PCC-IV Instruction Manual (Rev. 0.1)
Page 6-7
Section 6
– Blockware Functions
Technical Reference
F22
[BEFF] Boiler Efficiency
Function
BEFF
calculates Boiler or Process Heater Efficiency based upon the ASME Efficiency Test using the
Losses Method. For fuels with a known chemical composition (Natural Gas, Oils, …), this method is a more reliable
means of calculating efficiency than Input-Output based calculations. This method also applies to solid fuels (wood,
coal, …), however, more frequent fuel analysis and resultant parameter corrections are required to account for
moisture and chemical changes.
BEFF
(and ASME) considers boiler casing radiation losses and miscellaneous fixed percentage losses (blowdown,
unburned fuel, …). Most portable combustion analyzers do not account for these losses and will typically indicate
combustion efficiency, not boiler efficiency. Therefore, most portable combustion analyzers will indicate a higher
efficiency than the
BEFF
(and ASME) method.
Default Fuels: The "Fuel A" default Parameters below are for #6 fuel oil, "Fuel B" defaults are for Natural Gas.
Contact Preferred Instruments for Parameter values for other fuels.
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NAME: BEFF SINGLE USE FUNCTION: N OUTPUT TYPE: A
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Input Type Description Notes
_____________________________________________________________________________________________
1 A EXIT TEMPERATURE INPUT 1
2 A AMBIENT TEMP INPUT 1,2
3 A % OXYGEN INPUT 1
4 A PPM CO INPUT 1,3
5 A % FIRING RATE INPUT 1
6 D FUEL SELECT INPUT (0 = FUEL A, 1 = FUEL B) 4
Parameter Description Default Max Min Code Notes
_____________________________________________________________________________________________
1 % O2 FULL SCALE 10.00 25.00 10.00 2
2 PPM CO FULL SCALE 1000 5000 1000 2
3 EXIT TEMPERATURE FULL SCALE 1000 2000 300 2
4 AMBIENT TEMPERATURE FULL SCALE 100 1000 100 2
5 % LOSS DUE TO RADIATION AT
100% FIRING RATE 0.75 5.00 0.00 2 5
6 % LOSS DUE TO MISC FIXED
LOSSES 1.00 5.00 0.00 1
Fuel A Components: Moles/Unit of Fuel Burned (Default = #6 Oil) 6
7 FUEL A MOLES OF C 7.377 12.000 0.000 2
8 FUEL A MOLES OF H2 3.175 6.000 0.000 2
9 FUEL A MOLES OF S 0.027 6.000 0.000 2
10 FUEL A MOLES OF N2 0.011 2.000 0.000 2
11 FUEL A MOLES OF O2 0.022 2.000 0.000 2
12 FUEL A MOLES OF H2O 0.011 5.000 0.000 1
13 FUEL A HEATING VALUE
MILLIONS OF BTUS/UNIT OF FUEL 1.812 2.500 0.100 2
Fuel B Components: Moles/Unit of Fuel Burned (Default = Nat. Gas) 6
14 FUEL B MOLES OF C 1.050 12.000 0.000 2
15 FUEL B MOLES OF H2 2.000 6.000 0.000 2
16 FUEL B MOLES OF S 0.000 6.000 0.000 2
17 FUEL B MOLES OF N2 0.050 2.000 0.000 2
18 FUEL B MOLES OF O2 0.000 2.000 0.000 2
19 FUEL B MOLES OF H2O 0.000 5.000 0.000 1
20 FUEL B HEATING VALUE
MILLIONS OF BTUS/UNIT OF FUEL 0.409 2.500 0.100 2
Notes:
1. All analog input signals must be "zero" based. O% Input = 0 deg. F, 0% Oxygen, 0 ppm CO, 0%
Btu Input. Non-zero-based signals can be converted with a SCALE (F45) Block.
2. If the CO signal is not available, leave this block at its 0% default value.
3. This Input is 0-100% Fuel Btu Input, NOT 0-100% of operating range. If a burner has an 8:1
turndown, this Input should be 12.5% at low fire. A SCALE (F45) Block can be used to convert
a 0-100% operating range to Fuel Input %. This Input only affects the Radiation (i.e. boiler
sheathing) losses.
4. 0 = Fuel A = (#2 Oil by default), 1 = Fuel B = (Natural Gas by default)
