Dual heating. Oil and solid fuel.

ari2019 · 28 Dec 2018

2500sq ft house built during when things are good. The building regs wherent great, 50mm aeroboard in the cavity. 50mm fibreglass in the attic spaces. I have upgraded to 250mm fibreglass in attic voids and in the living area, dining and kitchen i have installed 75mm insulated plasterboard. Will be upgrading to external insulation next year and getting the house air tested to find leaks.

I have upgraded to a 30kw solid fuel stove however it hasnt been connected to the cylinder yet double coil cylinder. The house is already plumbed in for oil to a single coil but will be upgrading to double coil soon.

What i want to know is, is it possible that i can set it up that i can only heat downstairs instead of all over and when needed i can call for the heating upstairs when needed rather than running about the house turning off valves etc... . This is a large house and i would only need heat in some rooms rather than heating the full house.

oldbutnotdead · 28 Dec 2018

2 port motorised valves are your friend here, or you can get WiFi radiator valves. Remember you will need some sort of heat loss rad permanently linked to the solid fuel stove (to maintain thermal syphon).

ari2019 · 28 Dec 2018

oldbutnotdead said:
2 port motorised valves are your friend here, or you can get WiFi radiator valves. Remember you will need some sort of heat loss rad permanently linked to the solid fuel stove (to maintain thermal syphon).

Is the cylinder not a heat leak with it being vented?

oldbutnotdead · 28 Dec 2018

No because it is insulated (even if it isn't, heat loss is quite low due to surface area to volume ratio). Without the heat loss rad the thermal Syphon stops working when cylinder is up to 90-odd, the stove will then kettle like mad. Approved Docs require heatloss rad of about 10% of output of the uncontrolled device. There are other ways to comply (dumping cylinder hot water if it gets too hot & cooling the job with cold water from the header tank) but they are complex

ari2019 · 28 Dec 2018

oldbutnotdead said:
No because it is insulated (even if it isn't, heat loss is quite low due to surface area to volume ratio). Without the heat loss rad the thermal Syphon stops working when cylinder is up to 90-odd, the stove will then kettle like mad. Approved Docs require heatloss rad of about 10% of output of the uncontrolled device. There are other ways to comply (dumping cylinder hot water if it gets too hot & cooling the job with cold water from the header tank) but they are complex

So best thing is a heat loss rad. Doesnt the heat loss rad have to be above the cylinder.

oldbutnotdead · 28 Dec 2018

Doesn't have to be but you will lose less heat that way (the rad won't start getting really hot til the cylinder is up to temperatiure, likewise you won't get hot from the primary syphoning down into the rad when the solid fuel thing is off & the cylinder is still hot)

ari2019 · 28 Dec 2018

oldbutnotdead said:
Doesn't have to be but you will lose less heat that way (the rad won't start getting really hot til the cylinder is up to temperatiure, likewise you won't get hot from the primary syphoning down into the rad when the solid fuel thing is off & the cylinder is still hot)

Can it be done without a heat leak rad

oldbutnotdead · 29 Dec 2018

Yes but you then need a technical solution. Talk to your HETAS bod who put the stove in, see what options she can offer

Jay88 · 29 Dec 2018

Get rid of the cylinder and put a thermal store in, 3 lots of open tappings! 2 x 28mm for boiler stove(could be 1”1/4 if the stove is 30kw) 2 for oil boiler and 2 for heating circuit,plus a hot water coil then you can have mains pressure hot water. i wouldnt put a zonevalve on the downstairs circuit, just on the upstairs so whenever pump is on it goes round down stairs rads and a stat upstairs to control upstairs heating. Depending where cylinder goes put your heat leak rad fairly close, for example if in airing cupboard then put heat leak to a bathroom rad or landing rad, somewhere where you dont mind it been on quite alot!will also need to be piped to work of gravity so can be tricky sometimes. Bear in mind the distance from the stove to the cylinder, if un lagged then this can also class as abit of heat loss so no need to put a huge heat leak rad but should still be calculated.

How we do them is put a high limit stat on the stove flow pipe up by the store set at around 85-90 degrees, when this is reached it will automatically kick heating pump in sending water to rads, hence why only putting one zone valve on incase of powercut then hot water should still gravitate a small amount round the heating circs of the permantly open zone.
Oil boiler just works of a cylinder stat so if fire isnt on oil boiler will just run everything

You will need a copper high temperature F & E tank in the loft running a copper overflow to outside, no plastic allowed incase the worse happens

ari2019 · 29 Dec 2018

Jay88 said:
Get rid of the cylinder and put a thermal store in, 3 lots of open tappings! 2 x 28mm for boiler stove(could be 1”1/4 if the stove is 30kw) 2 for oil boiler and 2 for heating circuit,plus a hot water coil then you can have mains pressure hot water. i wouldnt put a zonevalve on the downstairs circuit, just on the upstairs so whenever pump is on it goes round down stairs rads and a stat upstairs to control upstairs heating. Depending where cylinder goes put your heat leak rad fairly close, for example if in airing cupboard then put heat leak to a bathroom rad or landing rad, somewhere where you dont mind it been on quite alot!will also need to be piped to work of gravity so can be tricky sometimes. Bear in mind the distance from the stove to the cylinder, if un lagged then this can also class as abit of heat loss so no need to put a huge heat leak rad but should still be calculated.

How we do them is put a high limit stat on the stove flow pipe up by the store set at around 85-90 degrees, when this is reached it will automatically kick heating pump in sending water to rads, hence why only putting one zone valve on incase of powercut then hot water should still gravitate a small amount round the heating circs of the permantly open zone.
Oil boiler just works of a cylinder stat so if fire isnt on oil boiler will just run everything

You will need a copper high temperature F & E tank in the loft running a copper overflow to outside, no plastic allowed incase the worse happens

I dont think i have enough room for a thermal store. Arent they larger than the copper cylinders!

This stove is already been set in position and piped to near the cylinder when i was doing works at the beginning of the year. I will draw a diagram or show pics of where the pipes are running. Basically the flow is leaving the stove sloping up then up the wall with a continuous slope up across the joist going towards the cylinder. The other pipe is piped near the cylinder and is slopping down towards the stove. One has a rise, the other a fall.

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Dual heating. Oil and solid fuel.

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