This shows the expected temp rise (Y-axis) vs. Flow in GPM (X-axis) for a 400,000 btu/hr heater at 84% efficiency.
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Pool heater is working but not heating water
- Thread starter Aigs92
- Start date
This shows the expected temp rise (Y-axis) vs. Flow in GPM (X-axis) for a 400,000 btu/hr heater at 84% efficiency.
- Apr 10, 2018
- 6,323
- Pool Size
- 18375
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-45 Plus
Try running the heater in spa mode. You should be able to see / feel results within 20 minutes.
For a 400,000 btu/hr heater, the ideal range is about 40 to 45 gpm, which puts the temperature rise between about 15 degrees to about 16.8 degrees.
Note that for a spa set to 104 degrees, the heater outlet temperature can get up to about (104 + 16.8) = 120.8 degrees, which is pretty hot.
If you have a SWG cell after the heater, that should show the SWG temperature which is the heater outlet temperature.
The system as well as the heater will show the heater inlet temperature.
So, the SWG temperature minus the inlet temperature is the temperature rise.
What is the spa volume and dimensions?
For example, a 500 gallon spa holds 4,170 lbs of water and the temperature rise should be about 336,000/4,170 = 80 degrees per hour or 1.34 degree per minute.
10 minutes should be 13.4 degrees and 20 minutes should be about 26.8 degrees.
You can also check the natural gas meter to see how much natural gas is being used.
A 400,000 btu/hr heater will use about 400 cubic feet of natural gas per hour or about 6.67 cubic feet per minute.
Note that for a spa set to 104 degrees, the heater outlet temperature can get up to about (104 + 16.8) = 120.8 degrees, which is pretty hot.
If you have a SWG cell after the heater, that should show the SWG temperature which is the heater outlet temperature.
The system as well as the heater will show the heater inlet temperature.
So, the SWG temperature minus the inlet temperature is the temperature rise.
What is the spa volume and dimensions?
For example, a 500 gallon spa holds 4,170 lbs of water and the temperature rise should be about 336,000/4,170 = 80 degrees per hour or 1.34 degree per minute.
10 minutes should be 13.4 degrees and 20 minutes should be about 26.8 degrees.
You can also check the natural gas meter to see how much natural gas is being used.
A 400,000 btu/hr heater will use about 400 cubic feet of natural gas per hour or about 6.67 cubic feet per minute.
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genuine curiosity but is there a difference in how the heater heats depending on if in pool or spa mode? I just thought it was an "On" or "off" and all the modes did was let you set a different temp for two different bodies of water on a shared system without having to adjust the temp.
I dont have automation up yet but have been running my spa heater in spa mode just because. I dont think it would heat any different in pool mode to be honest.
The heater heats the same way in Pool mode or Spa mode except for the temperature setting.
- Jul 21, 2013
- 65,150
- Pool Size
- 35000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-60
No.
Ranchos point was to try heating a smaller body of water, the spa, and you will see the effect of the heat sooner.
It will not make a difference. Pool heaters have a fixed BTU output.
If the water starts at 24 degrees Fahrenheit, how long will it take to heat to 104 degrees?
My guess would be a couple months, maybe March or April
but for real the pool heat time calculator I like to use only goes down to 40. For a 1000 gallon spa it says to get from 40 to 104 is an hour with a 400k btu heater. So if the spa wasn't frozen and the water was still liquid and moving id guess 2 hours??!
Note: Assumes the water is frozen but there is enough liquid water to get pumped through the system.
A 500 gallon spa holds 4,170 lbs
0.5 Btu of heat is required to raise 1 pound of ice 1° F when the temperature is below 32°F.
So, to go from 24 degrees Fahrenheit to 32 degrees Fahrenheit takes (8 x 4,170 x 0.5) = 16,680 btu.
One pound of ice requires 144 Btus to melt.
So, that’s (144 x 4,170) = 600,480 btu.
1 Btu of heat is required to raise 1 pound of water 1° F
So, that’s (72 x 4,170) = 300,240 btu.
The total heat required is (16,680 + 600,480 + 300,240) = 917,400 btu.
At 336,000 btu/hr, it will take 2.73 hours.
A 500 gallon spa holds 4,170 lbs
0.5 Btu of heat is required to raise 1 pound of ice 1° F when the temperature is below 32°F.
So, to go from 24 degrees Fahrenheit to 32 degrees Fahrenheit takes (8 x 4,170 x 0.5) = 16,680 btu.
One pound of ice requires 144 Btus to melt.
So, that’s (144 x 4,170) = 600,480 btu.
1 Btu of heat is required to raise 1 pound of water 1° F
So, that’s (72 x 4,170) = 300,240 btu.
The total heat required is (16,680 + 600,480 + 300,240) = 917,400 btu.
At 336,000 btu/hr, it will take 2.73 hours.
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- Oct 25, 2015
- 5,812
- Pool Size
- 28000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-60 Plus
Yes my heater was 260,000 BTU not exactly half but close. We swim almost every night and my wife is very picky about water temperature. During winter I used this heater many many times. I found the number about 1° per hour to be very very repeatable. Relied on this to keep the wife happy and it worked.
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260,000 at 84% = 218,400 btu/hr.
12,800 gallons = 106,752 lbs of water.
218,400/106,752 = 2.046 degrees per hour of heat added.
If you are getting 1 degree per hour of temperature rise, then you are losing about 1 degree per hour.
- Oct 25, 2015
- 5,812
- Pool Size
- 28000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-60 Plus
Interesting. I think it would be worse if I did not have the screen blocking wind but best think I can do to reduce loss is to add a cover. That's a part of the reason I went to a rectangular pool design for the next pool... we'll see how that works.
Chris