Rattling noise from central heating pump

Graeme1978uk

So the pump rattling noise did disappear, thanks for all the replies. A couple of weeks down the line though I now have this issue. When one of the heating zones calls for heat from the boiler, we now get this horrendous noise coming from the expansion vessel? Please see video below…..

https://1drv.ms/v/s!AiPZy0hMa6CQgagEXm6064A0mRR4nA

Any ideas from the helpful knowledgeable heating people!?

Bendy_House

Graeme1978uk said:

So the pump rattling noise did disappear, thanks for all the replies. A couple of weeks down the line though I now have this issue. When one of the heating zones calls for heat from the boiler, we now get this horrendous noise coming from the expansion vessel? Please see video below…..

https://1drv.ms/v/s!AiPZy0hMa6CQgagEXm6064A0mRR4nA

Any ideas from the helpful knowledgeable heating people!?

Good news about the pump noise - what did you do to make it go away? Anything?!

That new sound is a weird one. It happens when a CH zone opens? And not when you run a hot tap?

Do you have an unvented hot cylinder? That's a large EV - is it for the hot cylinder or for the boiler 'system'?

Graeme1978uk

Yeah we have an unvented cylinder. The EV is part of the heating system to the best of my knowledge. 

No noise when a hot tap is opened, just when the heating kicks in.

Bendy_House

With that EV set at only 1 bar, I'd agree that it's part of the boiler/heating system and not to pressurise the hot cylinder.

What appears to happen is that, when a zone valve opens to provide rad heating, the pressure drops suddenly, and then that hiss starts up as the pressure goes back up?

Could you post a wider photo to show the whole tank, EV and pipework? It looks as tho' the EV is plumber to the 'return' side of the pump, so what often does happen is that the pressure at that point will drop as soon as the pump fires up - 'cos the water is being 'sucked' from that end.

Q - did you change the pump setting? Or is it still on manual and its fastest setting of '3'? If so, that issue will certainly be expressed at its max...

And you haven't answered - did you do anything to make the original sound go away, or was it happenstance?!

You have a Smart pump there, so it ain't smart to have it on manual. That pump is/should be able to adjust to suit changing demand. Eg, if one zone is open, or two, or half the TRVs shut off, or all open, or...

And, on 'variable' speed, I imagine the pump will fire up slowly over a few seconds until it meets and matches demand, so this could also remove that shock your system is seemingly experiencing at the moment and could well sort your hissssss too.

coffeehound

Bendy_House said:

Could you post a wider photo to show the whole tank, EV and pipework? It looks as tho' the EV is plumber to the 'return' side of the pump, so what often does happen is that the pressure at that point will drop as soon as the pump fires up - 'cos the water is being 'sucked' from that end. 

Have a look at page 1, Bendy, there's a wider pic.  As you say it looks to be connected at the suction side of the pump.  The original problem seemed to be caused by some restriction in the system as though there wasn't enough provision of bypass for he pump when TRVs or zone valves were shut.  I wonder if this is also a symptom of the same restriction, causing the suction to be built up until the zone valve opens to allow water to circulate..

coffeehound

Are zone valves meant to be wired so the pump doesn't get power until and unless there is at least one ZV open? . .

Bendy_House

coffeehound said:

Bendy_House said:

Could you post a wider photo to show the whole tank, EV and pipework? It looks as tho' the EV is plumber to the 'return' side of the pump, so what often does happen is that the pressure at that point will drop as soon as the pump fires up - 'cos the water is being 'sucked' from that end. 

Have a look at page 1, Bendy, there's a wider pic.  As you say it looks to be connected at the suction side of the pump.  The original problem seemed to be caused by some restriction in the system as though there wasn't enough provision of bypass for he pump when TRVs or zone valves were shut.  I wonder if this is also a symptom of the same restriction, causing the suction to be built up until the zone valve opens to allow water to circulate..

The pic isn't very clear, tho', as it doesn't show the EV and the cylinder in the same pic. But, it looks as tho' it's the same pipe from the EV that goes to the underside of the pump.

Bendy_House

coffeehound said:

Are zone valves meant to be wired so the pump doesn't get power until and unless there is at least one ZV open? . .

Yes.

Neither the pump nor the boiler should come on until the zone valve is fully open and trips the wee microswitch inside it to send the switching signal onwards to the P&B.

And you highlight a very good point - if some twit has wired up the system so that the (wall thermostat) signal operates the zone valve AND the pump/boiler at the same time, that could well cause some aggro. Especially if that bludy pump is STILL on manual and max speed.

Graeme, this is easy to check. You stare at the cylinder/pump/EV malarkey whilst shouting at someone to turn up a wall 'stat. When that person confirms, "Done!", a zone valve should make an audible whirrrr for around 2 seconds, followed by a 'click'. Only THEN should the pump and boiler fire up.

Graeme1978uk

Thanks for all your replies, even though some of it as a bit over my head

I’ve attached a photo of the entire setup to clarify what’s piped to where.

I can confirm that I did adjust the pump settings as recommended earlier in the thread.

Bendy_House

Cool.

Could you also please try the "You stare at the cylinder/pump/EV malarkey whilst shouting at someone to turn up a wall 'stat (that's currently off, as should the DHW). When that person confirms, "Done!", a zone valve should make an audible whirrrr for around 2 seconds, followed by a 'click'. Only THEN should the pump and boiler fire up" test to see if Coffee is on to something?

You are comparing the action of a zone valve with the behaviour of the pump. You start with the three zone valves closed (off) and the pump not running, and you want to see if the valve FIRST goes whirrrr-click BEFORE the pump starts up. Or does the pump start up instantly, as soon as the valve begins to whirrrr.