Machine gun noise from boilermate

[samtheman1k]

Hi guys, can anyone explain this issue I have with our central heating system?

We had a Gledhill Boilermate mains pressure thermal store installed a while ago and there is a strange noise that I can't explain too well!

Sometimes, when I turn on the hot tap (opening it quickly), we get a very loud vibration throughout the pipes, boilermate and all the way to the expansion vessel. This noise is loud. It can only be explained by comparing it to a machine gun noise!!!

Strangely, if I immediately turn off the hot tap, wait a few seconds, turn it back on, there is no noise. Although sometimes, you can hearer it faintly, rising in tone until it completely disappears.

It is a bit unpredictable, as it only occurs when no hot water has been drawn for a while.

Any thoughts as I'm completely stumped?????

 

[BOB D.O.L.E]

water hammer on loose pipes not clipped properly get the floor boards up

 

[tonybhoy]

Probably a dodgy washer in a tap or a ballvalve either that or the boiler mate is over pressurised and the safety valve is discharging the pressure.

 

[doitall]

Expansion vessel pre-charge pressure too low.

 

[samtheman1k]

water hammer on loose pipes not clipped properly get the floor boards up

I'm pretty sure it's not water hammer as it's not consistent, but when it does happen, it happens when the tap is turned on, not off.

 

[samtheman1k]

Expansion vessel pre-charge pressure too low.

That's an interesting one, as the hot water expansion tank supplied from Gledhill was rated officially at 2.5bar, but they seemed to of lowered it somehow to 1.5bar (as recommended in the manual). I'm not sure how they did this or if it can even be done reliably!

Can you explain how this would cause this effect?

 

[samtheman1k]

Probably a dodgy washer in a tap or a ballvalve either that or the boiler mate is over pressurised and the safety valve is discharging the pressure.

I should say that it happens regardless of which hot tap is used. The Boilermate has a 1.5bar pressure reducer on the input, and our pressure is only just over a bar anyway, but could this still cause it?

 

[doitall]

Expansion vessel pre-charge pressure too low.

That's an interesting one, as the hot water expansion tank supplied from Gledhill was rated officially at 2.5bar, but they seemed to of lowered it somehow to 1.5bar (as recommended in the manual). I'm not sure how they did this or if it can even be done reliably!

Can you explain how this would cause this effect?

Take the system pressure off the vessel.

There's a valve on the vessel for checking the pre-charge pressure, get a pump and put it back to 2.5bar and the [problem will be gone.

fingers crossed

 

[mickyg]

Expansion vessel pre-charge pressure too low.

OR to high.. the expansion vessel charge should be matched to the dynamic pressure. Had this more times with charge to high then to low.