# Combining solar, solid fuel stove/boiler and gas.



## pjd (14 Feb 2012)

Hello,

I have spent a few hours reading many interesting and relevant posts but now I find I am totally bamboozled, and entirely unsure as to what I need to do.

I am renovating a single storey cottage and building a two storey extension. In plan, the cottage runs north south with hipped roof at south. The extension adjoins the cottage at this end and runs towards the east. So L-shaped. 

The architect has put solar tubes on the south facing hip of the cottage roof with the tank upstairs in the extension next to the main bathroom. Summer hot water sorted. We want to run a wood burning stove in the cottage (we have access to wood) with a boiler for heating and water in the winter. So far not so challenging. 

We want to cook with gas. Its a strong personal preference. So the architect suggests that a gas boiler for days when you don't want to light a stove or for a quick boost in the morning, or for when you are away etc. would be a useful addition. 

The thing is, fossil fuel prices are only going one way so I don't want  to be totally reliant on them. But the advantages of having gas or oil as a back  up for space and water heating are significant. And as we want gas for cooking anyway.........When I look at it seems that I want to have my cake  and eat it but I'd rather work this out now than have to revisit it  when the job is done.

Is this overly complex? Maybe there is a better way? I have experience of dual systems not working well or efficiently becasue they have not been installed correctly.

Any observations would be welcome.


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## lowCO2design (14 Feb 2012)

there is no issue with doing this its becoming quiet common. potential problems occur at the specification stage and finding a capable plumber to do the job correctly..


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## pjd (14 Feb 2012)

I'm encouraged to hear that it is becoming more common, as it strikes me as being fairly sensible. I would be keen to get a properly designed system, but who would design it and how would I know it is fit for purpose? 

IMO when you build a house it is wise to employ an architect. But who do you employ to design a bespoke heating system?

One thing I have noticed on the forum is that you rarely get consensus. Building regs and custom and practice often clash. People with a great deal of experience often can't agree. Doctors differ and patients die. 

If I had a better understanding of the over-riding principles I would be more confident. Is there anywhere I can find information about, at the very least, what to avoid?


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## villa 1 (14 Feb 2012)

Employ the services of a time served plumber with a past catalogue of systems/customers.
A lot of problems are encountered by plumbers who do not understand dual heating sustems and especially the design of a safe open vented solid fuel heating appliance.


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## lowCO2design (14 Feb 2012)

pjd said:


> I'm encouraged to hear that it is becoming more common, as it strikes me as being fairly sensible. I would be keen to get a properly designed system, but who would design it and how would I know it is fit for purpose?
> 
> IMO when you build a house it is wise to employ an architect. But who do you employ to design a bespoke heating system?
> 
> ...


 when designing low energy homes I often consult a M&E engineer to confirm/ design heating systems. It really depends on what the set-up is. I find that getting a competent heating engineer that is willing to put in the time and willing to learn new technologies will cost a premium.


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## villa 1 (14 Feb 2012)

lowCO2design said:


> when designing low energy homes I often consult a M&E engineer to confirm/ design heating systems. It really depends on what the set-up is. I find that getting a competent heating engineer that is willing to put in the time and willing to learn new technologies will cost a premium.


 Just wondering, is there such a person as a heating engineer in this country and if so, where does one get such a qualification? I'm not sure is there such a qualification/engineering degree available in any Irish university/Insitiute of Technology.
I know that heating services/control comes under the many aspects of Building services engineeriing.


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## lowCO2design (14 Feb 2012)

villa 1 said:


> Just wondering, is there such a person as a heating engineer in this country and if so, where does one get such a qualification? I'm not sure is there such a qualification/engineering degree available in any Irish university/Insitiute of Technology.
> I know that heating services/control comes under the many aspects of Building services engineeriing.


sorry, my bad, i'll stick with the terminology that - plumbers (deal with water, sewerage & gas pipework) and Mechanical and electrical engineers (specify heating systems) and heating engineers (deals with specific heat units/appliance's and certified to install/ service)


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## Shane007 (14 Feb 2012)

pjd said:


> The architect has put solar tubes on the south facing hip of the cottage roof with the tank upstairs in the extension next to the main bathroom. Summer hot water sorted.


 
Make sure there is enough room for the amount of tubes/panel on this location. In my experience hip locations can be fairly tight and most can only fit 20 tubes. You must take account that Regs stipulate that panels must be a minimum of 500mm from any roof edge.



pjd said:


> We want to cook with gas. Its a strong personal preference. So the architect suggests that a gas boiler for days when you don't want to light a stove or for a quick boost in the morning, or for when you are away etc. would be a useful addition.
> 
> The thing is, fossil fuel prices are only going one way so I don't want to be totally reliant on them. But the advantages of having gas or oil as a back up for space and water heating are significant. And as we want gas for cooking anyway.........When I look at it seems that I want to have my cake and eat it but I'd rather work this out now than have to revisit it when the job is done.
> 
> ...


 
Have you Natural Gas or LPG? There will be a significant price difference in running costs.
Secondly, I would not like to combine a gas boiler directly with solid fuel. Gas boiler heat exchangers are far more restrictive than say an oil boiler's exchanger and therefore can lead to expensive repairs down the line. Solid fuel system waters will always be much sludgier than other systems as the heat is always uncontrollable, therefore pitching can sometimes occur when overheated. This will re-oxygenate the system in time and create a sludged system affecting the gas boiler. 

You could install a buffer tank that would tie all the systems, for example, gas boiler into buffer directly and have the solid fuel through a coil or vica versa, keeing the solid fuel as an open vented system and the gas boiler & heating circuit as a pressurized system. The buffer would not have to be huge, enough to cope with the demand of the solid fuel boiler and it could be wired with a cylinder stat to switch on the pump to circulate from the buffer to the radiators indepently of the gas boiler. The gas boiler will of course be able to bring on this pump also through a relay to eliminate any back feeds.


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## Shane007 (14 Feb 2012)

villa 1 said:


> Just wondering, is there such a person as a heating engineer in this country and if so, where does one get such a qualification? I'm not sure is there such a qualification/engineering degree available in any Irish university/Insitiute of Technology.
> I know that heating services/control comes under the many aspects of Building services engineeriing.


 
[broken link removed]

Governed by the UK but it is a start!


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## pjd (14 Feb 2012)

Shane007 said:


> Make sure there is enough room for the amount of tubes/panel on this location. In my experience hip locations can be fairly tight and most can only fit 20 tubes. You must take account that Regs stipulate that panels must be a minimum of 500mm from any roof edge.
> 
> 
> 
> ...



Thanks Shane. I'll have to check that hip.

Gas will be LPG, but mainly for cooking. The gas boiler is strictly for occasional convenience. 

So if I interpret you correctly, you would recommend a vented system on the stove side, pressurised on the gas side, and a buffer tank to make them work in tandem. Of course if we have solar we will need a big tank for that. So two boilers, two tanks, a set of tubes, copper pipe, relay, timers and a half dozen rads..............I'm talking myself out of this already. Ball park what sort of premium are we talking, over and above a standard installation.


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## Shane007 (14 Feb 2012)

You are going with 2 boiler, tubes, pipework, etc. anyway. The only additional item you will have is a small buffer tank and it does not have to be that big. It only need to be able to take a gravity circuit from the stove and sized according to the output of the stove. A cylinder stat for a buffer is probably about €35. A 500 litre buffer is about a €1,000 but you may not need one that size. Most of the manufacturers will make any size to order. 

The buffer will also act a thermal store, in that if you do use the heat you have put into it from the stove, it will store it probably well into day 2 if it is well insulated and they normally come with extremely good insulation.

With regard to vented and sealed, that is correct, vented for stove and sealed for gas boiler. Just make sure that the circuit from the stove is completely gravity continuously rising (no drops) from the stove to the coil in the buffer. This bottom of the coil must also be above the top of the stove.


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## pjd (14 Feb 2012)

Thanks again Shane. Do you still need a separate tank for the solar or is it possible to use that as a buffer tank, to simplify the installation and save space. As I write this I'm guessing the answer is no.


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## pjd (15 Feb 2012)

Just came across a TiSUN Proclean cylinder that handles multple heat sources inc solar on the RVR website. Eye watering price. I should probably try to work out what the return on investment would be with a belt and braces system before blowing the kitchen budget.


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## Shane007 (15 Feb 2012)

There are a number of systems on the market, such as tank-in-tank, which are a small tank within the bigger buffer. There is also one that has a rapid heat coil that works in reverse taking heat out of the tank and then onto the domestic hot water taps, etc.

Both are there disadvantages as you must heat a large volume of water in order to just satisfy your dhw demand. It would still be cheaper to install a small buffer if you have the space.


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