DIY Doctor

Grundfos pump problems ?

Postby toplondonchef » Thu Jun 09, 2011 10:11 am

Hi all..
Posting this on behalf of my parents and any help/advice would be, as ever, appreciated;

Parents moved in to a block of flats approx 5 years ago and had their flat ripped apart, rewired, plumbed, kitchen, bathroom, building works, etc
Used local companies to carry out the works and most of them had been used before and also by friends and family. Very happy with the works carried out and no other problems during past 5 years

The flat has no boiler, heating is via electric rads, electric shower, hot water via emmersion heater which runs on economy 7 Juice overnight, cold fill washing machine. The only demand for hot water is from kitchen sink and bathroom basin and with just the 2 of them, hot water demand is not massive
Emmersion tank fitted in boiler cupboard with cold water tank on shelf at ceiling height

Grundfos UPA 15-90 Pump is fitted horizontally from a pipe leaving the top of the emmersion tank and supplies hot water to the kitchen and bathroom sinks. There is no splitter valve as pump is only connected to these 2 items

Ongoing problem is when bathroom hot tap is turned on, pump always switches on and provides good flow of hot water. Kitchen tap only activates pump 50 / 50, so my mum then turns bathroom tap on as well, pump kicks in, turns bathroom tap off and pump now continues to run with kitchen tap. Without pump running hot water is just a trickle. Cold water pressure is good

My mum has written to Grundfos many times over the years and Grundfos have actually changed the pump twice and provided fitted via a nominated fitter with no charge, even though both times the pump was out of warrenty

Pump has also been changed by the original fitter who felt that the pump was faulty - so that's 3 pumps in 5 years and still stuck with the same problem

Grundfos have this time refused to change pump or provide any service saying it's unlikely a pump issue, more likely to be with the instillation. They have made a token gesture and sent a new flow switch free of charge and suggest that if a plumber fits this it may improve the situation

I'm not a plumber and wont be carrying out any work on the system myself, just trying to get some impartial advice to help solve the problem
On the previous 3 pumps fitted, the installation was never mentioned to be a problem so how can it be the cause now

I have spoken to Grundfos and carried out a flow test on hot water with pump switched off and measured minimum of 1 pt in 15 seconds from both taps. Grundfos say this rate as enough to trigger pump, although a little on the low side

So what could be causing the problem with the intermittent pump ?
Sorry for the long post but wanted to include plenty of detail for you guys and girls to work on !!
Many thanks
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Simply Build It

Postby stoneyboy » Sat Jun 11, 2011 9:38 pm

It just has to be that the pressure switch is not sensitive enough - you could try fitting a stand alone flow switch or try replacing the pump with a different make - I'd recommend a ST Monsoon because I know this works in a similar situation.
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