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13
D.
STEAM CALCULATION FORMULAS
1. Refer to Table 5:
a. To determine the heating capacity (Btu/hr) of a
unit heater at a steam pressure and/or entering
air temperature other than standard conditions of
2 lb. Steam and 60°F entering air temperature.
b. To fi nd actual unit heater capacity when
operating at non-standard (actual) conditions:
Btu
A
= Btu
S
x Heating Capacity Factor
c. To select a heater capacity based on standard
conditions to meet a heating capacity at non-
standard (actual) conditions:
Btu
S
= Btu
A
/ Heating Capacity Factor
2. Refer to Table 6:
a. To determine the air temperature rise of a unit
heater at a steam pressure and/or entering air
temperature other than standard conditions of
2 lb. Steam, 60°F entering air temperature.
b. To fi nd actual air temperature rise of unit
heater when operating at non-standard (actual)
conditions:
ATR
A
= (FAT
S
- EAT
S
) x Air Temperature Rise
Factor
c. To fi nd actual fi nal air temperature of unit
heater when operating at non-standard (actual)
conditions:
FAT
A
= EAT
A
+ ATR
A
3. Refer to Table 7:
To determine how non-standard steam pressures
(other than 2 lb.) affect mounting height.
Max. Mounting Height
A
= Max. Mounting
Height
S
x Correction Factor
4. Refer to Table 8:
To determine the rate of condensate production at
steam pressures other than 2 lb.
Condensate Rate = Btu
A
/ Latent Heat of Steam
5. Terminology:
a. ATR
A
= Air temperature rise at non-standard
(actual) conditions
b. Btu
A
= Capacity at actual operating conditions
c. Btu
S
= Capacity at standard conditions (2 lb.
Steam, 60°F entering air temperature) from
Tables 3 and 4.
d. EAT
A
= Entering air temperature at non-standard
actual) conditions
e. EAT
S
= Entering air temperature at standard
conditions (60°F)
f. FAT
A
= Final air temperature at non-standard
(actual) conditions
g. FAT
S
= Final air temperature at standard
conditions from Tables 3 and 4.
h. Max. Mounting Height
A
= Maximum mounting
height at actual conditions
i. Max. Mounting Height
S
= Maximum mounting
height at standard conditions