Help! Wood fired heating system conumdrum!

[ramblehan]

Hi,
We are in the process of getting a wood fired, and PV system installed, but have received conflicting advice from 3 different plumbers! We're working to a tight deadline too - and feel completely confused! Hoping someone here can shed some light.
We have a 3 bed semi ex council house. We are having a wood burner with back boiler installed - it will give out just under 3kw to the room, which is fine, and then over 12kw to water. We are also having a 4KW PV panels on the roof which will power an immersion using an Iboost.
We've had conflicting advice about what tank to use - Originally we were advised to get a 250L thermal store. There would be no oil input to this this - just PV and wood. but the plumber has "disappeared" - The next person who came along offered something similar but didn't seem to have much experience so we were not confident of his advice.
The third plumber was concerned about us using a thermal store due to impact of heating system on hot water heating (so if we used heating, the water temp would be cold) He rang the thermal store company technical department and they advised him that this system would not work (ie not enough hot water) without a 3rd input like oil. However we think he was telling them we only could generate 9kw to water. He has recommended instead that we have a 120 litre conventional water tank, with a heat leak radiator, and an all-house pump to ensure water pressure.

We have a continuous supply of free wood, and expect to keep the stove burning a lot, but there will be days when both of us are out to work so will need to fire up when we get back.
With the 120 litre tank (steel with a 25 yr guarantee) - we are worried that it won't keep water hot enough overnight, if our fire goes out and the heating is going all the time.

Can anyone give us some insight on what is the best way to go for us?
We're working to a very tight timeline and we feel like the last plumber has got us over a barrel - his quote is the most expensive, but we seem to be getting a simpler system.

many thanks for your time.

 

[Millsy 82]

I am only gas and oil so other people will be able to advise you better on the system.

Most thermal stores are kept hot 24hrs a day so that you have constant hot water. The problem I could see is if you don't keep the fire going and you run the heating it will steal the heat from the store which will leave you with no hot water and the immersion heater will not run the heating. There may be ways round this but as I said others will be able to advise you better.

 

[ramblehan]

Thanks Millsy.
I think that's why we have been recommended not to use a thermal store but go for a standard water tank instead.
Our PV panel chap today has suggested that we go with a standard water tank, but that we should have a bigger one (250L) - this way it would contain more water than we would need, but we would never empty the tank fully - so when it refilled after use - we would not be heating water from scratch - Obviously it would take longer to heat up in the first instance, but as we would have PV panels working on this during the day this would help cover that - needing an extra boost in winter.

Be good to know people's thoughts? Thanks Hannah

 

[Ermintrude]

What? Utter babble mate tbh!!!!

1 get a log gasification boiler. Much better than a bbu. If not possible fit a large thermal store say 1500l open vent so easily compliant with requirements of stove. Then fit a 150 - 210l unvented hot water store heated by a pump and zoned supply from store. Have immersion in unvented too. As when you have excess solar it's going to be summer so u won't want any heating! Rads fed from thermal store. Boom Boosh sharinghgggg!

 

[lame plumber]

and the price for all that ermie???

 

[Ermintrude]

£5000 ?

 

[Ermintrude]

I have a megaflow that's up for grabs? £300 210l ? And u could get the Glasgow copper smiths to build u a sectional thermal store.

 

[Gray0689]

What area are you in
Maybe someone on here can help you out by looking at your job

 

[Reg Man]

Solid fuel is an uncontrolled heat source. PV/electric is a controllable heat source. Keep the two separate and tap into the uncontrolled heat source when required. This can be achieved by using (as Ermie said) a thermal store. Get a HETAS engineer with the wet qualification to do this work, and they will give you best advice, compliant install and Building Regulations Certificate for the works.

 

[Worcester]

Done properly he'd get all his capital expenditure back through the RHI and FiT so cost irrelavent

Forget plumbers get a heating engineer in, better still get an MCS registered firm in (biomass)

@ ramblehan, where in the country are you?

Log gasification you need a buffer tank / thermal store. That can easily be supplemented by the PV in the summer, or heat the DHW cylinder from the buffer and also from the PV. (Former possibly not RHI compliant, latter is)

Many simple, efficient solutions.

p.s. you don't have to be HETAS, there are other certification bodies - all MCS biomass certified are the equivalent of HETAS Plus.

 

[Gray0689]

Heating engineers = a plumber to me there all pipes and water nothing special about it and not everyone wants to be bothered with all the silly paperwork that MCS require just as easy to get a consultant to do that side

 

[Ermintrude]

Heating engineers = a plumber to me there all pipes and water nothing special about it and not everyone wants to be bothered with all the silly paperwork that MCS require just as easy to get a consultant to do that side

No way! Some people who mess with pipes are not heating engineers not even engineers

 

[Gray0689]

No way! Some people who mess with pipes are not heating engineers not even engineers

There not even plumbers lol

 

[Swift2506]

Copper smith that's a blast from the past worked with one for 3year very clever man
proper old skool

 

[Pipes Plumbing]

As has been said a few times here, an accumulator tank as large as possible (min 700l @ 50l/kw from the BBU), use that to heat an unvented cyl and heating zones. Put the solar output through an immersun or similar to divert any extra energy into the unvented cyl.

Don't forget the Back End Protection / Load Unit on the solid fuel boiler... Not only for protection but also to make sure you are getting only high grade heat pushed to the accumulator. Nothing worse than pushing warm water to the top of a tank and effectively destratifying the thing.

Remember your safety controls, overheat stats etc to make sure that everything is as safe and efficient as possible.

 

[itspaul]

I fitted a system in a converted pub with a brosely Hercules multi fuel stove 22kw bbu output into a 1000 litre open vent buffer using a load valve with a 210 unvented cyl for hot water the system was 12 large rads and works well the customer ordered the buffer and valve from these people https://kotly.com.pl/index.html?l=en. Took a while to arrive but good quality and reasonably priced