Specification

1-150.15
21
PERFORMANCE DATA
Hot Water Conversion Tables - Example Calculations
Conversion factor example #1:
What is the capacity (Btu/hr), water flow rate (GPM), water temperature drop (°F) and final air temperature (°F) for an HSB 86 at
240°F entering water temperature (EWT) and 70°F entering air temperature (EAT)? What is the maximum mounting height?
Solution:
The factors/data necessary to solve this problem are as follows:
• Hot water heating capacity conversion factor for 240°F EWT and 70°F entering air is 1.201, from Table 16.1.
• The standard rated capacity of an HSB 86 is 60,200 Btu/hr, from Table 19.1.
• The standard rated capacity of an HSB 86 is based on water flow rate of 6.3 GPM, from Table 19.1.
• The standard high motor speed airflow of an HSB 86 is 1340 CFM, from Table 19.1.
• The maximum mounting height, at standard conditions for an HSB 86 is 16 feet, from Table 19.1.
• The mounting height correction factor for 240°F EWT is 0.89 from Table 17.2.
Btu
A
= Btu
S
x Heating Capacity Factor = 60,200 x 1.201 = 72,300 Btu/hr
For water flow rate, since only the entering water and air temperature conditions have changed, the water flow rate will remain
6.3 GPM.
WTD
A
= Btu
A
÷ (480 x G
A
) = 72,300 Btu/hr ÷ (480 x 6.3 GPM) = 23.9°F
FAT
A
= EAT
A
+ [(460 + EAT
A
) x (Btu
A
) ÷ (576 x Cfm
s
)] = 70°F + [(460 + 70°F) x (72,300) ÷ (576 x 1340)] = 120°F
Max. Mounting Height
A
= Max. Mounting Height
S
x Correction Factor = 16 ft. x 0.89 = 14.2 feet
Conversion factor example #2:
Select a vertical unit heater model that can deliver at least 150,000 Btu/hr with 160°F EWT and 60°F EAT. What will be the required
water flow rate, water temperature drop, final air temperature and maximum mounting height?
Solution:
The factors/data necessary to solve this problem are as follows:
• Hot water heating capacity conversion factor for 160°F EWT and 60°F entering air is 0.714, from Table 16.1.
• The mounting height correction factor for 160°F EWT is 1.19, from Table 17.2.
Btu
S
= Btu
A
÷ Heating Capacity Factor = 150,000 ÷ 0.714 = 210,084 Btu/hr (at standard conditions)
From Table 19.1, a V 279 model will meet the requirement with a rated capacity of 212,600 Btu/hr at standard conditions.
The capacity of the V 279 at actual conditions will be Btu
A
= Btu
S
x Heating Capacity Factor = 212,600 x 0.714 =
151,796 Btu/hr.
Since the capacity was calculated based off standard conditions with factors for changes in entering water and air temperature
conditions, the water flow rate will remain 22.2 GPM.
WTD
A
= Btu
A
÷ (480 x GPM
A
) = 151,796 Btu/hr ÷ (480 x 22.2 GPM) = 14.2°F
FAT
A
= EAT
A
+ [(460 + EAT
A
) ÷ ((576 x Cfm
s
÷ Btu
A
) - 1)] = 60°F + [(460 + 60°F) ÷ ((576 x 5,460 ÷ 151,796) - 1)] = 86.4°F
Max. Mounting Height
A
= Max. Mounting Height
S
x Correction Factor = 40 ft. (with cone-jet deflector) x 1.19 = 47.6 feet