Disadvantage of a bigger boiler?

Maddie

I've asked this on the gas and electricity board but have been told you guys might be able to help also.

Apologies in advance for the long post...

We are about to install a new combi boiler and new central heating system are are trying to decide which boiler to go for.

The house is a 3 bed detached with secondary glazing on most windows (not double glazed) and a solid wall (no cavity or insulation). We will have 8 radiators in total.

However, we are hoping in the medium term to build an extension which would bring us to 4/5 bedrooms and increase the house size by almost 50%.

We have been quoted for the Vailliant 831 with this is mind. However I am concerned that we will end up wishing we had a slightly bigger boiler as I don't want to be worrying too much about using taps when someones having a shower etc.

Therefore I asked for a quote for the 837 which has come out about £200 more.

My question is - what is the disadvantage in going for the bigger one other than the upfront cost? Is it likely to be significantly less efficient etc?

Any advise would be appreciated!

Owain_Moneysaver

Why are you installing a combi boiler at all?

A 20% increase in power will give you a slightly better shower in cold weather, or a slightly quicker bath fill. It won't transform a combi boiler into an appliance capable of supporting multiple users simultaneously.

keystone

Agree - you need a system boiler particularly if, with your 4/5 bedrooms, you are going to have more than one bathroom.

Cheers

Maddie

I can understand why a system boiler would have advantages but we definitely want a combi. For a start, at the moment there are only 2 of us.

So the bigger boiler won't make much noticeable difference? Are there disadvantages of a bigger boiler?

DTDfanBoy

The main disadvantage you'll find with a larger combi boiler is that it won't overcome the problems you want to solve

"However, we are hoping in the medium term to build an extension which would bring us to 4/5 bedrooms and increase the house size by almost 50%.

We have been quoted for the Vailliant 831 with this is mind. However I am concerned that we will end up wishing we had a slightly bigger boiler as I don't want to be worrying too much about using taps when someones having a shower etc."

It would probably be more sensible for you to add a storage system to the combi boiler, or, as pointed out above, get the real thing and buy a system boiler.

FarleyFlavors

With only two of you in the house you won't really need a larger boiler, but you might want to consider the hot water flow rate.

We've got a roughly similar sized house - 4 bedrooms, secondary glazing, 10 radiators, and with two of us in the house. When we installed a combi boiler a year ago, we went for the Worcester Bosch 28i Junior. I don't know what the hot water output of the Valliant, is but ours is quoted at 11.4 litres per minute with a 35 degree temperature rise. To be honest, I think this is just a tad too low and in retrospect I wish we'd sprung the extra 200 or so to go for a larger boiler with a higher flow rate.

single_lonely

im in similar situation

3 storey house with 4 bedrooms

need radiators but also concerned about cost of pipes (its 3 floors!)
we have 2 'on demand' water heater (dont know what they are called)
i was thinking about putting a combi upstairs for radiators and showers and leaving the one downstairs for washing cooking etc.

also would warmfront do something like this?

thanks