Deafening noise from boiler

[rskaith]

Recently bought house 6 years old, with a Vokera Mynute 28SE gas boiler with rads with individual thermostats. Unless we have at least one radiator on full setting, there is a deafening noise (from the boiler itself, I think) soon after the heating comes on. (Not a problem with hot water only). This causes problems particularly at night in frosty weather when the CH is off, and the frostat kicks in. Any ideas what the problem might be?

 

[ChrisR]

What sort of noise?

 

[combiner]

You need to have at least one radiator without thermo valves. The valves to this rad must be open at all times, unable to be turned off. Currently, if all of your radiator thermo valves were to automatically close simultaneously, then the pumped central heating water has no where to go, hence the unusual noise.

 

[rskaith]

Chris, The noise is a sort of metallic grinding noise, a bit like the sound of pulling a very heavy iron lawn roller across gravel, and loud enough that the first time we heard it we thought it was an earthquake (till we remembered we were in England). It lasts about 5 seconds, and repeats itself perhaps every 30 seconds or so.

Thanks, combiner - I'll try this. I had thought that with one radiator on full in the house, when the froststat switched on the hot water would have had somewhere to go.