Boiling boiler

[Lazy Beetle]

Hello all,

I have a Halstead boiler that has been installed for approximately 10 months. I've not had any problems at all until tonight when the boiler started making strange noises.

After the boiler has been on for a few minutes there is a rattling sound heard on the landing. If you put you ear near to a radiator then the sound can be heard here also albeit slightly muted. I found the source of the sound to be at the boiler itself. There is a whistling sound and the noise a kettle makes coming to the boil, pops, cracks etc. I have a feeling that the boiler is literally boiling the water. This is strange for a number of reasons:-

1) Boiler only 10 months old 2) The system has been cleaned using Protex 3) The system has inhibitor in it, Protex again 4) Setting the thermostat lower on the boiler doesn't appear to make a difference, i.e. it eventually comes to the boil.

Does this sound like a faulty thermostat somewhere in the boiler? By the way the boiler is extremely hot to touch!

TIA

[BillR]

Are the rads getting hot? If not could be the pump has packed up. Surprised the boiler high limit thermostat hasn't cut in though.

[Christian McArdle]

This is usually due to poor flow through the boiler, although it could be a boiler thermostat issue (particularly on an older boiler with less sophisticated controls). Things that can prevent water getting through the boiler:

1. Sludge blocking pipes.
2. Broken pump.
3. Air locks in pipes.
4. Missing or badly designed bypass for the zoning and boiler interlock arrangements in use.

(1) is unlikely if the water is nice and clean.

(2) is easy to detect and fix

(3) bleed all radiators. check system design for high points in loops that don't have bleeding arrangements. if the boiler has an automatic bleed valve, leave it open for a week or so.

(4) describe the bypass arrangements and the zone valving. the bypass will consist of either:

a. An automatic bypass valve between flow and return (preferred).

b. A gate valve between flow and return (may clog up, or be turned off by curious experimenters).

c. A Honeywell Y plan system (3 port zone valve) with at least one radiator that may not be turned off and has no TRVs. Frequently a TRV (thermostatic radiator valve) or handwheel valve is added to the radiator, making the radiator no longer suitable as a bypass.

d. A radiator (usually in bathroom) that may not be turned off connected between unzoned flow and return. Again, the fitting of a TRV or handwheel valve makes it unsuitable.

e. Entirely omitted. (v.bad).

Christian.