Banging when zone valves close

[jonkem]

Hi, hoping someone can offer a solution!

I recently had to replace my circulating pump when the last one got very noisy (bearing noises). Since then I have very loud banging noises ( really loud!) from the CH pipes when the 2 port valves close when room stats tell them to.

I have turned the pump down to number one and noises are a little better but haven't gone completely. I have also dropped the system pressure to 1.5 bar. Am I right in assuming that the 2 port valves can easily cope with shutting and not cause the noise so it is probably over pumped?

I have watched the pressure gauge when the valves close and there is a slight fluctuation as the close, around 0.1bar flutter. The pump is identical make & size to the last one.

 

[scatmanjohn]

Is there a by pass and if so have you closed it when changing pump.

Was it a gate valve.

Could have snapped off inside and still be closed.

 

[Vic Spanner]

Check your bypass is open. Should be a valve on the pipework between pump and zone valves that goes back into the return.

 

[pannierstan]

Make sure the valve is the right way round! and while you are at it make sure that the pump is actually supposed to stay on when the valve shuts.
Some older boiler dont have pump overruns and bypasses.

If thats the case and the pumps still running then its either wired in wrong or you have a faulty(stuck) micro switch in one of the valve actuators.

Further more have you put the pump in the right way!

Stan

 

[jonkem]

There's a pressure relief bypass on the flow nearby the boiler, but this wasn't altered when pump was changed. This is normally set at 2.5bar. I tried turning it down to 1bar but it made no difference to the noise.

It is a big unvented system in an old & cold house with 170,000 condenser & 170L megaflow, 35mm (or was it 32?) primary pipework dropping to 22 & finally 15mm, 16 double rads. Zoned upstairs seperately from downstairs, both valves cause the noise.

 

[jonkem]

Make sure the valve is the right way round! and while you are at it make sure that the pump is actually supposed to stay on when the valve shuts.
Some older boiler dont have pump overruns and bypasses.

If thats the case and the pumps still running then its either wired in wrong or you have a faulty(stuck) micro switch in one of the valve actuators.

Further more have you put the pump in the right way!

Stan

Quite a bit to think about there Stan! Pump is fitted exactly as removed (I installed system 7 years ago) and yes there is overrun (Keston K170). Bypass fitted because 3 x 2 port valves could be closed at the same time so leaves a small loop for the boiler to keep circulating.

When the bypass was set at 2.5bar (before pump changed) there was no banging. The pressure increase at the point of the banging is only 0.1 - 0.2bar on the boilers pressure gauge and it is more of a flutter than a surge. There is no fluctuation on the gauge on the expansion vessel which is remote to the boiler.

 

[kevplumb]

what make are the zone valves ??

you might have a swollen ball (ooooohhh errrr missus)

 

[gas4you]

Are you sure pump is fitted the correct way round

 

[jonkem]

As several of you said about the direction of the pump & against my better judgement as it was an identical replacement, I just checked and guess what?

The direction arrows are the opposite way than the previous pump I guess I'll be getting the big Stilsons out tomorrow, firstly to rotate the pump and secondly to hit Grundfos over the head with them. Why on earth would they have assembled the pump differently? Is it normal for the motor body to be fitted in any direction they feel like fitting it? It's a big & expensive pump (32/80) so it should be right

Fingers crossed & thanks for all the help

 

[pannierstan]

The direction of the head against the body is erelevant. What you should have done was pay attention to the direction arrow which of course the instructions will tell you

However lesson learnt I guess. The head can be rotated to any position within the constraints of the 4 securing screws as this provides flexibility of installation regarding orientation.

 

[jonkem]

The direction of the head against the body is erelevant. What you should have done was pay attention to the direction arrow which of course the instructions will tell you

Of course, with hindsight, I shouldn't trust Grundfos to assemble 2 identical pumps identically but maybe some instructions instead of childrens cartoons might have reminded me to check the orientation of the pump and not assumed that it would have been built the same way.

As my installation has demonstrated the cartoon instructions aren't idiot proof

 

[kevplumb]

The direction of the head against the body is erelevant. What you should have done was pay attention to the direction arrow which of course the instructions will tell you

Of course, with hindsight, I shouldn't trust Grundfos to assemble 2 identical pumps identically but maybe some instructions instead of childrens cartoons might have reminded me to check the orientation of the pump and not assumed that it would have been built the same way.

As my installation has demonstrated the cartoon instructions aren't idiot proof

which is why you employ one of us (supposed )

clever gits

 

[jonkem]

As my installation has demonstrated the cartoon instructions aren't idiot proof

which is why you employ one of us (supposed )

clever gits

And the next time I've got some cartoons I'll be in touch

Of course the question needs to be asked....How come everyone thought about counter rotation? Could it be from personal experience? Perish the thought

 

[kevplumb]

na fella we read the books

far be it from any of us to ever drop a ******* we are above that

diff being marra we then have to sort it at our own expense

HARD LESSON