central heating head ache

[paulympauly]

can anyone help!!!
i have a two bed end terrace house with an open vented system with a cylinder in the 1st floor airing cupboard and the pump etc...
there are 3 rad's on this floor, 1xmain bedroom, 1xspare room and 1x bathroom... there are 4 rad's on the ground floor... 2x living room and 1x hall (entance hall) and 1x kitchen... all have trv's fitted which is unusal i think!! the problem is my radiators hiss and splutter and are boiling hot to touch... the hissing and spluttering only appears to stop once all l/s are open and trv's set fully open... i have tried closing one at a time and/ or opening one at a time to try and isolate which is the centre rad... or the order of heating up but its impossible to tell... the boiler water temperature knob is set below half way and as far as i know the thermostat for this sensor was changed 12mths ago... i have used an inhibitor and a flush was done not long back... i have bled the rad's on numerous occassions and they were fine... i currently have all l/s fully open and trv's on 4 just for some peace and quiet and even then it still splutters!!! please help

 

[jackthom]

Not really sure what to make of this. The noise could just be air trapped in the pipes.

I'd be a bit worried that the boiler thermostat might be faulty. Can you try turning the water temperature right down to make sure this is working? It may even help the noise problem.

 

[paulympauly]

hi jack, cheers for the reply... i have turned the thermostat down the temperature appears to have dropped slightly... im abit concerned because i was always under the impression that you needed one rad with no trv so to keep good flow and stop the pump working to hard etc...
my bolier is due a service from british gas, i have the homecare package so i think this might have to be the way forward... apart from this im stuck... any ideas greatly recieved... cheers again.

 

[apb1979]

It does seem that the boiler thermostat maybe getting the system too hot, the need for a bypass radiator is not always required dependent on the boiler/pipework in the airing cupboard (bypass valve), i think the best course of action is too describe the fault to the british gas engineer when they do the annual inspection as investigation maybe required.

 

[jackthom]

TRVs can be a bit noisy when they are just on the point of closing and water is rushing through a narrower opening in the valve.
You don't say what sort of boiler it is but with an older one you may get away with switching the pump to a lower speed setting, which will reduce circulation noise. (With modern condensing boilers the pump often needs to run flat out or they get upset.)

You are right that at least one of the radiators should have no TRV (Hall or Lounge?) both to act as a bypass and to enable the room thermostat to do its job.