Thermal Stove v Unvented Cylinder
Discussion
We've just extended our home and are now considering what to do in terms of heating and domestic hot water. We've had three plumbers out so far, all giving different answers.
The question is, should we have an unvented cylinder or a thermal store?
System will have to cater for the following:
5 bed house
Grant Vortex Eco 21-26kw Oil fuelled condensing boiler
Multi Fuel Stove (if we decide Thermal Store then this will be a boiler stove - 20kw to water - we get free logs)
12 large rads
70m2 wet UFH
1 bathroom
2 en-suites
We currently have an additional 2 multi fuel burning stoves + 1 open fire. All regularly lit during the winter months.
Unvented Cylinder (210 litre advised?)
Pro's:
"Only" £500-£700 to purchase (looking at OSO cylinders).
Mains pressure hot water.
Con's:
Won't be able to connect Multi fuel boiler stove to the system.
Requires an annual service.
Requires sealed system" conversion kit for the boiler.
Thermal Store (400 litre capacity advised?)
Pro's:
Can connect Multi fuel boiler stove.
Doesn't require an annual service.
Mains pressure hot water.
Ease of connecting radiators/UFH.
Not sure if I'll need the "sealed system" conversion kit for the boiler?
Will I need fewer pumps/components for UFH?
Con's:
Cost - £1500-£3000. Unsure how to spec it with all the different options.
Help.
p.s. Gas is currently a no go.
The question is, should we have an unvented cylinder or a thermal store?
System will have to cater for the following:
5 bed house
Grant Vortex Eco 21-26kw Oil fuelled condensing boiler
Multi Fuel Stove (if we decide Thermal Store then this will be a boiler stove - 20kw to water - we get free logs)
12 large rads
70m2 wet UFH
1 bathroom
2 en-suites
We currently have an additional 2 multi fuel burning stoves + 1 open fire. All regularly lit during the winter months.
Unvented Cylinder (210 litre advised?)
Pro's:
"Only" £500-£700 to purchase (looking at OSO cylinders).
Mains pressure hot water.
Con's:
Won't be able to connect Multi fuel boiler stove to the system.
Requires an annual service.
Requires sealed system" conversion kit for the boiler.
Thermal Store (400 litre capacity advised?)
Pro's:
Can connect Multi fuel boiler stove.
Doesn't require an annual service.
Mains pressure hot water.
Ease of connecting radiators/UFH.
Not sure if I'll need the "sealed system" conversion kit for the boiler?
Will I need fewer pumps/components for UFH?
Con's:
Cost - £1500-£3000. Unsure how to spec it with all the different options.
Help.
p.s. Gas is currently a no go.
If you're not on gas, and are fitting a completely new system, I suggest that you also consider adding solar thermal heating. A properly designed system can do most of your DHW in the summer.
Have a look at this forum, there's a lot of knowledge there about getting the best from several heat sources for water heating.
http://www.navitron.org.uk/forum/index.php/board,6...
Have a look at this forum, there's a lot of knowledge there about getting the best from several heat sources for water heating.
http://www.navitron.org.uk/forum/index.php/board,6...
Navitron will also sell you the cylinder with all the bits, so you can get an idea of the parts price.
Ours is a Navitron 210 litre, with taps for an lpg boiler, solar panels, stove with back boiler and electric coil. Our house is very, very well insulated though, so it doesn't have to do much work to keep it warm in winter (we have UFH downstairs and no heating at all upstairs). I think thermal stores are fantastic bits of kit.
We got an idiot (and I mean that sincerely) plumber to plumb it in, and it was a sufficiently straightforward job that he only ballsed up one bit (got the flow backwards). For a family of 2 adults (daily showers) and 2 young kids (daily bath) we can have a couple of days of 'no heat' before we run out of hot. On a good summer like this, everything comes off the solar panels.
If you have plans for a stove, the biggest complication is getting anything plumbed into it. It's classed as an uncontrolled heat source, so has to have safety mechanisms and be installed by a registered plumber (they're fairly rare). For your own sanity, the nearer the stove is to the store (preferably it's vertically below it), the simpler things become.
Ours is a Navitron 210 litre, with taps for an lpg boiler, solar panels, stove with back boiler and electric coil. Our house is very, very well insulated though, so it doesn't have to do much work to keep it warm in winter (we have UFH downstairs and no heating at all upstairs). I think thermal stores are fantastic bits of kit.
We got an idiot (and I mean that sincerely) plumber to plumb it in, and it was a sufficiently straightforward job that he only ballsed up one bit (got the flow backwards). For a family of 2 adults (daily showers) and 2 young kids (daily bath) we can have a couple of days of 'no heat' before we run out of hot. On a good summer like this, everything comes off the solar panels.
If you have plans for a stove, the biggest complication is getting anything plumbed into it. It's classed as an uncontrolled heat source, so has to have safety mechanisms and be installed by a registered plumber (they're fairly rare). For your own sanity, the nearer the stove is to the store (preferably it's vertically below it), the simpler things become.
Thanks for the replies!
Will have a look if we have a 22mm incoming main or not.
Our Extension will be to building regs, so is well insulated. The original part of the house (1700's) has 500mm thick solid stone walls, smallish windows and lots of insulation in the loft. To be fair when we moved in, we expected it to be a cold house, we were surprised to find out it actually isn't.
Solar panels - Not really too keen on the idea, as I think they would ruin what is a "Chocolate Box Cottage". We are Listed too and our front elevation is South facing. If I could hide them, it would be a consideration.
What worries me about a 400 litre thermal store is the weight of the thing, sat on my first floor joists. I can't imagine it being that light and with us wanting to install a stove, am I correct in saying it needs to be on the first floor for the gravity feed?
Will have a look if we have a 22mm incoming main or not.
Our Extension will be to building regs, so is well insulated. The original part of the house (1700's) has 500mm thick solid stone walls, smallish windows and lots of insulation in the loft. To be fair when we moved in, we expected it to be a cold house, we were surprised to find out it actually isn't.
Solar panels - Not really too keen on the idea, as I think they would ruin what is a "Chocolate Box Cottage". We are Listed too and our front elevation is South facing. If I could hide them, it would be a consideration.
What worries me about a 400 litre thermal store is the weight of the thing, sat on my first floor joists. I can't imagine it being that light and with us wanting to install a stove, am I correct in saying it needs to be on the first floor for the gravity feed?
I've been looking at these as well as we have high mains pressure.
Our current set up is a standard vented cylinder connected directly to a multifuel stove with a indirect connection to the oil boiler. The problem with this is that the water is brown when the stove is lit, presumably due to no inhibitor.
I have been looking at Gledhill Thermal stores.
http://www.gledhill.net/page/182/Torrent-GreenHeat...
I think I am right in thinking that as the oil boiler is completely separate in its own outhouse with its own header/expansion tank and the hot water cylinder and stove has its own header tank elsewhere in the house, I need the sealed primary coil version to keep the systems separate. I don't want to run any heating off it as this is too complicated due to distances between the oil boiler and stove.
The Gledhills come with an external plate heat exchanger which I am led to believe is more efficient than a simple coil inside the cylinder. We only have a 15mm supply to the cupboard where the cylinder is. Although this could be upgraded to 22mm, is it is truly necessary?
The bathroom is pumped at the moment and the noise drives us both insane.
Our current set up is a standard vented cylinder connected directly to a multifuel stove with a indirect connection to the oil boiler. The problem with this is that the water is brown when the stove is lit, presumably due to no inhibitor.
I have been looking at Gledhill Thermal stores.
http://www.gledhill.net/page/182/Torrent-GreenHeat...
I think I am right in thinking that as the oil boiler is completely separate in its own outhouse with its own header/expansion tank and the hot water cylinder and stove has its own header tank elsewhere in the house, I need the sealed primary coil version to keep the systems separate. I don't want to run any heating off it as this is too complicated due to distances between the oil boiler and stove.
The Gledhills come with an external plate heat exchanger which I am led to believe is more efficient than a simple coil inside the cylinder. We only have a 15mm supply to the cupboard where the cylinder is. Although this could be upgraded to 22mm, is it is truly necessary?
The bathroom is pumped at the moment and the noise drives us both insane.
Trevor450 said:
brown
If you mean the water coming out of your tap is brown, you need a new cylinder.External plate and shunt pump is ace if oversized enough. You can get much better performance than a coil when the store's pnly 50-60 degrees, but it don't work in a power cut! I've got a thermostatic valve on our shunt pipework which closes down the flow through the shunt pump/plate/store when the hot water flow reaches temp, maximising store energy and only sending sub-30 degree water back into the base of the store.
We have an incoming 15mm main at 2.5-3 bar with fairly hopeless flowrate, into a 250 litre accumulator with a non return valve, off which come the baths and showers hots and colds - and the shower is awesome. Bathroom is plumbed in 15mm and bath fills ok due to the extra flow from the accumulator - I'd recommend one over booster sets etc as they're cheap, silent, and don't break down.
eta you're saying your stove is connected directly into your cylinder? Ewww. Don't open your mouth while in the shower.
Edited by andy43 on Tuesday 29th July 15:46
The water is only brown when the stove is lit but yeah, it's not great.
We have 20l/min on 15mm at the kitchen sink.
ETA, that's interesting on the power cut angle - didn't think of that. In that case I am probably looking at a Navitron or a Kingspan.
We have 20l/min on 15mm at the kitchen sink.
ETA, that's interesting on the power cut angle - didn't think of that. In that case I am probably looking at a Navitron or a Kingspan.
Edited by Trevor450 on Tuesday 29th July 16:48
Trevor450 said:
ETA, that's interesting on the power cut angle - didn't think of that. In that case I am probably looking at a Navitron or a Kingspan.
This is why the law says you have to have a HETAS approved plumber - your setup has to be able to extract the heat from a stove even if the power goes, as you can't expect the stove to magically shut down. At best the stove will crack, at worst it can go boom.You can do it with a plate heat exchanger, using a failsafe valve to dump mains cold through it and relying on gravity to circulate the rest (according to one of the sites I read), but it's a bit complicated and our plumbers really weren't keen on the idea.
Tuna said:
Trevor450 said:
ETA, that's interesting on the power cut angle - didn't think of that. In that case I am probably looking at a Navitron or a Kingspan.
This is why the law says you have to have a HETAS approved plumber - your setup has to be able to extract the heat from a stove even if the power goes, as you can't expect the stove to magically shut down. At best the stove will crack, at worst it can go boom.You can do it with a plate heat exchanger, using a failsafe valve to dump mains cold through it and relying on gravity to circulate the rest (according to one of the sites I read), but it's a bit complicated and our plumbers really weren't keen on the idea.
Woody3 said:
What worries me about a 400 litre thermal store is the weight of the thing, sat on my first floor joists. I can't imagine it being that light and with us wanting to install a stove, am I correct in saying it needs to be on the first floor for the gravity feed?
See above plus this link explains it - http://www.broseleyfires.com/Technology.htmlI'd go as big as poss with the store, stick a solar coil in just in case, and make sure it's got loads of tappings to add extra in/outs or sensors if needed in the future.
So it appears that we have 15mm incoming mains. Pressure is 3 bar and flow rate is about 13+ litres/min. Apparently anything above 8.5 litres/min is good (according to Severn Trent water).
I've got a plumber coming out to us within the week, to confirm the above and discuss what will suit us best.
In the meantime, I've been offered a 400L Thermal Store with:
Pump assembly for the oil boiler
Pump assembly for the radiators
Hot water set
Under floor heating pack
Connections for the solid fuel appliance
Immersion heater,
2 temp dials,
safety overheat thermostat,
boiler thermostat.
I assume a header/expansion tank will be required, so that will be an extra cost.
The only thing putting me off a thermal store is the weight. There's going to be half a tonne sat on the joists. Ideally I'd keep it on the ground floor, but don't think this is viable.
Another thing I will look into now is sealed system compatible stoves; I didn't realise they made them, so thanks for pointing that out.
I will keep this thread updated in terms of any other info I find and what ends up happening.
I've got a plumber coming out to us within the week, to confirm the above and discuss what will suit us best.
In the meantime, I've been offered a 400L Thermal Store with:
Pump assembly for the oil boiler
Pump assembly for the radiators
Hot water set
Under floor heating pack
Connections for the solid fuel appliance
Immersion heater,
2 temp dials,
safety overheat thermostat,
boiler thermostat.
I assume a header/expansion tank will be required, so that will be an extra cost.
The only thing putting me off a thermal store is the weight. There's going to be half a tonne sat on the joists. Ideally I'd keep it on the ground floor, but don't think this is viable.
Another thing I will look into now is sealed system compatible stoves; I didn't realise they made them, so thanks for pointing that out.
I will keep this thread updated in terms of any other info I find and what ends up happening.
Our store is sealed, no header tank, ground floor so it can be done.
DPS website tells you everything you could ever need to know..... Not cheap though....
http://www.heatweb.com
DPS website tells you everything you could ever need to know..... Not cheap though....
http://www.heatweb.com
andy43 said:
Our store is sealed, no header tank, ground floor so it can be done.
DPS website tells you everything you could ever need to know..... Not cheap though....
http://www.heatweb.com
DPS have a wealth of information, but you need to be sure your installer is happy with it - they make it look very simple when an actual installation can get a bit complicated. We've ended up with four pumps, two header tanks, extra heat-dump rads and a lot of wiring for our installation. DPS website tells you everything you could ever need to know..... Not cheap though....
http://www.heatweb.com
Tuna said:
andy43 said:
Our store is sealed, no header tank, ground floor so it can be done.
DPS website tells you everything you could ever need to know..... Not cheap though....
http://www.heatweb.com
DPS have a wealth of information, but you need to be sure your installer is happy with it - they make it look very simple when an actual installation can get a bit complicated. We've ended up with four pumps, two header tanks, extra heat-dump rads and a lot of wiring for our installation. DPS website tells you everything you could ever need to know..... Not cheap though....
http://www.heatweb.com
And gauges - lots of gauges are very important.
Woody3 said:
I will keep this thread updated in terms of any other info I find and what ends up happening.
Do you have any updates? I have been looking into connecting my Rayburn Royal (solid fuel) & a Grant Vortex Eco 21/26 oil burner to a Gledhill TORRENT ECO OV thermal store (170L). We have one bathroom & one en suite.My only worry is the power cut scenario. We do have regular outages that last a few seconds. My plumber has been recommending an H2 panel & HW cylinder - http://www.h2panel.co.uk/
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