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Heater Sizing Chart for a 7 hour heating period  
per 24 hours with a floating solar cover.  
 
(If a floating solar blanket is not used increase the heater size by 50%). Running Costs > 
All heaters with Titanium elements 

HEATER SIZE 
METRIC 
 
24°C 
24°C 
27°C 
27°C 
30°C 
30°C 
 
 
 
 
 
 
 
3Kw 
6 
8 
5 
7 
4 
5 
6kW 
12 
16 
10 
13 
8 
11 
7.5kW 
15 
21 
12 
16 
10 
13 
9kW 
18 
25 
14 
20 
12 
16 
12kW 
24 
33 
19 
26 
15 
21 
 
 
 
 
 
 
 
15kW 
30 
41 
24 
33 
19 
27 
18kW 
36 
49 
29 
39 
23 
32 
21kW 
42 
58 
34 
46 
27 
37 
24kW 
48 
66 
38 
53 
31 
42 
 
 
 
 
 
 
 
30kW 
60 
82 
48 
66 
39 
53 
36kW 
72 
99 
58 
79 
46 
64 
 
 
 
 
 
 
 
48kW 
96 
132 
77 
105 
62 
85 
60kW 
120 
165 
96 
132 
77 
106 
72kW 
144 
197 
115 
158 
93 
127 
 
 
 
 
 
 
 
84kW 
168 
230 
134 
184 
108 
149 
96kW 
192 
263 
154 
210 
124 
170 
108kW 
216 
296 
173 
237 
139 
191 
120kW 
240 
329 
192 
263 
155 
212 

MODEL REF 

IMPERIAL 

 
75°F 
75°F 
80°F 
80°F 
85°F 
85°F 
 
SQ.FT. 
GALLS. 
SQ.FT. 
GALLS. 
SQ.FT. 
GALLS. 
12THR/3 
63 
1750 
50 
1400 
42 
1170 
12THR/6 
125 
3500 
100 
2800 
83 
2340 
12THR/7.5 
156 
4370 
125 
3500 
104 
2920 
12THR/9 
188 
5250 
150 
4200 
125 
3500 
12THR/12 
250 
7000 
200 
5600 
167 
4670 
 
 
 
 
 
 
 
24THR/15 
313 
8750 
250 
7000 
208 
5840 
24THR/18 
375 
10500 
300 
8400 
250 
7000 
24THR/21 
438 
12250 
350 
9800 
292 
8170 
24THR/24 
500 
14000 
400 
11200 
334 
9340 
 
 
 
 
 
 
 
36THR/30 
625 
17500 
500 
14000 
417 
11670 
36THR/36 
750 
21000 
600 
16800 
500 
14000 
 
 
 
 
 
 
 
72THR/48 
1000 
28000 
800 
22400 
667 
18680 
72THR/60 
1250 
35000 
1000 
28000 
834 
23350 
72THR/72 
1500 
42000 
1200 
33600 
1001 
28020 
 
 
 
 
 
 
 
120THR/84 
1750 
49000 
1400 
39200 
1167 
32680 
120THR/96 
2000 
56000 
1600 
44800 
1334 
37350 
120THR/108 
2250 
63000 
1800 
50400 
1501 
42020 
120THR/120 
2500 
70000 
2000 
56000 
1668 
46690 
 
The Thermalec sizing chart is for outdoor swimming pools in the South of England, running from the beginning of May until the end of September. For swimming pools in the North, multiply the heater size by 1.3 - 1.5 depending on the exposure of the pool. 
 
The figures shown for capacity of the pool - in gallons or M³ - are based upon an average depth of 4'6" (1.36m) and are provided as a guide when an exact surface area is not known. 
 
Indoor pools: providing the indoor air temperature is maintained at least 1°C above the pool temperature by an alternative form of heating 24 hours per day, the heater size may be reduced by multiplying by 0.7, but since running costs are related to the size of the pool and the temperature required, not the size of the heater, we advise keeping to the table where possible. 
 
In countries where off-peak electricity is not available, heaters sized at 1kW per 1000 gallons (4500 litres) with the heater operating 24 hours per day, will normally be adequate and will give an 8°F (4.4°C) rise in 24 hours assuming no losses 
 
All information given is an approximation, to get a more accurate sizing please contact our main sales office on +44 (0) 1752 313343 where our staff will be happy to answer alll your questions.