Under Pressure (indirect water heater fail)

evo2

Is it possible for an indirect water heater to fail so the domestic water pressure backs up into the boiler system and over pressurizes it?



I have a Buderus GB142 boiler with LT200 water tank and nothing is stopping the heating system from climbing to 30psi and blowing the relief valve.

I went so far as to shut off the water supply to the boiler (verified that it is shutting 100%), drained down the system and shut off the boiler for the night.

Woke up to the system at 30psi, the bucket under the relief valve overflowed and water all over the floor.



The only other access to street pressure is the hot water tank.

I shut off the water supply valve to the tank and the pressure stopped climbing.



Can the heat exchanger coils leak internally so that pressurized domestic water is entering the boiler system?



Thanks.

SpeyFitter

Yup

Sounds like you've got it figured out.  I've seen it once before on a BF White combi cor with a steel coil. I have yet to see it happen with a stainless coil but I guess it's only a matter of time.

Jamie Hall

Happens in steam

boilers too, and leads to an overfill condition.  In fact, it's one of the first things I think about when I see an overfill condition and there is a DHW coil in the boiler...

evo2

Buderus to Lochinvar ?

Thanks for the input, I figured it was the only possibility.



My heating guy confirmed the tank is leaking internally and Buderus will cover it 100%.

For some reason they (rep/supplier, not sure who) are offering to upgrade me to a Lochinvar as a replacement.



Never heard of them, any thoughts on this brand?

I must say I'm not happy the Buderus failed after 5 years.

I was thinking of the Stainless Superstor Ultra before this offer was brought to the table.