DIY Doctor UK DIY Forums

This dwelling is a chalet bungalow with the hot water tank on the ground floor. The hot water system has an in line Grudfoss Booster pump Type UPA 15-90. I have built an en-suite toilet and hand basin going off one of the upstairs bedrooms but the flow at the hot tap is just a dribble. After checking the spec for the pump I am coming to the conclusion that it is not man enough to push the water up to the en-suite. ( approx. 5/6 meters) Would a normal central heating pump do the trick? I am at a loss now on how to solve this problem, is there anyone out there who can help?
Regards
Peter

The 15-90 is a booster pump. It only adds between 0.5 and 0.75 bar to the pressure in the circuit and works the same way as a shower pump. Tghat is to say it has a flow switch that detects flow and turns the pump on.

A CH pump doesn't work that way - it works when the room or cylinder stat calls for heat. A CH pump would be useless for you.

Suggest a shower pump is needed.

Cheers

Thanks for your reply. My idea was to also install a pressure switch which would supply power to the pump when the pressure fell i.e. when a tap was opened thereby boosting the flow to the upstairs en-suite. Much the same way as a donkey pump works on a factory sprinkler system. From an engineering point of view I cannot see why this should not work. What do you think?
Peter

[quote="gotabelt"]Thanks for your reply. My idea was to also install a pressure switch which would supply power to the pump when the pressure fell i.e. when a tap was opened thereby boosting the flow to the upstairs en-suite. Much the same way as a donkey pump works on a factory sprinkler system. From an engineering point of view I cannot see why this should not work. What do you think?
Peter[/quote]

No its a flow switch you want not a pressure switch. Use a shower pump!

Firstly, the problem with fitting a pump as you suggest is it may result in "hunting" where the pump is constantly switching on and off regardless of demand.

Does the pump kick in at all when the tap is turned on or is the flow just abysmal?

The problem may be caused by having high pressure taps fitted or you have a negative head system.

Check out the Screwfix site for Salamander pumps particularly the schematics for possible pipework designs.

OK I bent to your superior knowkedge and have installed a shower pump. I now have a similar situation as someone else on this site. I still do not have any hot water upstairs unless I go downstairs and turn on one of ther hot taps to initiate the pump. Once the pump is running plent of hot water upstairs until you turn off the tap and then ziltch. Would a check valve in the line to the upstars tap help? If so where would it best sited? I would hazzad a gues as close to the pump as possible. Thanks for your patients.
Peter

You are not supposed to fit a check valve in a pump circuit. The instructions should say this, and it won't rectify the problem you have.

The reason the pump won't switch on is because you maybe have a negative head. This is where the ensuite outlet height is too close to the water level height in the header tank and as the pump needs a flow of water to activate, it doesn't sense the request for water so won't start. That's why it works when you open the tap downstairs.

I did suggest you check the Salamander instructions for pipework designs to help avoid this situation, but it is possible you have fitted a pump that won't do the job you want.

Can you confirm a negative head?

The hot water tap upstairs is on the same level at the cold water tank which supplys the hot water tank. The pump is situated downstairs next to the hot warer tank and takes it supply from the usual hot water feed. My theory with the check valve was that once the hot water line is primed the valve would keep the line filled and when the pressure dropped by opening the tap the pump would start.

W K R

Peter

"I did suggest you check the Salamander instructions for pipework designs to help avoid this situation, but it is possible you have fitted a pump that won't do the job you want."

Very good point. As per the other thread - is it piped correctly?

Cheers

The problem is, the pump is not triggered by a fall in pressure but by a flow of water so fitting a check valve will make no difference to your problem. Either raise the header tank so water naturally flows or change/ convert the pump to a pressure (negative head) operated one.

Hi Plumbob.
Your are right of course. The pump is fed from the hot water take off from the hot tank. I cannot see how raising the header tank would help, I cannot do this anyway as there is insufficent room. What I need to do is to initiate the pump prio to opening the en-suite tap. I can do this by energising a relay via the en-siute light. By opening the supply to the flow switch via the relay n/c contacts and then via the n/o contacts which will close when the relay is energised I can supply the pump by by passing the flow switch. This raises another problem in as much that the pump would run when the light is always switched on which may cause the pump to stall. If I fit a PRV between the incoming and outgoung ports of the pump I should be able to set it so that it opens in the event of a near stall. It all sound very complicated but I have almost finished the control side but would value your opnion.

I think you are in the process of invalidating the warranty of the pump you have fitted.

You'd be much better off looking at a negative head scenario as Bob has suggested IMHO.

Cheers

I see where you are coming from, and there is one bit of good news. You don't need to worry about the pump from stalling. It won't. The pump will run quite happily with no water flowing.

Where you will run in to a problem though is if the light is inadvertently left on and the pump is left running for a long period. These pumps are only rated for intermittent use. Something like 20mins in an hour and a half.

You know though, I can't help feeling you are going from London to Birmingham via Aberdeen here! Most pump manufacturers recognise this problem and supply a negative head attachment that converts the pump from flow to pressure activation.

Hi plumbob.
I have finished this installation and it is working well. Your point about the pump running when water is not being drawn off is a valid one but nobody spends more than about ten minutes in the upstairs en-suite. Sadly another problem has arisen which I cannot understand. After closing a tap the pump is "hunting" (switching on & off once per second or so.) The only way I can stop it is turn of the power and then switch it back on. Any ideas? I have been told that there could be air getting into the system, if so I cannot see how. I have also been told that there could be a leak but of course that would be self evident.
Regards
Peter

"After closing a tap the pump is "hunting" (switching on & off once per second or so.) The only way I can stop it is turn of the power and then switch it back on. Any ideas? I have been told that there could be air getting into the system, if so I cannot see how. I have also been told that there could be a leak but of course that would be self evident."

First there could be air getting in and I come back to the question I have now asked twice - how is it piped? You could well be sucking air in via the open vent. How it is piped is a very crucial issue here.

Second it could be that the flow switches are set at too sensitive a level. There'll be instructions in the MIs on how to adjust.

I still have a feeling you can easily sort this problem by either piping it orrectly or using a negative head installation without all the complications you seem hell bent on installing.

Cheers