow from the heat exchanger to the conditioned space. Too much airflow cools the heat exchanger too much and could cause condensation and rotting from rust. Not enough air flow causes the heat exchanger to overheat and crack.



A sign that this is the problem is a short cycling burner. The heat exchanger gets so hot that the limit control turns off the burner but the fan continues to deliver heat. Then the burner comes back on and continues this on/off cycling until the thermostat is satisfied. The high temp limit is there to protect your unit from overheating due to some failure to your unit. It isn't there to operate continually as part of normal operation.

billtwocase

Heat exchanger

Heil furnace says it all. I would switch to Thermopride.

icesailor

Fool me once:

Fool me once, shame on it(my carelessness for not being thorough). Fool me twice, MY disgrace. Fool me three times, I'm incompetent.

If I serviced it once THOROUGHLY, and it went out again. it's time for the serious look.

I keep my old Bacharach Wet Kit ready at all times for the big 6" X 8" draft meter that I can see from across the room while my digital analyzer is on.

What was the draft pressure +/- before the burner started. Did it change when the furnace blower came on? Was it steady while the burner and blower were running together? Did the pressure on the draft gauge drop when the burner stopped and the fan kept running?



Was it tried "over the fire" in the draft port to check the over fire draft?

If it was within specs at first, and now is out to lunch, it sounds like the HX plugged up and the fan couldn't keep it cool with proper airflow.

It probably hasn't been properly cleaned for years. May be time for a new service company and a new one. Or, Gas.

earl burnermann

Other side of heat exchanger

Before replacing the furnace with any brand of furnace or fuel I would make sure the ductwork was properly sized, all vents open, and a clean filter always in the air path. Installing new equipment that will have high external static pressure and a temperature rise higher or lower than the appliance is rated for is just going to lead to another hx failure as in the past.

fprintf

Wish the repair company was as reputable as you all

I really wish the repair guys seemed like actual technicians. There were no flow meters or CO detectors or anything. What a bunch of yahoos, and I'm gonna be on the hook for a new furnace. And because it is 17 years old, they're recommending a new AC coil and exterior unit too. Merry Christmas this is, a $7500 job and of course it is all a rush because it is supposed to be 9 deg. F here on Christmas eve.



One competitor we got in said it was the size of my ducts that did it. Another guy said it was that I have a bonus room on its own zone. And another said it was likely just because Heil is a piece of crap.



The local favorite furnace seems to be Williamson. We're not planning on staying here for more than a few more years, so we're not going to spring for the Thermopride.



Thanks again for all the help. It seems I can't really blame the original installer or the service technician.

earl burnermann

blame

Would fall first on the designer if the ducts are undersized. Next would be the tech that commissioned the unit and did not test or not care what the external static pressure or heat rise was. Last is the service tech that checks it each year. Oil companies don't usually go into checking ESP and the system's temperature rise.

icesailor

Someone knows:

+++One competitor we got in said it was the size of my ducts that did it. Another guy said it was that I have a bonus room on its own zone. And another said it was likely just because Heil is a piece of crap. ++++



He's the one that knows what's probably up. The addition is on it's own zone damper. A "zoned" system. If the system is 100,000 BTU's and you added 20,000 BTU's, the original furnace could probably handle the additional load because it was still less than 100,000 BTU's. But, if the old, main zone is off and the new 20,000 is running, there won't be enough air flow through the HX to keep it from overheating. That's what they make by-passes from the supply and return for.

Heil's may or may not be a piece of crap, but don't blame the Heil Appliance for failing on a bad installation. It was probably oversized from the old furnace when it could have been undersized.

jimwest

Heil furnaces

We are on our 2nd heat exchanger in our Heil 120,000 BTU natural gas furnace.  First one by warranty, now another outside of warranty.



Solution ?? Switching to York this week.  

fprintf

Replaced the heat exchanger

The warranty covered the heat exchanger, so we paid the labor for 4 hours to replace it. We know full well that the design of our system is sub-par, and now that we think about it everything started failing when we installed a wood burning fireplace insert downstairs, so it is likely that static pressure is killing the heat exchanger.



So when this one goes or if the AC goes, we'll replace the whole unit and get a new AC and have them add in some pressure balancers or whatever they call them, and plus possibly a multi-speed unit for when we only need to heat the bonus room or the upstairs.



Thanks again to all for the advice.

icesailor

Passing Bye:

Did they install a by-pass circuit so that if and when the small zone is on and the main zone is off, the excess static pressure has a place to go? Back to the return? 

There's probably a proper name for them but I once saw a job where a house had two zone dampers and the installer put a "Dump Damper" on the outlet so that if the static pressure went too high when the smallest zone was running, it would open up and dump excessive hot pressurized  air into the cellar.