Radiators Hissing

Discussion in 'Plumbing and Central Heating' started by simoney, 11 Aug 2008.

  1. simoney


    11 Aug 2008
    Thanks Received:
    United Kingdom
    Could any-one give advice on what to do with hissing radiators.

    I have a Worcester 24i junior boiler and radiators all with thermostatic valves. Once the heating system is up and running a hissing sound can be heard from 1 radiator. Sometimes it's quite loud other times not very.

    The noise comes from the thermostatic valve. If I adjust the valve by turning it up or down the noise stops, but then another radiator somewhere else will start hissing.

    As I go around the house I find myself adjusting most of the valves when one hisses.

    Also should this type of boiler be very noisy when it's on and just supplying the radiators? An engineer said it was a very good boiler but when I asked if the noise was normal he said it was just the fan and that all boilers are different. I have never come across a boiler as noisy as mine just whilst supplying the radiators.

    Any tips or ideas greatly welcome
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  3. Gasguru


    9 Sep 2005
    Thanks Received:
    United Kingdom
    Is this the non-ccondensing version?

    You should not have TRV's on all the radiators...one should be fitted with 2 lockshield valves (where the room stat is located..if fitted :rolleyes: )....this will allow a minimum flow at all times.

    On the Band D version, Worcester at one time were permitting the pump speed to be turned down (that will reduce flow noise)...it leaves the factory at maximum (speed 3). I have left small systems with the pump on speed 1 with no effect. However when I last enquired, Worcester were saying not to downspeed the pump.

    Because the heating ramps up to maximum rate (the burner output can't be matched to system size) there is a possibility of overheating when dropping the pump speed. The pump is also used to dissapate heat after a hot water draw-off so again possibilty of overheat.

    Try the pump on speed 2 but you may need to install an automatic bypass valve between the flow and return connections under the boiler.

    These boilers normally run quiet...if you have TRVs on all the radiators there will be insufficient flow through the heat exchanger. In addition a heat exchanger that has suffered from debris in the system may "kettle" and these boilers are more suceptable due to the fact the output can't be matched to the system.
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