Undersink instantaneous water heaters

[denso13]

Thanks I think the electricians mentioned putting it on a fuse spur

It can't, it's too big for a 13A fuse.

 

[Fredstudio]

Thanks so would need it's own supply from the board Rcbo protected maybe

 

[denso13]

Yes, own supply, ideally with RCBO.

 

[Fredstudio]

There the units

 

[flameport]

There the units

This affair: https://www.amazon.co.uk/Instant-Electric-Water-Heater-Instantaneous/dp/B0DRCCHXPM

It's a direct from China import, so there will be no complaining or warranty when it goes wrong.
Doubtful it complies with any UK requirements for electrical or plumbing.

It claims to be supplied with a UK plug but this is useless, as the 3500W rating is too high for that.
3500W at the stated 220V is 16 amps, far more than the 13A maximum for a UK plug.
When used in the UK on a more likely ~240V supply, that will become 17.4 amps and about 4200W.

If you insist on having it installed - good luck, you'll need it. As will anyone else unfortunate enough to use it.

 

[Fredstudio]

Someone got them me to install, if they don't comply with regs etc I'll get them to get something else.

 

[Fredstudio]

Is there anything similar that is UK approved. Maybe the Hyco rho one or similar

 

[ericmark]

Most of Europe has 16 amp radial supplies, and that unit would work with a 16 amp supply, we see the same with overs, rated at 3.5 kW for Europe in UK they need a dedicated supply, in fact the regulations say

The load current in any part of the circuit should be unlikely to exceed for long periods the current-carrying capacity of the cable (Regulation 433.1.5 refers). This can generally be achieved by:
(i) locating socket-outlets to provide reasonable sharing of the load around the ring
(ii) not supplying immersion heaters, comprehensive electric space heating or loads of a similar profile from the ring circuit
(iii) connecting cookers, ovens and hobs with a rated power exceeding 2 kW on their own dedicated radial circuit
(iv) taking account of the total floor area being served. (Historically, limit of 100 m² has been adopted.)

There is also a plumbing consideration, water when heated expands, and there needs to be room for it to expand when often there is a non-return valve on the supply. The under sink units we fitted into portacabins had a special tap, it controlled water into the heater, the outlet was open, and as the water heated up, it would drip out of the faucet.
An expansion tank

which has gas one side of a diaphragm and water the other can be used to allow expansion, this is what we have with sealed central heating units, often built into the boiler, but this is moving away from my comfort zone, need to ask plumbers about this.

I have considered having a unit under the sink, it would stop having to wait for hot water to arrive, if fitted to the hot water supply, or even cold from the storage tank, then no problem with expansion or any rules on items connected directly to the cold water supply. So rules and regulations will likely change depending on where the water supply is taken from, as well as the electrical supply.

Post #3 I showed the unit often used in the UK, physical size is the problem, it means no cupboard space under the sink, but having on in a caravan I can say they work well.

 

[Fredstudio]

Thanks. It's just then if the unit does comply with UK plumbing and electrical regs. Electricians would be wiring it up so they would take a dedicated supply from the main board.

 

[Fredstudio]

What size reservoir does the one you linked have? I imagine if it's a small reservoir the hot water could expand back in to the mains without the need of a vessel. But then have to considered if a single check valve is needed. Depends on how close the nearest cold water draw off (tap) is

 

[Fredstudio]

If it doesn't comply with wras and any UK electrical regs. I will advise against. I had my reservations about them

 

[ericmark]

What size reservoir does the one you linked have?

It says on the picture, 10 litres. I just picked on at random. Think the one we used was 7 litres, which was ample for handwashing.