Garage Heater Vent Rusting Out

[Chadley]

Hey Guys noticed the garage heater exhaust vent looking a little rough/rust staining, poked with a screwdriver and went right through. Is it normal for these these things to eventually rust out? I assumed cat 3 stainless would last longer. This one is 8 years old.

Its a Reznor 45,000 BTU in a 24 x 24 garage. The flue pipe is pitched towards the outlet 1/4 in per foot for condensate drainage.

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[dewalt18]

No, that’s not typical on the “new” stainless z vent. In fact, side wall venting is now done in stainless because the old B vent material would rot out quickly. Is it typical of all the material in your system, or just the one fitting?

[Chadley]

The lower elbow has some pin holes starting can see in the pic same with the termination box. Upper elbow is in much better shape. Haven't had much luck with Reznor, first one's heat exchanger was rusting out after one winter so they replaced it to their credit.

At the time I thought it might have been from high humidity, the garage floor wasn't level when the builder poured the concrete leaving pools of water from snow melt. Put a drain in, fixed that and was good for the next 8 years When I get a new flue I'll go with a more aggressive pitch.

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[dewalt18]

You’re sloping to exterior of the building, correct?

Edit, just looked at the pictures 🤦*♂️

Brace yourself, 4” Z vent is pricey. Quoted an install today, and my venting material came out to $30 more than the cost of the unit.

[Chadley]

I remember it being $300 to $400 for the Z-vent back then when it was installed. I'm sure its going to suck pretty bad now. Anyone know the average lifespan of these Reznor heaters?

[dewalt18]

Indefinite as long as you’re willing to replace the occasional part. Flame sensor will
Likely go first, then a race between the igniter and the inducer motor. Baring the heat exchanger failing, they last decades longer than most people own a house these days.

[Big Grey Wolf]

The NOX gases produced when we burn natural gas, mix with moisture and produce nitric acid which then chews up galvenized/zinc pipe. Stainless much better long term piping but much more expensive.

[dewalt18]

Originally Posted by Big Grey Wolf

The NOX gases produced when we burn natural gas, mix with moisture and produce nitric acid which then chews up galvenized/zinc pipe. Stainless much better long term piping but much more expensive.

That is stainless steel pipe.

My guess is this. Either during install, or fabrication of the material, it may have come into contact with a non stainless tool, or abrasive that had been used on not stainless material, compromising the venting material

[Big Grey Wolf]

Our favorite companies in East manufacture many different grades of Stainless. Also save lots of $$$ when you manufacture with very thin gauge SS. Nitric acid will chew up 304 stainless but not touch 316 (high Molly) SS.

[Chadley]

Originally Posted by dewalt18

That is stainless steel pipe.

My guess is this. Either during install, or fabrication of the material, it may have come into contact with a non stainless tool, or abrasive that had been used on not stainless material, compromising the venting material

That's is interesting... A cut off wheel was used to shortened on of the 24 in pipe down a couple inches. The contractor who sold me the vents said z flex can be cut without issue didn't mention any special instructions on how to cut it

[dewalt18]

Originally Posted by Chadley

That's is interesting... A cut off wheel was used to shortened on of the 24 in pipe down a couple inches. The contractor who sold me the vents said z flex can be cut without issue didn't mention any special instructions on how to cut it

Cutting it should really only compromise the direct area around the cut. However, that said, your contractor was wrong, and you can’t cut or alter anything that has a ULC sticker on it. It has to be installed as was designed and tested.

[Chadley]

Curiosity got the better of me went digging a little further. Flue collection box/exhaust vent motor looked ok from the outside till they were removed and a pile of rust fell out of it. Heater is eating itself from the inside out it appears.

Who knows, maybe this thread might help someone for future reference.

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[Chadley]

Some advice to future garage heater owners bigger is not always better. Learned way more about garage heaters than I care to know but in hindsight I should have went with a smaller 30,000 btu for my 24 X 24 garage as per Reznor's sq ft. calculator.

Pretty certain the shortened cycle times were not getting the heater hot enough to deal with the condensate properly and over time just ate itself. Oh well live and learn don't be like me lol.

[dewalt18]

Moving forward, if you’re going to replace it, the Modine hot dawg is a much better unit that the Reznor.

[Dewey Cox]

Originally Posted by dewalt18

Moving forward, if you’re going to replace it, the Modine hot dawg is a much better unit that the Reznor.

Why do you say that?
Not disagreeing with you, I'm just curious about your reasons.

[CNP]

I did the install for my Mr Heater Big Maxx 50,000 BTU 6 years ago. The horizontal stainless vent is sloped towards the heater as per installation instructions. The vent pipe connection direction will determine if the slope must be towards the heater or the exterior. Pay attention on how the pipe goes together and the instructions must match that installation. My pipes look brand new after six years of use.

[dewalt18]

Originally Posted by Dewey Cox

Why do you say that?
Not disagreeing with you, I'm just curious about your reasons.

My primary reason is that typical residential size Reznors use a single orifice and a single flame into a single larger heat exchanger tube. Modine uses multiple orifices into a multi tube heat exchanger. Multiple smaller exchanger tubes equals higher surface area and better heat exchange. Also the Modine has a slightly smaller cabinet depth which is handy in lower ceiling garages.

All of my other reasons are based on ease of install.

[vinny]

Originally Posted by CNP

I did the install for my Mr Heater Big Maxx 50,000 BTU 6 years ago. The horizontal stainless vent is sloped towards the heater as per installation instructions. The vent pipe connection direction will determine if the slope must be towards the heater or the exterior. Pay attention on how the pipe goes together and the instructions must match that installation. My pipes look brand new after six years of use.

Exact same scenario here. Mine looks like the day I installed it. I have a condensate loop on mine. Probably around 7 years as well.