which Vaillant High Efficiency Combination Boiler do i choose

bernlyn

help please

i am replacing old heating with a condensing combi. i want to use Vaillant High Efficiency Combination Boiler but dont know which 1. i have worked out with rad calc that i will need BTU 34186 for the radiators but how do do calculate the size of the boiler when you want it for hotwater aswell, keeping in mind that i will have a thermastatic shower as well

jos22

I am never surprised what members can come up with, but if you get no response try posting on https://www.diynot.com forum - it's free. I think Screwfix also have a forum that may help. :beer:

bernlyn

just to clear something up. i know that the boiler is for hot water aswell meaning for bath shower etc and the central heating. the question i think that i am trying find answers for the choice of the boiler BTU should it be 35 000 as i need this for my rads or do you choose 1 that is 80 000. does this mean that the hot water supply and central heating is already calculated into the BTU of the 80 000

MyUserNamesTaken

The BTU you need depends on the number of rads you're looking to run off the boiler. I've got a Vaillant Ecomax 828, by the way. Excellent boiler.


http://www.gasapplianceguide.co.uk/vaillant_ecomax.htm

Eyesparky

The limiting factor on a combi boiler is the requirement for hot water not really the number of radiators. Personally I would go for the highest flow rate you can afford otherwise you will be disappointed with the shower and bath filling rate.

economiser

One of the drawbacks of combination boilers is that you are trying to do two things with the same burner. As eyesparky says you really need as big as you can to get a good flow of hot water but if this means it is greatly oversized for the heating requirement you will lose some efficiency. Still life is like that - you can't have everything.

By the way you need good mains water pressure as well. Try asking any neighbours who have combination boilers how they get on with them.

botmission

Combis run at at least 80,000 btu's (24 kw) for hot water regardless of the heating requirements.

A 28kw Ecomax is what I would recommend, bearing in mind that the important factor here is the hot water.

Make sure whoever installs it flushes out the existing system first. The guarentee will be worthless if the water in the system is found to be 'dirty'.

Oh, and position the flue terminal so that the 'plume' doesn't annoy the neighbours!