Shower pump pulsating when water is hot

[poshman]

Hello helpers Recently I had a Stuart Turner shower mate. Water pump connected to my immersion heater but it keeps pulsating well not always .
I have tested the shower over the last couple of days 8 times and it worked great each time without hot water
But when I heated up the water I tried it the 9th time it kept on pulsating ie on & off
Is this a coincidence or something else ? The guy who fitted it is on holiday so I will be having cold showers for 2 weeks unless you guys have any ideas !! Thank you P M
Oh one other thing the guy did come back and fitted some sort of bleed valve on the top of the immersion heater

 

[Exedon]

Some clear pictures of installation would be useful.

 

[stem]

It could be temperature related. Most shower pumps specify a maximum hot water temperature of around 60 to 65 degrees C. Often hot water from cylinders that are heated by immersion heaters are in access of this; particularly when they are heated by an off peak tariff to maximise the heat stored.

If the hot water entering the pump is in excess of the max temp specified a thermostatic mixing valve should be fitted to the hot water inlet. This blends the hot water with some cold to keep the temperature inside the specified operating temperature.

 

[gas112]

possible cavitation within the pump due to excessive heat cut the immersion stat temp down

 

[poshman]

Stem & gas 112 thank you for your suggestions will hopefully reach a positive conclusion

 

[Johntheo5]

Can you post a photo of the HW take off, also google "Surrey Flange" to see if your plumber has installed something like that.