Discuss Is Pumped water into a Combi Boiler recommended? in the Plumbing Jobs | The Job-board area at PlumbersForums.net

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mtotowamungu

Hi I am new to the forum , yes with a problem. Hope some one can enlighten me Thanks
Situation:
New Vaillant Ecotec 837 plus installed in the loft is supplied by mains water feed (old house limited pressure),
Cold water from the loft tank is pumped a to thermostatic Hans Grohe shower through 2 bar pressure regulator. The pump ia a 3 Bar Positive head twin Monsoon situated on bath room floor in airing cupboard where old cylinder lived.
All cold taps and toilets also fed via the same pump except kitchen which is mains fed as ususal.

Problem.
Shower in bathroom starts of with a normal stong flow, as warm water reaches thermostat, the flow reduces to a drip, on lowering shower head the water pump startsup and shower resumes normal function. But only sometimes cuts off during the shower.
Two solutions have been proposed but not everybody agrees with them and there is no certainty either will solve the problem.

1. To use a single 3.5 bar negative head water pump instead of the positive head pump to feed the cold water to the shower again regulated to 2 bar to match mains pressure.
or
2. To use a single 3.5 bar negative head water pump to feed the boiler from the cold water tank and to T off the cold water supply before it gets into the boiler . i.e. share the pump for Both the boiler and cold water .
This is expected to provide the most balanced supply.

Some say we cannot or should not pump water into a combi boiler !

I would have used the mains water for cold supply , but the pressure is likely to be insufficient to meet needs of 2 bathroom and the rest of the house.
A jpeg water diagram is also attached.

Will be grateful for any comment or guidance. thanks
:)
 

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I would contact stuart turner pumps for advice but your problem may well be the pressure reducing valve in the outlet.

As the pressure downstream of the prv increases the diaphragm slowly closes the valve, then, as the downstream pressure decreases the diaphragm opens the valve. This isn't a problem when used on a mains supply but on a pumped supply with a flow switch as the prv shuts the flow switch will shut off the pump. The thermostatic shower will then sense the lack of cold water and go into a failsafe shutdown. Lowering the shower head will start the cold water flowing again and rerstart the cycle.

Removal of the prv may resolve the problem but I would suggest that a booster pump would be a better solution than a shower pump. These rely on a pressure switch in the outlet pipework rather than a flow switch and keep the outlet pipework at a constant pressure at all times.

I would either go for a booster pump in place of the existing unit or you could opt for a whole house booster set to give you good pressure and flow throughout the property.

Have a look at

[DLMURL="http://www.ukplumbersforums.co.uk/redirector.php?url=http%3A%2F%2Fwww.grundfos.co.uk%2Fweb%2FhomeUK.nsf%2FWebopslag%2F2DA7E2448C4137C9C1256C7C002C7ED2"]Grundfos United Kingdom[/DLMURL]

and choose water pressure boosting. The two units to look at are the Grundfos home booster and the MQ.

Mike
 
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Thank you Mike . The 2 options were suggested by Stuart Turner, but not fully approved by my installer, he has some doubts.

The booster is a new option I have not been aware of . I liked the look of the MQ but the website had limited information on it . The Home server is too large to accommodate in my home. I will contact the manufacturer for more info.

I welcome your idea and will explore it further . Thanks again
 
Dear Mike
Thank you again - I have the information - I will discuss this with my installer and post progress.

I just wanted to be clear about one thing , The MQ is capable of boosting supply to the whole home Right?. and is compatible with using on the boiler.
regards
 
According to the literature it will supply up to 1l/s, that's 60l/min so should be fine for a whole house application. I'd give them a call anyway to make sure and they may have a better solution for you.

No problem with pumped water to combi.

If you go this route make sure you have sufficient storage capacity to cope with the demand.

Mike
 
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