Operating instructions

22
Outdoor Swimming Pool Heat Pump Sizing Worksheet
For In-ground Pool Applications
Project Name:
Date:
1) Pool Length in Ft.
2) Pool Width in Ft. ======> 4) Pool Surface Area in Sq. Ft.
3) Average Pool Depth in Ft. ======> 5) Pool Volume in Cu. Ft.
6) Pool Volume in U.S. Gallons
7) Calculated Pounds of Water to be Heated.
Initial Maintain
8) Desired Pool Water Temperature in
o
F 80 80
9) Starting Pool Water Temperature in
o
F
10) Average Ambient Air Temperature in
o
F
11) Calculated Water Temperature Difference in
o
F
12) Calculated Air Temperature Difference in
o
F
13) Initial BTU's to Heat the Pool Water with no Surface Heat Loss
14) Hours Allowed to Heat the Pool Water to Desired Temperature 120
15) Initial BTU/hr Needed to Heat Pool Water in Time Allowed
16) Average Wind Speed Factor (see below)
17) Heat Loss from Pool Surface in BTU/hr
18) Total BTU/hr Required to Heat & Maintain Pool Water Temperature
Instructions, Assumptions, and Additional Notes
A) Enter the appropriate pool dimensions where requested on lined 1, 2, and 3. If the pool depth is not constant,
please enter the overall average depth. If the pool is not rectangular in shape, please move on to the next step.
B) Calculate lines 4, 5, and 6 after lines 1-3 are filled in. There are 7.48 Gal Water per Cu. Ft. If the pool is not
rectangular in shape, such as elliptical, oval, & kidney shapes, manually calculate the information needed for
lines 4 and 5 and enter the results in the appropriate boxes where requested on these lines.
C) Line 7: There are 62.42 Lb. Water per Cu. Ft., and 8.34 Lb. Water per U.S. Gallon.
D) Enter the desired pool temperature in both boxes on line 8. If this temperature is not known, 80
o
F is a good
default to use.
E) Enter the initial pool water temperature in the box on line 9. Generally, this will not be any colder than average
well water temperature (approximately 50
o
F.)
F) Enter the average ambient outdoor air temperature for the coldest month that the swimming pool will be in use
in the box on line 10.
G) Line 13: Use the following equation to calculate the initial BTU's required to heat the pool without any
consideration to time or to surface heat loss via convection.
Initial BTU's = 1.0 [BTU/LB*
o
F] x Line 7 x Line 11
H) Line 14: Enter the amount of time in hours that will be allowed to initially heat the pool. (4 to 5 days [120 hours]
is normally acceptable and economical for private pools.)
I) Line 15: Calculates the heating capacity (BTU/hr) required to initially heat the pool.
Heating Capacity [BTU/hr] = Line 13 / Line 14
J) Line 16: Enter the average wind speed correction factor as listed below. (typically 3-5 MPH)
(<3 MPH = .75, 3 to 5 MPH = 1.0, 5 to 10 MPH = 1.25, >10 MPH = 2)
K) Line 17: Calculate the BTU/hr heat loss from the surface of the pool due to convection.
Convection Losses [BTU/hr] = 10.5 [BTU/hr*Sq Ft*
o
F] x Line 4 x Line 12 x Line 16
The greatest heat loss (typically 50-60%) in a swimming pool is through evaporation. Radiation and evaporative
losses can be reduced 50% through the use of a pool cover. Solar gains in unshaded pools can add up to 100,000
BTU/hr which offsets some convective loss. Because of these solar gains and economic reasons, total heating
capacity for only one half of the convective losses are required when sizing. Heat loss by conduction through pool
is minimal in an in-ground pool. Conduction losses for above ground pools can be compensated for by
the average wind speed correction factor.
L) Line 18: Total BTU/hr = Lines 15 + (Line 17 x 1/2)
Appendix 1 – Outdoor Swimming Pool Heat Pump Sizing Worksheet