combi boiler/ wood burner with back boiler

[rugeleyboy]

hello,

is there a way of plumbing a woodburning stove with a back boiler into my combi boiler heating system?

i already have the combi boiler but im talking about having a multi stove and wondered if it could all work together?

[KARL]

It is entirely possible - you would use one heat source and have that part of the circuit that contains the other disabled. However, this would likely only be usable for space heating because the hot taps are served with mains water directly via the gas boiler. But in principle and broadly speaking, yes.

[rugeleyboy]

ok so its possible. thanks

but you say disabled?... i was hoping to keep both in working order?

ie.... whilst im burning wood the back boiler pumps to the radiators and when the fire has died over night the combi kicks in and does its job?

[seadogg]

We just have a big kettle on ours.but my post is to warn you that the price of solid fuel has become nigh on uneconomic. If you can get cheap or free wood its fine and the sawing and carrying give a good workout. In a house the heat keeps upstairs warm and really cuts heating bills.

[KARL]

For example, if the gas boiler is on when the woodburning stove is supplying heat then the gas will keep coming in and heating to its set level (of the circulating water). There is nothing wrong with that and indeed the stove can operate simply as a secondary heat source as a kind of assistant (when doing something the gas tops up, if doing nothing the gas does the whole job). However, if the stove is doing nothing then unless it is excluded from the gas boiler's circulation path then heated water will pass through the stove body and a certain amount of heat loss will likely take place, possibly going where you don't have use of it such as up the chimney. You need to ensure the system is set up to suit your aims and general criteria whereby you understand what will happen and are satisfied with that.

[The Builder]

If I understand Karl correctly, the b/boiler would be connected into the rad circuit, and act as a kind of "radiator in reverse"................ putting heat INTO the water, rather than radiating it OUT of the water.
Just a couple of things............. boiler connections are usually 28mm....... therefore lots of water volume (flow). The rad circuit would have to be mainly at least 22mm, with 15mm only at the take-offs. Without something like that, I can envisage the rad circuit NOT taking the heated water away from the b/boiler at a fast enough rate.
Also, it would be essential that the b/boiler is completely clean internally before sending any of that water through a Combi and contaminating it.
The other thing............ you'd have no b/boiler benefit to the hot water (taps etc). That would stuill be Combi only.

[The Builder]

^^^^ "still"

[rugeleyboy]

ok thanks guys, your info is much appreciated!!

seadogg......... i have a timber business that generates a lot of waste?..... thats why we are having a burner?..... the back boiler idea got thrown in the mix today.

the taps will always be on the combi, i understand i can get a eco fan on top of the fire that will generate electricity from the heat of the fire?

[scoob101]

firstly you would be pressurising the log burner off the combi, but the main problem I can see is that a log burner has no real thermostat control so you could seriously damage your combi boiler (pressure vessel) as burning logs or wood gets very hot and cant decrease its heat from a stat that is why all solid fuel systems are open system tank fed so if it does get too hot it can vent itself into the expansion tank normally located in the loft. If you connect this to your combi boiler at the very least you will cause your combi to overpressurise and blow off through the safety valve fitted in your combi.

[KARL]

As I said, in principle and broadly speaking the proposed inclusion of a stove in the circuit is possible and examples exist. But there are a lot of things to consider (as other posts point to) and the system needs to be appropriately modified/designed/installed by someone who knows what he is doing. Pumping, screens, controls, venting, etc. all need to be correctly balanced - ideally the stove needs to be a modern type and temperature regulated (actually, probably mandatory) and also with separately pumped flow. This is not a subject that lends itself to detailed discussion on a forum like this one.

[rugeleyboy]

hi guys..... the expantion and heat control were 2 of the subjects i didnt quite understand?... thus this question..... but KARL has bought up more subjects for me .. ie, the heating waste in the back boiler and now the use of a stand alone pump??

but i have seen <a href=http://cgi.ebay.co.uk/ws/eBayISAPI.dll?V
iewItem&item=260715339448&ru=http%3A%2F%2Fsho
p.ebay.co.uk%3A80%2F%3F_from%3DR40%26_trksid%
3Dp4522.m570.l1313%26_nkw%3D260715339448%26_s
acat%3DSee-All-Categories%26_fvi%3D1&_rdc=1>t
his</a>
on ebay?

i was wondering to myself if this would help me??

[rugeleyboy]

that didnt work???

ill try again!!

[rugeleyboy]

<a href=http://cgi.ebay.co.uk/ws/eBayISAPI.dll?V
iewItem&item=260715339448&ru=http%3A%2F%2Fsho
p.ebay.co.uk%3A80%2F%3F_from%3DR40%26_trksid%
3Dp4522.m570.l1313%26_nkw%3D260715339448%26_s
acat%3DSee-All-Categories%26_fvi%3D1&_rdc=1>t
ry
again</a>

[rugeleyboy]

nope....... my days of posting hyperlinks on here have obviously passed me by.

heres the ebay item number if you fancy having a butchers?

260715339448

[scoob101]

This will not work on a sealed heating system, which if you have a combi boiler is what you have got.
I have never heard of a dual fuel system with one of the systems being a sealed system.
Normally a dual fuel system is a conventional system with a twin coil hot water cylinder and an open vented heating system.

[scoob101]

You may be able to convert your combi from a sealed system to an open vented system, but you will have to check the boiler manufacturers specs to see if you can do this.
You should get in touch with a solid fuel specialist who will be able to advise you exactly what would be involved with doing this, and if it is possible at all.
Good luck.

[sherrardk]

My husband installs wood burners and you can get ones with their own back boilers but you need a specialist to look at your needs (I am not clued up on the technical details).