Multifuel Stove + Gas

B

buyingabroad

Registered User
Messages
159
Hi,

Is it possible to have a stove in the kitchen (which will primarily use wood) and have a gas fired central heating system and for the two to be interconnected? If so, would this heat the water and radiators?

Thanks,

B.
 
It can be done but IMO is a bit messy.

A number of issues arise, the following is just a sample

The stove will need to be vented so will dictate an open CH system which means that u will need a header tank somewhere above the highest rad.

It will also need to be plumbed so as when the power dies and the circulation pump stops that the excess heat can be safely dissipated


The plumbing to have the stove SAFELY not act as a rad when it is off and the gas is on, is a bit tricky.

Typical back boiler stoves heat-wise are 2/3 water and 1/3 room which means that if u are maxing the rads off the stove, it may be bikinis and shorts in the kitchen.

I just dont think its worth the effort, have the stove as stand alone, independent of elec and water and just enjoy it: we have 2 this way
 
It's possible. How complicated it is will depend on your existing system.

The most basic way of doing it is using a dual coiled cylinder and non return valves. as already stated the system will have to be open vented and you must have natural circulation between the stove and the cylinder.

It can also be done through a buffer tank system.

If you heating is zoned things get a bit more complex. It the system has interlocking controls, external electrical relays will need to be fitted to stop the gas boiler firing when motorised valves are opened.

The stove will need an open circuit when temperature is up and cylinder is hot enough.

Get a few experienced installers to price, it is advisable to fit a cleaner on the return of the gas boiler, something like this, as stoves may dirty the system water more and boiler manufacturers don't take kindly to their fragile heat exchangers being dirty.


It will make more sense when you talk to an installer face to face.
 
Thanks for the replies. Would it be fair to say that having the stove heating the water only would be a simpler system and the way to go?
 
buyingabroad said:
Thanks for the replies. Would it be fair to say that having the stove heating the water only would be a simpler system and the way to go?
Click to expand...

0: not really, however if u 'insist'
1: depends where the tank is vis a vis the stove: the first few I did were gravity only, with no pump
2: what do u do with excess heat once the HW cylinder reaches temp, u will have to stat it as u can risk v hot water, will scald people.
3: it would allow u , if done right, have the gas side a closed system and the stove an open one with coil through the cylinder
4: if u do this lag the overflow pipe in the attic and fit a pressure relief valve some where
 
It costs nothing to get installers into price. I would recommend getting a few in, be sure and listen to what they say. Site lay out has a massive part to play in how easy an installation is.
 
Hi. I am interested in installing this type of system. I see you say you have installed a few.
I live in the Drogheda area. I have a Vokera minute '12e' gas boiler. Would it interest you in having a look with a view to carrying out the installation.

Also, is this configuration in compliance with RGI specifications.

thanks,Eoin.
 

No longer do installs, just offer opinions

Neither do I find installers.

If I can be of any further help send a PM, I am not 2 far away from Drogheda area
 

The Vokera Minute 12e can only operate on a pressurized system. If you convert your system to an open vented system, then you will have to change your gas boiler to an open vented gas boiler, such as the Vokera VHE, particular for open vented systems. See [broken link removed]. Also do not install what is commonly known in Ireland as a "semi-sealed" system. They are illegal and rely too heavily on non-return valves.

If you are installing a back boiler, then your system MUST BE open vented and it MUST have a 1" natural rising gravity flow to the hw cylinder with no valves or drop downs in the flow pipework. It MUST also be able to operate without a circulating pump in case of power or pump failure. A flap type non-return valve (not the spring type) should be installed on the horizontal pipework on the positive side of each circulating pump to avoid each boiler heating the heat exchanger of the other boiler.

A very common badly installed back boiler installation is for example in a bungalow where the flow from the back boiler rises into the attic, across the ceiling and drops back down to the cylinder and the return pipework drops from the cylinder to the floor and travels under the floor back to the back boiler. This installation will definitely not work as a gravity only circuit and the common result is banging pipes! Why, because the heat naturally rises and travels along the pipe until it meets the elbow to drop down to the cylinder. Heat naturally wants to rise and therefore will not travel down. The heat backs up and overheats, resulting the banging. It will work when the circulating pump is on because the heat is forced down, but nothing has been accounted for when there is a fire lit to heat the parish and suddenly the circulating pump packs in or there is a power failure. This type of property should have the hw cylinder located very close to and above the back boiler to eliminate the need to take the flow pipe into the attic space. Heating pipes should not be routed through the attic space, however, if they are, a minimum distance of 1/3 of the static pump head should be between the pipework and the feed & expansion tank.

Another common issue is the incorrect location of the two circulating pumps and the location of the open safety vent pipe and also the incorrect location of the feed and expansion pipe.

Many installations have the oil boiler pump and the solid fuel pump both on the returns. In most instances this will lead to both pumps pulling against each other, again leading to banging. This is the main reason why many installations cannot have the fire lit whilst the oil boiler on or vica versa. One pump should be on the flow with the second pump on the return so that they can work in unison. Careful positioning of the OSVP and feed/expansion pipe must also be adhered to otherwise pitching and other issues can ocur.
 
Whilst I agree with what a lot of what Shane is saying I have to disagree with his comments regarding the pipework from backboilers to cylinders in bungalow construction.
There is absolutely no problem running a 1 inch primary flow pipe from the stove/boiler up into the attic and running horizontally until dropping down in to the hot press area and connect to the cylinder. The 1 inch primary return can be ran under the floor and up into the hot press and connect to the cylinder. This circuit will indeed be free from any valves or pumps. This circuit will work perfectly well once the dip in the return pipe will not exceed one sixth of the circulating height between the centre of the boiler/stove and the centre of the hot water cylinder.
The pipework will have to be metallic and be installed using as many bends as possible to ensure proper circulation.
This system was used extensively because in most bungalow design the cylinder was located in the hot press area which was 6/10m down the hallway. All solid fuel boilers will boil if the circulation is not assisted with a heat leak gravity heating circuit/radiator or by using a circulator.
The open vent will be taken off the primary flow into the attic and as with all dual systems incorporating a solid fuel appliance tha cold feed to the system is brought down to the solid fuel appliance and connected into the return.
I have mixed views on non-return valves. I cannot see a problem with spring type walves as they can be fitted on any plane once in the right direction. Flap type valves have a habit of passing.
Down through the years I have fitted many a dual system in a bungalow and I have had no problems with restricted circulation. I would stay away from garden hose/ pex pipes on the primary circuit.
 
villa 1 said:
...
The pipework will have to be metallic and be installed using as many bends as possible to ensure proper circulation.
Click to expand...

How do as many bends as possible ensure proper circulation?

Shane007
If the OP changes his cylinder to a dual cylinder than he can have a pressurized gas system and an open back boiler system. Might be cheaper than trashing the existing burner

Vila and Shane007: given your experience in this area it would be useful to pen a few lines on the header tank for such a system.
 
I disagree. What happens if there is a circulating pump failure or a power cut? The heat will rise and travel to the point where it must drop. The heat will back up within the solid fuel boiler and boil. This will cause banging and possible joint leaks. It will also cause enough expansion within the circuit to pitch from the OVSP back into the expansion tank, re-oxygenating the system, causing sludge and rust.
A well known case in the UK was where this happened, the heat melted the expansion tank, it leaked and scalded to death a sleeping baby below it.
Just because it is commonly installed does not make it right. Do you not remember all the cylinders fitted in a cupboard in the living room close to the back boiler to ensure a gravity circuit? There was never an issue as there was no circulating pump in the first instance so it had to be installed correctly.

To explain, when water is heated it becomes less dense that cooler water resulting in the heated water wanting to naturally rise. The circulation of water can be achieved by convection currents being set up within the flow and return pipework, resulting in a natural circulation. Do not get me wrong, a fully pumped system is by far more the better option and it is against Building Regulation to install a heating system unpumped. However, allowances in solid fuel systems must have the ability to disapate heat when there is a pump failure or power failure.

Bends must be kept to a minimum. The maximum pipe length permissable is 25.5ft or 7.8m between the boiler and the cylinder coil. It should also be well lagged. This is ensure the velocity of the circuit to the coil. Each 90 bend (from horizontal to vertical & from horizontal to horizontal) is equivalent to 4ft of the total allowable length of pipe run. Therefore 3 x 90 bends = 12ft, so now the total allowable length of pipework is now halved! Bends from vertical to horizontal should preferably be made with a pipe bender rather than an elbow joint to allow a sweeping bend. 90 elbows are, of course, acceptable.

villa 1 said:
I have mixed views on non-return valves. I cannot see a problem with spring type walves as they can be fitted on any plane once in the right direction. Flap type valves have a habit of passing.
Click to expand...

I agree somewhat but only if they are located in a suitable position. Spring type should not be located on the flow pipe close to the boiler as excessive heat can melt the plastic inards of the valve. I have no problem installing them on the return pipework between the pump and the boiler where temperatures are cooler and only if of course the pump in this situation is located on the return.
Flap types should not pass if they are located on the driving side of the pump and close to same.

villa 1 said:
Down through the years I have fitted many a dual system in a bungalow and I have had no problems with restricted circulation.
Click to expand...

The installation installed in the way you have described will of course work each and every day as long as there is a circulating pump in operation. My argument and Building Regulations willl argue what happens when there is not and who will suffer the possible consequences of it!

A little test for anybody who has this installation: Light a good fire and switch off the pump. The amount of installations that I have seen where the pump is wired through a switch and not a pipe thermostat and when I have asked the homeowner when do you switch on the pump, the reply is the pipes tell me (banging!).

villa 1 said:
I would stay away from garden hose/ pex pipes on the primary circuit.
Click to expand...

I completely agree. They cannot take the heat and will sag and melt. Also do not use push fit connections. The plastic inards can also melt.
 
hastalavista said:
Shane007
If the OP changes his cylinder to a dual cylinder than he can have a pressurized gas system and an open back boiler system. Might be cheaper than trashing the existing burner
Click to expand...

True but what happens when the cylinder has reached is maximum temperature and it cannot take anymore heat?

hastalavista said:
Vila and Shane007: given your experience in this area it would be useful to pen a few lines on the header tank for such a system.
Click to expand...

The header tank or the feed & expansion tank should be sized correctly for the volume of water within the system and the kw output of the boiler. A general rule of thumb is for boilers upto 25kw should have a minimum of 45 litre tank and a boiler of 25 - 45kw should have 70 lite tank and 45kw - 60kw should be 90 litres.

There are many different layouts pipework to & from the f & e tank. This will depend on the type of system, boiler & number of boilers. All layouts are designed to elimate sucking in of air and pitching, etc. As much of the system should be in positive pressure as possible rather than in negative pressure. The neutral point will be where the feed & expansion pipe is teed in.
 
As I have stated already I see no problem whatsoever with an "up and over gravity primary circuit" between a solid fuel appliance and a cylinder (in bungalow design) once there is a proper circulating head/pressure generated.
I can certainly say that I have never had a problem with any of the solid fuel installations that I have fitted in the past 25 yrs. I do not need to be reminded of the design features of convectional circulation in systems and length allowances for elbows/bends/ tees and internal pipe surface.
If the cylinder is fitted right beside the boiler (optimal) or 8m down a hallway in a bungalow makes no diference whatsoever if there is a power cut. The water in the boiler will boil and if the hot water cylinder is satisfied this heated water will take a safe route and expand up into the feed and expansion cistern. This expansion will only happen in extraordinary circumstances such as a power/pump failure and is deemed as a fail safe method of protecting the heating system.

The fatal incident in UK was caused by a faulty immersion element in a hot water cylinder overheating and spilling boiling water into a polythene cold water storage tank that in turn collapsed on top of the room occupant.

What is wrong with a gravity heating system? Having this type of system is a great advantage in a multistorey dwelling (even two storey) whereby heat will rise to heat emitters without the need for electric pump circulators. If this is the case according to the building regs it is wrong to install a gravity solid fuel heating system, weather independantly or link it to another heating appliance.
Looks like our Irish plumbing apprenticeship training system that covers both industrial and domestic heating installations is flawed as this is what I was taught all those years ago!!
Maybe people should take their advice from the guy behind counter in the builders providers and fully pump the system!!
 

My point exactly!

villa 1 said:
I do not need to be reminded of the design features of convectional circulation in systems and length allowances for elbows/bends/ tees and internal pipe surface.
Click to expand...

You stated that the system must be installed with as many bends as possible to ensure proper circulation. This is not true.

villa 1 said:
The fatal incident in UK was caused by a faulty immersion element in a hot water cylinder overheating and spilling boiling water into a polythene cold water storage tank that in turn collapsed on top of the room occupant.
Click to expand...

Now that you mention it, you are correct. My mistake, however, the principles and the risks are the same!


Building Regs states that for new dwellings, systems for space heating and domestic hot water primary circuits should be fully pumped. It also states that when boilers are replaced, existing systems with semi-gravity circuits should be converted to fully pumped circulation. It is not stating that you cannot install a gravity circuit. You can. It is a requirement that the system is fully pumped also.

Provisions should always be taken into account for component failure and this is where a gravity circuit comes into its own.
 
I will have to look up the building regs on heating requirements. If what you say is correct you will not be able to install a solid fuel appliance unless you fully pump every circuit. nasty!! The days of the unrestricted primary circuit are gone. Dangerous installations here we come
Oh and I may have confused people by saying as many bends as possible. My mistake. I meant using bends for direction change instead of the more restrictive "elbows"
 
You can. Where installations have a heat leak radiator installed to dissipate heat from a smoldering fire, such as a bathroom towel rail, a thermosiphon system maybe used for this circuit. In some cases, a fully pumped system can reduce efficiency and therefore should not be used.

In normal circumstances, having the system fully pumped will increase efficiency, but during pump or power failure, the gravity circuit acts as a fail safe device to safely take heat away from the boiler.

Building Regs are not in place to make systems more dangerous but to make them safer and more efficient, with particular attention to conservation of fuel and energy.

The UK goes to great lengths and expense in research and development in developing these standards and also with Building Control departments in place to ensure compliance.
In Ireland, we just copy their regulations, make minor adjustments so we can call them our own and then have no compliance monitoring!
 
Shane could you let me know where I can find the Irish building regulations in relation to solid fuel/ dual heating systems as I would be interested to give them a viewing?
In relation to us Irish copying the uk in relation to Building regs/control you will have to agree that the practice of training people to be plumbers in short spaces of time in the uk is a recipe for disaster. I would definetly recommend the Irish apprenticeship training system over the uk system (NVQ) as it is much broader and covers far more aspects of the heating/plumbing industry. Our craftspersons are after all much in demand all over the world (thanks be to god!!)
 
http://www.environ.ie/en/Publications/DevelopmentandHousing/BuildingStandards/FileDownLoad,18691,en.pdf

I completely agree with you that the Irish training system is far superior than the UK system. There are far too many rugue builders in the UK. In Ireland, most work is won by referral whereas in the UK, an advert is all you need. Different populations. Where we dramatically fail is what happens next. We just get them qualified and let them loose. No monitoring, no ensuring of compliance, no nothing. Then the "sure it will be grand" mentality sets in. The other part is that we do not update trades people as Building Regs change/updated. In the UK, compliance and certification is very strict and getting stricter.

Wouldn't it be great if we trained them and put in place a Building Control?

By the way, I am not trying to be argumentative with you and I completely respect your knowledge and experience. It is extremely valued here.
 
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