Lukewarm shower mystery

[sherryglasses]

Hello forumites!

Hopefully you can help solve a mystery that 2 plumbers have not been able to?

I can get heating and hot water in all taps except the one shower in my flat.
The shower is an Aqualisa Aquamixa Thermo Combi mixer and the shower is situated approx 1.5m from the combi boiler.
Boiler is an Ariston (yes I know I didn't choose it) microCombi 23 MFFI.

We've replaced the heat exchanger last week and the grey cartridge in the shower mixer about 6 months ago but still can only get a lukewarm shower. Occasionally their is a clicking sound in the boiler that sounds like the spark generator. I've got this part but not had it fitted yet as we are still not sure if that could cause the lukewarm shower.

I've spent nearly £400 on call outs and parts and still not solved the mystery.

Can anyone help?
MTIA

 

[sdsparks]

This product MUST NOT be fitted to an appliance rated at less than 24kW (80.000 Btu).

 

[sherryglasses]

@ sdsparks the spark generator part is a replacement to the one on their already. Part # 65100514

 

[sdsparks]

Sorry not following, spark generator? My comment was straight from the Aqulisa site, it also suggests that the flow through the shower is to high, has a flow test been done?

 

[Plumbstar Tom]

ah so you are implying it has not been fitted as per the manufacturers insturctions then

in that case it sounds like you need a new/different shower

some flow limiters on the product may help though

 

[sherryglasses]

@ sdsparks Spark generator is in the boiler.
No flow test performed however the pressure has always been good.

@ Plumbstar Tom Are you suggesting fitting something like this:
Shower Flow Limiter 8 Litres Per Minute

BTW I have to run the hot bath filler tap on the slow side to get constant hot (not lukewarm water). Means it takes a while to fill...

Thanks guys for your help so far.

 

[sdsparks]

Flow and pressure are two different things, now you have mentioned your bath tap it makes complete sense that the flow is too great, the water is passing through the boiler to quickly, it doesn't help that the boiler is so close. Have a plumber fit a flow reducer although most showers these days come with similar devices that go in the actual mixer. Good luck