Instant water heaters

raggy_ann

Has anyone info/experience of the small size, instantaneous,electric water heaters that fit within a kitchen unit?
I am considering buying one for my one-bed flat. It should fit under the kitchen sink to serve that tap and also feed the hot water tap of the adjacent bathroom hand basin. The idea is to replace a large immersion heater. I do not want to waste my money if they are thought to be useless

daveyjp

The small ones are similar to an electric shower so very limited output.

Larger ones are like a small emersion heater system - tank of water with an element to warm it.

EliteHeat

Something like this?

If you want it to work and be small it must be unvented. The maximum size that can be installed by an unlicensed person is 15 litres. Performance should be reasonable as long as you don't want to do anything other than wash the dishes and your face.

Don't try and fit it yourself, it still needs specialist knowledge. These things can explode with the force of a gas explosion if all the safety systems are bypassed.

Wookey

Instant water heaters with enough power to give reasonably strong heated water flow need from 7-9kw of power which is up to 3 times the power usage of an immersion heater within a hot water tank. You would have a large wiring job on your hands to power something like this... http://www.cnmonline.co.uk/Redring-Powerstream-Unvented-Instantaneous-Water-Heater-pr-30749.html. They are useful in certain situations where no hot water storage is possible and they will only use electric when the tap is turned on. TBH though if its for a kitchen and for washing dishes etc i would use a kettle rather than pay the running costs/purchase costs/installation costs of any point of use heater.

If you have an internal immersion heater in your hot water tank then you may find installing a willis type much more cost effective, its basically just a smaller element within its own copper tank which will heat your hot water tank from the top down opposed to an internal immersion which will tend to heat the whole tank.

mikey72

I recently fitted one of the small storage type, it appears to work well.
The instant heat ones are no good to service a kitchen sink, the water isn't hot enough to wash up in. More like a shower temperature, so ok for hand washing.
The 15l storage ones are good, look for a 3kw if you need quicker heating time, some are only 1.5kw. You can fill a couple of washing up bowls, but by the time you have used the first one it's heated up again anyway. They stay hot for ages, and don't lose heat through the case either.
Some calculations are needed for pipework, water pressure, and relief valve needs to be sorted.
Water regs and wiring regs, and maybe even part P to consider if you get one.

raggy_ann

Thank you for the replies, it is just the sort of information that I need