shower pump doesnt work when central heating on!

[a1]

I wonder, If like ours, your Clients Water Company has reduced the pressure on their mains supply?

The reason down here? ...

The Pipes are too old and will not keep up with the 'old' pressure that we used to have. :_|

 

[kme]

[quote name='Andy

 

[monkey5]

Sounds like a Plumbing job then, maybe water flow too low when Heating on to trigger flow switch in Pump.

my initial thought but i mentioned i would talk to a friend whos a plumber and he was quite insistant that it wasnt a plumbing problem - sounded to me like he had a plumber round who had blamed the wiring!

 

[Andy™]

Available commercially as a "negative head switch kit" for shower pumps.the flow switches are magnetic in nature - we`ve done a mod on one with an old type doorbell - induce a magnetic field around the flow pipe, and the pump`ll start

KME

ive used a pneumatic push button in shower - air line to a pneumatic switch, and connected to existing switch in pump

 

[ianmacd]

surely the water flow through the shower pump shouldn't be affected just because the heating is on?

Depends on a few things like if its a combi maybe it can't heat enough water fast enough with heating on too so flow isn't high enough to kick pump in but I would guess its a gravity fed system with a pump (otherwise why need a pump) so it could also be some funky wiring somewhere. Guess until you bet a voltmeter on the pump and check its still got power we cant really tell if its lack of power or lack of flow rate.

 

[kme]

Ian - you can`t put a shower pump on a combi - pressure`s too high. The ONLY reason for a seperate shower pump is bad flow rate - low pressure.

Unless the heating is of a very odd type, the flow (or not) of heating water has ZERO effect on the water pressure - it is either stored pressurised water (e.g. combi, system boiler, thermal store), or stored vented water (eg small header tank to loft). In neither case does the water circulating through the heating system have any connection whatsoever to the water that comes out of the taps.

KME

 

[kme]

Depends on a few things like if its a combi maybe it can't heat enough water fast enough with heating on too so flow isn't high enough to kick pump in.

Can I just clarify something here - Combi`s are fitted with a "diverter valve", which is the piece of kit which tells it if its heating CH or DHW. IF the heating is on, and you turn the tap on, the boiler stops throwing heat to the rads, the diverter moves across, and your mains pressure water is fed through the heat exchanger. The flow rate of a combi doesn`t drop because the heating is on - it "diverts" the heat away from the CH to supply hot water while its being demanded, then drops back to CH when the hot tap is turned off.

KME

 

[Apache]

In neither case does the water circulating through the heating system have any connection whatsoever to the water that comes out of the taps.

other than the filling loop

 

[kme]

Well, yes, but then again no.

The filling loop is the point where the water stops being potable, and becomes part of the CH fluid - its a transfer point (1 way), and, unless you manually opened the filling loop whilst drawing hot water, you wouldn`t get a reduction in pressure on the water from your taps

KME

 

[Apache]

you know I'm just being obstinate

(do we have a word of the day?)

 

[kme]

(do we have a word of the day?)

Yup, its on the "multiple RCD" thread - impervious

 

[ianmacd]

The pressure may not be too high on a cambi, depends on the pressure going in (although it should be over a threashold). It could be at the top of a huge hill in a flat on the 10th floor. Could need a pump then.

Also you described indirect heating but not direct where the DHW is headed directly.

There could be many reasons for this, I was just using an example. I can think of a few more too, although if its electrical then its probable someone has wired it into the wrong terminals in the multiway junction box thingie.

 

[septiclecky]

Sounds to me that they have connected the supply for the shower pump from a normally closed contact on the heating valve so that when the heating is off them shower pump will run but when the heating kicks in the supply to the shower pump is opened thus pump will not run.