Cloakroom in our loft conversion has a small over sink instant electric water heater on a 13A fused spur. This is ugly and we’ve never really used it since we moved in.

I’d like to replace it with a hidden instant unvented water heater that then plumbs into a standard mixer tap and the heater lives in a vanity unit/cupboard under the sink. Needs to run off the existing electrics.

Smallest of this style I can find is 3ish kw – is that going to be OK?

Oso RM5, not instant as such but a good little unit. Quite expensive though.

Only one that springs to mind is a Zip InLine. Specs say it draws 12A at 2.8kw on 230V supply. Most instantaneous ones will be higher power as they have much less time to raise the water to the required temp, even the little spray handwash ones are 3kw.

http://www.zipheaters.co.uk/SiteMedia/W3SVC1317/Uploads/Documents/InLine%20ES%20cropped.pdf

I’ve fitted a few 3kw Zip heaters and found the flow rate not very good. It slows to a trickle when the supply water is very cold, is most of the winter.

That Zip one looks about right.

It’s only used about twice a day for hand washing so anything that stores hot water is going to be expensive to run.

Ive recently been playing with Zip 3kW inlines in an experiment/heath robinson/prototype “wet” heating system for a vineyard.

….and…it’s been a bit dissappointing. It seems very picky on flow rates and pressure, it really has v little grunt. Fortunately I got mine from ebay, a second one too. They come up on ebay fairly often, for between £50 and £100 instead of £250 new, perhaps people are removing them for being rubbish.

Anyway, I shall recycle mine in the shed, routing outside to a small shower head on the end for splashing off mud off me before traipsing into the house. Im not confident it will manage to do that either.

3kW is approx. 13A (3000/230). Fine with a fused spur with a 13A fuse in.
Rich.

Edit:
I should add that the cable to the fused spur should probably be 2.5mm.
1.5mm would probably be ok but I would like to know more about how it’s routed and the rating of the main fuse before committing to use it.

Flex from the FCU to the heater is ok in 1.5mm.