Under sink water heater

[Timlouth]

Help,

I am going to be fitting a new kitchen soon.
Can I fit an under sink electric water heater and connect it to the existing socket ring circuit?
Is it legal and is it safe?
Does anyone know a good trick for adding sockets to a ring circuit without replacing the cables back to the consumer unit. I want to add a couple of double sockets, preferably as part of the ring rather than as spurs. I don't mind pulling wires out of the wall in the kitchen but the rest of the house has been decorated and wood floors put down so I would prefer not to have to lift floors etc.
Many thanks.

Tim

 

[Dartlec]

If you choose the right type then there is no problem connecting an under sink heater to the existing circuit.

There are two types - one has a tank and heats the water with a small element, therefore draws less than 13A and can be connected to the circuit (normally via a FCU is best) The other type is the instantaneous type heater that is similar to an electric shower and therefore generally requires a much higher draw, and hence its own circuit.

Adding sockets to a ring is not difficult - the trick is to connect at two adjacent sockets to extend the ring, bypassing the existing connection. It is very important that you ensure there is a ring though, and that you aren't adding a bridge. There are also considerations of current draw for the whole circuit, and rcd protection if that is not there already.

Elsewhere this would not be notifiable work, but because you are in a kitchen it will be. That means you either pay the LABC and get them to check it, or employ the services of a registered competent person. For a small job like this it may well work out cheaper to go the latter route, and you can be sure that everything is tested properly.

Hope that helps

Gavin

 

[Davesomerset]

We are putting in a small sink with cupboard underneath in our new cloakroom. We have an electrician coming to do the wiring in this area and it will include updating our consumer unit, etc.

Our question is - could you advise what type of heater you would have?

It is just the two of us and we have no hot water to this area and no knowledge of cost effective sink heaters.

Our thoughts go to the unit that sits over the sink but it would be nice to have one hidden away. But we see there is one that keeps a tank heated and that maybe more costly to run than one that just heats as it is needed.

Thoughts would really be appreciated.

 

[PrenticeBoyofDerry]

As previous post an instantaneous heater would require a dedicate circuit but a small storage tank of about 10 litre capacity could be connected to the ring via fused connection. Extending the ring in the kitchen would not require notification in England as that requirement was amended in April last year, but would require at least a minor works cert.
A new circuit would require notification, as would your CU change. I would ask the electrician to install a dedicated circuit though as part of the CU change, regardless of whether you go for stored or instantaneous type.
The Wijas brand do small compact units.

 

[EFLImpudence]

I don't see the point of the under-sink continuous heaters.

You can get kettles which keep the water hot and they are pointless as well.

 

[OwainDIYer]

We are putting in a small sink with cupboard underneath in our new cloakroom. We have an electrician coming to do the wiring in this area and it will include updating our consumer unit, etc.

Our question is - could you advise what type of heater you would have?

you can get 3kW instantaneous heaters for hand washing which would be adequate if this is the only purpose of the heater.

See here.

With the instantaneous heating there will be no standing losses and no waiting time for the storage tank to heat up.

With the small storage water heaters,
- the unvented type, the cost goes up if you have to add pressure relief valve and expansion vessel due to your plumbing configuration
- the vented type, if you want the heater in under-sink mode you have to use special vented taps, which are expensive

 

[Taylortwocities]

A 3KW instant heater MUST have its own dedicated circuit.

 

[WabbitPoo]

For a cloakroom, why bother with a hot feed at all - just washing hands after using the loo doesn't need hot really.

 

[mfarrow]

I'm surprised if you can get water, you can't get the hot water piped there too?

I have a 9kW instantaneous heater in a separate building that gives a nice temperature at a low-ish flowrate this time of year. In the summer I'd class it as 'hot' but still bearable. As with an electric shower, you control the temperature by altering the flowrate. So I'd advise on a flowrate restrictor so it doesn't get too cold, and maybe a thermostatic valve so it's not too hot (but not required IMHO, even at 9kW they don't exactly get scalding).

I fear a stored heater will end up heating the room and you'll regret it.

 

[Lectrician]

The cost of a heater is probably similar to some new pipework for the hot feed instead.

 

[Davesomerset]

Thank you for replies and will look at them in more detail later. Just to cover the point on hot water supply - this cloakroom - is a little way from the kitchen where the nearest hot water supply is and our cottage had very thick walls, etc, etc. in a way more like an 'outside loo' and pipe work would have to travel there past a doorway, etc.

 

[slippyr4]

A 3KW instant heater MUST have its own dedicated circuit.

Why? < 13A @ 240V.

I'll concur with "really ought to", but "must"?

Genuine question, not stirring or anything.

 

[OwainDIYer]

A 3KW instant heater MUST have its own dedicated circuit.

I would suggest that intermittent use in a domestic cloakroom is not going to present an unacceptable sustained load on the ring in the same way a hot water cylinder immersion heater would.

It would be different if it were a village hall with 50 people queueing up after the bingo ...