# Real and effective efficiency of your oil or wood boiler?

Heating, insulation, ventilation, VMC, cooling ... short thermal comfort. Insulation, wood energy, heat pumps but also electricity, gas or oil, VMC ... Help in choosing and implementation, problem solving, optimization, tips and tricks ...
Christophe
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posts: 79353
Registration: 10/02/03, 14:06
Location: Greenhouse planet
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## Real and effective efficiency of your oil or wood boiler?

I just estimated the yield real and effective of our wooden deom on the DHW tank and it's not famous at all !!!
See assembly here: https://www.econologie.com/forums/chaudiere- ... t4589.html

How did I do? Very easily: I closed all the other valves except those of the DHW tank and I measured the T ° before / during / after.
Thus the only energy, apart from the "losses" in the pipes and at the level of the boiler, is that which will heat the sanitary water. Obviously I had turned off the hot water during these measurements.

Then we bring everything in kWh (or other) and the effective output is given by: "energy supplied to the DHW tank / energy contained in the fuel"

Measurement protocol:

- boiler start off
- weighing the mass of wood (= fuel load)
- the T ° of the DHW tank is periodically noted (every 1 hour)
- For the initial and final T ° we take the T ° between 2 measurement point (stratification in the flask)
- "Full" draft all the time (turbo draft plate turned upside down) and continuous circulator (power 65W)

Data and results:

- Initial tank temperature: 31.5 ° C
- Final tank temperature: 50.5 ° C
- Tank volume: 300L or energy to raise the tank by 1 ° C: 0,35 kWh (= 300 * 4.18 / 3600)
- Energy "gained" by the balloon: (50.5-31.5) * 0.35 = 6.65 kWh
- Fuel load: 7,9 kg, burnt mass estimated at 7 kg.
- PCI wood: 4 kWh / kg (probably a little more, compressed sawdust of oak or exotic wood)
- Energy "burned" by the boiler: 7 * 4 = 28 kWh

Yield (miserable) of: 6.65 / 28 = 24% !!!

I found that beyond 45 ° C the boiler had great difficulty in heating. The best (quickest) rise in T ° was between 35 and 45 ° C (tank temperature). The maximum power recovered by the DHW and averaged over one hour was 2.1 kW (boiler given for 13 to 15kW but the fuel load was not maximum I grant you!)!

Here is the diagram of the assembly:

I don't think this is the deom boiler assembly which is mediocre (we have already discussed it a lot) but the capacity of the boiler to recover calories. Obviously there are some losses in the non-insulated pipe.

Once again we see the difference between a REAL yield and a "laboratory" yield under ideal conditions (the Deoms are given for 65 to 70% yield !!!).

Are some of you ready to do the same manipulation on your wood boiler (or fuel oil, possibly with a container?)? I would like to have the actual effective output of an ökofen boiler for example. For fuel oil I could possibly do it myself as soon as the repair of ours is finished.

For my part I would do a test by changing the parameter: automatic mode (with comparator) for the circulator and draft regulated by the valve integrated in the boiler. I thus hope to be able to go up to 50% effective return. Beyond that I no longer believe in it too much.

ps: the test was carried out after the sweeping mentioned here https://www.econologie.com/forums/eviter-le- ... t6976.html
Last edited by Christophe the 21 / 11 / 11, 11: 08, 1 edited once.
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loop
Grand Econologue
posts: 816
Registration: 03/10/07, 06:33
Location: Picardie

hi Christophe

On solar installations, some install a flow measurement system and two temperature sensors.
The regulation then calculates the temperature gain between the departure and the return of the panels. The flow meter sends the flow information and voila for calculating the instantaneous power.
On an oil boiler it suffices to know the quantity of fuel burned per unit of time (manufacturer data?) And the theoretical power dissipated by combustion is obtained.

A+
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Did67
Moderator
posts: 20362
Registration: 20/01/08, 16:34
Location: Alsace
x 8685

## Re: Actual and actual performance of your fuel oil or b boiler

Christophe wrote:
Are some of you ready to do the same manipulation on your wood boiler (or fuel oil, possibly with a container?)? I would like to have the actual effective output of an ökofen boiler for example. For fuel oil I could possibly do it myself as soon as the repair of ours is finished.

On I no longer know which wire I defended the idea that it was necessary to combine the pellet boiler with a CESI to use it as little as possible to heat the DHW.

It is a disaster from the point of view of efficiency, but also of condensation and wear (on-off with cooling!). PS: the problem is the same for fuel!

In my case, assuming that the efficiency "in" the boiler is 100%, I heat 110 l (I believe) of water contained in the boiler plus all that is contained in the pipes to heat the only "top" of my mixed preparer (which is 300 l, but the upper part therefore only represents roughly 150 l).

So when I reheated 150 l of "useful" hot water, I actually reheated 260 l (of which 110 l will cool for "nothing" in summer; in winter, the water in the boiler + circuit is already hot and then used for heating, so no problem).

So :

1) The experiment contains a lot of uncertainties (exact volumes concerned in the boiler + circuit and in the calorifier: I ignore them; homogeneity of the temperature in the boiler and in the calorifier ???). And we still have the unresolved problem of measuring the quantities of pellets "swallowed" by the boiler that we do not know how to measure.

2) The result will be a maximum of 58% (if my boiler is 100%!).
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Christophe
Moderator
posts: 79353
Registration: 10/02/03, 14:06
Location: Greenhouse planet
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Yes I have already seen these calorimeters (I was looking for our solar system but it did not stick: they do not like the big flow of 4m3 / h apparently ...), very interesting but a little expensive (400 to 500 € d 'after what I had seen) to make a yield estimate.

For the oil boiler yes it is true that with the nozzle we have the quantity per hour on the other hand

a) is this theoretical flow guaranteed in practice (fouling, tired pump?)

b) the boiler must run continuously long enough to be able to make a fairly precise measurement: over 5 or 10 minutes it's not worth it I think ...

Are there candidates in the room to try? Capt Maloche wouldn't you say? Wouldn't it be nice to complement your blue flame burner?
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Christophe
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posts: 79353
Registration: 10/02/03, 14:06
Location: Greenhouse planet
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## Re: Actual and actual performance of your fuel oil or b boiler

Did67 wrote:So when I reheated 150 l of "useful" hot water, I actually reheated 260 l (of which 110 l will cool for "nothing" in summer; in winter, the water in the boiler + circuit is already hot and then used for heating, so no problem).

Good remark I had not taken into account this dead "volume" but in my case:

a) I connected the deom to the "low" heat exchanger of the balloon so I warmed up "approximately" 300L

b) the "dead" volume is limited: the deom exchanger is a "crushed" copper pipe wound around the hearth.

I would have to calculate but we must have a large max (deom exchanger included) 40m of hose 1/2 so not much in terms of volume. A 1/2 inch pipe (14mm internal) contains 0,16 L / m or 6.4 L in my case, go 10 L large max (I have 22 mm in some places) +, let's be crazy, 20L of volume the tank heat exchanger is 30L and therefore 10% more than expected!

So: ok I could correct my 24% by 330/300 = 26,4% ... it remains very poor.

By cons I have some non-isolated pipe and I used PER for a large part of the network.

Did67 wrote:1) The experiment contains a lot of uncertainties (exact volumes concerned in the boiler + circuit and in the calorifier: I ignore them; homogeneity of the temperature in the boiler and in the calorifier ???). And we still have the unresolved problem of measuring the quantities of pellets "swallowed" by the boiler that we do not know how to measure.

1) Exact, a lot of uncertainties but what really matters in an installation is the usable energy and not that of the boiler itself! No?

2) For the volumes, we just talked about it.

3) The T ° of the balloon, as indicated above: average between a high and a low measurement (the are are about 1/3 of the end). The low measurement is just above the low heat exchanger.

It is a safe bet that in reality I heated therefore less than 300L and therefore that the yield is even worse!

4) For the quantity of pellets, I suppose you would like to give it a try?

If this is the case, don't you have the possibility of feeding the worm screw with a smaller volume than that of your silot? Anyway, to shunt the silot?

Did67 wrote:2) The result will be a maximum of 58% (if my boiler is 100%!).

Excellent remark but (unfortunately) in my case it does not really apply ...

By cons: now as I said I had 100% full draft all the time, ditto for the circulator. These 2 aspects can, I think improve performance ... next scheduled test!
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Did67
Moderator
posts: 20362
Registration: 20/01/08, 16:34
Location: Alsace
x 8685

## Re: Actual and actual performance of your fuel oil or b boiler

Christophe wrote:
Excellent remark but (unfortunately) in my case it does not really apply ...

I paralyze the difficulty of measuring something in my case. I only have an "average" probe on the preparer ....

And then no, on an Okofen, with the intermediate tank, impossible to hack as you think, without it being automatically anything. The combustion control works at the stroke of a tenth of a second for the pellet feed screw and the changes in the controlled ventilation (air intake and extraction of smoke) are done at the percent ... So if I put pellets at pif, the control systems will stop it!
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Christophe
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posts: 79353
Registration: 10/02/03, 14:06
Location: Greenhouse planet
x 11059

Yes I see well ... the game is not worth the candle too!

By cons if there are other owners of ökofen (or other automatic pellet boiler?) Motivated?

For my part, as soon as possible I would do a test on our boiler + DHW heating oil tank ... unless someone has done it before?
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Did67
Moderator
posts: 20362
Registration: 20/01/08, 16:34
Location: Alsace
x 8685

Christophe wrote:Yes I see well ... the game is not worth the candle too!

I forgot to say it I think: my Okofen being condensing, it contains almost twice as much water, at the level of the exchangers + condenser!

And indeed, I am not very motivated because it is ultra marginal in my use. It is the "recovery in rainy weather in summer". A few tens of kg of pellets on my 8 tons. Insignificant. Even if catastrophic in terms of yield, since the theoretical maximum is 58%! It is the yield actually observed in chuaffage which would interest me !!! But having no flow-meters in my circuit, nor measurement of the return temperature, nor software which could "integrate" all that ...

And I don't see myself taking it apart (remember the photos!) To weigh the pellets she swallows!
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Christophe
Moderator
posts: 79353
Registration: 10/02/03, 14:06
Location: Greenhouse planet
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I completely agree!
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I learn econologic
posts: 18
Registration: 12/11/07, 22:36

in fact, the exact subject is "the efficiency of a boiler in summer for DHW", right?

because in winter the problem is different.

Also, where do the calories go?
-in the flue: it's really lost
- in the air: it is not lost if the boiler and the pipes are in the heated volume

So effectively, 5m² of solar panels solve the problem by making DHW heating by the boiler unnecessary the 6 or 7 months when the heating is off.
0 x
David
to no longer move alone with 1 tons of steel!

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