Woodburner water heating system(unconventional )

Unfortunately the loft tank is plastic bought new this year 70 gall I think also the pipes for vent and feed are JG speedfit PEX but the last 3 metres to the tank will be copper will this be a problem?

I would suggest that you ask the plastic tank manufacturer if they consider their tank is suitable for use with an uncontrolled wood burner.

Sponsored Links
Just spoke to a friend who has a solid fuel burner that does his rads and hot water. He uses the hot water from the tank so it has indirect heating via a single coil which quite happily convects to the tank he then has a pump tee'd off the convection loop to the rads which is basically what I will have.
In the event of a power cut don't put any more wood in there and shut the flaps.
I looked into gizmo's like the "bla bla neutralizer" and charging devices they would certainly help with efficiency and corrosion but main cause of rust is oxygen in the water and you'll never get rid of it completely with an open vented system

Temp ratings for JG pipe and the poly tank is 114 degreeC
main cause of rust is oxygen in the water and you'll never get rid of it completely with an open vented system

Temp ratings for JG pipe and the poly tank is 114 degreeC

An open vented system will absorb oxygen through the exposed water surface. You avoid this causing corrosion by adding an inhibitor. Some inhibitors have an oxygen scavenger which reacts with and neutralises the oxygen, before it reacts with and rusts the insides of the radiators. There is usually more oxygen absorption in a solid fuel system, if it boils, due to the evaporation of water, the intake of fresh, oxygenated water, and the turn over of water through the F&E tank.

I doubt that the tank is rated at 114 degC; not many plastic tanks are used on pressurized MTHW systems or on systems filled with oil.
I have an old but good galvanised tank which I could use for the FE and it would be easy to fit. I could then use inhibitor without risk of contaminating the other system-thats 2 problems gone :D
Sponsored Links
Something to consider maybe?? overflow in copper , float on ball valve copper ?? would also suggest that the exp tank in loft is not postioned over a bed !!?? overflow discharge in a safe postion maybe ??
I'll consider anything that makes good sense with safety paramount
I need to figure how to activate the main CH pump and valve without firing the oil boiler using a tank stat it would be the best way of removing heat
You need to consider the electrics carefully.
The relay box below is for a solid fuel system integrated to a four zone heating system with an oil boiler. Its some of my own bodging to help a spark out on a job.

It has back feed protection for the programmer, HW priority , oil boiler interlock and opens all heating zone valves on heat dump. :D
Don't get me going I'll be having sensors fitted to the tank rigged up to the house alarm in case I fall asleep in front of the fire :LOL:

That looks like a nice job there did you use DIN rails and what components did you use?

I found what looks like a suitable relay

230v 8 Pin Ac Relay 2 Pole 10 amp

mounting base

It seems to be suitable but no wiring schematic available

I'd connect the oil boiler trigger wire normally connected then
on a activation signal it would switch the main pump and valve on
and disconnect the boiler wire
........ main cause of rust is oxygen in the water and you'll never get rid of it completely with an open vented system

Main cause of rust /corrosion is inside the combustion chamber when the return water causes the combustion gases to condense.
You mean actually inside the fire box where the wood goes? On mine which is an old Hunter most of the housing is the boiler back and sides and it's completely covered with fire bricks no signs of corrosion at all
Galvanised Tank connected to Copper Pipe? Sounds like electrolysis...

Could electrolytic corrosion not be a concern with that arrangement?

What an interesting project.
Will it work or is it a waste of time and effort ?

Good question.
Yes it will work but you need to weigh up the potential cost of integrating the wet side to your existing plumbing system and all the pit falls that entails.
Plus the control aspect.

The relay box I posted above is interfacing between an oil boiler and a fan assisted log batch boiler sited in a garage.
You need a design plan before starting. Both for the plumbing and for the electrics or you will end up doing a lot of head scratching.
What wood stove/boiler are you proposing fitting?
The woodburner was installed in the house and it's Hunter with 29000btu boiler.
As far as integration goes I was going to use a 210 litre albion with a single coil but use the coil for getting heat out rather than putting in then simply connect it up with a pair of 22mm to the existing flow and return. Maybe use a cylinder design for indirect hot water as the coil is bigger and more efficient
I believe.
The single large UFH zone will feed diectly from the 28mm WB boiler pipes this will help the convection process triggered by a pipe stat set at say 40 degrees and control by a blending valve.
Once the UFH has had it's fill and the cylinder temp rises to 70 degrees this will trigger the main CH pump and open the CH valve.
Only problem would be if I wanted to run the underfloor zone and the oil boiler heat would back flow into the WB stove and tank and turn off the oil boiler at 70 degrees
The tank will also have a single exchanger coil that can be used either to extract heat into the existing radiators or put heat in from the oil boiler.

To heat the cylinder, the coil would need to be at the bottom. To extract heat, the coil would need to be near the top.
I assume the coil is at the bottom.
Coil would be nearer the bottom as per standard cylinder or I was contemplating a dual coil which don't cost much more which would shift the main coil up to leave room for the lower coil which is usually for solar.
With the UFH pump working on the gravity pipes and the tank contents maybe the stratification goes out the window and becomes less important

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

Sponsored Links