thermostatic valve/ shower pump problem

[jimmy73]

i recently fitted a crosswater shower valve, the hot is fed via a suuey flange and a 1.5bar single impeller pump situated inthe airing cupboard. The cold is fed from its dedicated small tank through a 1 bar single impeller tank situated in the loft. this was the existing arrangement before i fitted the new bathroom. The shower wont maintain pressue with the hot pump kicking in and out and the shower going hot and cold. After advice from crosswater i've removed the check valves in the valve, these were supposidly conflicting with the ones in the valve, I've also change the cartridge. But the problem still exists. Not sure if its a valve problem of a supply problem. Scratching my head.

 

[WHPES]

Sounds like pressure and supply problems. I would take a tapping from the DHW header tank in the loft and fit a twin impeller pump instead to feed the shower.

Shouldn't ever touch the check valves!

 

[REDSAW]

unequall preasure.

 

[Puddle]

could be hot water to hot,causing thermostatic valve to close,try reducing temp on cylinder thermostat or could be motorised valve letting by when heating only on,raising hot water temp to high
could also be faulty flow switch on hot pump

 

[WHPES]

If you bypass both pumps and work the mixer on gravity supply, does it still fluctuate?