Solid fuel back boiler and gas?

pitstop

Hi There

I want to have a solid fuel stove in my sitting room with a back boiler and gas heating. So having the luxury of turning off the gas when the fire is on??

My plumber says I cannot combine the two?? Does anyone know if this is true - I will have UFH downstairs and radiators upstairs?

Many thanks

Pitsy

crosstownk

I was looking into this a while back but I have other projects that are higher priority. It is possible though some people frown on it. You cannot use the two systems together or BOOM was the general negative I got on it. I reckon though its a matter of having the correct controls in place. I'll be looking into it again soon.

Check out this site www.solidfuel.co.uk

karltimber

was also thinking of this BUT my plummer advised against it.

Mainly similar to what crosstownk said - having 2 systems combined.
it is physically possible but would need a lot of controls to segment/isolate each system -for which ever one is on at the time.

If any of these controls fail - it can have serious problems.

I was also told that to have a solid fuel boiler onto a heating system ,the system cannot be sealed - and hence less effcient than a sealed one.

will see what other folks say.

you can connect it to your hot water tank - the tank will just have 2 coils instead of one.

crosstownk

My back boiler is connected only to my HWC and has no pump. Its one of those thermosiphon systems. On one occasion I had the fire burning and forgot to stop the timer for the HW. I ran the bath and thought the house was gonna blow with the noise. The coil from the back boiler is mounted much lower in the HWC than the GFCH coil so as the heating system was heating the water so was the back boiler BUT as the water at the top of the cylinder was already hot there were little or no convection currents at the bottom so the water there got very hot (about 70-75oC I reckon). When I opened the hot water tap at the bath to full a similar quantity of cold water entered the HWC at the bottom and caused serious pressure differences in the back boiler loop and subsequent very very lound knocking in the pipework until the system eventually equalised itself. While the system is not sealed it has a valve in the coil in the HWC which bleeds or sucks water from your hot water cylinder to maintain the correct level - I think it's called a prymatic valve.

I won't make that mistake again.

I'll be watching this thread as I'd be very interested to hear from a poster who has both installed.

pitstop

Guys

Thanks a million for the replies - VERY interesting. In the house, we are currently renting - we have solid fuel back boiler and OIL central heating - sorry to be thick - but what's the difference to the gas??

Having said that - twice I forgot to switch the controls and thought the roof was going to blow off (once I had left the house for a few hours:eek: :eek: :eek: )

So, if I can't do gas and SF back boiler - can I use the back boiler only for hot water - I'm trying to grasp at straws here because it seems such a waste to have the fire on and not be able to use the energy!

Thanks a million

Pitsy

crosstownk

Gas and oil heating is practically identical. Both burn fuel to heat water to pump around your heating system. It's a bit like petrol engines v diesel engines - same thing just different fuels and slightly different engines!

Given most of the heat from a fire goes up the chimney it would be nice to harness some of it to heat the house. I have sort of designed a system that would turn off the gas if the water temperature in the back boiler reaches a certain temperature but actally fitting and wiring this is another story altogether and I haven't got the time at the moment but it will work.

pitstop

Crosstownk

Hope u patent it - sounds like there would be a HUGE market for it!! let us know how u get on!!

Pitsy!

crosstownk

Its a relatively simple set up just using motorised and thermostat switches. I'll email you the details if I ever finalise it!!!!!! You can be my guinea pig!!!

JamesM

Solid fuel backboilers and oil boilers have been linked for years. (There may be some restrictions for gas )
On the backboiler side there must be no valves between the backboiler and the hot water cylinder (and the pipes on up to the header tank in the attic.)
The oil boiler has its own thermostat and will shut off when the water in the system reaches the set temp. (If the fire is hotter, the oil boiler will not come on ).
After that, you need non return valves to stop the oil boiler being heated by the back boiler and vice versa.
Also a thermostat to switch on the backboiler circulating pump and off the oil boiler pump when the fire gets hot enough. There are many other methods of controlling things using motorised valves etc. The important thing is that, when the water in the backboiler reaches a certain temperature, the circulating pump comes on automatically and the water does not boil.
Jim.

rooferPete

Hi,

It is possible to run the two systems but as crosstownk has pointed out it is only possible if done by a tradesman who has taken the time to look outside the normal installations.

In Italy sealed systems are frowned on regardless of the type of boiler, they prefer an open system.

There are times when the cost of the extra safety valves make the job too expensive, that does not mean impossible

.

endplate

My parents house has a dual system for years without problems. A solid fuel back boiler and a Range that was originaly solid fuel now burning oil. I believe it works because of the 1 way valves that are fitted to the system. Any decent plumber should know

JamesM

rooferPete wrote:

Hi,

It is possible to run the two systems but as crosstownk has pointed out it is only possible if done by a tradesman who has taken the time to look outside the normal installations.

In Italy sealed systems are frowned on regardless of the type of boiler, they prefer an open system.

There are times when the cost of the extra safety valves make the job too expensive, that does not mean impossible

.

I am pretty sure that a sealed system would not be allowed with a backboiler in Ireland. You must have a flow of water from the header tank in case the water boils.
Jim.

crosstownk

We used to have a dual system in parents house (oil & SF). As far as I can remember there were 2 pumps - 1 for each system and they pumped in opposite directions. The switch for the pumps was manual and only one could be on at a time.

The reason the pumps pumped in opposite directions was because there was a one-way valve at each boiler so if the back boiler was the heat source it wouldn't be pumping water in to the oil boiler which would be wasting hot water. The system was not sealed but there was a dedicated expansion tank in the attic.

JohnBoy

we used have a back boiler at our old house at home, as far as i can remember there was just two seperate coils in the cylinder and they basically ran as two seperate systems with seperate thermostatically controlled pumps and one way valves to limit heat loss through thermosiphoning

sometimes the master switch on one of the stats would get switched off and the pipes would bang like hell alright though

frankdrebbin

I have to replace an old ch system because my gun-barrel pipes are leaking.
The boiler, stove and pumps are from the old system.

Here is my proposed CH System Layout with a couple of questions at the end.

Double pipe flow and return in 28mm qualpex and copper.

10 radiators and a hot water cylinder connected. The radiator branches are in 15mm qualpex and copper with 4.5m the longest length. All the radiators have TRVs.

An oil boiler and pump at one end of the flow and return with a motorised valve that bypasses the boiler and boiler pump with a short length of pipe between the flow and return if the central heating is not on. When the central heating comes on, via a programmer, the motorised valve switches, the boiler and boiler pump come on and the boiler is no longer bypassed.

A 3 bar pressure release valve is connected to the boiler to vent water outside if the pump or valve fails.

A solid fuel stove and pump at the other end of the flow and return with a motorised valve that bypasses the stove and stove pump, in the same manner as above, until it gets to the required temperature i.e. 80 degrees C. When the stove reaches the required temperature the motorised valve switches, the stove pump comes on and the stove is no longer bypassed.

A 3 bar pressure release valve is connected to the stove to vent water outside if the pump or valve fails.

There is no gravity circuit and it is not practical to install one without a lot of work that I would really rather not do.

Both the stove and boiler pump are pumping in the same direction in case both systems are on at the same time.

The boiler and stove are always connected to the header tank because one side of each bypass is just a tee connecter and hence is always open.

The feed and expansion pipes to the header tank are about half way between the stove and the boiler.

Questions:

Are there any glaring mistakes in this system?

Is the system safe in regards to the solid fuel stove i.e. is a 3 bar pressure release valve enough should the electricity/pump/motorised valve fail?

Feel free to be as critical as you like. I have done lots of diy plumbing including installing radiators, pumps etc. but I am no expert.

JamesM

If the water in the stove boils, there must be somewhere for the steam to go first of all, and then there must be a fresh water feed from the header tank. From the stove, the flow pipe must go to the coil in the hot water cylinder and continue up to above the header tank. The return must come from the header tank down, branch into the coil in the cylinder and continue down to the stove. After that you can connect almost anything you like.
Think, if you have a power failure - all your pumps and motorised valves do not work. Your oil boiler will switch off, but your stove does not know that it should stop heating the water. If you are depending on a safety valve, OK, it will blow. Then there will be only steam in the stove, the metal will get very hot (no water to cool it down). It may crack - steam on hot coals - blast out into a room :eek: Take it further - Granny babysitting - power failure - "Come on children, we will sit around the Stove (or fire) and stay warm" BOOM ! :eek: :eek: :eek:

Jim.

crosstownk

Sounds OK to me - but I'm no expert either. Do you have the oil boiler bypassed for when the stove is boiler is pumping hot water and vice-versa?
Would you not put a motorised valve on the supply to the HWC coil for better effeciency? It might be an idea to get a pipe stat which would shut the system down in case of overheating. You could also fit a bulb to the pipe stat so a light would come on to let you know whats up.

JamesM

Endplate, Crosstownk and john Boy have all described systems which were fitted in the '80s when almost everyone added a backboiler to their oil system when grants became available. Then we got too much smog and we all took them out again
The whole thing about solid fuel fires or stoves is that, because they cannot be automatically controlled, they must be safe if there is a power failure - so no valves or controls between the fire, cylinder and header tank. (If the water boils, it goes up the expansion pipe to the header tank and the cold water comes down to take its place.)( The hot water cylinder will initially help to cool the water and is an extra safety feature)
You can have a motorised valve on the coil from the oil boiler, but not on the coil from the backboiler or stove.
At least, they were the rules in the '80s.
Jim.

frankdrebbin

Thanks for the advice

JamesM:

I cannot connect the stove to the hwc as it is too far away for a gravity circuit.

I could vent without a pressure release valve to the header tank???

Even if the electricity fails the stove can still get water from the header tank as one side of the bypass is always open.

crosstownk:

Yes the boiler is also bypassed when the stove is on. The motorised valve on the hwc is also an interesting idea.

My no. 1 concern is that the system be safe if the electricity goes.

JamesM

frankdrebbin wrote:

Even if the electricity fails the stove can still get water from the header tank as one side of the bypass is always open.

My no. 1 concern is that the system be safe if the electricity goes.

For safety, I believe that as long as you have an expansion pipe venting from the top of the stove going up higher than the header tank (usually curving down above the header tank) and a feed pipe from the header tank to the bottom of the stove, you are OK. This allows the circulation of water if the system overheats. It is no good having only one side of the circuit open - ie. - just the feed from the header tank.
Jim.

crosstownk

frankdrebbin wrote:

Thanks for the advice




My no. 1 concern is that the system be safe if the electricity goes.

I doubt the fire would be left on with the house unattended so at least somebody would be there and take appropriate action in the event of a power failure. The first thing would be to run your hot taps to cool some of the water passing through the HWC coil. Close the damper and pull the fire forward.

JamesM

crosstownk wrote:

I doubt the fire would be left on with the house unattended so at least somebody would be there and take appropriate action in the event of a power failure. The first thing would be to run your hot taps to cool some of the water passing through the HWC coil. Close the damper and pull the fire forward.

No offence, but it doesn't matter what you think that you will do or not do. The regulations cover every eventuality and make sure that nothing can go wrong. They assume that there will be no human intervention.
Jim.

crosstownk

JamesM wrote:

Endplate, Crosstownk and john Boy have all described systems which were fitted in the '80s when almost everyone added a backboiler to their oil system when grants became available. Then we got too much smog and we all took them out again

Jim.

We have shown our age.....................

rooferPete

Hi,

I have to agree with Jim, the solid fuel system must remain as an open system, I would not expect any sympathy from a loss adjuster or surveyor if the solid fuel section failed because a valve stuck or there was a power failure.

All systems should be safe to the point that anyone even a person who knows nothing about the house should be left in charge at some time, even a smouldering fire can cause the water to expand in the boiler.

On the system we use all motorised valves are left on the system that requires electricity to fire up, the solid fuel side remains safe at all times.

Solid fuel boilers can implode if the header tank is not checked to ensure the ball valve is not stuck which can happen if a system has not been used for a while.

So take care and preferably use a qualified plumber like I do

.

JamesM

crosstownk wrote:

We have shown our age.....................

Never tried to hide it
Check back any of my posts - I have always stated my limitations and experience. I do not comment too much on gas, but I do have some experience of oil and backboiler systems.
Over all these years :rolleyes: , I have seen some very dangerous oil / backboiler systems installed by qualified plumbers. So pardon me if I seem over the top.
Jim.
P.S. Thanks Pete

nick 56

as a plumber that in years gone by fitted loads of these systems i would say that JamesM is dead on. At least one house i knew in wicklow had the back wall blown off by a cowboy fitting a dual system. I would say that back boilers are the hardest heating systems to fit properly. Christmas day - big fire + power failure.

JamesM

nick 56 wrote:

as a plumber that in years gone by fitted loads of these systems i would say that JamesM is dead on. At least one house i knew in wicklow had the back wall blown off by a cowboy fitting a dual system. I would say that back boilers are the hardest heating systems to fit properly. Christmas day - big fire + power failure.

I thought the thread looked familiar - that was back in March !
Once I actually saw 1/2 inch copper pipes from a backboiler connected straight into the flow and return from the oil boiler - a sealed system - no expansion - nothing :eek:
Jim.

Andy_Hirst

Hi all.

I've recently moved into a oldish house and we are in the process of decorating. We've deceided to go for a Dover 2000 series open fire with glass doors so can leave fire lit when out. We have also added a backbolier on the fire and plumbed in and wired up a thermo storage tank in the spare bedroom (as there is a celler, the tank is on the 3rd floor) The tank works fine in conjuction with the gas bolier to provide the DHW. For safty it has a heat leak raditor and a motorised valve that fails open so if the power goes off and the fire is on but we're not home and the power fails the raditor wil take away the heat from the system which is gravity fed with the hot water rising from the fire but mains pressure cold water going though the tank.

Sorry to bore with the detail but my question is this;

How can I connect this up to also fed the raditors rather then using just the gas bolier for the rads?

Thanks all

ircoha

Andy_Hirst wrote:

Hi all.

I've recently moved into a oldish house and we are in the process of decorating. We've deceided to go for a Dover 2000 series open fire with glass doors so can leave fire lit when out. We have also added a backbolier on the fire and plumbed in and wired up a thermo storage tank in the spare bedroom (as there is a celler, the tank is on the 3rd floor) The tank works fine in conjuction with the gas bolier to provide the DHW. For safty it has a heat leak raditor and a motorised valve that fails open so if the power goes off and the fire is on but we're not home and the power fails the raditor wil take away the heat from the system which is gravity fed with the hot water rising from the fire but mains pressure cold water going though the tank.

Sorry to bore with the detail but my question is this;

How can I connect this up to also feed the raditors rather then using just the gas bolier for the rads?

Thanks all

The consenus from a quick review of this thread is that u cant easily do it as the BB needs to be an open system for expansion reasons in case the power fails etc, whereas I presume the gas system is a closed system.

If you do decide to splice the BB into the GFCH circuit it will need to be plumbed so as the BB is not a radiator when fire is off. Eamonn Ryan and John Gormley would not be best pleased: P McKenna would prolly love it.:D