Is it better to have separate heating and hot water controls

[ricardo1974]

I have a Danfoss Randall 102E5 programmer that currently allows for hot water only or hot water and heating.

My question is can the programmer be changed to a full programmer instead, so that I can select just the option to have the central heating on without the hot water, and will this save money on heating bills?

Also, am I limited by the type of boiler system I have? - Its a condensing boiler with a hot water cylinder, so I assume its not a combi?
Any help much appreciated...Thanks.

 

[stem]

As your boiler is condensing I assume it has been installed fairly recently and so to meet building regulations, at the same time the cylinder would be equipped with a thermostat, normally strapped on about a third of the way up from the bottom, and a motorised valve controlling the flow of hot water from the boiler to the hot water cylinder. If you have these, then the answer is yes, although you may have to change some of the wiring.

Regarding achieving energy savings, if the cylinder is well insulated, then I doubt you will even notice any difference at all.

At the moment, the cylinder will be heated by the boiler (usually in minutes) when the programmer first switches the system on. Once the cylinder is hot, and even though the programmer remains 'on' the thermostat will turn off the water coming to it from the boiler. If the cylinder is well insulated, and no hot water is used, it will sit there in the 'off' position for hours, possibly even all day.

If you use sufficient hot water to cool the cylinder then the thermostat will open the valve and reheat the cylinder. Which it would still have to do at some point anyway.

Quite a bit of heat can be lost from the first section of pipe leaving the top of the cylinder to feed the hot water taps if it's not insulated, but any heat emitted by the cylinder and pipes would add to the heating of the house anyway, so it's not wasted. (Except in the summer of course, but the programmer question doesn't apply then as you have 'hot water only' function for the summer)

 

[MJN]

Quite a bit of heat can be lost from the first section of pipe leaving the top of the cylinder to feed the hot water taps if it's not insulated, but any heat emitted by the cylinder and pipes would add to the heating of the house anyway, so it's not wasted.

Just to add to this; it's still worth insulating the top feed to at least as far as the pipe dropping (stratification will minimise onward travel of the hot water) as this pipe is outside of the CH control loop. The airing cupboard, assuming that's where the cylinder is located, will still gain sufficient heat to provide its expected benefits.

Mathew