Shower Pump, Negative Head advice please!

[IUK]

Hi, I would appreciate any advice on this.

I need to install a shower pump for my open vent system, it's all in a flat so I am investigating negative head pumps (CWS and HW cylinder are in the airing cupboard, no loft!!). However, i was wondering if I could still use a 'normal' pump (non negative head). I understand that I can 'kick start' a normal pump by lowering the shower head, but what will happen when i raise the shower head back up and the pressure drops, will the pump stop pumping (as it reads it as a 'turn off' off the taps??) It seems lowering the shower head to waist height would be enough to get it going.


Thanks for any advice!

 

[Terrywookfit]

You can activate the pump by using a non contactive pull switch!!
(I think that is the correct description but could be wrong)!
Method of use is, Turn on water at the shower valve and then pull the cord which makes a temporary contact to activate pump!
Once running the pump will operate until water is turned off!!
Saves on expense of N H pump!!

 

[IUK]

Hi Terry,
Yes that's what i was thinking, but at the moment when i lift the shower head above my head, the water cuts out completely (as it goes negative...) and so would a pump interprete this as me 'turning off the taps' or would it carry on pumping until i actually turn off the taps/shower ??

 

[Terrywookfit]

Once the pump is running the flow switches will stay activated until the water flow is stopped by manually turning the valve off!!

The difference between a negative and positive head pump is mainly in the flow switch and also the price!!

 

[IUK]

Thanks Terry,
I also just phoned Flowtech and they confirmed that the pump would 'kick start' if i lower my shower head to waist height into 'positive head' territory and also continue running even if i lift the showerhead up into NH territory.. That's great! I've just ordered a QT45-2. Just updating this thread for the sake of anyone else going through the same thing.. It would seem you only need a Negative Head system if no part of your shower outlet is in 'posi' territory (such as a loft conversion with the tanks on the 1st floor).

 

[hi-spec plumbing heating]

anything above your cws is neg
anything below is pos.

easy terms

 

[hi-spec plumbing heating]

It would seem you only need a Negative Head system if no part of your shower outlet is in 'posi' territory

no .
you need a certain gravity l/pmin to operate a pos pump if this can't be obtained a neg pump is to be used.