This shows the expected temp rise (Y-axis) vs. Flow in GPM (X-axis).
The minimum required flow is 40 gpm.
So, the maximum temp rise should be 16.8 degrees Fahrenheit.
Heater Outlet Temperature
- Thread starter icepop456
- Start date
This shows the expected temp rise (Y-axis) vs. Flow in GPM (X-axis).
The minimum required flow is 40 gpm.
So, the maximum temp rise should be 16.8 degrees Fahrenheit.
Even in the digital age where we can take very precise readings we only need to be accurate, not precise with a pool. That 406A is rated at its maximum efficiency under lab conditions at standard temperature and pressure, 68F, 29.92 in mercury (basically sea level). Trying to be precise will make you crazy. Talk with the manufacturers and they will all indicate that +/- 10% is accurate. Does the OP have exactly 30k gallons? Does his gas actually supply 1 therm per 100 cubic feet? Most don't, but are close enough. The heater he has is an "atmospheric" heater. Air temp, barometric pressure, elevation all have an affect.
A temperature of 1.4, (1.34 generously rounded) per hour for the pool is well within what that heater should do if the rest of the numbers are correct.
A temperature of 1.4, (1.34 generously rounded) per hour for the pool is well within what that heater should do if the rest of the numbers are correct.
Water in the heat exchanger is +/- 105 degrees at all times. Whatever temperature the water is at the outlet is the result of the cooler and hot water mixing. So, yes it all gets heated, just not all directly in the heat exchanger, where, if memory serves, there is less than 10 gallons at any one time.
8/14.92 = 53.6% of expected rise.
That is pretty far off.
Are you sure about the heater size?
Check the gas consumption to see if it uses 400 cubic feet per hour.
Are you reading the flow meter correctly?
That is pretty far off.
Are you sure about the heater size?
Check the gas consumption to see if it uses 400 cubic feet per hour.
Are you reading the flow meter correctly?
From 4:25pm to 5:05pm the pool went from 80.1 to 80.8. This is with a solar cover but sun was not full blast. It was 80 F at the time.
This implies 1 F per hour with some help from the sun. I think the old observation of overall pool rise was optimistic. I’ll try to measure the gas usage tomorrow.
Heater model from the label. The flow is in the ballpark considering the Hi Limit trip at slower pump speeds around 30/35GPM.
This implies 1 F per hour with some help from the sun. I think the old observation of overall pool rise was optimistic. I’ll try to measure the gas usage tomorrow.
Heater model from the label. The flow is in the ballpark considering the Hi Limit trip at slower pump speeds around 30/35GPM.
I would estimate the flow in the 53 to 58 GPM range, but that is not super accurate.
Even accounting for measurement tolerances, the numbers seem off.
See what the gas usage is.
Check the stack flue temperature.
See what the gas usage is.
Check the stack flue temperature.
If we use a flow of 60 GPM, that gets us to about 9.84 degrees of expected temperature rise, which is pretty close to the measured 8 degrees.
295,200/30,000 = 9.84 degrees temperature rise.
295,200/30,000 = 9.84 degrees temperature rise.
It might be a combination of things.
If the gas usage is less than 360 cubic feet per hour, the gas pressure might be too low.
1 cubic foot of gas is about 1,000 btu/hr. (Input).
If the heat exchanger is sooted on the outside or scaled on the inside, the heat transfer efficiency will be reduced.
Maybe the temperature sensors are 1 degree off each for a total of 2 degrees.
Maybe the flow is higher than the flow meter is indicating.
If the gas usage is less than 360 cubic feet per hour, the gas pressure might be too low.
1 cubic foot of gas is about 1,000 btu/hr. (Input).
If the heat exchanger is sooted on the outside or scaled on the inside, the heat transfer efficiency will be reduced.
Maybe the temperature sensors are 1 degree off each for a total of 2 degrees.
Maybe the flow is higher than the flow meter is indicating.
- Jun 7, 2017
- 9,101
- Pool Size
- 29000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Jandy Aquapure 1400
Did you say you were bypassing some of the water through the heater? I run my heater at 3000rpm with no bypassing. I haven't measured my output temp but I can tell you it feels warm and sometimes even hot. We do keep our pool at 88+ though. I'll try to do a test and see what my output temp is. I guess just put a temp gauge in one of the returns?
Gas meter shows about 250 cubic ft per hour. I think that is the source of my problem. Took about 28.5s for the 2ft^3 dial to complete a revolution. Found a chart online about gas meter clocking.
Also ran for an hour and my meter incremented 300 ft3 but it only increments in 100s. Close enough.
At 8 F rise, this works out to be about 53 GPM at 84% efficiency. If my math works out right.
Also ran for an hour and my meter incremented 300 ft3 but it only increments in 100s. Close enough.
At 8 F rise, this works out to be about 53 GPM at 84% efficiency. If my math works out right.
- Jul 21, 2013
- 52,817
- Pool Size
- 35000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-60
Check the gas pressure at the heater inlet before the heater fires and during operation.
Here’s the meter. Nothing else was running at the time. We currently have a standard gas tank hot water heater that should get replaced soon. Ideally we go tankless and I suspect I’ll need more supply to the house.
I’m going to have to call the pool guys as I’m not messing with gas.
I’m going to have to call the pool guys as I’m not messing with gas.
Attachments
- Jul 21, 2013
- 52,817
- Pool Size
- 35000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-60
Call your gas company. You need a meter upgrade.
You have a 275 CFH meter that is limiting your gas flow.
I have a 900 CFH meter serving my house and my 400K BTU pool heater.
Check the size of the gas line from the meter to your pool heater and see that it can handle a 400 CFH flow.
You have a 275 CFH meter that is limiting your gas flow.
I have a 900 CFH meter serving my house and my 400K BTU pool heater.
Check the size of the gas line from the meter to your pool heater and see that it can handle a 400 CFH flow.
- Jun 7, 2017
- 9,101
- Pool Size
- 29000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Jandy Aquapure 1400
Who installed that heater? In my county there are many inspections and they never would have allowed a heater to be installed that couldn't be supplied the correct amount of gas by the existing meter. In fact, my meter required an upgrade with a high pressure port for the pool heater when the pool was installed. Running appliances without enough gas creates a carbon monoxide situation.
Using an input of 275,000 btu/hr at 82% efficiency, that gives us 225,500 btu/hr.
Temp rise = 225,500/(GPM x 60 x 8.34)
Temp rise = 450.64/GPM
GPM = 450.64/Temp rise.
Using a temp rise of 8 degrees, we get 56.33 GPM.
The gas meter is too small and needs to be upsized.
The gas supplier needs to do that.
Check the gas piping to see the size and length to see if it is sufficient.
If the gas pipe is big enough, check the gas pressure during operation after the gas meter is replaced.
A minimum of 6 in. WC and a maximum of 10.5 in. WC upstream pressure under load and no-load conditions must be provided for natural gas.
The pressure at the gas valve, taken with a manometer, should be about 4.0 in. WC natural gas.
Temp rise = 225,500/(GPM x 60 x 8.34)
Temp rise = 450.64/GPM
GPM = 450.64/Temp rise.
Using a temp rise of 8 degrees, we get 56.33 GPM.
The gas meter is too small and needs to be upsized.
The gas supplier needs to do that.
Check the gas piping to see the size and length to see if it is sufficient.
If the gas pipe is big enough, check the gas pressure during operation after the gas meter is replaced.
A minimum of 6 in. WC and a maximum of 10.5 in. WC upstream pressure under load and no-load conditions must be provided for natural gas.
The pressure at the gas valve, taken with a manometer, should be about 4.0 in. WC natural gas.
Thanks everyone. The install was 100% inspected as we redid the entire pool area, etc back in 2021.
- Jun 7, 2017
- 9,101
- Pool Size
- 29000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Jandy Aquapure 1400