Combi bolier installation location

[rowsonj]

I want to install a combi boiler to an old house together with a central heating system and a thermostaic mixer shower. I have been told that to get adequate pressure for the shower the boiler will have to be installed upstairs on the same level as the shower. I thought that combi's supplied hot water at mains pressure and don't understand what I have been told.
Comments / help much appreciated

[htg engineer]

You're correct, the hot and cold will both be at mains pressure - therefore it doesn't matter where your shower is in relation to the boiler (without going to extremes).

As long as your mains cold flow rate and pressure are good now, then there shouldn't be any problem once the combi is fitted.

If your hot water is currently 22mm pipe I'd suggest replacing with 15mm to feed the shower.

My combi is downstairs, and I'm fitting a thermostatic bath shower mixer upstairs. I have seen many like this and there's no problem.