Boiler Replacement 2 small ones or 1 large

nickjohn

Hi, not sure if this is in the right area for this post forgive me if it is not...

I have an old Ideal Mexico 2 floor standing system boiler and have been advised that it is getting to the end of its useful life and I should seriously consider replacing it. I have also been told that due to the size of the property ( victorian 5 bed semi over 3 floors with cellar) the boiler could do with being bigger, circa 120,000 btu..

Whilst I have had a quick look at the costs for new 120k btu boilers I was wondering if it would be more efficient to install 2 smaller boilers and split the heating into 2 zones, I have no problem with space as the boiler is in the cellar and there is a pipe riser in the house so altering the pipe work is easy enough.. I have also looked at the cost of smaller 80,000 btu boilers and I can get 2 of them for less that the cost of 1 x 120,000 btu boiler.

Just wasn't sure if the cost of running 2 new small boilers together would be more that the 1 larger one (given that using 1 large boiler will be heating the whole of the property when its running) and if the initial cost saving on the boilers would soon be lost....

Any feedback would be appreciated..

silvercar

We moved into a house with two boilers. One is a combi and provides heat to 6 rads and two bathrooms, the other is an ordinary boiler with a hot water tank. It works well for us and means we never run out of hot water. Can't comment on running costs as never had just one boiler.

ormus

its nearly always better to split a large property into 2 zones.
running costs for 1 large boiler or 2 smaller ones should be very similar.

27col

Running two smaller boilers would certainly give you more flexibility as to how the property was heated.

ormus

esp in winter if one breaks down.
very unlikely to get both breaking down at the same time.

Owain_Moneysaver

You can have separate zones without having separate boilers. You can have each room on a separate zone if you really want.

For larger installations it's common to have two or more boilers linked together with a boiler management system. Boilers run most efficiently fully loaded, so have both on (sharing the load) when needed and then drop back to one boiler on full output when the heating demand is partially satisfied.

Boiler management systems tend to be expensive as they're aimed at commercial installations. Also you will have two lots of servicing fees.

C_Mababejive

With a house of this size,my first priority would be to assess the level of insulation and energy efficiency,spending money in this area first.

I would then source a suitable single high efficiency system boiler and upgrade controls i.e zone area,fit TRVs etc.. install a weather compensator..

gas4you

If you had 2 boilers you would fit them onto a low loss header and then have a control that would only fire one until the heat demand needed 2. The control would monitor each boiler, to make sure they both got used the same amount, rather than one getting used all the time and the other only occasionally.

The heating system would still be zoned into as many zones as you wanted.