# Best fuel for multi-fuel stove fitted with a back boiler to heat the rads & hot water



## tipperary (4 Oct 2010)

Hi

We have a multi-fuel stove installed in our house, fitted with a back  boiler to heat the rads and hot water.  The system worked fab for us  last winter burning all the off-cuts from the building of the house.   Unfortunately however we have all but used up the off-cuts and will have  to start paying for fuel again!  

We found the wood worked very well, with a good flame heating the back  boiler and hence the rads in the house.  We used coal occassionally but  didn't find it as good at heating the backboiler, although we didn't  play around with the settings that much.

Just wondering what peoples experiences have been with different fuels  (solid wood / coal / eco-logs) with solid fuel stoves?  We are using a  Hunter Herald 14 if that helps.


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## Paddyman (4 Oct 2010)

*Best fuel for multi-fuel stove*

Hi,

We have something similar. We use well-seasoned logs (when we can get them), peat briquettes and EcoBrite coal. Ordinary coal can generate too high a temperature and can damage your stove.

It is important to have a good initial draught with the EcoBrite. When it starts to glow you can close the dampers slowly. Important to know the controls to get the best out of the stove and not waste money.


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## allthedoyles (4 Oct 2010)

So what is best for your stove ?
First you need to consider your situation , and you are heating radiators with back boiler .

Obviously a lot depends on the climate and especially the air temperate. So if it is 15 degrees today , you should not need the same fuel necessary when the temperature is -1 degrees as all fuels have different heat output..

I would suggest you start with Nuggets along with some firewood , and as the winter sets in you can switch to higher heat types like smokeless mixed blend , and eventually when it does turn really cold , you could use the anthracites .

Beware though and check your manual to find out the types of fuel not recommended to burn .

If your stove has restrictions , watch out for products containing petcoke / certain anthracites


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## fmmc (8 Oct 2010)

Folks,
Interested in the replies above as I'm in a similar position to the OP (i.e. a
relative solid fuel stove novice) but hoping to rely on the stove to help 
reduce primary fuel bill (especially after last winter!)  Differ a little in that I'm 
running underfloor heating, so wondering if that makes any difference to the
optimum fuel source recommended or suitable running method.  Thanks
in advance.


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## pache (9 Oct 2010)

*solid fuel/underfloor*

fmmc you mentioned underfloor whilst asking about fuel for your solid fuel stove.Just as a precaution let it be known that underfloor heating can only successfully operate correctly when its connected to a sealed heating system and a solid fuel stove can only successfully operate correctly when it is connected to an open vented heating system!!.


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## villa 1 (10 Oct 2010)

What is wrong with running underfloor heating off an open vented heating system/solid fuel heating appliance


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## pache (11 Oct 2010)

what would be wrong is a pressure drop within the system.


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## fmmc (11 Oct 2010)

Hi pache, I'm running both with no issues.  The plumber connected both sources in the hotpress using a "box" called a 'system link' that effectively takes inputs from both the primary heating source and the stove.  Depending then on the nature of the calls for heat, i.e. UFH or hot water, a different pump kicks in to send the heated water around as necessary.  This system link as I understand it facilitates the use of both vented and sealed systems.


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## villa 1 (11 Oct 2010)

pache said:


> what would be wrong is a pressure drop within the system.


Pressure drop where? How much pressure drop are you going to get from smooth bore underfloor polyethelyene pipes? Very little.
There is no problem running an underfloor heating system from an open vented heating appliance.


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## pache (12 Oct 2010)

There is if the pressure drop across the underfloor circut is greater than the head of water from the f&e cistern,which it usually is!!.
fmmc,has your solid fuel been operational with the underfloor for long?


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## villa 1 (12 Oct 2010)

Does that mean that there can be a pressure drop of between 8/10psi -5.5kPa in an underfloor circuit.


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## fmmc (13 Oct 2010)

Hi Pache.  No - both are installed for over a year, but I didn't use the stove last winter at all (more laziness than anything else!), but my plumber did assure me that he had successfully combined both sources in previous installations using the system zone box - I appreciate that tradesmen will tell you lots of things though!  Now that I am actually using both, is there anything in particular I should be aware of or on the look out for, and how?  Thanks,


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## pache (13 Oct 2010)

Fmmc,
no not much to look out for now but i would recommend you ensure your heating system has been chemically treated and treatment renewed on a yearly basis to ensure efficiency.

Try,as much as possible,to keep a good fire in the solid fuel appliance whilst in use as the higher the water temperature and flue gas temperature the higher the all round efficiency and the better the burn.

Do not (on a very regular basis) burn wet timber,only use seasoned wood.

I would not still recommend underfloor heating connected to a solid fuel open vented appliance.


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## pache (13 Oct 2010)

Its relatively straight forward to work out the amount of pressure lost across any given length/diameter of pipe.
To overcome this pressure loss the head of fluid(water) needs to be set accordingly to reach the desired design flow rate.(hence various head of pressure pumps) 

The point being that to reach the desired flow rate across say 600 meters of 16mm underfloor heating pipe, the head of pressure required to push the required volume of water through the circuit to satisfy the demand could,quite easily,create a vacume in the primary circuit which with its 22mm smooth bore pipework openly venting the system can be a major design flaw and lead to operational issues.


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## villa 1 (14 Oct 2010)

How will a vacuum be created in the primary circuit when this is seperate to the heating circuit in an open vented heating system fed from solid fuel heating system?
If your circulating pump needs to overcome the pressure losses induced by long pipe runs what happens when sections/areas/zones shut down leading to niosy pump operation.
I am still of the opinion that underfloor heating circuits can be heated from a solid fuel heating source once the system is installed properly with an open vented primary circuit and a fully pumped heating circuit. The problems are that many plumbers in this country do not know how to install open vented heating systems properly and safely.


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## pache (14 Oct 2010)

Can you explain how the primary circuit is seperate to the heating circuit?.

In a correctly installed heating system to overcome fluctuations in pressure from different sections of any zones shutting down a simple solution to this is a tried and trusted method called an auto by-pass valve(readly avalable from most reputable suppliers) as any accredited seai/hes installer should know.


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## villa 1 (14 Oct 2010)

Yes very simply. One set of 28mm diameter unrestricted metal flow and return pipes connecting the solid fuel appliance and the hot water storage cylinder on a gravity circuit. The flow pipe in then open vented (22mm) and a seperate cold feed (15mm) is brought down to the appliance The heating circuit is then taken away in fully pumped mode to the space heating requirement.
There are also many accredited seai/hes installers who do not know the fundamentals regarding the design reqiurements of open vented heating systems simply because they have not been enlightened during their apprenticeship training in the past


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## pache (14 Oct 2010)

Do you allow the same water thats used in the solid fuel appliance to flow through the underfloor circuit also? without a heat exchanger?


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## villa 1 (14 Oct 2010)

Yes, depending on the size of the underfloor circuit(s). A buffer tank may be required but this will have to backed up with solar/oil/gas unless you want a steam engine sized solid fuel boiler to satisfy a large heating load.


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## pache (14 Oct 2010)

Would you not be concerened that the solid fuel appliance would cause partial blockages/blockages in the underfloor due to low return water temperatures


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## villa 1 (14 Oct 2010)

No, I would have no concerns as long as the solid fuel system was designed properly and not induce the entry of oxygeneted water into the system causing corrosion and sludge build up, re: position of open vent and cold feed.


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## fmmc (14 Oct 2010)

Hi Pache (& villa1 if you can help also), why do I need to chemically treat my system each year & how do I do same?  What is the reference to oxygenated water and as I presume it is "unhealthy", how do I seek to avoid this issue?  Thanks


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## villa 1 (14 Oct 2010)

Firstly, I would not treat your heating system water every year because there is no need. The plumbing/heating contrator will add a corrosion prohibitor when finally filling your heating system(after flushing out). I would recommend topping up your corrosion inhibitor approximatelly once every three years in conjunction with any servicing that has to carried out on in-situ heating appliances.
Oxygenated water in your heating system is caused by pump-over via the open vent in an open heating system. This water is pumped up the vent pipe (because of poor heating design) and flows into the feed and expansion cistern taking with it oxygen. Oxygen +water +steel(radiators/boiler) = rust build up and sludging, then pinholes in radiators and leaks.
Oxygenated water will also enter a heating system due to a leak(s).
Do not confuse treating heating water with the treatment of private water supplies, whether they are hard or soft.


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## pache (16 Oct 2010)

fmmc said:


> Hi Pache (& villa1 if you can help also), why do I need to chemically treat my system each year & how do I do same? What is the reference to oxygenated water and as I presume it is "unhealthy", how do I seek to avoid this issue? Thanks


 
Because running your underfloor heating directly linked to solid fuel on an open vented heating system will cause furring,a process where the inner walls of your underfloor heating pipe become coated with a layer of oxide thus reducing the flow of water through the pipework and in severe,untreated cases,total blockage.
This results in an inefficient,lasy, system that cannot serve the purpose for which it was intended.  

Underfloor heating should be pressurised for it to operate efficiently.

Locate the make of your underfloor system through any brand name visable on the system components or contacting your installer or supplier and ask this supplier/manafacturer does your system carry any warranty against corrosion whilst not connected to a pressurised system.

Please post these findings.

Meanwhile fmmc,you should not have any worries in relation to causing permenant damage to your underfloor system as the associated problems can  be rectified.

This means in straight forward language the pipework that is your underfloor heating will need a good flushing out and re-treated with an addative every so often.This flushing takes place at your underfloor heating manifold .


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## villa 1 (17 Oct 2010)

Firstly "Furring" is caused by temporary hard water and results in hard limescale deposits on electical heating elements in hot water systems and in some exteme cases primary flow and return pipes fitted in Direct hot water systems
Furring is not found in central heating systems, but sludging and corrosion poblems will become prevelant in as I have already explained - badly designed open vented heating systems.
I will state again that I see no problem with running underfloor heating from an open vented appliance.
If underfloor has to run on a closed system, this rules out all open vented heating appliance, stoves, ranges etc.
The system is not a huge feat of engineering

Boiler to hot water cyclinder, open vented gravity circuit
Boiler to buffer tank, buffer tank to underfloor manifold, manifold to circuits.


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## villa 1 (3 Feb 2011)

As I said previously, nothing, once the system is designed and installed by a competant plumbing contractor.


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