Noisy auto-bypass (rushing noise)

[ironsidebod]

Hi,

I've posted before about a similar problem. When we moved in the boiler was kettling a lot. Turns out the radiators were not balanced properly and closed down too much. We have TRVs fitted where appropriate and a honeywell autobypass.

The boiler is a Baxi Solo2 PF60 with the output set at 3.5, pump speed is two. Everything runs fine, it's really quiet and the house heats up nicely. There are 16 radiators and 5 have no TRV.

However, when the MV closes there is a very loud whoosing noise of water - not sure if it's acutally water noise or boiler kettling or both. It makes this noise regardless of what setting the auto-bypass is set to (currently .25).

I can post a pic of the pump/valve set-up if required. Any ideas as you can hear it all over the house?

Thanks

 

[Agile]

It sounds as if the auto bypass may not be fitted in the correct place?

Photo showing all the pipework?

Tony

 

[ironsidebod]

Here you go:

Bypass is labelled F. The MV is below the wiring centre (G) after the take off for the bypass. AB is fitted where the old manual valve was installed.

 

[45yearsagasman]

Pipe configuration is OK. It maybe that the auto bypass is restricted or not set correctly to match the system. Have a check with a magnet around area marked A and B to see if there is any magnetic attraction. This may help:- View media item 55283

 

[ironsidebod]

Thanks. I'm happy to replace the bypass with a different make if you're aware of one with a larger internal bore, it's quite small on the honeywell?

I calculated around .3 as the correct bypass setting but in reality the current set-up is the least noisey and the boiler cycles as you'd expect, if I open the valve completely whilst the boiler is running and then stop the thermostat calling for heat the noise is virtually the same.

I've checked with a magnet and there is a small amount of attraction around the H but that was removed and checked around 18months ago and it was only a light black film no clumps. Worth doing again?

Cheers again

 

[ChrisR]

I'd be suspicious that it's the Motorised Valve rather than the Auto Bypass Valve that the noise is coming from. (Honeywells are quieter (MVs) sometimes.)
Are you sure it's the ABV? (Stick of wood, ear on one end, valve the other...)

While the system's running, MV open, (so ABV should be shut) does it start making the noise if you crank the ABV to a low setting so the ABV opens?

[Edited to spell it out!]

 

[joe-90]

Are you sure you aren't listening to the pump? It's pretty close by.

 

[ironsidebod]

it's not the pump. You can hear the noise by the boiler which is downstairs, you can hear it really loudly in the living room. The pump makes very little noise on speed 2 and only a small hum on 3. Definately not that lol


It doesn't do it with the system running normally, when the thermostat stops calling for heat the boiler shuts down and the valve closes, at this point we get the loud noise, which persists for 20-30 seconds so I was thinking it was heat related originally. After this time the rest of the overrun period is virtually silent i.e. you wouldn't know the pump was running.

With it running and TS calling for heat there is no noise regardless of the ABV setting. It's almost as if the bypass circuit is too small, so could it be the ABV internal bore is too small? Boiler output too high? Once balanced the system was working fine on the old manual valve, no noise when the MV closed.

Confused!

 

[ChrisR]

Did you understand what I wrote above?? 2 questions you haven't answered...

 

[Agile]

Are you saying the ABV was only recently fitted and the noise started just then?

Only a very small flow is needed through the ABV because its close to the boiler and just enabling the boiler to control itself.

I dont see enough pipework to convince myself its correctly piped. Where does the lower end connect to?

Tony

 

[ironsidebod]

Did you understand what I wrote above?? 2 questions you haven't answered...

Yes. You can feel it in the piping, it's so loud you can pinpoint it. However, to answer your question specifically using a piece of wood on the pipe below the ABV you can hear loud rushing water when the MV shuts, placing it on the ABV itself you can hear the higher pitched noises that constitutes most of the rushing noise.

To answer the other part of your question. No, opening the ABV from closed whilst the system is running does not cause any of the noise to occur.

Thanks for you help.

 

[ironsidebod]

Are you saying the ABV was only recently fitted and the noise started just then?

Only a very small flow is needed through the ABV because its close to the boiler and just enabling the boiler to control itself.

I dont see enough pipework to convince myself its correctly piped. Where does the lower end connect to?

Tony

The TRVs and ABV were fitted a while ago (not had chance to look at it properly until now just been putting up with the noise) but without TRVs and the old manual bypass there was no noise once the radiators were balanced.

The pipe from the ABV goes under the floor, I have to suppose it goes to the return as it was ok without TRVs.

The system is all original from when the house was built, this is the only change.

I checked the header tank whilst the heating was running earlier and the water was warm (not hot) should it be? How much water should there be in the tank?

Thanks again.

 

[ChrisR]

I've just remembered one abv which did have to be set very high because it was making a racket! That was a Hwell DU 145 ( doesn't look like yours). It did it forever on overrun not just 20-30 seconds.

If you turn the abv to max and maybe the pump down to 1 it shoudn't open at all, which may prove the point.

 

[gaswizzard]

Had to change the last two I fitted due to a 'rattle' , these were also the straight type as opposed to the angled , maybe a bad batch.

Same noise with some of the gate type pump valves , try to do the right thing and crack em back a little but they rattle so end up turning the gates fully open to eliminate the noise.

 

[ironsidebod]

Thanks both, I've had a little success by cranking the valve higher than it should be and tweaking a few of the radiators but your comments are interesting as it's a honeywell DU144.

Any suggestions on what make/model to swap it for?

cheers