What Size Unvented Cylinder

[jon26]

Hi guys, same mate of mine that needs the new boiler...

He is looking to get a new HW system installed. The house is a 3 bedroom (2 double and 1 single) with 1 bathroom (containing a large bath and a shower cubicle) and 1 en-suite (containing a shower)

Thinking of using a Heatrae Megaflo, what capacity would normally fit the bill in this case. Not sure what is there at the moment and he really dosent want a combi.

He can work computers, so I am having to help, thanks.

 

[moliver34]

Is your 'mate' qualified to install an unvented hot water cylinder;

In order to install a unvented cylinder you need to have completed and passed a test!

 

[jon26]

Is your 'mate' qualified to install an unvented hot water cylinder;

In order to install a unvented cylinder you need to have completed and passed a test!

He won't be installing it. He is trying to get an idea of what size cylinder is needed.

 

[lightning]

your looking at about 210 litres {indirect}

 

[gas4you]

I think in this case you would be ok with a 170 litre Megaflo.

 

[Agile]

What a lot of possibly wrong answers!

The capacity of the cylinder depends on the number of PEOPLE who normally live there.

Its 50 litres per person as the rule of thumb! Ideally plus 50 litres extra !

We are told that "He can work computers, so I am having to help, thanks." In that case one wonders why he is not asking the questions himself.

As always, the best advice is from the qualified installer who is going to fit it ( and be responsible for his design advice! ).

Tony

 

[gas4you]

My answer is not wrong.

Perhaps you should look at the heatrae site before piping up Tony

 

[Agile]

Dave, do you really think that the same size cylinder is needed in a six bed, five bathroom house occupied by a pensioner couple?

As compared with a three bed two bathroom occupied by six tenants all from third world countries and working in the building trade ( so getting very dirty ) and all wanting to bath/shower at 6 pm ?

The required size is assessed on the number of people! With some adjustment according to their ages and occupations!

Tony

 

[billy bob]

You would not size a cylinder to the present occupier, as you say you could have a six bed five bathroom house with a pensioner couple, you should not size the cylinder just for two people, that would be stupid, you would size the cylinder to the amount of bathrooms, what would be the point in installing a 170L cylinder in that size house, they will not live for ever and the next occupants might be a large family, which you would expect for that size house, what good would the 170L tank be then, as I said, you should size the cylinder to the maximum demand possible, in this case 5 bathrooms.

 

[rssteve]

Tony you really are annoying.

quote - Its 50 litres per person as the rule of thumb! Ideally plus 50 litres extra !

so in a one bed flat with one person living there, you think 100l is plenty, they may have a big bath, fill that up then want to use the shower whilst in it for say washing down and washing hair. what about them there partner stays one night and they both want a shower? ******************

deleted - Mod

 

[The Baker]

As a non G3 Herbert I can only watch and learn from the friendly advice forthcoming from the Experts on this bit of the forum.

But having read the reply,s a few things have occurred to me.

Gas 4 you was trying to be helpful.

Agile displayed his usual "get straight up peoples noses" style of reply.(a, get on that diplomacy course Tony, emoticon)

And Mr Bob gave his usual informative comments, however, the words "they will not live for ever" made me smile as I am sure he will when he reads the thought that flashed across my mind as I read them. This thought was; neither do the Copper cylinders

Tim

 

[Paul Barker]

Just to throw a spanner in the works

With a lrage you can store it at a lower temperature for the same number of people as a smaller store. The temperature gradient between stored water and the environment affects heat transfer; losses are greater where the gradiant is greater.

 

[simond]

An ACV unvented surrounds the hot water with boiler water in a buffer store. This might appeal, a smaller cylinder can be used because of the faster reheat time.

I would avoid 'bubble top' cylinders (like Megaflo and some OSOs) because they need periodic air gap replenishment.

I can see no advantages whatsoever in bubble top designs, only problems.

 

[billy bob]

As a non G3 Herbert I can only watch and learn from the friendly advice forthcoming from the Experts on this bit of the forum.

But having read the reply,s a few things have occurred to me.

Gas 4 you was trying to be helpful.

Agile displayed his usual "get straight up peoples noses" style of reply.(a, get on that diplomacy course Tony, emoticon)

And Mr Bob gave his usual informative comments, however, the words "they will not live for ever" made me smile as I am sure he will when he reads the thought that flashed across my mind as I read them. This thought was; neither do the Copper cylinders

Tim

I never use copper cylinders for unvented Tim, only stainless steel, I realise no one lives for ever, maybe I should re-phrase that to "they will probably not live in the house for ever"

 

[Paul Barker]

Sorry needed to get my head round the next benefit of larger store.

I knew that larger volume meant ratio surface area to volume in favour of lower heat losses but couldn't get head round it in relation to cylinders.

in a cube it is easy to prove.

a cube of 2m sides area is 24m squared volume = 8m cubed or 8000 litre ratio 3:1

4m sides is 96 sq vol = 64 cub 3:2 ratio

and so on.

then I imagined a cylinder of twice the hight same diameter. on the face ofit the ratio of surface area to volume is the same. Then you realise that to put two small cylinders

beside each other gives an extra top and extra bottom surface area. So a larger cylinder as same volume has better ratio and so less losses.