Specifications

Instruction 0011-9026 Page 13
Excess combustion air is heated and carries some of this heat to the fl ue where it is
wasted. The FYRITE CO
2
Analyzer is used to adjust combustion excess air to a mini-
mum (maximum CO
2
), which will permit clean effi cient combustion.
Calculation of combustion effi ciency is possible (assuming com plete combustion) if
percentage of CO
2
and net temperature of combustion products are known.
5.4.3 What is Proper CO
2
Value?
Proper CO
2
is that which will ensure complete, clean combustion with some safety
margin for variations in fuel, draft, atmospheric con ditions, and mechanical wear.
Consult manufacturer of heating equipment for specifi c recommendations. Generally
accepted values for good combustion practice in residential furnaces and boilers when
fi ring the following fuels are:
Natural Gas ......8 to 9.5% CO
2
No.2 Oil ............10 to 12.5% CO
2
These are only guidelines, however, and in all cases recommendations of the equip-
ment or fuel supplier would also include recommendations for allowable smoke (oil
fi ring) or combustibles (gas fi ring), which are undesirable combustion by-products.
Testing for smoke, CO, or combustibles is important since in extreme fuel rich fi ring,
high CO
2
values also occur (see Figure 16).
5.4.4 How To Calculate Combustion Effi ciency
Measure percent CO
2
in fl ue gases with FYRITE. Then measure fl ue gas temperature
with a suitable thermometer (e.g., TEMPOINT) at the same sampling point. Deduct
temperature of basement or combustion air supplied from measured fl ue gas tem-
perature to obtain net fl ue gas temperature. Use a Bacharach FIRE EFFICIENCY
FINDER to calculate combustion effi ciency. Instructions for using the FIRE EFFI-
CIENCY FINDER are printed on the face of this slide rule calculator.
5.5 O
2
FYRITE Only Combustion Testing
5.5.1 Percent O
2
Shows Volume of Excess Combustion Air (Refer to Fig. 15)
All fuels require some excess air (in addition to air theoretically re quired to burn the
fuel) to ensure clean, complete combustion. As the amount of this excess air increases,
the percentage of O
2
in combustion products increase.
5.5.2 Too Much Excess Air Means Ineffi cient Combustion
Excess combustion air is heated and carries some of this heat to the fl ue where it is
wasted. The FYRITE O
2
analyzer is used when adjusting combustion air to minimum
excess air (minimum O
2
) which will permit clean, effi cient combustion.
5.5.3 What is Proper O
2
Value?