I need a gas boiler. After four years of wood searching and sawing for my wood burner which also heats the central heating system, I have realised that a small amount of automatic heating will make a vast difference in my life.

Does anyone know what kind of boiler I need to run in series with the wood burner? It slightly flummoxes plumbers so I want to do some researching in advance.

Couple of options

1 a thermal store heated from gas / stove plus solar thermal etc. if required, used to run ch and hw
2 dunsley neutralizer http://www.dunsleyheat.co.uk/linkupsys.htm

I’ve gone for a small 300l thermal store

I did draft long post about thermal stores and call-for-heat and hot water cylinders etc, but there’s also ,I imagine, fangled widgets that handle things too.

Although I reckon Im not bad at some of this stuff, your particular problem I think is out of my comfort zone.

Bear (of this ‘ere parish) might be your man though.

Evening! Stoner don’t put yourself down you know as much as me. I just have a practical approach and experience.
Surely a pellet boiler is automatic. Believe there is a pellet / log boiler unit. Uses pellets to light logs boiler which charges accumulator then if more demand needed then pellet kicks back in.
Can also link gas boiler in though. Give me an idea of what you are heating.

B – I think the OP has a back boiler CH system, so is talking about adding a boiler to do call for heating that augments a back boiler set up.

A thermal store obviously deals with buffering and multiple sources but I imagine there’s also kit out there that can deal with a call for and a back boiler without a big water store?

Hi,
Thanks for replying. I currently have an aarrow wood burning stove with back boiler which burns logs, and pretty much anything else I feed it. Bought a few years ago before pellet boilers became all the rage. The back boiler runs about 12 radiators (there’s a pump). Hot water runs off a separate system.

I need something which I can use to get the house warm quickly on cold mornings and which will warm the house in spring summer when a full on log burning session seems a bit like overkill. I think that a combi burner needs a pressurised system and I am pretty sure that is not what I have (there’s an expansion radiator) but I don’t want two lots of radiators which has been suggested. Will a conventional boiler do the job?

Ps I am heating a stupidly big house built out of Yorkshire stone. I bought it by accident but that is another story.

As above densely neutraliser if not using a thermal store or accumulator. Not sure a buffer would be the right thing with a log, you really need to be able to store all the heat that the stove can produce.
I’m sure with pipe stats etc and motorised valves you can do an automatic arrangement. Think you need a normally open valve in the system to make sure in the event of power failure you can get rid of the heat from the stove.
Probably best gravity to a thermal store with pipe and cylinder stats to control gas boiler.

I’ve never heard of a thermal store before. Where did you get yours geoffj? And how big is it – where in the house have you put it? Does it have to be on the ground floor?

I can see the benefits that you can add on other heat sources as funds allow (currently self-employed and weathering recession by living on air but would dearly like to add some solar panels to set up eventually) but if you’re not using it for hot water does that reduce its efficiency?

I have a header tank on my central heating so that’s one tick.

I assume your CH circuit feeds, expands and vents into your header?

How is hot water done? Single point of delivery?

Thermal stores can be quite heavy, my preference would be ground floor, but if the joists are rated for it, then nothing wrong with having it higher in the house. Help with gravity feed if you did.

My thermal store links my solar panels and my biomass boiler and then all my CH and DHW needs come off it either directly (Rads, UFH) or indirectly, DHW at the taps @ mains pressure.

Theres no problem not using it for hot water as well, although why wouldnt you – esp if using solar thermal heat during the summer – free hot showers.

geoff has his linked to his back boiler via a load charger which would be a good idea.

I’ve never heard of a thermal store before. Where did you get yours geoffj? And how big is it – where in the house have you put it? Does it have to be on the ground floor?

Its just a big hot water tank, but you don’t use the hot water in it, rather you use it to heat the radiator circuit and there is a heat exchanger for mains pressure hotwater.
Ours is a small 300l one which lives on the ground floor.

Have a look here – http://www.plumbingpages.com/featurepages/HWdpsThermstore.cfm
and here – http://www.soloheatinginstallations.co.uk/thermal_stores.htm

curiously i need new heating in my gaff and im curious – issue i have at the moment is i do not use the heating – which in turn means i have no hot water due to current set up i need to have the heating on first thing to heat the hot water – PIA to go around and turn all the rads off and on all the time and some dont even have valves on.

How does the thermal store idea get round this ? Presuming we just had a back boiler and a oil fired boiler of some kind driving it – could i have hot water without having the heating on.

im being driven more and more towards a combi at the moment ! especially as currently i have to wait an age for a trickle of hot water with zero pressure ( hot tanks entirely lower than the taps !)

which in turn means i have no hot water due to current set up i need to have the heating on first thing to heat the hot water

trai_rat – your system really ought not need to have the heating on to get DHW. there should be a valve controller somewhere that heats your hot water tank from the boiler but doest divert to your rads.

How does the thermal store idea get round this ? Presuming we just had a back boiler and a oil fired boiler of some kind driving it – could i have hot water without having the heating on.

Yes. Much like how your system currently ought to operate, the pumped supply to the rads only comes on when a thermostat says so. Meanwhile a tank thermostat calls for heat when it needs to top itself up. That hot water can then be used at anytime to indirectly heat your DHW water, or directly to your rads via the pump. Also, whenever the back boiler is running it will heat up the water int he thermal store, allowing you to use it for either the rads or for DHW.

A 300 litre thermal store won’t give you much time without a heat source IMO. I have a 1500litre thermal store and it’ll only give a day max in cold weather and that’s with the heating system hot.

Having gravity fed may be a problem with a large thermal store as that’s a hell of a lot of water that’ll expand and contact with the heat, unless youe F&E tank is big and has a good capacity. I’ve got a closed system and the expansion vessel is pretty big.

stoner – my boiler will not fire unless i turn on the heating system.

so unless i walk round the house turning off all the radiators at the dial i have to heat the house to get hot water

or use the immersion

its the old case of never buy a mechanics car. – the geezer was a heating engineer …..

Stoner, the CH is fed from the header tank but has a separate expansion radiator below the header. There’s a pump which circulates water round the radiators which is a normal central heating system pump.

Hot water is on a separate system (Aga 😳 ). The Aga loop keeps a bit of the house constantly warm – it would be unbearable without it plus it takes quite a lot of effort to empty the hot water tank. This thermal store thing makes me wonder whether you could link the Aga in too.

Thanks for the links geoffj and Dobbo. Will look and digest contents.

This thermal store thing makes me wonder whether you could link the Aga in too.

yes you could.

If you have a big enough place, you could link your back boiler, oil boiler, solar thermal and Aga to it to make the most of various heat sources as and when they are in surplus, and the Oil boiler when other sources arent running and you need heat for DHW and/or rads.

I have a 700L thermal store, with another 200L in the boiler itself.

Jaspi make some large stores that can take loads of indirect coils.
http://www.northmangroup.co.uk/Oval.html

If the Aga is gas or oil that modulates to maintain the load unless you have demands that can’t be met by the Aga then I wouldn’t store heat from it, you’ll load the Aga up to have heat sitting in a tank that might not be needed. I’d use a thermal store to store up excess heat from wood burner or as a buffer for excess periods like a small store on a heat pump to smooth out demand fluctuations. Not that I’m an expert, just how I kind of see it!

I’d throw the bloody lot away and buy a pellet boiler…….

Sorry Bear I am too poor! Waiting for the recession to end so that people actually buy the things we make again 😕

Need a medium term solution so that we keep warm in the meantime. Was looking at boilers and hoping to get a good deal under 1k. Thermal store as well might not be realistic thinking about it.

The Aga is ancient and came with the house and runs on coal. Sigh. But it makes nice dinners.

My comment was partly sensible too. With all the money you will be spending on configuring your system to work properly and safely you may be better advised to think long term. Bite the bullet for another year or so, or do it in stages, add the thermal store first (which you can dump Aga into) then see where you are in a year or so as to what alternative fuel source you choose.

Take it you are up north then?

Coal = northern affliction 😉

Also manufacturing 😉

Yep, up north.

Funny that bloke who did my biomass course was northern, left a funny black dusty trail wherever he walked….

How about a cheap air/air air-con/heat exchanger. The DC inverter ones perform reasonably (similar to burning gas) unless it’s below freezing outside in which case you could fall back on the wood burner.

Not sure I’d like to put a heat pump into a system designed for a higher mean water temperature.

Cheap? Last time I looked one the right size worked out at £6k but if they’re now cheaper please can you point me in the right direction? Cheers

for that money buy a pellet boiler!

Airton

Airton is Brico Depot’s own brand. Brico Depot is owned by the Kingfisher group. Kingfisher owns B&Q, try the B&Q site. They’re popular here in SW France where the outside temperature is warmer. They work down to -15°C at which point they are little more efficent than plugging in a convector. In a well-insulated house they’re all you need.

I don’t use one but have friends here that heat the whole house with a basic 3500W air/air. I also have German friends that use a much bigger air/air of the £6000 type, the last time I visited it was -16°C and the house was OK – mainly due double/triple glazing and excellent insulation.

And the cheaper ones if you only want to heat one room or have an exceptionally well-insulated abode.

I don’t use one but have friends here that heat the whole house with a basic 3500W air/air.

What’s the running cost of one of those?

In a well-insulated house they’re all you need.

Have a look at improving insulation before alternative sources of supply.

I have realised that a small amount of automatic heating will make a vast difference in my life.

Why do you think this?
Perhaps it would be a good idea talking some experts to find out where the weakness is. http://www.sapservice.co.uk/ and tell them Simon sent you. Better to spend 50 odd notes before £1k+ on something unecessary.

Not designed to work with a radiator system using a flow of 82 and return of 71 deg C then?

Air/air costs a half to a third of the running cost of convectors. In France that makes them competetive with gas but in the UK gas is cheaper. They also mean one less standing charge and no annual service charge on the gas installation. Better are the heat pumps that use ground heat, efficiency is up to 480% but the investment is 12 – 15 000e.

The Sapservice thing is great but a simple start is to look at passive house standards for your climatic region and aim for that.

but a simple start is to look at passive house standards for your climatic region and aim for that.

How does that work?

Well for the UK you’d need an R7 roof, R3-4 walls and an R3 floor. R7 being about 350 – 400mm of rockwool/polyester/hemp etc. Google passivhaus or passive home or passive house or la maison passive or… .

I think that before the OP goes rushing off to do that it might be a good idea do try and work out what the starting point is, don’t you?
Passivhaus might just be a bit of overkill too, no? A wonderful, yet quite expensive, solution.
And you forgot to mention windows. 😉

“mew”w better than 1.6 for the windows. Mew isn’t on my keyboard and it’s too late to hunt for it on a copy/paste symbols site. Standard double glazed on windows that get sun. Triple on north facing windows but there we really are talking big bucks. 😉

Passivhaus = overkill, or the minimum?

Edit: and yes the start point would be useful.

May I remind you energy cannot be created therefore heat pumps are not 480% efficient.
Marketing rubbish.

When the OP thinks

I have realised that a small amount of automatic heating will make a vast difference in my life.

then yes, aiming for Passivhaus is a little over the top.
If the question and budget, I assume there is a budget, were different then yes I’d be right behind you on Passivhaus, but I don’t think that’s the objective here. 😉
Air source HP
GSHP
Lots more info here.

RE GSHP – They can operate at a cop of 5 which means that for every 1 khw of electricity used, 5 khw of heat is produced, the “missing” 4 comes from the ground loop. Colloquially it would be reasonable to say they are 480% efficient.