Pulsing shower pump

[Sellma]

Hi All
I'm a plumber and this has stumped me so i'm open to suggestions.

We have a shower pump that pulses for a second when the hot tap downstairs is opened.

The only common factor between the hot tap and shower pump is the hot tank. Works perfectly when the shower is used.


The shower pump details:
Positive head (reed switches) pump fitted at the base of the tank
Hot connected to dedicated secondary circuit on the hot tank
Cold connected to a dedicated connection to the cold tank
Feeds a single thermostatic shower.
Wickes shower pump

Anyone have any ideas how opening the hot tap can trigger the pump?

Many thanks

 

[vicvapour]

Are the connections plumbed the right way round?

Are all the valves open?

Check the filters aren't blocked and contain no debris,and you've checked the pump is operating in the corret mode (pos not neg) ((if that option is on your pump)).

 

[Sellma]

It is a replacement pump, the old one didn't do this. It may have something to do with the sensitivity of the flow sensors, but i can not see how.

It is the correct way round and the filters are new.

 

[Jordon]

Movement above can cause the switches to turn on fit a non return to the outlets close to the pump usually solves it, can also be air still left in one of the pipes to say a shower or tap air moves more than water so makes them pop on the off.