Any opinions on my heating system?

[FrankE]

i forgot about the rads...if they are the priority, what output are they?

to FrankE: i wouldn't argue with you when you say that you doubt it would be feasible, but i am interested in this sort of system for myself so i would ask you to explain the reasons why you have come to that conclusion...

I won;t claim my doubts were calculated. Just a hunch from working on bio-mass boilers recently that you'd be doing rather a lot of stoking to heat a house from a stove. That clearly wasn't factoring in the biomass burner in the sitting room.

Also I note now you are in France where it's probably a warmer climate (hope so, my next holiday is in France).

Less doubtul then, though I'd defer to the heating guys.

 

[mointainwalker]

Have you considered what I said about the manifold ?

When I did this, I found that my initial notion of having it somewhere out of the way was unrealistic because on a couple of circuits I was looking at up to 15 lm of pipe just to connect .

If you could locate the manifold downstairs, it could be fed from heat bank with one 20 mm pipe which would give you more flexibility in how to use the available 100 lm in your circuits.

 

[aggy]

I can assure you that although the winter feels shorter here it still gets pretty cold. But firewood is also cheaper than the UK.
I have considered putting the manifold downstairs but having it upstairs with the heat store, pump for the rads etc would mean it was in the centre of the area to be heated, whereas if it was downstairs it would be trickier to find a central point for it. Becaus of the more central location it would only add a couple of metres to 2 of the circuits and not really effect the length of the 3rd.
Is the heat bank enough of a heat dump or does it need a rad connected before the bank as well?

 

[Agile]

My friend who lives a little further south near Limoges says that the winters in his area get significantly colder then the UK and can easily be -15°C.

The costal areas of the west coast may be a bit warmer then the UK though.

My property in 50250 is about the same temperature as the south of the UK though.

Tony

 

[igotalake]

Agile: i think you've missed one of the relevant points here a little; Aggy has said he/she does not have the intention or the funds to employ anyone to do this for her so i suppose getting a free quote would just be a unfair waste of resources for the company you suggested. i guess she just wants a little bit of technical advice from those who have some knowledge in this area...

i think Mointainwalker would know better about this than me but if you only need (or will only be able to extract) between 50 w/m2 and 80 w/m2 then the output requirements of the stove and heat store are significantly reduced, maybe down to somewhere like 6kw for UFH. as to whether the 200l heat store is enough of a dump then i think you will have no problems in that respect if you also have 4 rads and perhaps DHW.

how does this sound:

this may require some valves and control equipment that do not exist in the plumbers' merchants but anyway... once upto a suitable temp for UFH have the hot water from the heat store directed to the UFH until the temp is suitable for rads. at this point the return from the rads is directed through the UFH.

if the temp of the thermal store continues to rise once the UFH is 'on' there is heat available for the rads. if there is excess heat available when both UFH and rads are 'on' then that could be used for DHW which would otherwise be heated electrically....

complicated enough?

MW: out of interest, how do you heat your underfloor circuits?

 

[aggy]

Igo, you're right. I don't want to pay anyone to do work that I'm capable of doing with a bit of advice.

The reason I'm asking about the heat dump is that it must be able to dump heat if theres a power failure so it must be able to function by gravity alone.

I kind of imagined the two outlets from the heat store having pipe stats so that when they reach the right temperature the pumps start working. The rads output is higher up the tank so the water will be warmer and the ufh is lower so the water will not be as hot. Is this correct?

Igo, I hope you're not just helping because I'm female?

 

[Agile]

Thats right, the heat dump must be able to adsorb by gravity flow the heat output from an uncontrolled solid fuel boiler during a power cut.

Normally one would assume a fully charged boiler and require the heat dump to be able to adsorb the heat output until that fuel had been burnt away.

Gussing a bit but 180 litres would probably adsorb about 8-10 kWh to bring it up to boiling point if starting at say 10°C.

However the problem is that in normal operation of the system, the whole idea of the heat store is that its kept hot at say 80°. That does not give much scope for further heat adsorption!

Its rather questionable but some might say that as it will be open vented in an emergency situation it could just BOIL away any excess heat to maintain a safe condition.

UFH should only be distributed at a maximum of 50°C. That can be obtained from anywhere on the thermal store as the usual way to run UFH is with its own circulating pump which is supplied by a blending valve to achieve the required 50°C regardless of any higher supply temperature.

Many might want to keep the top half of the store hotter for hot water supplies and take the heating from say half way down if there were tappings in these positions.

My friend near Linoges uses wood as his heating source but is totally happy with his electric water heating. He does have an unvented cylinder which could be heated from the wood boiler but that needs to be pumped to heat quickly and he does not want to bother with that. Since he has about 3 hectares much covered with trees he has enough wood to supply all his needs. As its an old water mill, I would love him to renovate the water wheel which could generate about 6-12 kW but that does not interest him either. It was grinding corn apparently until about 1960 with two sets of mill stones. I have always wanted to own a water mill !

I know its not very fair but there are still many people who use companies, like the one I linked to, to provide free quotes and designs. I was interested that they state that UFH is not suitable for wooden floor coverings. I think thats based on the French perchant for thick wood floors rather than the thin ones we mostly use in the UK.

Finally I would remind you that in the UK we mostly expect the maximum heat output from UFH to be about 50w/m² ( metres carre, pas cube ! ).

Tony

 

[igotalake]

180 litres should absorb about 19kwh between 10 degrees and boiling (0.00000116 x 180000 x 90 - please check my calcs.) which should cope with Aggy's stove running flat out for about 2 hours (assuming it's 10kw). i don't suppose many stoves would have the capacity to run flat out for more than two hours without reloading.

the problem, as you say Agile, is when the store is already at 80 degrees, which would hopefully be most of the time...my rayburn has a towel rad in the primary circuit as a heat dump but i think as Aggy's stove has a much bigger output (rayburns aren't that powerful) she will need a proper rad the size of which could be calculated to cover worst case scenario,...but would that cause the rad to dump too much heat during normal operation?

and by the way Aggy, i am not a chauvinist, i would help anyone where i can...but if you want to meet up for a drink some time..

 

[aggy]

Igo, I know its valentines day but don't get any ideas! You're right though, how do I stop a heat dump rad dumping heat when I dont want it to? Or maybe it doesn't matter if a bathroom radiator heats up before the heat store? I'd guess that either the heat dump is plumbed into the pipes between the boiler and store or that it has its own connections into the store. The latter might be trickier to plumb in gravitationaly but might mean it doesn't dump heat before the store is heated.
Does anyone know how its usually done?
Are the chances of a power failure going unnoticed at the same time as the boiler being in full flame pretty slim?

 

[igotalake]

by the way, cool motor a few posts back Agile....

 

[Agile]

C'est le Renault C15 !

Le fourgon prefere par la plupart des plombiers en France dans l'anne 1980.

 

[igotalake]

par contre, beaucoup ca change depuis 1980!

anyway, Tony, how would you arrange a heat dump in this system to give good safety cover but avoid unnecessary heat losses to the wrong areas when all was functioning well?

and mountainwater, what is your heat source and could you post some diagrams of your setup ?

muchas gracias,

 

[Agile]

Thats the problem now that people are trying to use high output wood stoves to heat hot water cylinders.

The old situation was a stove with a direct heat outpout of say 7 kW for space heating and say 3 kW heating output which would heat up a cylinder in a few hours. A smaller rad could be used as the heat sink and producing useful heat.

A boiler with 10 kW of heating output is difficult to use because the output is way in excess of the water heating requirement. In practice it would be teamed with many rads on a pumped system and a few on a gravity circuit which also serve as a heat dump.

Tony