house pressurised water pump turns on and off all the time.

davgtrek · 13-01-2014 4:40pm #1

Hi all.
last year we had this issue when our hot water pump kept flicking on and off when in use and the plumber changed the capacitor/board in the pump which was "fried" according to plumber. These past few months its doing it again.

When having a shower for eg. the pump and pressure will be high for about 10seconds then drop as pump flicks off for 5 seconds before flicking back on again. It does this all the time when taps being ran.

Any ideas what may be causing this. There are no visible leaks anywhere and generally water system fine apart from this.

Its a grundfoss 4bar pump which is 6 years old......

Thanks

rightjob! · 13-01-2014 4:59pm

might be the pressure switch,faulty non return either aswel
what model is it?

davgtrek · 13-01-2014 6:07pm

Hi rightjob.
Don't know which model pump but I know its a Grundfoss 4bar. It looks like this one
http://www.pjmatthews.ie/grundfos-mq345-4-bar-single-impeller-pump/pjmbpmq4pd.html

faulty non-return could be the problem alright.

Irish Steve · 13-01-2014 8:00pm

Is there a pressure vessel on the system, if there is, the diaphragm may have split, which will mean it's not storing water as it should, so the pump will short cycle a lot more.

Dtp1979 · 13-01-2014 9:48pm

Have a look at the filters on the inlet of the pump. Probably partially blocked up

MOTM · 13-01-2014 10:00pm

davgtrek wrote: »

Hi rightjob.
Don't know which model pump but I know its a Grundfoss 4bar. It looks like this one
http://www.pjmatthews.ie/grundfos-mq345-4-bar-single-impeller-pump/pjmbpmq4pd.html

faulty non-return could be the problem alright.

I've the same pump, similar problem. Off for 3 seconds, on for ten seconds ad nauseum. I looked into it before. I think it was the flow sensor. The grundfos website has good troubleshooting guides to diagnose and repair.

I haven't repaired mine...just going to wait till it collapses and replace it.

alfa beta · 13-01-2014 10:03pm

had this prob recently - Irish Steve's solution above sorted it for me

davgtrek · 14-01-2014 2:04pm

brilliant feedback lads thanks.
@alpha & Irishp is that pressure vessel an expensive thing ?

@motm good to hear its not just mine. I wouldnt be running to buy a new grundfoss again after this.

alfa beta · 14-01-2014 3:26pm

i can't imagine it being too expensive - it's only looks like a sort of smallish tank

(in our case the plumber owed me a favour and just got it sorted - so i'm afraid i've no idea about potential costs really)

sorry can't be of more help - perhaps Irishsteve knows better.

Irish Steve · 15-01-2014 2:07am

Tried to reply earlier, then the system fell over.

Last Pressure Vessel I got was a commercial one, 100 Ltr, and was just under €200. On E-bay, they are between £20 and £200, there will be a € factor, which will increase it, and it will depend on where you have to go to get it, and how urgently you need it, if that's what it is.

If it's the normal domestic size that's about 15 litres, then I guess you will get it for well under €80, but I've not had to get one recently.

Hope that helps

davgtrek · 15-01-2014 5:20pm

thats great thanks irishsteve. yea its a normal domestic one alright.
hope to get it sorted this month.

p

house pressurised water pump turns on and off all the time.

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