wood burner back boiler instalation?

[jbenny1]

Hi all,

I've got a couple of questions regarding the instalation of a log burner with a back boiler.

I've looked at a couple of systems to link it into my existing centeral heating but if you consider the additional costs of the installation, it will take years to pay back so i might as well keep with just a gas boiler. Hence the system i have come up with needs only a bit of additional pipe work and a couple of new rads in rooms which need addational radiator capacity anyway.

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The plan is to run a completely seperate system along side the exsiting gas boiler. I've checked the regs regarding the copper float and overflow for the F&E tank.

Can anyone offer any advise on my system design, all comments welcome, good or bad!

i've also got a couple of questions.

1) does the expansion pipe have to be 22mm and can the feed pipe be 15mm?

2) is 60°C ok for the stat controlling the pump.

3) are the 2 rads located on the gravity loop (bedroom and bathroom)2.1Kw enough capacity for the 5Kw back boiler of will i need additional rads on the gravity loop, to prevent the system from over heating if the pump fails due to a power cut?

4)will the 2 additional rads mounted downstairs off of the gravity loop still get hot if the pump fails?

5) could i run the pump off of a large car battery via and inverter, which is keeped trickle charged from the main, but will provide a couple of hours run time in the event of a power failure to allow the fire to die down.

thanks in advance as i'm new to this older style of gravity centeral heating design.

 

[Agile]

I think that the pump needs to be in the return so the boiler to vent is a free run.

If you want gravity circulation then the rads will need to be piped appropriately and not like your parallel drawing.

I would pipe them as a single pipe system if they are not to be the primary heat source.

A drawback is that their heat output cannot be controlled so many are fitted on landlings where they will not overheat bedrooms etc.

It seems quite common for heat sink rads to be only a smaller proportion of the max stove output.

The heat dissipation is achieved by boiling the water in the system from the vent. This is why the float and tank should not be plastic. ( Although some will argue that the latest plastic tanks are suitable ).

Tony

 

[jbenny1]

Hi thanks for the quick reply

I did think that the pipe from the stove to the vent needs to be free of obstructions. If i move it to the return do i still need the 2 port valve bypass?

Also using a single pipe system would make temperature control non exsitant but as i can't fit any valves on the rads anyway, i've got nothing to loose.

Thanks for the info on the rad sizing i assumed to could go a little under the boiler size but i've got less that half the rated output, but manufactures are always a little generaous on their outputs

 

[dcawkwell]

I strongly suggest you give the idea up.
Log burners are a waste of time for the following reasons.
1. You will soon get bored with filling it with wood.
2. Hassle and expensive of getting wood/coal and getting
is ready for the stove. I have better things to do with my time.
3. Lighting the thing.
4. No useful heat for ages once lit.
5. Cleaning the thing out.
6. Lighting it again.
7. The huge quantity of wood you will require for any useful quantity of heat.
8. Very inefficient way of producing heat all the heat is going straight up
the chimney.

 

[Hufty]

Ignore him he always posts something along those lines at the mention of the words "wood burner". Think he was abused by/with a log as a child.

 

[dcawkwell]

Ignore him he always posts something along those lines at the mention of the words "wood burner". Think he was abused by/with a log as a child.

Just trying to prevent another customer from wasting money on something
that will be left and used only once in a blue moon.
Please feel free to pick faults with the points I have made about them.
It's import to keep these in mind. If the customer is willing to
put up with that then fine. I haven't met many yet who are used
to modern gas appliances who don't get bored with them.

 

[XtraRaptor]

8. Very inefficient way of producing heat all the heat is going straight up
the chimney.

So how come the paperwork with my new "logburner" states an efficiency of 72%

 

[dcawkwell]

8. Very inefficient way of producing heat all the heat is going straight up
the chimney.

So how come the paperwork with my new "logburner" states an efficiency of 72%

72% is poor compared
to a gas combi with heat recovery unit approaching 97%.
It also ignores all the haulage costs, fuel preparation, of getting the fuel to the burner.

Log burners should be banned they are environmentally unfriendly.

This also ignores the fact that wood used in them comes from trees hence reducing the amount of carbon absorbing trees unless coming
from a maintained woodland.

 

[Agile]

Thanks for the info on the rad sizing i assumed to could go a little under the boiler size but i've got less that half the rated output, but manufactures are always a little generaous on their outputs

Rads are sized for a flow/return temp of 70/50 typically.

The output is probably DOUBLE when the flow temp is 100 C and when on a gravity circuit the differential will be quite small.

People often forget that.

Tony

 

[jbenny1]

Thanks Tony i'd forgotten about the temp difference being a lot higher especially at the critical point when the system's about to boil over, the temp difference will be more than double, hence doubling the rad outputs, so mine should be OK.

In response to "dcawkwell" i guess log burner as not for everyone.

But as for the pro's and con's of burning wood.

1) A friend of mines a tree surgeon and supplies me with all the wood i need, all from dead or unwanted tree's so there's very little environmental impact there.

2) If you select the wood carefully it can be split very easily with a splitting axe, warms you up twice once cutting and again when burned!

3) If the wood is correctly seasoned and burt in a stove that is well maintained very little ash will be created, ours will do a good job of heating most of the house and only needs emptying every 3/4 days.

4) A lot of the heat does go up the chimney but, our chimney passes through, 2 bedrooms, warms the adjoining dining room wall up as well as the loft

5) last year we only had the gas heating on a dozen or so times and our gas bill for the winter 6 months was less than £100, compared to the previous year of well over £400.

Finally with a real fire you only light the fire if you really need it, where as with central heating controlled with a timer/ thermostat it comes on regardless of building occupancy and heat requirements. This wastes a lot of energy needlessly.

I will be the first person to agree heating your whole house using solid fuel is more of a way of life and you need to be prepared for the odd morning when the fire has gone out over night and the house if freezing but with a few minor alterations, and a bit of peservisence i think it's more than worth it.

But that just my humble opionion.