Best insulated hot water cylinder

[andrewfd]

We have a lagged copper cylinder fed from cold water tanks in the loft with gas boiler heating it plus an immersion for backup.

As the kids grow up we need to upgrade the second bathroom and increase the size of the HW cylinder as it runs out when we all 4 have a shower (power shower eats up the water fast!).

I'd really like to get the best performing replacement and have read a bit about thermal losses (watts per hour?).

Who can tell me which make and model is best for keeping the water hot?

Thanks for suggestions in advance.

 

[Dan Robinson]

They're all much of a muchness. Heat pump cylinders may be better but are more expensive.


Unvented cylinders are much better though.

Look at the OSO Super series.

 

[OwainDIYer]

Thermal losses from a modern cylinder are negligible. More important is the actual capacity in litres, and the heat output of the boiler and making best use of it.

Easiest way is to reduce hot water use by turning down the shower punp and fitting a low-water spray.

 

[St0rmer66]

Go for a "high recovery" cylinder and you might get away with the same size (it will reheat much faster). If you've got space you could still increase the size at the same time for an extra buffer.

 

[andrewfd]

A couple more questions

1) Copper or stainless steel or other or "doesn't matter"?

2) Which brands are known for quality and which to avoid?

3) 210 l or 300 l for a family of 4 with two showers (using S Turner Monsoon pump) and only occasional baths.

4) Timer comes on once at 5am and again in the evening with the existing copper (Badly) lagged cylinder. Would a new efficient cylinder mean I could heat it once in the morning and it would still retain heat for the evening so I don't need to heat again each day?

5) How much would you think I should spend on this to get good quality?

For example, I can't see what the difference is between these two - £500 more for the second one?

http://www.bhl.co.uk/oso-super-s-250-litre-indirect-unvented-cylinder-sci250.html

http://www.bhl.co.uk/oso-20ri250f1-indirect-unvented-cylinder-1-inch-fittings.html

 

[St0rmer66]

If you want a straight swap then you can't go for unvented. They use mains pressure and need to be installed by someone qualified to work on them. Your shower pump won't be usable. If your mains water pressure is up to it then it might be a good thing.

Something like the Gledhill CondenCyl would be a straight swap for you.

The whole point of a better insulated cylinder is that you can leave the hot water set to heat for LONGER, not less! If you want a constant supply then it's the only way. Bare in mind it will only heat until it's at the set temperature anyway, your boiler won't be actually on for long at all (and they lose so little heat because of the insulation it won't come back on until you start actually showering).

 

[andrewfd]

If you want a straight swap then you can't go for unvented. They use mains pressure and need to be installed by someone qualified to work on them. Your shower pump won't be usable. If your mains water pressure is up to it then it might be a good thing.

Something like the Gledhill CondenCyl would be a straight swap for you.

The whole point of a better insulated cylinder is that you can leave the hot water set to heat for LONGER, not less! If you want a constant supply then it's the only way. Bare in mind it will only heat until it's at the set temperature anyway, your boiler won't be actually on for long at all (and they lose so little heat because of the insulation it won't come back on until you start actually showering).

Thanks. Sorry I was dumb confusing vented and unvented.

Much cheaper suggestion too!

So could I actually leave my condensing boiler HW on 24/7 with this cylinder, knowing that it would only kick in to replenish the HW and the losses would be minimal? Is that likely to be worse than a timed cycle (say 1 hour in the morning and 1 hour in the early evening)?

 

[OwainDIYer]

It will be slightly worse heating continuously. A 300 litre indirect cylinder will typically lose about 2kWh over 24 hours. (the data is available on manufacturers' websites) At 6p per kWh for gas, and assuming 80% boiler efficiency, that will cost you about £1 per week to keep your cylinder at full temp all the time.

However if you use timed setting you probably won't notice any difference in showering, presumably the hot is mixed with cold at the point of use anyway.

 

[Agile]

The rule of thumb is 50 litres plus 50 liters per person. For four that would give 250 li.

But as the cost difference is so small then I would always advise getting a 300 li cylinder.

The cost difference between heating water 24/7 is so small but its better to time the reheat during hours when heating is likely to be used and to prevent the boiler firing at night when it could disturb people.

The hot water should be timed about 30 min before the heating so the water is always kept up to temperature.

Tony