Installation of 3kw instantaneous handwash water heater...

[Jim K..]

Mmm don't think I need 15 litres to wash me pandies?! (Plus the £ spent keeping it hot)...

[Jim K..]

See the vid in post 6 from ARW...

[Jim K..]

"Useful many thanks" :-\

[Jim K..]

If it's a stainless steel sink & existing copper H & C supply pipes, do I need to look at equipotential bonding?

[Jim K..]

Indeed. More plumbing needed with the storage one, costs more to buy & run... I'll start with the sprinkler & see how it goes. Cheers

[Jim K..]

C19: from Latin pande (manum) stretch out (the hand), from pandere to spread or extend

[Jim K..]

Oh? I didn't realise you asked a question :-D To be fair I only put a clue to intended use in the thread title ;-)

Ta :-)

[Jim K..]

Looking into fitting one of these at the far end of the house where the run from hot water tank is excessive.

Found a 3kw one that looks ok.

Plumbing shouldn't be a problem.

Elecs - thinking 13a plugs are nono, so a spur to a FCU from a nearby socket should do? Double pole switch?

Electrically, what do I need to check (& how) before proceeding? Perhaps make sure the socket I would be spurring from is on a circuit protected by a 32A breaker? RCD "required"?

Er... Any other pointers please?

[Jim K..]

Urine? C'mon!

[ARW]

Kettle and washing up bowl?

[Tim+]

Hmm, we have a long run from our unvented cylinder to our kitchen sink. Theoretically, could one of these be plumbed to the hot supply, and if so, what would ?standby? annual running costs be like?

I don?t mind paying a bit for more instant hot water in the kitchen, but not if the insulation is poor and it?s gonna cost a lot to keep it warm. (Having said that, it would be easy enough to reduce losses by putting it on a time switch to run for 8 - 12 hours a day say).

Tim

[Chris Green]

I installed an 'under sink' water heater fed by the hot water supply a year or so ago. It's one of those "why didn't we do it years ago" things!

The main reason in our case for feeding it from the hot supply is that our mains pressure is relatively high and requires all sorts of silliness for this type of heater. Putting it in the hot feed (low pressure, gravity from tank in loft) solved all the issues.

I'm thinking of putting another in an upstairs room which also suffers from "hot water takes ages to get through".

[Fredxx]

I did the same, no expansion valves or any other complication warranted.

[ARW]

[Charles F]

We had the same problem with an ensuite in an extension at the "wrong" end of the house from the hot water source, and a pipe run of maybe 20 metres.

Initially a hot and cold run in 15mm PEX - shower delay to hot quite reasonable, but hot tap in the basin took an eternity, esp. in winter.

Solution was a separate hot feed to basin in 10mm PEX, well insulated, which reduced the delay to less than 40% of that with the 15mm. Flow to the tap, with initial pressure (via pressure reduction valve) of 3.5 bar, perfectly reasonable for hand washing.

Simple, cheap, no ongoing costs

Charles F

[Chris Green]

It still costs to heat the water. Depending on how much heat you 'lose' by heating the water in the pipe each time (agreed, it's less with a smaller pipe) it could still be cheaper in the long run to have 'locally' heated water. There's also the cost of any wasted water to take into account if you're on a meter, though I'd guess that's pretty trivial.

Whatever, it's the lovely, near instant, availability that we like with our under sink heater. Even if it was costing a little more (which I doubt) we'd go for it. Initial cost was very little, something like £70 I think and I plumbed it myself so that cost very little indeed.

[Martin Brown]

It will be underpowered for the duty. 5-6kW will work OK.

In the ballpark of 30-50W per unit continuous 24/7. We had this problem in our VH when people left them on regularly (and there were several). You could obviously cut this by 1/3 by using a timed switch. The water stays reasonably hot overnight but it also warms the cupboard it is in.

The most annoying one being in the downstairs kitchen where people would turn on the tap to "run warm" exhaust all the 15L of hot water to waste and then complain that it was running cold. It was about 3m from the mains supply and flash boiler would have been so much easier all round.

It might be viable but you would also need to check that your cold supply water pressure was within limits or add a non-return valve, pressure adjuster and failure/overflow vent. In a place where instant hot water is important and usage is intermittent they are OK but if a decent high power supply is available I would go for a 6kW flash boiler. (but not in a hard water area)

[Jeff Layman]

Heh. There was an Ariston undersink heater in the garage when we moved it. As soon as I switched it on it tripped the RCD. I took it apart but couldn't see anything obviously wrong (element shorting to earth maybe?). So it had to go.

I got it replaced with an instant-heat Triton. It was, and still is 6 years on, perfect for what I needed - just hand washing after getting grubby in the garage or garden.

[ARW]

Hence my reason for asking why Jim K wanted one.

Electrically he seems to have got everything in order.

[GB]

Pandies? Handies or panties?