[Stoves] When does a test end?

[Crispin Pemberton-Pigott]

Dear Friends

 

Of the age-old questions I when to end a stove test in order to calculate
the CO and PM emissions (which are the things usually legislated).

 

There has been little agreement in different US states and few other
countries outside Europe have anything at all. Stoves have very different
burning times, heat generating capacities, fuel loads, burning properties,
refuelling capabilities and purposes. What can we do that will make
comparisons fair and possible?

 

So, here follows a proposal which seems to work in practise.

 

The test is started at the time of ignition.

The test ends when 95% of the combustion portion of the fuel has burned,
leaving 5%.

 

The combustible portion is the non-moisture, non-ash portion of the fuel as
received (meaning as it is used in the stove).

 

When the fuel is weighed, say 5 kg, and either set aside or loaded into the
stove, the total amount is noted and the moisture content calculated, for
example at 15% = 750 g. That means there is 4250 g of dry fuel there.  Then
subtract the ash portion, say it was 3% of the initial mass = 30 g. Final
number is 4250-30 = 4220. That is the mass of 'things which can burn'. 95%
of that is 4220 x .95 = 4009 g.

 

All the moisture is expected to be gone. So if the whole stove is mounted on
a scale the mass change will be burnables + moisture = 4009+750 = 4759. One
the scaled mass has dropped 4759 g the test is over. 

 

Then the emissions are calculated based on the MJ of heat theoretically
generated (using LHV as received).

 

If a scale is not used, then the mass burned can be determined by weighing
the fuel as it is use, fuel remaining or anything else that shows when 95%
of the fuel is gone. Typically this is late in the dying fire stage so it is
a bit easier then it perhaps sounds.

 

When do test a stove that includes refuelling or a number of refuellings,
the same calculation applies. It seems to work very well, gives results
representative of real life and normally has a test time that is less than a
working day.

 

It is offered a test method for rating the emissions of any type of testing
from water boiling to 24/7 space heating.

 

Regards

Crispin

 

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