Buderus G124 II boiling sound occurring starting at 160 degrees

mikemenard

I've had this boiler for 9 years. The kettling sound started 3 winters ago. Would like to run it around 200 degrees to get satisfactory heat on the coldest days, but too much kettling noisy to accept allowing it to operate at that temperature. Lowered the boiler temp setting to 180, it's much quieter but still kettles enough to notice, especially when nearing 170 to 180 degrees. 20 lbs water pressure on gage which appears to worked correctly. Rapidly drained 2 gallons water from boiler into bucket to check for contaminates. All I saw were some rust specs. I'm on town water which is super clean and near nuetral ph. Took out burner to inspect burner compartment. Found dusting of rust specs which I take as normal, but also vacuumed up clay I believe dropped from between the boiler casting and outside insulation. Is clay droppings normal? Don' think the system has mineral build up mainly because town water quality is near ideal and I don't have mineral built up on any plumbing fixtures within the house. Air pressure in bottle is 15, checked when system pressure was relieved. Boiler heats one floor with 3 zones. Maybe the boiler is oversized, but the kettling still happens when servicing all 3 zones at once.

I'm leaning towards believing the boiler casting is the issue. Any thoughts what else to chec that could be causing kettling? It didn't do this when it was new.

Thank you in advance
Mike Menard
Dartmouth Ma

unclejohn

Do you baseboard or cast iron rads? That sound is normally associated with low flow through boiler. Is pump running? any valves turned.

mikemenard

I have baseboard radiators. Each of the 3 zones has its own circulator pump. The pumps do function drawing water back into bottom of boiler. Pumps are three speed. Two smaller rooms are set to medium, largest room set to high. Unsure what you're asking when you say "any valves turned".

Jamie Hall

Has the water side of the boiler ever been descaled? Even if the town water is very clean, it is still possible for scale to build up, and a localized buildup could cause that noise.

mikemenard

No descaling has been done to the boiler or system. If it adds anything, the 2 gallons I drained out of the boiler to inspect was very clean. I don't think the system has any leaks. Hot water is separate heater.

Jamie Hall

I only mention it because a small area of scale in the heat exchanger can cause a local hot spot which will boil and make boiling noises quite cheerfully. The fact that the water is clean is nice -- but hardly indicative.

I might add that that localized hot spot (or hot spots) also stress the metal of the heat exchanger, and can lead to leaks over time...

mikemenard

Assuming the kettling is caused by mineral buildup. Is there a product and procedure someone can attest to for use on a homes gas boiler?

Ironman

Fernox boiler cleaner.

mikemenard

Ironman, is it your opinion I should go ahead and perform the Fernox cleaning to eliminate the boiling sound?

Ironman

No, it's my opinion you should have done it when it started 3 years ago.

mikemenard

The radiators and piping are 1960's vintage. The boiler is 9 years old. If I have this correct from Fernox site 1 - Add F3 or F5 circulate for 1 hour or up to a week for bad scaling. Drain and flush until water tests within 10% of tap water. Add Fernox protector F1 with final water. Anything in particular to watch out for?

mikemenard

Finally got around to adding the Fernox cleaner to my boiler and the horrid kettling noise disappeared the same day. What a difference. I then flushed system and added the protector. Hopefully the kettling will never return. My boiler couldn't sound better! Thanks for the Fernox recommendation.