What size boiler is required please?

[REDSAW34]

exactly as myles says.

[Cab]

Originally Posted by Blackcatgas

Yes, It takes the big Kw to instantly heat the hot water, combis are modulating so if you require 14kw for your heating they will modulate down and then run full rate say 30kw for the hot water demand.

I have a 'regular' boiler at present which i want changing to a 'system' boiler. I have a cylinder (unvented 170ltr) and don't require a combi .

My dilema is what would be the best power output to go for to have fast re-heat times on the cylider and central heating. At present if i let the temp of my house drop right down to about 12 deg C it takes a good 12 hours or more to get back up to 19 deg C. Also heating the cylinder takes ages too if i've got both the heating and the hot water on.

Thanks

[doitmyself]

Originally Posted by Cab

I have a 'regular' boiler at present which i want changing to a 'system' boiler. I have a cylinder (unvented 170ltr) and don't require a combi .

Thanks for repeating that, even though it was quite clear from your original question. Some contributors seem, somehow, to never read the original question properly and automatically assume that you want/need a combi boiler.

My dilema is what would be the best power output to go for to have fast re-heat times on the cylider and central heating.

The two calculators came up with 13kW, i.e 11kW for heating and 2kW for HW. There is no point going over the top and installing a 30kW boiler as the rads will not be able to dissipate that amount of heat. I suggest you install a 15kW boiler. That leaves 4kW for the hot water, which should be sufficient for the cylinder.

Does your house cool down quickly when the heating is turned off? If it doesn't, one possible solution is to install a system with hot water priority. This means that, while the HW is being heated, the Central Heating is temporarily turned off. The full output of the boiler is then allocated to heating the HW, resulting in reduced heating up times. Obviously the cylinder must be capable of handling this amount of heat. The other advantage is that you do not have to allow any extra in the boiler size for HW so you would only need an 11 or 12kW boiler.

Having 14kW of rads when you only need 11kW is a good thing. The boiler will be able to run at lower temperatures. This means that weather compensation should be considered.

I know you say you want a WB boiler, but you should have a look at the Broag-Remeha Avanta Range - 18s. This boiler can provide both weather compensation and HW priority. It might seem to be oversized, but the CH output can be set to a lower amount if necessary, without affecting the output to the HW cylinder.

[Blackcatgas]

Originally Posted by Cab

I have a 'regular' boiler at present which i want changing to a 'system' boiler. I have a cylinder (unvented 170ltr) and don't require a combi .

My dilema is what would be the best power output to go for to have fast re-heat times on the cylider and central heating. At present if i let the temp of my house drop right down to about 12 deg C it takes a good 12 hours or more to get back up to 19 deg C. Also heating the cylinder takes ages too if i've got both the heating and the hot water on.

Thanks

Sorry cab I was replying to Derrybongos post not yours, even though he hijacked the thread.

[QUOTE=doitmyself;43433]Thanks for repeating that, even though it was quite clear from your original question. Some contributors seem, somehow, to never read the original question properly and automatically assume that you want/need a combi boiler.


My reply was to Derybongos question

[Cab]

Just a quick note to say thanks to all for your input/advice/suggestions. It is very much appreciated

Thanks