Boiler/Megaflo pipework vibration - sounds like a helicopter

[Yanntoe]

This has probably been done before but .........

Pressurized System, Vaillant Condensing Gas boiler, around 4 years old, Megaflo, system has 12 Rads 2 of which are towel rails. All with TRVs except one towel rail.

When boiler starts there is a loud persistent noise, sounds like someone hammer drilling in the boiler room. Persists until system gets up to temperature and then subsides. Doesn't always do it.

If I open all the lock valves and TRV's it seems to stop, if I open the TRV on the rad closest to the boiler it stops. However, at "start up" it may occur again.

The pipework on the front of the Megaflo is vibrating and causing the noise.
If I manually slide either of the 2 motorised valves to the left, the noise stops.
If I turn up or turn down the pump the noise changes/may stop, may re-occur.

There are 2 automatic air bleed valves on the Megaflo, one of which leaks water due to the vibration.

Have bled the radiators many many times. Usually OK, i.e. no significant air present.

Have drained system. worse after draining.

Got everything settled down last week, but now its vibrating again.

Any ideas as to what might be causing this and what I might do to stop it - it's very disturbing!

Had two plumbers (one of whom is a heating engineer) look at it but as it happens somewhat randomly, I can't get the noise to occur when they are there. They have no suggestions.

Any help, much appreciated.

Many thanks

Y

 

[dcawkwell]

There will be 2 port valves in the system. Latch these opening using the little lever at the side. See if the noise goes away.

 

[sooey]

He's already said it does, sounds like an auto bypass valve needs fitting, or adjusting whatever the case may be.

 

[dcawkwell]

No circulation going on. Make sure the bypass radiator valves are fully open. Or possibly one of the 2 port valves maybe the hot water tank isn't opening.

 

[Yanntoe]

He's already said it does, sounds like an auto bypass valve needs fitting, or adjusting whatever the case may be.

Thanks Sooey,

Can anyone point me in the direction of an auto bypass valve? Where does it go in the system?

I'll have a chat with my plumber in the next few days, but it sounds like I might need a (different) heating engineer.

And yes, there are two valves (about 3inches by 2 inches) in square housings on the front of the megaflo. they have leavers on the top which can be locked off to the left side. If I push one of these leavers to the left the noise stops but re-occurs if I let them go.

Cheers

Y

 

[sooey]

As DC said are the rad valves on the towel warmer with no TRV fully open?

 

[Yanntoe]

As DC said are the rad valves on the towel warmer with no TRV fully open?

Yes, the towel rail valve is fully open ...... unless someone has closed it recently. I thought I'd sorted it last week, but now there's a problem again.

I'll check to see if the valves still fully open.

Thanks

Y

 

[sooey]

That's both valves, not just one.

 

[Agile]

Can you see if there are direction arrows on the motor valves and see if they are installed with the arrow pointing in the direction of the flow.

Have you had the boiler properly serviced regularly?

Tony

 

[Yanntoe]

Can you see if there are direction arrows on the motor valves and see if they are installed with the arrow pointing in the direction of the flow.

Have you had the boiler properly serviced regularly?

Tony

Thanks Tony,

Boiler serviced regularly, last time Oct 2013. Both valves have the arrows pointing in the right direction, as far as I can tell.

Sooey,
The Towel Rail has an oddly angled, "thin" lock shield valve at one end and an ordinary manual valve at the other end. It's dual fuel, if that makes a difference. Certainly the adjustable valve was fully open, but I haven't worked out how to check the other end - I'll explore.

Thanks everyone - I'm already wiser than I was this morning and will experiment for a few days now. I did think that by creatively adjusting all the flow and return valves around 10 days ago I'd sorted it, but it seems to re-occur just when one thinks its all sorted. I'll check everything again, ensure the valves are correctly set and wait with baited breath.

Cheers

Y

 

[Agile]

Have you found the auto bypass valve yet?

Tony

 

[Yanntoe]

Have you found the auto bypass valve yet?

Tony

Hi Tony,

Not quite sure what I'm looking for - any clues?

Thanks

Y

 

[sooey]

Post a pic of your cylinder cupboard pipework.

 

[Yanntoe]

Post a pic of your cylinder cupboard pipework.

Great - can't do that until Friday evening/Saturday morning - but I'll do so then.

Cheers

Y

 

[steveoelliott]

Great - can't do that until Friday evening/Saturday morning - but I'll do so then.

Cheers

Y

Did you solve this? I have very similar as per: https://forum.buildhub.org.uk/topic...ot-tap-opened-first-time-after-heating-cycle/ and https://www.plumberstalk.net/threads/megaflo-uvc-very-loud-noise-when-hot-tap-opened.133709/