HELP: New Boiler BTU to KW

ArunanandM

Hi

Am planning to install a new boiler in my home. Its 4 bed house with 1 bath and 1 WC.

1) I have calculated BTU for all the radiators including towel radiator. And its 62000 BTU.
2) I'm installing water underfloor heating for 20 sq meter approximately.
3) As I mentioned we have 1 bath and 1 WC.

At the moment I've Vaillant EcoTech Plus 824. I think its not enough for the above mentioned heating requirement. Therefore I'm planning to upgrade it to higher KW boiler or should I!?

If yes, I'm looking at Vaillant Green IQ 835 or 843. Is this good model as I cant find enough information around.

If its good model, which one should I go for, 835 (35 KW) or 843 (43 KW).

if this model is not recommended, could you please recommend some other model in Vaillant.

Basically am trying to understand how much KW I would need for the above mentioned heating requirement.

Thank you very much.

D_M_E

62000 btu is about 19Kw - 1Kw=3412 btu.

If you get the 35Kw model that leaves you about 16Kw for the underfloor heating.

Cannot reccomend a boiler as I'm not all that familiar with them.

matelodave

It's not just the size of the boiler that you have to take into account it's the size or capacity of the heat emitters (radiators/underfloor heating). Si

Look at the sizing and output of your radiators to see how much heat they can dissipate and calculate whether you need to upgrade those as well. Just bunging on a bigger boiler wont get you any warmer if the radiators can't deliver it's output.

Underfloor heating runs at a lower temperature than radiators and will usually have a mixing valve and it's own pump. A reasonable estimate for u/f heating would be about 100w/sq.m which in your case would equate to around 2kw. (my u/f heating is around 70w/sq.m over 140 sq/m)

If you think you need around 20kw then putting a 35 or 43kwh boiler is probably well oversizing it. The only advantage is that a combi boiler of those sizes would give you a higher flow rate of hot water fom your hot water taps.

Is your present heating system inadequate

ArunanandM

matelodave wrote: »

It's not just the size of the boiler that you have to take into account it's the size or capacity of the heat emitters (radiators/underfloor heating). Si

Look at the sizing and output of your radiators to see how much heat they can dissipate and calculate whether you need to upgrade those as well. Just bunging on a bigger boiler wont get you any warmer if the radiators can't deliver it's output.

Underfloor heating runs at a lower temperature than radiators and will usually have a mixing valve and it's own pump. A reasonable estimate for u/f heating would be about 100w/sq.m which in your case would equate to around 2kw. (my u/f heating is around 70w/sq.m over 140 sq/m)

If you think you need around 20kw then putting a 35 or 43kwh boiler is probably well oversizing it. The only advantage is that a combi boiler of those sizes would give you a higher flow rate of hot water fom your hot water taps.

Is your present heating system inadequate

Thanks for your input. We've had Warm Air Unit for heating and combi boiler (Vaillant 824 ecoTech plus 824) for hot water only. We have now removed WAU and replacing it with radiators. Plus we are also installing underfloor heating as I mentioned. Therefore am trying to work out if the current combi boiler is capable of running everything or should I upgrade it to the new one.

Cardew

ArunanandM wrote: »

Therefore am trying to work out if the current combi boiler is capable of running everything or should I upgrade it to the new one.

The output(size) of a combi is determined more by the demand for heating hot water, for baths/showers/taps, than the heating load.