Faulty Salamander Pump?

[Trebuchet95]

We've had a Salamander RP50TU installed for our ensuite shower and although the shower is adequate for washing, it's too weak for a pleasant experience.

So I decided to buy a second hand RP75TU to see if would solve our issue. Following the instructions I commissioned the pump properly and after getting all the air out, the water flow from the shower was vastly improved.

Unfortunately though, the pump keeps on stopping with the dry run indicator. If the shower is on it'll keep on running, but after stopping the shower, it'll turn on with the dry run light flashing until it eventually stops with the dry run light on all the time and I have to turn it off and on again be able to use it.

The pump is above the hot water tank with essex flange and anti-gravity loop. Water comes from cold water tank about 1m above the pump. I've checked the hot and cold flow with the pump off and the flow is good with no air coming out. I've also checked the pressure of the pressure vessel and it is at the specified 18 psi.

I'm not sure what else I can do now. I guess the pump may be a dud and I'll need to request a refund from the seller, though to be 100% sure I guess I need to buy a new RP75TU to test.

Any advice for me?

 

[just pumps]

Are the inlet and outlet pipe sizes to spec.

 

[Trebuchet95]

Are the inlet and outlet pipe sizes to spec.

Yes, both inlets and both outlets are 22mm.

 

[Trebuchet95]

If I close the valves on the output flexible couplers and I switch on the pump and it still stops with the dry run protection, is that proof the pump is faulty?
I'm assuming the pumps can't run dry if the outputs are closed off.

 

[Trebuchet95]

Turned out the second hand pump I bought was faulty. After installing a brand new RP75TU, my shower performs beautifully.