Water Hammer When Motorised Valve Closes

[Axel]

G'day folks,

I recently upped the speed on my Grundfoss 15-60 to setting 3 and the CH works like a dream now, even with it being a little noisier when the pump is running.

But now the problem is: If the CH is running and the 2 port valve to the DHW cylinder closes (when the cylinder stat is satisfied), the pump continues to run whilst the motorised valve feeding the cylinder closes, leading to a nasty thump sound, because of the pressure from the pump on the valve. Didn't do this with the pump on 2. If the CH is off then the pump switches off before the valve finishes closing and there is no thump, but often the CH is required whilst the DHW is heating.

Any clever solutions?

 

[Beerlover]

It sounds like a wring fault or the microswitch on the HW valve is stuck.

BTW is the valve fitted the right way round? there is an arrow showing direction on the brass bit.

 

[Axel]

Microswitch is ok - as I said, the pump switches off when the valve starts to close, but if the CH valve is open at the same time, the pump will not stop pumping when the DHW valve is closed because there is still a call for heat from the room stat keeping the microswitch in the CH valve closed circuit.

I will check the valve orientation.

Thanks.

 

[D_Hailsham]

I recently upped the speed on my Grundfoss 15-60 to setting 3 and the CH works like a dream now, even with it being a little noisier when the pump is running.

What were the symptoms which caused you to up the speed to 3?

 

[Axel]

The rads furthest from the boiler were taking a little long to warm up. There are 14 radiators in a large house being pumped by the 15-60, so it needs setting 3 really.

Also there has been an issue with air in the system, even after converting to a sealed system last years. Setting 3 has helped a bit.

Boiler kettles a bit; have put in 2 bottles of X200. Still a mystery with occasional sound of air in pump. I would have thought that 1.5 bar pressure would prevent air being sucked in, even with the pump running.

 

[D_Hailsham]

The rads furthest from the boiler were taking a little long to warm up. There are 14 radiators in a large house being pumped by the 15-60, so it needs setting 3 really.

14 rads is not that many; it all depends on how many kW they add up to.

Is there a bypass in the system?

Also there has been an issue with air in the system, even after converting to a sealed system last years.

Have all rads and the pump been bled (ground floor first) with the system off and the water cold?

Has the system been balanced?

 

[Axel]

Yes, yes and yes.

The bypass is an auto bypass valve that is set to just open when the pump overrun is operational but all 3 motorised valves are closed (2 CH zones). I don't want to open the bypass too much - a common cause of CH circulation issues.

The valve is probably the right way round - can't see an arrow - it's a drayton, but it's vertical with the writing on the front label the right way up! Flow is from bottom to top.

 

[D_Hailsham]

The valve is probably the right way round - can't see an arrow - it's a drayton, but it's vertical with the writing on the front label the right way up! Flow is from bottom to top.

The ports are labelled (A and B) on the brass body. Port A should be at the bottom.

 

[Axel]

A H A !!!

A is at the top.

First of all I must point out that it wasn't me that fitted it!

It was fitted by some geezer sent by my Bank accounts free household insurance. Should have just changed the old one myself considering how long I waited for the bloke to turn up! Only reason I used the policy was to get the part for free!!

Presumably the orientation as it should be is with the flow from A TO B, ie upwards?

I shall depressurise next week and do a quick reversal! Small splash no doubt!

The geezer probably went by the orientation of the paper label on the valve rather than the A & B markings.

Cheers mate, forum has done good service again, and without any b!tching ! (yet...)

 

[D_Hailsham]

A is at the top.

Presumably the orientation as it should be is with the flow from A TO B, ie upwards?

Correct.

A H A !!!

I though that was a new shorthand (like FFS) but couldn't work out what it stood for. Then the penny dropped - it was just Aha!