"IMM" wrote
| "Owain" wrote
| Tank and cylinder systems also offer the option of a back-up immersion
| heater at negligible extra cost for if the boiler ever breaks down.
| And if there's a power cut there's at least a hope you have a cylinder
| of stored warm water to tide you over.
| If back up is really an issue then feed the output of the combi into a
small
| instantaneous electric heater. These are not expensive. They will supply
| one tap or one shower. OK for backup until the combi is back up. see:
| http://www.tlc-direct.co.uk/Products/TTTW10I.html

£110 + VAT plus 10mm cable at 1.60/metre is expensive compared to about £12
for a 3kW 36" immersion heater + thermostat on a cylinder.

And the unit you suggest is only suitable for handwashing purposes or low
fill rates to a sink. It cannot supply two taps simultaneously, and is also
not suitable for basin/sink mixer taps, shower mixer valves, or bath taps.
And 9.5kW is only going to give a max of 4 l/min at below 40C output temp
under winter ambient conditions. (All according to the product manual.)

More importantly, it will give you nothing if there is a power cut.
Depending on water use and reheating patterns, a cylinder can have a day's
or more warm water stored. It may not be a big issue for the OP but it is
worth considering.

Owain