We've ruled out a power shower because you can't use them with combi boilers apparently. Is this true?
It is true. The difference between an "electric shower" and a "power shower" is that the former has a heater but no pump, and the latter has a pump but no heater. If you have a combi boiler, your hot water system is mains pressurised, and you're not allowed to pump the mains because that's unfair to other consumers. (A power shower pumps water from the hot water tank of a conventional boiler system, which is not mains pressurised.)
This leads us to look at electric showers. My understanding is that they're only connected to mains-pressure cold water, which doesn't go anywhere near the combi boiler. Is this correct?
Yes.
Another question: I saw a recommendation (in Which? magazine, I believe) that recommended thermostatic controls. These, theoretically, deal with a drop in the water pressure and maintain the temperature, so that you don't get alternately frozen and boiled when someone runs the cold tap in the kitchen. However, given that the electric shower runs from a single, cold, feed, what's the point?
All electric showers have thermostatic controls. Many power showers do. The new thing is (passive, mechanical) thermostatic controls for
mixer showers.
Can we use an electric shower or not?
I don't see why not.
Can we use it at the same time as the mixer shower?
If you're doing that, you probably want thermostatic controls on the mixer. The mains pressure will drop a little when the electric shower comes on, and it might affect hot and cold pressure differently.
Peter
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