Rusting RayPak Digital / Atmospheric / RP2100 Heater

[jpcallan]

This post was intended as continuation of "Rusting / Rot in Base of Raypak Heater" from June of 2018, but the blog system automatically created a new thread. See: Rusting / Rot in Base of RayPak Heater

I'm am working on a base rust problem on a RayPak Atmospheric R336. One thing I noticed is the base is made up of two pieces of sheet metal - an upper one and a lower stamping. Both can die due to clumsy accidents, like spilling a bottle of liquid chemical that runs under the heater and rusts from the outside in, or a partially blocked flue from the inside due to condensate formation.



Another problem I'm am sure you have is rusted flame spreaders. See attached. These are sheets of 16 gauge aluminized steel sheet metal that lay across the heat exchanger fins. When they rust they fall to pieces, blocking the free passage of exhaust gases and tend to cause condensate to drip into the firebox. Later the crumbling flame spreaders block the passage through the heat exchanger so much the flame starts to come out under the front and blow the flame-rollout fuse. In the photo attached I vacuumed up all the rust chips before I realized I should have taken a "before" photo. These flame spreaders were about $250 as replacement parts - I had a local sheet metal shop fabricate new ones from 20 gauge 304 stainless steel for under $60 and these new ones will never rust.

 

[ajw22]

Welcome to TFP.

Thanks for sharing what may be helpful to others. I hope you check in regularly and can share your expertise with folks here.

 

[jseyfert3]

I had a local sheet metal shop fabricate new ones from 20 gauge 304 stainless steel for under $60 and these new ones will never rust.

Seems doubtful. Stainless looses much of its corrosion resistance at high temps. My stainless Weber flame guards rust, albiet much slower than steel would. Car mufflers and exhaust piping is made from stainless, and also rusts over time.

Im any case, that's a lot cheaper and it should last for a good amount of time at least, so it's probably better than stock.

 

[jpcallan]

While I haven't inserted a pyrometer into the pool heater's exhaust stream, the temperature the baffles confront isn't all that high. Remember these baffles are located above the copper fins of the heat exchanger, which itself is far above the flames. Their purpose is to slow and prolong the passage of the hot exhaust gases to keep them in contact with the heat exchanger fins longer and thus cooling the exhaust gases.

l did first try to source stainless alloy 321, a refractory alloy, which is rare and super expensive to bring in from out of town in a full 4' x 8' sheet. Next I tried to source alloy 316, but had not much better luck, again due to lack of local availability of less than a full sheet.

Hesitating about using alloy 304 (classic 18-8) stainless, my main guy at the sheet metal fabricator asked me if I had a stainless steel barbecue, which I do have; it's a really nice Front Gate/DCS model I am very proud of. The sheet metal company makes (among other things) range hoods and counters for restaurants and institutional kitchens. He asked how corroded the insides of the gas barbecue was, to which I replied it was not at all corroded. He then pointed out that since the baffles were down stream of the heat exchanger, they were unlikely to get as hot as the inside components of the DCS barbecue. His last point was at $60 for the finished 304 parts versus nearly $500 for a sheet of 321, the cost of being wrong was really pretty low. And I wouldn't have to store the remaining 29 square feet of unused 321!

Another point is the RayPak Professional ASME versions of the Atmospheric heater line (models R268A and R408A) are made with stainless steel flame spreader baffles, so I don't feel I'm taking much of a stride into the unknown.

 

[jseyfert3]

Oh, I was thinking they were right above the flames. Yeah they should last just about forever above the heat exchanger.

My stainless steel Weber grates don't rust, only the burner guards, which are right above the flames.

 

[PMellin]

Thanks for your post. I like your ideas. Looks like you're doing some pretty nice work. We haven't used the heater much since we found the problem. We plan on just replacing the whole thing when we can.