Single-Impeller Negative-Head Stuart Turner Pump Running

[psarinuk]

Hello,

I've a Single-impeller negative-head Stuart Turner Monsoon N2.0 pump on the Hot side and Mains-pumped on the Cold side in my house. The house has two showers, both of them equipped with a pressure equalising/ balancing valve.

Lately the pump seems to come on for a couple of seconds when the cold water tap is operated (mostly when its shut). It also comes on when the toilet cisterns are at the end of their filling after use.

The pump is around 10 years old and never caused an issue otherwise.

Any idea what might be causing it and how can it be fixed?

Thanks.

 

[picasso]

Try recharging the expansion vessel on the pump.

 

[psarinuk]

Recharged the vessel. It seemed flat when connected to mains powered tyre-inflator. Now pressurised to ~1bar.

Alas, its worse now. The pump is coming on while opening a tap too. Previously, it was only when tap was closed.

 

[picasso]

At a guess I reckon you have a stuck non return valve causing cross over between the hot and cold, usually its a shower valve or mixer tap,

 

[psarinuk]

At a guess I reckon you have a stuck non return valve causing cross over between the hot and cold, usually its a shower valve or mixer tap,

I do not have any NRCs on any mixer or shower valves. Besides, the pump is also coming on when cistern (that has a cold connection only) is flushed.

There seems to be a NRC valve on the outlet leg of pump, do you think that might have something to do here?

 

[picasso]

Has the pressure of the cold dropped lower than the hot ?

 

[psarinuk]

Has the pressure of the cold dropped lower than the hot ?

No noticeable pressure change at all in any cold/hot outlets.