Specification

1-150.16
18
Table 18.1 is used to determine how water temperature drop affects heater capacity in Btu, water flow rate in GPM and pressure
drop in feet of water. These factors should be applied to the values at actual entering water and air temperature conditions.
Table 18.1
Correction Factors for Varying Water Temperature Drop M
Water Temperature Drop, °F
5 10 15 20 25 30 35 40 45 50 55 60
Btu Correction Factor 1.23 1.13 1.06 1.00 0.95 0.90 0.86 0.82 0.78 0.72 0.69 0.67
GPM Correction Factor 4.64 2.21 1.40 1.00 0.76 0.61 0.50 0.42 0.36 0.30 0.26 0.23
WPD Correction Factor 17.24 4.32 1.85 1.00 0.61 0.41 0.30 0.22 0.18 0.14 0.12 0.11
M Water temperature drop correction factors valid only for standard 200°F entering water and 60°F air temperature conditions.
Applicable formulas (examples on page 21):
To find actual unit heater capacity or flow rate or water pressure drop when operated at non-standard (actual) conditions:
Btu
A
= Btu
S
x Btu Correction Factor
GPM
A
= GPM
S
x GPM Correction Factor
WPD
A
= WPD
S
x WPD Correction Factor
To select a heater capacity based on standard conditions to meet a heating capacity at non-standard (actual) conditions:
Btu
S
= Btu
A
÷ Btu Correction Factor
Where:
Btu
S
= Capacity at standard conditions (200°F entering water temperature, 60°F entering air temperature) from Tables 19.1
through 20.2
Btu
A
= Capacity at non-standard (actual) conditions
GPM
S
= Flow rate at standard conditions (200°F entering water temperature, 60°F entering air temperature) from Tables 19.1
through 20.2
GPM
A
= Flow rate at non-standard (actual) conditions
WPD
S
= Water pressure drop at standard conditions (200°F entering water temperature, 60°F entering air temperature) from
Tables 19.1 through 20.2
WPD
A
= Water pressure drop at non-standard (actual) conditions
Other miscellaneous useful formulas:
FAT
A
= EAT
A
+ [(460 + EAT
A
) x (Btu
A
) ÷ (573 x Cfm
s
)] for HSB and HC units only
FAT
A
= EAT
A
+ [(460 + EAT
A
) ÷ ((573 x Cfm
s
÷ Btu
A
) - 1)] for V/VN and PT/PTN units only
WTD
A
= Btu
A
÷ (480 x GPM
A
)
Where:
EAT
A
= Entering air temperature at actual conditions
FAT
A
= Final air temperature at actual conditions
Btu
A
= Capacity at actual conditions
Cfm
S
= Unit airflow as found in Tables 19.1 through 20.2
GPM
A
= Water flow rate at actual conditions in GPM
WTD
A
= Water temperature drop at actual conditions
PERFORMANCE DATA
Hot Water Conversion Tables - Miscellaneous Formulas