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Thread: Noisy Radiators

  1. #1
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    Post Noisy Radiators

    Hi All,

    Does anyone have any knowledge of what might be causing noisy radiators - it's a gurgling / rushing water sound? It's only started happening since I fitted some TRV's (HR92's), before then the radiators never made any noise.

    Any help appreciated.

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    Quote Originally Posted by rugbyscottie View Post
    Hi All,

    Does anyone have any knowledge of what might be causing noisy radiators - it's a gurgling / rushing water sound? It's only started happening since I fitted some TRV's (HR92's), before then the radiators never made any noise.

    Any help appreciated.
    So you had no TRV's on the radiators at all before ? They were just full on ?

    If so, it's normal to hear a gentle hiss when a TRV is restricting the flow - there will be particular openings that will give the most hiss, just like a tap.

    If there is also a gurgle or a lot of noise it could be either pump speed too high or air in the system. Have you bled the radiators recently ? A crackling/gurgling noise that comes and goes in a radiator could also be a sign of kettling in the boilers heat exchanger generating small steam bubbles.

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    We always have gurgles, no matter how much I bleed the rads. I think some (vented) systems just naturally suck a bit of air in from the vent pipe.

    Pain in the bum!

    P.

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    Quote Originally Posted by paulockenden View Post
    We always have gurgles, no matter how much I bleed the rads. I think some (vented) systems just naturally suck a bit of air in from the vent pipe.

    Pain in the bum!

    P.
    Yep, we have an old vented system too and sometimes get gurgles. I haven't been able to track down the cause, or even determine whether it is "fixable" within the limitations of the old vented system.

    There is no air at all in the system - I've checked the radiators regularly recently and there is not the slightest bit of air to be bled. Most of the time the radiators are quiet with just a gentle "hiss" from a TRV that is partially closed to maintain temperature equilibrium...

    But sometimes when the system is warmed up and a radiator is scheduled to come on there will be quite a bit of gurgling and noise from that radiator for the first minute or so. Also I sometimes get a bit of intermittent crackle/rushing noise if there is only one or two radiators active, but only after they have been on for quite a while.

    I suspect that part of the cause is a little bit of micro boiling in the boiler heat exchanger due to lime-scale build up - I've treated the system for lime-scale and that did help a lot, also if I keep the flow temperature no higher than 70 it is generally quiet most of the time.

    If I try to set it to 75 or 80 it will be noisy a lot more frequently, especially if only one or two radiators are open as the flow temperature tends to overshoot a lot more when there is a larger flow through the ABV. I have a retrofitted digital flow temperature controller that helped a lot as it is much more accurate and faster acting than the original flow thermostat which is of the old fashioned diaphragm and gas filled tube type.... but because the cast iron heat exchanger has so much thermal mass and the boiler is a non-modulating type, (full flame burn or nothing...) significant overshoot is still inevitable.
    Last edited by DBMandrake; 12th February 2016 at 11:10 AM.

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    The radiators had manual trv's previously. Radiators have been bled and there was no air in them. The boiler is a condensing boiler and was fitted new in Sept 14.

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    Quote Originally Posted by rugbyscottie View Post
    The radiators had manual trv's previously. Radiators have been bled and there was no air in them. The boiler is a condensing boiler and was fitted new in Sept 14.
    Did you previously have a bypass radiator with no TRV fitted to it, and if so do you still have no TRV on it or did you fit an HR92 to what used to be a bypass radiator ?

    Do you have an automatic bypass valve installed on the pipe work near the boiler ?

    Has the system been drained down or de-pressurised at all when the HR92's were fitted, or did you simply replace the TRV heads without touching any plumbing ?

    Can't really think of any reason why replacing one kind of TRV with another (and presumably keeping the valve base itself) would make any difference to radiator gurgle. It's going to be something else in the system.

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    I have similar sounds from some rads since they had HR92s fitted. Mostly it seems to happen at night when only our bedroom has a higher set point that causes calls for heat. Doesn't go away with bleeding.

    After consulting a plumber, I added a can of Fernox F2 via the filling loop and things have improved a lot.

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    Quote Originally Posted by aspender View Post
    I have similar sounds from some rads since they had HR92s fitted. Mostly it seems to happen at night when only our bedroom has a higher set point that causes calls for heat. Doesn't go away with bleeding.

    After consulting a plumber, I added a can of Fernox F2 via the filling loop and things have improved a lot.
    Fernox F2 is a lime scale remover, so if it helped quieten down your system then your noise was probably due to lime scale build up in the boiler heat exchanger causing kettling which generates small steam bubbles. These bubbles can travel noisily around the system.

    I used Sentinel X200 which does much the same thing, and it did help a lot but didn't completely cure the noises.

    If it only happens when one radiator is running it's possible that you have an automatic bypass valve whose differential pressure is set a bit too low - with only one radiator running most of the hot water output of the boiler will go straight back into the boiler heat exchanger again via the ABV without the 10-15 degree temperature drop that you would get if it only travelled through the radiator and back, losing heat along the way.

    So for a given flow output temperature the average temperature in the heat exchanger is higher, this would make it more prone to kettling if there is any lime scale buildup. I found through trial and error that my system is a lot quieter if I set the ABV differential relatively high - about 0.5 bars. Although it increases the flow rate through the radiators when only one or two are open and thus produces a little bit more "hiss", the tendency to kettle is reduced by the higher pressure and it gurgles far less often than it did when it was set to 0.2 to 0.3 bars.

    Another thing I found helped a LOT was installing a pump overrun timer, which my ancient vented system did not have. The BDR91 cycles on and off frequently when there is only a small demand (every 10 minutes by default) and I found that if the pump keeps stopping at the same time the boiler is switched off the heat soak from the heat exchanger with no water flow generates a lot more steam bubbles, that then travel noisily around the system when the pump is started again. Every time the pump stops more bubbles are generated so after a while it gets very noisy.

    If the pump is on the output side of the head exchanger (which I think is most common) when the pump starts up again it will cause a momentary drop in pressure inside the heat exchanger, this can cause steam bubbles to be produced as well. (If the water temperature is on the verge of producing steam bubbles, a sudden pressure drop will cause the steam bubbles to manifest) Preventing the pump from unnecessarily stopping and starting in every 10 minute cycle avoids this.

    I have the overrun timer set to 12 minutes which is slightly longer than the 10 minute cycle time of the relay, thus when the BDR91 is cycling the boiler on and off the pump runs continuously, only when it turns the relay off for at least 12 minutes (no heat demand at all) will the pump stop. This dramatically reduced the noises in my system.

    A combination of increasing the ABV differential a bit, a dose of lime scale remover, and adding the pump overrun timer have got me from the point of having a very noisy, cranky sounding system to one that runs quietly and smoothly the vast majority of the time.
    Last edited by DBMandrake; 12th February 2016 at 12:59 PM.

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    Quote Originally Posted by DBMandrake View Post
    If it only happens when one radiator is running it's possible that you have an automatic bypass valve whose differential pressure is set a bit too low - with only one radiator running most of the hot water output of the boiler will go straight back into the boiler heat exchanger again via the ABV without the 10-15 degree temperature drop that you would get if it only travelled through the radiator and back, losing heat along the way.

    So for a given flow output temperature the average temperature in the heat exchanger is higher, this would make it more prone to kettling if there is any lime scale buildup. I found through trial and error that my system is a lot quieter if I set the ABV differential relatively high - about 0.5 bars. Although it increases the flow rate through the radiators when only one or two are open and thus produces a little bit more "hiss", the tendency to kettle is reduced by the higher pressure and it gurgles far less often than it did when it was set to 0.2 to 0.3 bars.
    We do indeed have an ABV as all the rads now have HR92s. The ABV was fitted when the boiler started tripping (due to overheating) and subsequently tuned to stop the trips happening. Therefore I am hesitant to play around with it much more and am happy with the current level of noise. If things change then I'll look again. Thanks for the advice!

    Quote Originally Posted by DBMandrake View Post
    Another thing I found helped a LOT was installing a pump overrun timer, which my ancient vented system did not have. The BDR91 cycles on and off frequently when there is only a small demand (every 10 minutes by default) and I found that if the pump keeps stopping at the same time the boiler is switched off the heat soak from the heat exchanger with no water flow generates a lot more steam bubbles, that then travel noisily around the system when the pump is started again.
    My boiler is a Potterton Netaheat Profile 50 and I believe it has a pump over-run thermostat built in

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    Hopefully not hijacking the thread, but I have a similar problem which I was going to start a thread about but it seems to be close enough to this one to just post in this thread.

    I replaced all but two (a decorative panel radiator in the dining room and a small radiator in the downstairs toilet) of my manual TRV's with HR92s and everything was fine. I then ordered another HR92 and fitted it to the panel radiator in the dining room (which previously had a manual Honeywell TRV) and the valve is whistling so much it's almost constantly turned off. The valve did not whistle with the manual TRV so there's something about the HR92 that's upsetting the system.

    The only difference between this one TRV and the rest in the house is that this one appears to be a European model (i.e. the display is upside down) but apart from that I believe there is no physical difference (it responds to the controller absolutely fine).

    The one remaining radiator with no TRV's at all is the closest one to the boiler (which is in the garage next to the downstairs toilet) and that is always left fully open as I was of the understanding one radiator should be used for the bypass and it seemed logical to use the one closest to the boiler (and the one frankly which is most appreciated when left on full )

    Any idea's folks? I've tried balancing the rad by opening/closing the valve on the opposite side of the radiator but it made no difference. Would replacing the actual valve make any difference?

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