Combi question

[a9blue]

Can anyone tell me if a combi provides pressure to DHW or is it all down to mains pressure?
The reason I ask is my upstairs HW isnt that strong and my thermostatic shower is cold and not kicking the boiler in.

 

[mikeyd]

It's just down to mains pressure. If anything the boiler will 'rob' a bit of pressure as the water makes it's way through the heat exchanger so there will normally be slightly less pressure at the hot tap than the cold but it shouldn't stop your mixer working.

Has it always been like this? Have you checked all the service / isolation valves are fully open? Any work done lately?

 

[a9blue]

I'm starting to wonder if the pressure was ever good enough as I only ever use it with CH on and the boiler is fired up.
I've only recently tried it with HW only and it never works.
It requires min 2 bar and I am not getting that from my boiler.