4
SECTION 2. HEATER SIZING
Selecting the correct size heater:
Factors inuencing heater sizing include pool/ spa size, aver-
age wind velocity, ambient temperature and desired increase in
temperature over ambient. A pool/spa in a warm area with little
or no wind will not require as large a heater as one in a cool,
windy location. Detailed sizing information is provided below.
For a swimming pool:
1. Determine pool’s surface area in square feet. For indoor pool
installations divide the pool’s surface area by 3.
2. Determine desired pool water temperature
(usually 78 -82°F).
3. Determine average air temperature of coldest month of use.
4. The temperature rise is the difference between
2 & 3.
5. Locate in Figure 2 the surface area equal to or just greater
than the pool’s surface area and the temperature degree rise
and select the appropriate heater model.
Figure 2 is based on 3 1/2 MPH wind velocity and elevation of
up to 2,000 feet above sea level.
When not in use, keep pool covered to reduce heat loss,
chemical usage and dirt load on the ltering system.
For a spa or hot tub:
Determine spa capacity in gallons (surface area x average
depth x 7 1/2).
The reference table lists the time required in minutes to raise
the temperature of the spa/hot tub by 30°F. Locate in the table
below the spa/hot tub size in gallons equal to or just greater than
the spa/hot tub size in gallons. Select the desired time to raise
the spa/hot tub temperature 30°F, read to the left and select the
appropriate heater model.
This guide can be adjusted for other temperatures rises. For
example, if a 15°F increase in temperature is desired, simply
divide the time for 30°F rise by the ratio of 30/15 = 2.
! NOTE: Heat losses and/or heat absorbed by spa walls
(such as concrete) or other objects will add to the heat-up time.
Spa sizing is based on an insulated and covered spa. Always
cover spa or hot tub when not in use to minimize heat loss and
evaporation.
Pool Surface Area:
Figure 1
Temp. Rise °F 10° 15° 20° 25° 30° 35°
Model
H150 1,385 924 693 554 462 396
H200 1,848 1,232 924 739 616 528
H210 1,988 1,326 994 795 663 568
H250 2,309 1,540 1,155 924 770 660
H300 2,771 1,848 1,386 1,109 924 792
H350 3,233 2,156 1,617 1,293 1,078 924
H400 3,695 2,463 1,848 1,478 1,232 1,056
Pool Surface Area in Square Feet
Figure 2 - Recommended Heater Model
New Figure 2 for Manual 1302704001 rev F, page 4
200 300 400 500 600 700 800 900 1,000
H400 9 14 19 23 28 33 37 42 47
H350 11 16 21 27 32 37 43 48 54
H300 12 19 25 31 37 44 50 56 62
H250 15 22 30 37 45 52 60 67 75
H210 17 26 35 44 52 61 70 78 87
H200 19 28 37 47 56 66 75 84 94
H150 25 37 50 62 75 87 100 112 125
New Figure 3 for Manual 1302704001 rev F, page 4
Model
Spa/Hot Tub Size in Gallons
Figure 3 - Recommended Heater Model
Time in Minutes to Raise Spa/Tub Temperature 30°F
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