Small electric boiler? Featured

The ones in our VH are 25L capacity 3kW so best off hardwired in. They are fine so long as you don't turn the tap on and leave it running until it gets hot. There is only 25L of hot water available and when it is gone it takes a while to heat back up again.

Things to watch are you will need an overflow/vent outlet and you might need a pressure regulator to bring your mains water pressure down to something that the boiler will cope with. They seem to last 5-7 years.

Otherwise you will find it leaks/drips overnight when the water pressure is at its highest. Apart from that they are relatively trouble free.

Decent ones at 3kW need a bit too much power for that. Proper flash boilers that do hot water on demand need even more power to work.

Really informative, thanks Martin. Considering all that, I think I would prefer to go for the flash/instantaneous option, even though the power supply would need to be hard wired.

Are you in a hard water area ?. If so, you need to think about how you will descale it from time to time.

Spot on Andrew! You should see the outside of our kettle, let alone the inside.

A mate replaced the 'boiler' type water heater for an instant oversink type in his shop:

It was easy to install, didn't necessitate having to modify the existing tap feeds and can be run as long / often as he needs (which has turned out to be quite a lot because it's a shop that's considered an essential service so open during lockdown and Covid itself).

He said it's at full hand washing temp in about 5-6 seconds but as it's a spray that's not a lot of water. And that's why I was interested in something like that as my bathroom hand basin feed is reasonably long from the multipoint gas water heater, in 22mm copper (for the bath when there was going to be indirect HW cylinder there) and whilst we aren't on a water meter (yet), do try not to waste any if possible.

Cheers, T i m

Crikey! Yet more unexpected possibilities for consideration.

Oh, forgot to mention, we are also in a fairly hard water area.

Cheers, T i m

Someone in another group fitted an electric boiler that stores energy using a phase-change material, he seemed much happier with it than I expected.

So what's inside, some storage heater bricks wrapped with copper pipe? ;-)

Cheers, T i m

Yes but is it any less expensive than plastic surgury?

I got one of those (3Kw) put in our garage after I found the Ariston under-sink heater left by the previous owner tripped the RCD when I switched it on.

It's worked well for 8 years, although in winter when the water feeding it is very cold, it needs to be on full, and even then the flow is fairly low. It's quite sufficient, though, for washing hands after a messy job, and the spray head actually helps shift the grime. We are in a hard/very hard water area (Ca CO3 level is 281mg/litre), as it comes from a chalk aquifer under the Downs. I've used descaler now and again on the spray head, but never on the heater itself.

;-(

That's good to learn (for our potential use) as it will be indoors.

Yes, I was thinking that might be the case. My circulating de-greasing tank works better because of the constant flow washing the debris away.

Very posh. ;-)

No. We have had a Triton T80 shower for maybe 30 years now and I don't think I've ever de scaled the guts of that (but have done the nozzle(s) a good few times). [1]

I find leaving anything like that to soak in a container of suitably diluted 'Green stuff' moves the calcium very well.

Cheers, T i m

I am sure that I have seen some that don't have to have overflows or vents. They work by allowing expansion due to heating to push back into the inlet pipe - the limited volume of expansion not being in any danger of pushing warm water back into any other leg.

Ah, the wonders of hard-water areas. We are in a very soft water area and a 20 year old kettle looks like new inside. In fact the water treatment plants have to add phosphates to stop the soft water dissolving the (very clean) inside surfaces of old lead pipes.

Mike

How much water do you need for a washing up bowl? 5 litres, 10 litres?

A 3kw instantaneous water heater only delivers around 1 litre of hand hot water per minute. So, it will take you 5-10 minutes to fill the washing up bowl. Are you okay with that?

That's for water coming in at 5C, and washing up water at 50C.

Sadia heaters were the usual choice in the past, which usually were over the sink with a long spout that dripped as the water heated up in the tank and expanded - the tap was on the inlet. I stayed at a place where the tank was under the sink and the hot tap knob was connected via a rod through the tap to the inlet tap underneath - it just looked like a normal hot tap.

If fitted to a cold water supply you will need a non-return valve, pressure relief valve and an expansion vessel (though a length of pipe is allowed for some heaters in lieu of an expansion vessel).

As I had a water supply from a hot water tank it meant I didn't need any of these protection devices.

At the time my hot water tank was badly lagged and heated by electric only and I had a shower, so I only turned the immersion on if necessary.

Ah, there we go.

If that be so, an irksome non-solution.