Thermostatic mixer showers
These are suited to combination and instantaneous boilers, they are also suited to cylinder type installations as long as there is adequate pressure for the water to flow, otherwise a pump will be required. (power shower)
A good general rule for mixers with a cylinder is the Cold Water Storage cistern has to be at least 1m above the shower heads highest point ( illustraited)
(this is the tank that feeds the cylinder not the cylinder itself
*A shower pump cannot be fitted to combination boiler systems
These are typically pumped mixer showers, they are fitted if the water pressure is low or if you just want extra pressure for showering, often used if muliple outlets are used such as body jets ect. negative pumps are used if there is not at least 1m between the bottom of the cold water storage cistern and the shower heads highest point.
are suitable for all installations, if there is no cold mains the shower can be fed off the Cold water storage cistern.
Showers usually come in a range of Kilowatt sizes generally 8.5KW, 9KW, 9.5Kw and 10KW
8.5KW showers can usually be wired in 6mm cable whereas anything higher will need to be wired in 10mm additional work may be needed dependant on your electric supply and protective fuses