Heating with Boiler Stove

DollyDD · 2 December 2017 at 3:55PM

Hi All,

We currently have a boiler stove heating the hot water tank and radiators. It isn't really up to the job, as the underfloor heating we have in one room I think takes a lot of heat out of the system. There are only three radiators. The hot water tank is also an immersion heater so we can top the heat up for a bath. It is a vented system, (obviously), with an expansion tank in the spare bedroom, (we have no loft as the bedrooms are in the roof).
What I would like to know is can we have the stove for heating the radiators and underfloor only, and would the cost be worth it - that is - would we be warmer ?:) Thanks.

matelodave · 2 December 2017 at 5:00PM

It depends what sort of stove it is. Any stove will only produce a certain amound of heat based on it's size and how often you feed it. Some of that heat will heat the stove and some will heat the water that flows through it. If the stove is undersized then it won't produce as much heat as you need.

There will also be a limitation of how much heat can be transferred from the stove to the water, the same with how much heat you can get out of the radiators and underfloor system and into the hot water tank as they will all be sharing some of it at the same time.

Most heating systems are unable to heat both hot water and central heating simultaneously and have diverter valves to transfer the heat from the stove/boiler from one to the other. Adding extra rads or underfloor systems to an existing system that might have been just about adequate will make it just about inadequate.

Without knowing how big your stove is, how big the rads are, how big your hot water tank is and how your u/f system is configured and how much area it's trying to heat it's an impossible question to answer. What sort of controls has it all got, programmer, thermostats, pumps, diverters, trvs etc.

It's likely that if you stop heating the hot water from the stove then there will be more available to heat the rads and u/f system however you'll then be using the immersion to heat your hot water which will increase you leccy bill.

J_B · 3 December 2017 at 4:15PM

matelodave wrote: »

.......... using the immersion to heat your hot water which will increase you leccy bill.

I was going to suggest switching to 'economy7' and just using the immersion for water heating at the cheap rate ... if you could somehow turn off the stove water from doing that?

DollyDD · 5 December 2017 at 8:34AM

Hello MateloDave,

Well, it is an 18 kw stove, one of the rads is a small bathroom radiator and towel rail combined, which is useless. The other two rads are not large by any means. The underfloor is heating a 12 x 14 ft space. The water tank is standard size, and is situated on the other side of the wall from the back of the stove, so quite close. There is a pump which pumps the water round the system when the water is hot enough in the tank. There is a seperate pump on the underfloor which only lets the water in when it is a certain temperature. Not being a plumber, that is all I can tell you I am afraid. I don't know why the stove does not heat all that, it should be man enough, but it isn't. I burn largely hard wood, with a bit of pine. We have to have the upstairs rads turned off to get any heat in the underfloor at all. I think that is the culprit. I think the rads would be nice and hot without that, but as there is no radiator in that room, (and I don't want one), I am loath to get rid. It was also quite expensive to buy. Hope this helps your analysis ! I thought of having the immersion on all the time when the stove is being lit every day. That would help the heating come on quicker and not use much electric with the stove heat back up, BUT, that would mean the pump would be running constantly and pumping cold water round the rads at night, which it often does anyway even when the tank is switched off. My plumber, unknown to me, fitted an obsolete sensor dial switch to the side of the hot water tank, which does not work very well. Sorry I can't be more help.

Cardew · 5 December 2017 at 10:37AM

Oh it is a wood stove!

matelodave · 5 December 2017 at 10:46AM

It's difficult to work out what might be going wrong without actually knowing how your system is configured and what controls you've got.

You've got a solid fuel boiler which isn't as controllable as a normal boiler and generally can't fire up or shut down on demand like a gas boiler and needs to dump excess heat.

Some systems have a gravity hot water system with just the heating being pumped. The tank water can then get very hot unless there's a blending or thermostatic valve in the circuit.

I'm guessing that you've got a main circulating pump which pumps water through the boiler and heating ciruit and possibly the tank. Has it got a thermostat & programmer to control it. If so where is it located) and is there a stat on the tank or is it just a thermostatic valve. Is there a diverter valve anywhere. Do your upstairs rads have thermostatic valves.

Most single room u/f systems have their own pump and a blending valve together with a thermostat to control the pump however the main pump has to run at the same time as the u/f pump.

You need to ensure that both pumps are running when the u/f calls for heat and that the main pump runs when it's just the hot water or radiator heating that's required.

Make sure that any programmer or stat on the u/f doesn't shut down the main pump when the the u/f room is satisfied and dont have any thermostats in the room where the boiler is situated as the heat from the boiler will shut the pumps down and stop heating the the other rooms.

If you can't work out what's going on then you really need a heating engineer to come in and sort it out

Heating with Boiler Stove

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