Grohtherm 3000 and Combi

[Big Phil]

I've got a 28kW combi providing my hot water and am about to install a new shower room in a cupboard above the stairs. I've sorted out drainage and water supplies via 15mm pipes to the cupboard and am deciding exactly which shower to fit.

I'm looking at the Grohtherm 3000 thermostatic shower, but the blurb on the website selling this says "high pressure only". Will a 28kW combi be classified as "high pressure"? Is there any easy way of measuring the pressure?

Has anyone done anything similar?

Thanks Phil

[Tony Bryer]

High pressure = mains as opposed to a c.w. cistern in the loft. It's

99.9% certain that your combi is mains fed so the h.w. is classed as high pressure. You'll need a mains cold feed too.

[Christian McArdle]

Combis are normally connected to the mains, which is normally considered high pressure. Only if you have a weird setup with the combi fed from a tank, or abnormally low mains pressure from the street would it not be high pressure.

Note that the pressure has little to do with flow rate per se. The size of the combi would affect the maximum flow rate available, but not the pressure it was supplied at. You should check that the flow rate required by the shower is within the ability of the combi (and your water supply). Most normal showers would be happily supplied by 28kW, but larger drencher units and panel showers may require more.

Christian.

[Andy P]

I installed the very same last week with a 28kW combi. It works as well as can be expected. The shower is better than our old electric shower (9.5kW) and the thermostatic feature of the Grohtherm 3000 works fine, ie if someone turns a tap on the shower flow reduces but so does the temperature.

I hope you haven't really used 15mm pipes for the drainage ;-).

Andy

[Big Phil]

Thanks for all the advice. The combi is supplied direct from the mains so it looks like it should all work well. I've got both hot and cold

15mm pipes passing the room to tap into and you'll be pleased to hear a 40mm drain is present, thank you :-)

I'll start collecting the bits required then and then look behind the settee for some time.

Thanks again. Phil

[IMM]

It is best to use a dedicated mains pressure mixer with an in-built pressure equalising valve. Or install one before the mixer with the cold and hot feeds running through it. Then only a glitch if someone turns on a tap.