Probably not cost effective to replace large hot water cylinder? Or remove?

AnotherJoe

I've just moved into a new (to me) house) and the hot water tank is huge. Must be 5ft tall.

Ideally Id replace it with a smaller one to get some space in my airing cupboard, but I presume once its been heated up then apart from slightly larger losses it wont actually cost me much more to heat it ongoing, since I am only heating what I am using. 

I guess i could replace it entirely with a system that heats water to demand (is that a 'combi') but as the boiler is in the attached garage that could be quite a long wait for hot water to come through and also its not that old, maybe 5 years.

Any thoughts?

tim_p

How is it currently heated? Gas boiler or immersion?

coffeehound

A good thing about a larger DHW cylinder is that you can heat it to a lower temperature while still getting enough hot water for your needs.  This benefits in a few ways: it loses less temperature during the day; the boiler runs more economically as it's in the condensing mode more; and it lessens the chance of scalds and burns.

Tallerdave

Keep it! If you went to a combi your water consumption will rocket as you quietly slip into a coma waiting for hot water to flow every time you turn on a tap.

nottsphil

Does the house have solar PV? Is it all - electric? 

AnotherJoe

Its gas heated , no solar. The sums I've done on solar and batteries, without any feed in tariff (at the moment?) show roughly at least a 10 year pay back. It seems to make sense to get my solar from a supplier who offers that, I switch to Octopus next week (along with cheap 4 hour nighttime period).

@Tallerdave, yes that was my thought about a combi.

Hasbeen

AnotherJoe said:

I've just moved into a new (to me) house) and the hot water tank is huge. Must be 5ft tall.

Ideally Id replace it with a smaller one to get some space in my airing cupboard, but I presume once its been heated up then apart from slightly larger losses it wont actually cost me much more to heat it ongoing, since I am only heating what I am using. 

I guess i could replace it entirely with a system that heats water to demand (is that a 'combi') but as the boiler is in the attached garage that could be quite a long wait for hot water to come through and also its not that old, maybe 5 years.

Any thoughts?

Keep it. Mines is over 6 feet tall. Lots of hot water! 

bobfredbob

Just ensure the tank is insulated.  So, if you can see copper, then add a jacket.  They also say to add insulation around the pipework that you can see.  Any heat lost from the tank goes to warm up your house, which is useful for most of the year.  New tanks apparently lose very little.

If you ever did get solar, you could apparently get a "smart" switch that uses the immersion to heat your water during the day with the "free" electricity, though last time I checked it was unclear whether the savings outweighed the costs.

You may want to replace the tank for other reasons, such as to more easily run a shower off the boiler rather than using an electric shower/pumped shower/unvented cylinder.

Shedman

coffeehound said:

A good thing about a larger DHW cylinder is that you can heat it to a lower temperature while still getting enough hot water for your needs.  This benefits in a few ways: it loses less temperature during the day; the boiler runs more economically as it's in the condensing mode more; and it lessens the chance of scalds and burns.

As a note of caution, the advice is that Hot water cylinders should be heated to 60°C  to kill off bacteria, especially Legionella, so need to be careful that temp is not set too low.

https://www.stuff.co.nz/national/health/70285141/legionnaires-disease-from-hot-water-cylinder-results-in-amputations

[Deleted User]

Shedman said:

coffeehound said:

A good thing about a larger DHW cylinder is that you can heat it to a lower temperature while still getting enough hot water for your needs.  This benefits in a few ways: it loses less temperature during the day; the boiler runs more economically as it's in the condensing mode more; and it lessens the chance of scalds and burns.

As a note of caution, the advice is that Hot water cylinders should be heated to 60°C  to kill off bacteria, especially Legionella, so need to be careful that temp is not set too low.

https://www.stuff.co.nz/national/health/70285141/legionnaires-disease-from-hot-water-cylinder-results-in-amputations

The OP only asked about changing her large hot water cylinder for a smaller one to free up more space in the airing cupboard -presumably to air more clothes - and she ends up getting advice on cylinder lagging; solar diversion and Legionella.

bobfredbob

To be fair, the OP wrote about combi boilers, solar, tariffs, and heat loss, and they hinted that they are unused to hot water tanks.  It's not unreasonable that people give advice about those things and also warn against turning down the hot water thermostat.