Run gas combi in open vented system

[Master of None]

OK, first post on here - I’ve got a question.
I want to integrate a wood burner into my central heating system. I have currently got a combi boiler. I don’t have a hot water tank and nor do I have room for one, or a thermal store.
As I want to install a wood burner with a boiler I need an open vented system. My plan would be to install a low loss header with the open vented system. I would run the central heating off a combination of the wood burner and combi, the domestic hot water would solely come from the combi. The big question I have is can I convert the combi so it will run at the pressure of an open vented system rather than the pressure they normally run at, I think mine currently trips in at about 0.25 Bar. i.e. I’d need to somehow fool it into thinking the pressure was high enough for it to turn on. A conventional boiler runs at a lower pressure and I can’t think of a good reason why a combi wouldn’t. I’m not keen on putting a plate heat exchanger between the combi and the low loss header as I think it would just make it unnecessarily complicated.
In addition I want to put both the combi and the tank in the attic so I would only have about 2m head of water (0.2 Bar) between the boiler and the water level in the tank. I’ve done loads of research into the fitting of wood burners so I get all the stuff about thermo syphoning, pipe runs and heat leak rads, I can post a schematic of my proposal if it would help. I’d really appreciate any advice.
I put the question in the general heating section as the question is primarily about a gas combi boiler than about the wood burner installation.

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[SimonG]

Your hetas engineer will be able to assist with your queries.

 

[Mike Jackson]

There is a combi available that will run on an open vented system but combining it with a wood burner could give all sorts of design issues.

Stick with what you've got, fit a wood burner and leave doors open.

 

[Master of None]

Not sure why I'd ask a HETAS enginer about a gas boiler. Also why would I reduce the efficiency of the woodburner from over 70% to less than 20% by opening the doors? In my proposal the dhw function is unchanged. From a heating point of view the combi is acting like any conventional boiler. A conventional boiler installed along with a woodburner in an open vented system and a low loss header is a standard installation method. So my question is can an existing combi bd converted to run at the lower pressure of an open vented system?

 

[PhoenixServices]

There is only one manufacturer that you can do this with as far as I'm aware. And that is intergas.
So unless you have one of them you will have to get your combi changed, which hardly seems worth it.

 

[Dotty]

In a short answer, no.

The reason you need a HETAS qualified guy is because the dangers associated with solid fuel appliance fired systems outweigh those by either oil or gas.

Additional considerations need to be made.

 

[Dotty]

Oh, and don't be playing with the safety features of your boiler. Leave them alone. They're set where they are for a very good reason.

 

[SimonG]

Im feeling all macdonalds

 

[Mike Jackson]

Not sure why I'd ask a HETAS enginer about a gas boiler. Also why would I reduce the efficiency of the woodburner from over 70% to less than 20% by opening the doors? In my proposal the dhw function is unchanged. From a heating point of view the combi is acting like any conventional boiler. A conventional boiler installed along with a woodburner in an open vented system and a low loss header is a standard installation method. So my question is can an existing combi bd converted to run at the lower pressure of an open vented system?

Wrong doors. Leave the doors in the house open to allow the heat to circulate. You'll probably do what you want anyway but post up your address first so that we can make sure none of us are anywhere near when the system goes bang.

 

[walterwhite]

Integrating a sealed boiler with a wood burning stove can be done. You don't need to 'convert' your combi to an open vented. But you do need a HETAS engineer unless you want it to go bang.

 

[Jimbob]

You will require some form of heat exchanger, or an intergas boiler.

I can honestly never fathom why people get such a rock on over running back boiler stoves. Logs are expensive, (nat) gas is cheap. Installation is expensive and system control is minimal. I'm a firm believer of them being nice as a space heater (still not cheap), but if you want to burn wood for central heating, buy a gasification boiler.