Domestic "Instant" Hot Water Boiler

[KJR]

My 91 year old dad lives in a block of retirement flats which are electric only, no gas supply. He has a Gledhill Pulsacoil electric water boiler/store which is 20 years old and currently not heating up unless he uses the peak boost function. He has a shower, bathroom sink and kitchen sink.

Given the age of the Pulsacoil it might be time to look at a replacement which is approx. £1500 - £2000 for a direct replacement or something else possibly an "instant" water boiler for around £400 - something like Rheem 18kW 240V Tankless Electric Water Heater.

Does anyone have any experience of "instant" hot water heaters and care to comment on your experience ?

[LooneyTunes]

We’re planning on using a couple in non-residential properties where there’s very little water demand (so don’t want to maintain a tank of hot water). There are a few different ones to choose from but a high power one will give you better flow rates than than the smaller ones.

18kW is a pretty similar output to a typical gas combi boiler so should give a decent flow rate but will need a very meaty electrical feed (18kW @ 240v is 75A). Does he have sufficient capacity to run that? It could be that you might get away with a smaller one.

The one you’ve linked to isn’t a brand I recall seeing and is cheaper than I remember them being. Might be worth looking for reviews?

[KJR]

LooneyTunes said:

We re planning on using a couple in non-residential properties where there s very little water demand (so don t want to maintain a tank of hot water). There are a few different ones to choose from but a high power one will give you better flow rates than than the smaller ones.

18kW is a pretty similar output to a typical gas combi boiler so should give a decent flow rate but will need a very meaty electrical feed (18kW @ 240v is 75A). Does he have sufficient capacity to run that? It could be that you might get away with a smaller one.

The one you ve linked to isn t a brand I recall seeing and is cheaper than I remember them being. Might be worth looking for reviews?

Thanks for the info. For the electrical supply side the Pulsacoil system currently in place is in the same cupboard as the incoming electrical supply, fuse boards, associated wiring and incoming water supply so should be easy to upgrade if required. There is a 100 amp fuse on the main supply coming in. The water heater I linked to was the first I found with a high heat capacity which would help with a high flow rate with the shower but we could go with a less powerful water heater if that would meet his needs.

[LooneyTunes]

If it helps, a typical electric shower is usually around 8-10kW (but flow rates do drop off as temperatures increase).

This was the site I last looked for them on https://www.heatershop.co.uk/water-heaters/instant... , it seems like the single phase ones are quite a bit cheaper than the 3p ones we were looking at. Worth a look as they link to the technical and installation docs.

[Pistonsquirter]

78 amps damnn!!!! if someone turns the oven on when there's a shower going you could blow the main fuse lol.

To aid your calculations, a shower typically uses 9l/s, and sinks & whb's about 3l/s each.

So ideally you would find something which provides about 50 degrees Celsius at 12 l/s continuous ](9+3+3)x0.8 diversity].

I would hope you can get away with something much smaller, typically I'd expect an EWH with a small tank inbuild so more like a small calorifier cylinder.

Also.. You could also think about point of use heating i.e. an electric shower and electric heater for handwash outlets only, benefit usually if you are in a hard water area it's cheaper to replace a smaller thing more often than a great big heater costing thousands as you found our (though 20 years is good going but it sounds like its been heating just calcium for the last decade..)

Also also... what about filling the original heater with acid for a week? Sounds like it works just the element has an inch of calcium build up, might work fine if decalcified..

[jet_noise]

Might be a faulty element or controller. AIUI either can usually be replaced. I've had a standard immersion heater element die and replaced at some point.