Small HW cylinder for shower?

[niceboy]

Hi all

Problem. We're about to add an ensuite to a bedroom. Elsewhere in the house is a shower fed from the main hot water cylinder, and another which is a Mira electric. This takes about 45 amps. The main incoming house fuse is rated at 80 amps, which rules out another electric shower.

Looks like I'll need to run the new shower on stored hot water. Don't fancy taking it from the existing cylinder which is already stretched to the limit and often runs cold after baths etc. The simple solution would be to provide it with its own storage cylinder. Can't heat that one from the boiler which is already worked hard and is too far away anyway.

The immersion heater principle looks good but a full-on domestic cylinder seems like overkill for just one shower. Otherwise I can only find small under-counter heaters like the Ariston.

Would a "local" immersion-powered cylinder be good practice and does anyone know of suitable one of around 50 litres? (Missus and I don't hang around too long in the shower!)

 

[JohnD]

how does that compare with the idea of replacing your current undersized cylinder with one that is big enough?

How do you know your boiler is underpowered?

I suppose you know that energy from electricity currently costs four times as much as energy from gas.

 

[Dan Robinson]

Is this an electric only house?

 

[niceboy]

Sorry guys, should have said - oil boiler heats the main cylinder. Also this is part of a 30 sq m, 2-storey extension

JohnD - "Underpowered" is a bit subjective. Boiler is big enough currently but does take its time getting everything up to temp.

A bigger cylinder is a good idea but the existing one is already tight in a cupboard.

I've just been looking at a dedicated Megaflo system. Seems like overkill for one shower? All we really need is a simple direct-heated tank in the loft. The cold tank is on raised piers and provides a decent enough head for the other shower.

Yes, I'm aware of the added cost of electric. A quick shower uses about one unit of juice. Fairly painless, esp if heated offpeak.

So - any ideas on a suitable cylinder?

 

[JohnD]

JohnD - "Underpowered" is a bit subjective. Boiler is big enough currently but does take its time getting everything up to temp.

Do you mean it is slow to make the radiators hot, or the radiators are slow to make the house warm?

 

[Dan Robinson]

A 50 litre cylinder will take 50 minutes to heat up off 3kW. 3kW for one hour costs???

 

[niceboy]

JohnD - bit of both. But it's quite a big house (five bedrooms, heat zoned upstairs /downstairs). It's OK at the moment but I'm not sure how much it will like another 30+ sq m of underfloor heating.

Dan - what was your temp target there? I have a formula that's showing 50 litres heated in one hour from 14 to 40 deg will use 1.52kW.

 

[Dan Robinson]

You heat your water to 60 degrees for legionella. DT50

 

[Dan Robinson]

Which is actually nearer 60 minutes... I did my sums wrong before

 

[niceboy]

Fine, I didn't know the 60 degree requirement. But if it's heated water from the mains only feeding a shower would that matter?

 

[Dan Robinson]

yes.

 

[Agile]

Only during the two summer months does the mains water come in at 14 C.

Right now its more like 6 C and will get colder over the next few weeks!

Tony