AQUA
Swimming Pool Supplies
 

 

Pool Heater Sizing - How to select pool heater

Basic Pool Heater Selection Information

 

- [POOL HEATER SELECTION]

- [POOL HEATER GAS PIPE SIZING]

- [OPERATION & MAINTENACE]

 

 

The chart below shows simple pool/spa heater sizing using desired temprature rise and amount of water to be heated. This gives you a general idea which size heater will be suitable for your needs. The color coded "pool heater size" chart below is in 1,000 of BTUs.

MiniMax NT heater required to heat spa in one hour
Pool Heater btu size required to heat SPA in 1 hour

MiniMax NT heater required to heat pool in 24 hours
Pool Heater btu size required to heat POOL in 6 hours


 

POOL HEATER SIZING

Determine your pool’s surface area in square feet.

Laars Jandy pool heater sizing and selection  determine your pool size using these simple instructions

Rectangular Pool: Area = L x W

Round Pool: Area = R x R x 3.14

Kidney-shaped Pool: Area = (A + B) x L x .45

In the table below, locate the surface area equal to or slightly greater than the pool’s surface area, read to the left and select the appropriate heater.

Pool Heater
125,000 BTU
175,000 BTU
250,000 BTU
325,000 BTU
400,000 BTU
Maximum Pool Surface Area (Sq. Ft.)
Temp Difference
125
125
175
175
250
250
325
325
400
400
15 °F
667
889
933
1244
1333
1778
1733
2311
2133
2844
20 °F
500
667
700
933
1000
1333
1300
1733
1600
2133
25 °F
400
533
560
747
800
1067
1040
1387
1280
1707
30 °F
333
444
467
622
687
889
867
1556
1067
1422
35 °F
286
381
400
533
571
762
743
990
914
1219

Shaded coJumns indicate sizing with a 0 MPH wind. Example: Rectangular pool, 20 feet x 40 feet, with desired temperature rise of 25°F: 20 x 40 = 800 square foot surface area, the recommended heater is a 250. 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 71/2). 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.

SPA HEATER
125,000 BTU
175,000 BTU
250,000 BTU
325,000 BTU
400,000 BTU
 
Time to heat spa by 30 0F (in minutes)
Spa Size (gal.)
125
175
250
325
400
200
30
21
15
12
9
400
60
43
30
23
19
600
90
64
45
35
28
800
120
86
60
46
37
1000
150
107
75
58
47

Example: To heat a 400 gallon spa 30°F in 30 minutes, the recommended heater is a 250.

 

Natural Gas Pipe Size Requirements: Distance from gas meter determines the required gas pipe size for specific heater model/size

Heater Size
0 - 50 ft.
50 - 100 ft.
100 - 200 ft.
250
1"
1 1/4"
1 1/4"
400
1 1/4"
1 1/2"
1 1/2"

 

Pool Heater Air Venting

Natural gas and liquid propane typically serve as the fuel source for pool and spa heaters. Yet combustion requires two ingredients: fuel and air. All too often, pool and spa heaters fail to perform properly (or at all) because they're starving for the latter ingredient, air. Of course, not only is adequate air supply needed for combustion, adequate exhaust venting is then needed for removal of post-combustion air. Failure to ensure sufficient combustion air supply will choke a heater, while insufficient post-combustion ventilation could result in potentially lethal exhaust problems. Certain aspects of post-combustion ventilation vary from one heater model to the next and some heaters are unable to be installed indoors. Prior to any installation, consult the specific product's installation manual for location and air supply specifications.

The other aspect of air supply - combustion air supply - is relatively consistent for all gas installations regulated by the C.S.A.

Minimum Free.Space Per Top Vent
Minimum Free.Space Per Top Vent
Minimum Free.Space Per Top Vent
AIR
When Air to the Room is Supplied FROM
When Air to the Room is Supplied FROM
When Air to the Room is Supplied FROM
SUPPLY
(A) 1sq. in. of free air per 1000 BTU
(B) 1sq. in. of free air per 2000 BTU
(C) 1sq. in. of free air per 1000 BTU
STANDARD
Indoors Using Adj. Rooms, Vent only No Ducts
Outdoors Using Horizontal Dusts
Outdoors Using exterior wall vents or vertical Ducts
Heater Size (BTU)

Free Area (sq. ft.) needed on Vent Combustion / Ventilation

Free Area (sq. ft.) needed on Vent Combustion / Ventilation
Free Area (sq. ft.) needed on Vent Combustion / Ventilation
150,000
150 / 150
75 /75
37.5 / 37.5
200,000
200 / 200
100 / 100
50 / 50
250,000
250 250
125 / 125
62.5 / 62.5
300,000
300 / 300
150 / 150
75 / 75
350,000
350 / 350
175 / 175
81.8 / 81.8
400,000
400 / 400
200 / 200
100 / 100

 

Pool heater venting and installation facts

Sources of Air Supply


1. Air to the room is supplied FROM INSIDE the building.
(A) The vents must provide:
1 square inch of free air per 1,000 BTU's (see Table A above).
For air supply openings that communicate directly with adjacent rooms, the adjacent rooms must be of sufficient volume so that the combined volumes of all spaces meet the criteria for an unconfined space.
The unconfined space volume requirement is "not less then 50 cubic feet per 1000 81UH. " This translates into 20,000 cubic feet of space (a 50' x 40' x1 0' room) for a 400,000 BTU heater.


2. Air to the room is supplied FROM the OUTDOORS.
(B) If the air is supplied through horizontal ducts to the outdoors, they must provide:
1 square inch of free air per 2,000 BTU's (see Table B above).


(C) If the vents are placed in an exterior wall that gets air from the outdoors OR from via vertical ducts which supply air from the outdoors,
then the vents must provide:
1 square inch of free air per 4,000 BTU's (see Table C at right).

 

 

Air Supply (for combustion)

If the heating system is entirely outdoors (not enclosed), air supply will likely never be an
issue, unless trees or shrubbery have overgrown around the heater. Increasing numbers of pool owners are starting to partially or totally enclose the equipment pad - particularly in parts of the country where property sizes are getting smaller. So it's important for technicians to be aware that combustion air supply requirements for gas heaters vary as these and other factors change. Technicians must recognize where the heater's air supply is coming from, and how it is being supplied. Indoor installations and outdoor shelters must be provided with adequate air vents for combustion to ensure proper heater operation. To ensure these air supply needs are fulfilled, the confined space, where the heater is located, shall be provided with two (2) permanent openings (vents) communicating directly with the air supply: . one commencing within 12" of the top, and . one commencing within 12" of the bottom. See the Sources of Air Supply section above along with Tables A, B, and C for determining vent sizes. Also, remember to factor in (add) the air supply needs for any other gas appliances in the same room or enclosure. Air supply openings must be unrestricted, but can utilize permanently opened veins or louvers like those in an attic gable. However, if using louvered panels for air supply openings, the total surface area of the louvers and panel frame must be subtracted when determining actual air supply. (Example: A 7 Ox I 0 louvered panel does NOT provide 100 inches of free area for air supply, but approximately 52 - 56 sq. in.) Most vent manufacturers will provide the "unobstructed free area" for their products.


Propane Gas Usage

Liquid propane is externally compact and portable, but must vaporize to be released as a gas that can be used to fuel your heater. An insufficient gas supply causes reduced efficiency and poor combustion, which leads to soothing.

As a rule of thumb, Propane tank size should be 100 gallons for every 100,00 btu of heater rating.

If you're buying a Propane gas heater, the following information will help you decide how big a propane tank to select.

The rate at which a liquid propane converts to vaporized Propane gas is determined by many factors including: Humidity, Ambient Temperature, Surface Area of the liquid in the Propane tank. The "Rule of Thumb" for factoring these variables is to assume that a heater's Propane tank should be refilled when 60% of it's full-tank capacity has been used.

Propane Tank Size
Usable Propane @ 20 o/F
Usable Propane @ 60 o/F
120
235,008
417,792
150
290,304
516,096
200
341,280
606,720
250
406,080
721,920
325
514,100
937,900
500
634,032
1127,168
1000
1088,472
1978,051

(BTU per hour - with 60 % Liquid in Tank)

Propane's ability to vaporize decreases with the temperature - particularly as the temperature dips below 60 o/F. On the other-hand, when the temperature outside is warm, say 85 o/F and the Propane tank has been 60% depleted, it will continue to provide sufficient gas flow for a while.

However, as the thermometer dips below 60 o/F, a Propane tank's ability to produce vaporized gas decreases sharply. In fact, as the chart above indicates, a Propane tank will yield barely HALF as much capacity at 20 o/F as it does at 60 o/F.

Also, keep in mind that cooler overnight temperatures can have lingering effect during the following day, causing the tank to not supply sufficient gas to the heater. "Low gas" conditions like these should be avoided, as they result in sporadic, inefficient operation.

Calculating a Propane heater's operating time

A single gallon of Propane will produce 91,000 British Thermal Unit (BTUs) in an hour. This fact coupled with the 60% usable rule of thumb allows anyone to determine how long a propane tank will supply enough gas to properly run a heater.

Calculating a Propane heater's operating time involves three-step formula illustrated below - though we should emphasize that these shortcut calculations are general in nature. The accompanying shortcut calculation are quite convenient, but are not foolproof method for estimating when a heater's Propane tank needs to be refilled. The safes method to use is the 60% rule of thumb.

AS propane tank is used or emptied, the tank contents steadily shift from liquid state to vaporized gas, reaching a point at which the remaining liquid propane no longer vaporizes enough to supply the proper amount of gas to the heater or appliance.

Calculating how long a full-tank of Propane will last

- Multiply the Propane tank's capacity by 0.6 (this is the "usable" Propane available with a full tank)

Step 1: Usable Propane = Propane tank capacity X 0.6

- Divide the heater's BTU rating by 91,000 (this is the gallons of Propane used in an hour)

Step 2: Propane Needed / Hour = BTU Rating / 91,000

- Divide "Usable Propane" (step 1) by heater's per hour gas demand (step 2)

Step 3: Hours of Operation = Usable Propane / Propane Needed per hour

The result estimates how many hours of operation can be expected for a specific BTU rating heater using a specific Propane tank size.

 

Hayward Heater Technical Information

GAS PIPE SIZING

Hayward heaters use a full gas fire design. To ensure adequate gas firing and proper performance, the following guidelines should be used to size gas piping.

1. Make sure the 1 st and 2nd stage regulators are large enough to handle the BTU I isted for each model.
2. Reduction of the gas supply pipe or tubing to the inlet of the valve must be made at the valve only - Natural or Propane.
3. Do not use flexible connectors on any gas connections.
4. If more than one appliance is installed on the gas line, contact your local gas company or Hayward for proper pipe size.
5. If you have any question concerning the installation of the proper gas line size, call Hayward before you install the line.

Low Pressure Natural Gas Pipe Sizing (Pipe or Tubing):

Distance from Model H150 H200 H250 H300 H350 H400
meter to inlet BTU 150,000 200,000 250,000 300,000 350,000 400,000
of gas valve 0 to 50 feet 3/4" 1" 1" 1 1/4" 1 1/4" 1 1/4"
50 to 1 00 feet 1" 1" 1 1/4" 1 1/4" 1 1/4" 1 1/4"
100 to 200 feet 1 1/4" 1 1/4" 1 1/4" 1 1/2" 1 1/2" 1 1/2"
200 to 300 feet 1 1/4" 1 1/4" 1 1/2" 2" 2" 2"

"Single Stage" Low Pressure Propane Pipe Sizing:

Distance from outlet of
Model
H150
H200
H250
H300
H350
H400
H400
regulator to
BTU
150,000
150,000
200,000
200,000
250,000
250,000
300,000
300,000
350,000
350,000
400,000
400,000
gas valve inlet
Pipe
Tube
Pipe
Tube
Pipe
Tube
Pipe
Tube
Pipe
Tube
Pipe
Tube
0 to 50 ft.
3/4"
7/8"
3/4"
7/8"
1"
1 1/8"
1"
1 1/8"
1"
1 1/8"
1"
--
50 to 100 ft.
3/4"
1 1/8"
1"
1 1/8"
1"
1 1/8"
1"
--
1 1/4"
--
1 1/4"
--
100 to 200 ft.
1"
1 1/8"
1"
--
1 1/4"
--
1 1/4"
--
1 1/4"
--
1 1/4"
--
200 to 300 ft.
1"
---
1 1/4"
---
1 1/4"
--
1 1/4"
--
1 1/4"
--
1 1/2"
--

It is VERY IMPORTANT, when installing a Hayward Full Fired propane heater on a two (2) stage regulation system, to follow the gas line sizing chart below - without exception.


 

"First Stage" High Pressure Propane Gas Pipe Sizing:

Distance from outlet of
Model
H150
H200
H250
H300
H350
H400
H400
1st stage regulator to
BTU
150,000
150,000
200,000
200,000
250,000
250,000
300,000
300,000
350,000
350,000
400,000
400,000
2nd stage regulator inlet
Pipe
Tube
Pipe
Tube
Pipe
Tube
Pipe
Tube
Pipe
Tube
Pipe
Tube
0 to 50 ft.
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
50 to 100 ft.
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
100 to 200 ft.
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
200 to 300 ft.
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
5/8"
1/2"
5/8"
1/2"
5/8"

 

"Second Stage" Low Pressure Propane Gas Pipe Sizing:

Distance from outlet of 2nd stage
Model
H150
H200
H250
H300
H350
H400
H400
regulator to
BTU
150,000
150,000
200,000
200,000
250,000
250,000
300,000
300,000
350,000
350,000
400,000
400,000
gas valve inlet
Pipe
Tube
Pipe
Tube
Pipe
Tube
Pipe
Tube
Pipe
Tube
Pipe
Tube
0 to 50 ft.
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
50 to 100 ft.
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
100 to 200 ft.
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
200 to 300 ft.
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
1/2"
5/8"
1/2"
5/8"
1/2"
5/8"