Diagnosis? Corrosion on Tankless Coil on Boiler

rjobrien

I've been increasingly concerned about the corrosion build-up on the tankless coil plate installed on my natural-gas fired steam boiler. This week I noticed I could see the fire box through the jacket around the seam of the indirect and some combustion gasses were escaping. (After shutting down the boiler,) I removed the jacket to examine the patterns of corrosion. Any ideas about the issue I'm looking at? Is this as simple as a failed sealant, or do I have a complete appliance failure?

Jamie Hall

I believe that what you are looking at is a tankless coil, not an indirect water heater.

Whatever -- that's pretty crusty. My own feeling would be that that boiler is toast...

BDR529

I'll take a stab at it.. 3-78 Weil-Mclain with failed fire rope causing corrosion at tankless from flue gases.

Don't think I would put a dime into it. Time to start getting quotes.

clammy

Looks like the clean out plates where never properly sealed either after a cleaning or when the block was assembled . If the coil gaskets are not leaking you may be able to get it sealed w either rope or just some furnace cement . Being it’s set upas a gas fired unit was this oil at one time and converted or was it a straight up gas install with the gas gun , if so then the clean out plates where not sealed properly when assembled and installed , that being said because most gas guy would never pull the plates and brush the section being it’s gas fire . Just a observation . Ps that clean out plate is a pain to seal being the tankless coil plate slightly blocks access to get it cement good Peace and good luck clammy

rjobrien

@Jamie Hall -- You're right, it's a tankless coil. Thanks for the correction; I just edited original post. @BDR529 -- Damn good guess: it's a 3-80 Weil-Mclain. @clammy -- Spot on. The boiler is 11 years old (2009); it was oil fired originally for about 3 years, then converted to gas. You're probably right that it wasn't sealed right when the conversion happened. I haven't had it cleaned since the conversion to gas. I sent some photos to the plumber who installed it and did the conversion (he's not available to work on it now), and he replied that it needs a new gasket and sealant. Hopefully the boiler can be salvaged and we're just looking at aesthetic damage. The steam heat and hot water systems are running fine right now.

BDR529

Fantastic! Sounds like you dodged a bullet