Keep immersion or replace with under sink point of use water heaters?

embraer170 · 30-12-2021 9:12pm #1

My parents are upgrading their downstairs bathroom to make it more disabled friendly given their health situation. As part of this work, the (currently little used) thermostatic valve shower/bath will be replaced with a "wet area" and electric shower. The upstairs (and previously most used) shower had always been electric anyway.

That only leaves the kitchen sink and 2 bathroom washbasins (1 downstairs, 1 upstairs which will probably be see little use) as consumers of hot water from immersion. It got me wondering if there is a point in running an immersion for 3 taps or would one get better value from installing under sink point of use water heaters?

Saladin Ane · 03-01-2022 9:43pm

I've got a somewhat similar query. Instead of a boiler I aim to have 1 shower and 3 point of use water heaters in handbasins.

Does this make financial sense for just two people in a house?

10-10-20 · 04-01-2022 12:47pm

In fairness, maybe not. But it all comes down to a financial decision.

If the immersion is well insulated (or can be significantly improved) and the pipe-run from the tank to the basins isn't excessively long, then no change would be best.

Otherwise if the tank is un-insulated and cannot be improved and/or the pipe run is long, then a point-of-use tank may be worthwhile on the basis of efficiency.

Finally, is one point-of-use tank going to serve three basins without excessive rework of the piping and how much will this upgrade cost in total? Will it be financially more cost effective than remaining with the existing solution... probably not.

GreeBo · 04-01-2022 2:19pm

How often do they actually have the immersion on?

Unless they are in a newish, high rated house, the heating will be on probably at least an hour a day?

If they do use it a lot, considering it will be just used for 2 sinks, get a smaller & well insulated cylinder/immersion?

embraer170 · 04-01-2022 4:18pm

https://www.boards.ie/discussion/comment/118415185#Comment_118415185

It is an an early 80s immersion with a cylinder jacket loosely wrapped around. No particularly long pipe run.

I was more imagining a point-of-use heater under each sink/washbasin rather one than serving all, but you are probably right that the whole thing probably would not make sense.

embraer170 · 04-01-2022 4:21pm

https://www.boards.ie/discussion/comment/118415704#Comment_118415704

The heating is certainly on for an hour or two a day and sometimes more.

The immersion is on a timer, which for the moment runs for about two hours in the morning and one hour in the evening (and there is never a lack of hot water in the taps). The timer used to be set for much longer but I have gradually been cutting it down to see if I notice any difference.

Calahonda52 · 17-01-2022 10:04am

it depends on the pipe run really.

My kitchen sink pipe run is 2.8 litres, which, once a day for a year, wastes c 60 kW of energy, which will bring me 320 kms in my Leaf

FOR BERS, the focus by SEAI going forward once you sort out the building fabric is DHW usage

so elec showers, under sink heaters and no cylinder will be the order of the day in a few years.

Markcheese · 17-01-2022 10:18am

Just from a convenience point of view ,the fact that the hot water is right there - so no waiting for hot water is a plus - it probably will save energy but not really money ..( if you factor in the the cost of buying and installing the water heaters ) ...

Calahonda52 · 17-01-2022 6:26pm

https://www.boards.ie/discussion/comment/118487966#Comment_118487966

Agreed but if we were paying for water it would help because my kitchen setup is 1,000 litre of cold wasted pa if i run the hot once a day for a year

Markcheese · 17-01-2022 6:36pm

https://www.boards.ie/discussion/comment/118490644#Comment_118490644

True, and at a metered rate 1000 l till wouldnt save that much when compared to fitting new electric heaters ,buying them , a plumber and a Sparks on site -

I'd still go with the electric though 🙂

Calahonda52 · 18-01-2022 3:26pm

Agreed, if you look at the carbon foot print, waste water is 6 times higher than potable so the 1,000 litres adds twice

kildarejohn · 19-01-2022 12:24pm

https://www.boards.ie/discussion/comment/118416575#Comment_118416575

In terms of economy, I think the very first thing to do that gives the greatest saving for the least cost is to fit a good quality cylinder jacket. You havent said if the cylinder is actually heated by the central heating system? If so, then you should be aware that oil or gas heating is currently about one third the price of electricity per kWhr, so if you can heat the water from the central heating this is the most economical, far more economical than either electric showers, immersions or point-of-use elec heaters.

Calahonda52 · 20-01-2022 4:23pm

https://www.boards.ie/discussion/comment/118499067#Comment_118499067

Perhaps on a kWh cost basis, but not from a full energy cost consideration, including losses/heating more water than you need/ etc

When you heat say 60 litres to 60 degrees, do you use it all....

embraer170 · 20-01-2022 7:06pm

Thanks everyone!

Keep immersion or replace with under sink point of use water heaters?

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