PoolStore.com

HEATER SELECTION GUIDE

POOL SIZING

Determine your pool’s surface area in square feet.

Area=L x W Area=R x R x 3.14 Area=(A + B) x L x .45

Determine the temperature difference the heater will
maintain. In the table below, locate the surface area equal
to or slightly greater than the pool’s surface area in the
selected temperature difference row. The minimum
heater size is indicated at the top of the column.

Tables are based on a 3½ MPH wind velocity and elevation
of up to 2,000 feet above sea level.

 SPA SIZING

Determine your spa capacity in U.S. gallons (surface
area x average depth x 7½).

The reference tables list the time required in minutes to raise the temperature of the spa/hot tub by 30°F. In the table below, locate the spa/ hot tub size in U.S. gallons. Select the desired time to raise the spa/hot tub temperature 30°F, read to the left and select the appropriate heater.

This guide can be adjusted for other temperature rises. For example, if you desire a 15°F increase in temperature, simply divide the time for 30°F rise by the 15°F increase (30/15=2).

Note: Heat losses and/or heat absorbed by spa walls or other objects will add to heat-up time.

Spa sizing is based on an insulated and covered spa. Always cover your spa or hot tub when not in use to minimize heat loss and evaporation.

HEATER SIZING CHART

POOL HEATER

Model
125
175
250
325
400
Maximum Area Heater (width x length)
Temp Diff.
0
Wind
3 ½
MPH
0
Wind
3 ½
MPH
0
Wind
3 ½
MPH
0
Wind
3 ½
MPH
0
Wind
3 ½
MPH
15° F
875
675
1250
925
1775
1325
2300
1725
2850
2125
20° F
675
500
925
700
1325
1000
1725
1300
2125
1600
25° F
525
400
750
550
1075
800
1400
1050
1700
1300
30° F
450
325
625
475
900
700
1250
875
1425
1075
35° F
400
300
550
400
775
575
1000
750
1225
900

SPA HEATER

Model
125
175
250
325
400
Spa Size
Time Required to Raise Temp 30°
200 Gallons
30 Mins
25 Mins
20 Mins
15 Mins
10 Mins
400 Gallons
60 Mins
45 Mins
30 Mins
25 Mins
20 Mins
600 Gallons
90 Mins
65 Mins
45 Mins
35 Mins
30 Mins
800 Gallons
120 Mins
90 Mins
60 Mins
50 Mins
40 Mins
1000 Gallons
150 Mins
110 Mins
75 Mins
60 Mins
50 Mins

Natural Gas Pipe Size Requirements

Distance from Gas Meter
Heater Size
0-50 feet
(0-15 m)
50-100 feet
(15-30 m)
100-200 feet
(30-60 m)
in.
in.
in.
250
1
1 - 1/4
1 - 1/4
400
1 - 1/4
1 - 1/2
1 - 1/2
Notes:
1. These numbers are for natural gas (.65 Sp. Gr.) and are based on 1/2 inch water column pressure drop. Check supply pressure with a manometer, and
local code requirements for variations. For liquefied petroleum gas, reduce pipe diameter one size, but maintain a 3/4 inch minimum diameter.

2. Check supply pressure and local code requirements before proceeding with work.

3. Pipe fittings must be considered when determining gas pipe sizing.