Combi boiler/shower mixer problem

[steve131]

Hi. I have a Baxi Combi Instant 105e boiler.
The problem is that the shower ran cold. So I called Brit Gas and they came and changed the DHW diaphragm and a temp sensor.
The Hot water to all the taps is fine and constant but the hot water to the shower mixer goes cold more or less as soon as soon as the burner goes off in the boiler.
Brit Gas engineer returned and said I needed to renew the thermo mixer on the shower, which I've done but the problem still exists. I want to call the Brit Gas man back but I need something to tell him really as he's insisting that the boiler is working fine. Any ideas? Thanks. Steve

 

[steve131]

Well not exactly inundated with answers or help with this problem. Looking on here there's quite a lot of this sort of problem going on and I haven't seen any conclusions yet.
Is this just a winter thing when the mains water temp is quite low?
I've changed the mixer for one of these Solepearl Chrome Thermostatic Shower Mixer, Modern Thermostatic Bar Shower Mixer Valve Anti Scald Tap, Bathroom Thermostatic Bar Valve Diverter: Amazon.co.uk: DIY & Tools - https://www.amazon.co.uk/gp/product/B07XNWDFV7/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&th=1
and I've re routed some of the pipework to remove a few right angle bends to aid the flow of the hot water. There was no scale inside the pipes as there is a softener in the house and the route to the mixer is now about a two metres. The boiler is adjacent to the shower enclosure so not far for the water to travel.
The duration when it goes cold has now shortened and it only goes cold for a couple of seconds, so an improvement!

The next thing to change will be the shower head and what I want to know is do I buy one of the Couradric heads or just find one with either a wider head with larger exit holes? Some of them I notice have a restrictor that I can remove. I already have a 10mm flexi hose.
Thanks. Steve

 

[OffshoreGas]

Well not exactly inundated with answers or help with this problem. Looking on here there's quite a lot of this sort of problem going on and I haven't seen any conclusions yet.
Is this just a winter thing when the mains water temp is quite low?
I've changed the mixer for one of these Solepearl Chrome Thermostatic Shower Mixer, Modern Thermostatic Bar Shower Mixer Valve Anti Scald Tap, Bathroom Thermostatic Bar Valve Diverter: Amazon.co.uk: DIY & Tools - https://www.amazon.co.uk/gp/product/B07XNWDFV7/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&th=1
and I've re routed some of the pipework to remove a few right angle bends to aid the flow of the hot water. There was no scale inside the pipes as there is a softener in the house and the route to the mixer is now about a two metres. The boiler is adjacent to the shower enclosure so not far for the water to travel.
The duration when it goes cold has now shortened and it only goes cold for a couple of seconds, so an improvement!

The next thing to change will be the shower head and what I want to know is do I buy one of the Couradric heads or just find one with either a wider head with larger exit holes? Some of them I notice have a restrictor that I can remove. I already have a 10mm flexi hose.
Thanks. Steve

If you run a tap do you get they same problem? If not the problem may well be with your shower.