New unvented central heating system.

purpleparrotuk

I have ordered an unvented install along with Honeywell evo system. The boiler will be a ideal vogue 32kw and a Stelflow 150L unvented cylinder. Having my one pipe system converted to 2 pipe and 4 new rads. It’s a 3 bed detached with 1 bathroom with shower, 1 bathroom with bath and also a downstairs loo. Also a downstairs loo.
I have 8/9 rads at the moment.

Other people have advised me the cylinder is way too small and that the boiler is way too big. Can anyone please help before the parts are ordered by the plumber?

Alex1983

The boiler is massively over sized, as a very rough guide allow 1.5kw per rad and 3kw for hot water which gives you a rough est of 16.5kw.

The unvented, it’s suggested you allow 45 litres per person in the property, remember the most new unvented cylinders will reheat from cold in around 20/30mims.

purpleparrotuk

Alex1983 wrote: »

The boiler is massively over sized, as a very rough guide allow 1.5kw per rad and 3kw for hot water which gives you a rough est of 16.5kw.

The unvented, it’s suggested you allow 45 litres per person in the property, remember the most new unvented cylinders will reheat from cold in around 20/30mims.

Hi. There’s only the 2 of us but if I sell in the future then I want it to be future proof for families. The cylinder is going in the airing cupboard replacing the existing cyclinder. Did you think he has gone for that size because of space limitations?

nofoollikeold

Heating requirements are going to be around 13 x 1.5 = 19.5Kw.
150L cylinder reheat in 17 minutes requires 18.5 Kw.
Total 38Kw, but ONLY if you want to re-heat tank from cold at the same time as heating house from cold.

Set the timer / controls to separate central heating and hot water and you should only need a peak rating of, say 20Kw. The nearest Ideal Vogue system boiler above 20Kw is the 26Kw one.

150L is on the small side for a 3 bedroom house, which has the potential for, say 2 adults and 3 or 4 children occupancy. I'd go for the 210L, the heat loss is only 0.4 Kw per day more than the 150L

Alex1983

Are you have 4 extra rads so you will have 13 when finished if so then ignore my 1st comment I thought you had a total of 9, but the hot water allowance doesn’t change you work it out with 3kw for hot water and to be honest that a high usage but that’s what I’ve always allowed, have a read of the energy saving trust website about central heating sizing it will explain more. With 13 rads your rough requirements will be 22.5kw and with 9 rads will be 16.5kw.

I would personally do some research of boiler manufacturers as ideal have made some of the most unreliable boilers since the days of the Mexico and classic ranges, there after care doesn’t have a great reputation either.

Alex1983

Also with regards to the unvented size, there is probably not much price difference between 150l and 200l so I’d have the 200l.

bris

150l is to small, sounds a lot but in practice its not. 200ml is about as small as you want to go.


As already said 32kw is overkill a 24kw is even more than you need but is what I would suggest.

purpleparrotuk

Thanks for all your replies. The problem is if I go bigger than 150 for the cylinder it will need to go in the loft and I cannot afford the expense of that. At the moment I have a 90l cylinder and that’s more than enough for the 2 of us. We have 2 showers one after the other and shave etc and that’s after only heating the cylinder for 1 hour every day. There’s never going to be more than 2 of us. I spoke with my plumber about the size of the boiler and he said he chose the size in case we extend etc in the future. He says he can downsize for about £50 difference. The boiler is self modulation so it will adapt to the output needed. Shall I ask the plumber for a different brand then since Ideal is not ideal apparently.

southcoastrgi

Is the boiler going in the airing cupboard as well ?
If not a 210 will fit in there,
Personally I wouldn’t fit Ideal if I was given it free

purpleparrotuk

Not all airing cupboards are the same size surely? Mine isn’t massive. It’s only like half a cupboard. The boiler is under the stairs.

What system boiler would you go for then?

ComicGeek

purpleparrotuk wrote: »

At the moment I have a 90l cylinder and that’s more than enough for the 2 of us. We have 2 showers one after the other and shave etc and that’s after only heating the cylinder for 1 hour every day. There’s never going to be more than 2 of us.

If that's sufficient for you, and you don't have the space, then stick with the proposed 150 litre cylinder. Not many people will look at the cylinder size when you come to sell in the future. Worst case is that you have to wait for the cylinder to reheat.

purpleparrotuk wrote: »

I spoke with my plumber about the size of the boiler and he said he chose the size in case we extend etc in the future. He says he can downsize for about £50 difference. The boiler is self modulation so it will adapt to the output needed. Shall I ask the plumber for a different brand then since Ideal is not ideal apparently.

It is self modulating, but only down to 6.4 kW. A smaller boiler would modulate down further, so will be turning on and off fewer times. I would agree with others that a 24 kW is the biggest than you should go for with the current situation. Crazy to massively oversize for an extension that may never happen, unless you have concrete plans for this?

And definitely not Ideal, almost anyone else but them!! I personally prefer the Vaillant Ecotec Plus range, but even those aren't as reliable as they were and over priced.