We have a new pool/spa combo with a new MasterTemp 400. Everything with the heater seems to work OK except for one thing. In the spa, the heater heats up to the called-for temperature (104 for example). Then, the heater cuts off and the water keeps circulating. When the temperature drops below the called-for temperature, the heater kicks back on, except now, the water coming out of the jets is 115 degrees. We had literally almost this exact same set up in our previous home and we did not have this problem. Pentair customer service reps have assigned this case to two different pool repair companies. Collectively, they all cannot decide whether this is a problem or expected behavior. For us, it’s a big problem, especially since we did not have this issue in our previous set up. We do have a heater bypass valve, and it’s been suggested we should adjust that to achieve a mix of heated and cooler water, but that is not an ideal solution because the pool equipment is not convenient to access. If that was a workable solution, perhaps we could automate that valve somehow. Does anyone have any experience with this issue?
MasterTemp 400 too hot
- Thread starter wildpony
- Start date
-
- Tags
- mastertemp
- Jul 21, 2013
- 52,225
- Pool Size
- 35000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-60
Welcome to TFP.
What speed are you running your VS pump with the heater on?
Water temperature rise is inversely proportional to flow rate. Increase your pump speed and flow rate and the heater water temperature will decrease.
What speed are you running your VS pump with the heater on?
Water temperature rise is inversely proportional to flow rate. Increase your pump speed and flow rate and the heater water temperature will decrease.
Allen, thanks for your help. The pump is running at 2,300 RPM in spa mode. Do you have a suggestion of what I should try in terms of an increase? The spa is 500 gallons and has six jets.
The heater output temperature is simply a thermodynamics question. The temperature rise depends on the amount of heat being added to the amount of water. The rise depends on the flow rate. Assuming an input temperature of 104 degrees Fahrenheit, the output temperature is going to be as follows.
GPM......Rise.......output
40.........16.8........120.8
50.........13.4........117.4
60........11.2.........115.5
70.........9.6..........113.6
80........8.4...........112.4
90.......7.5............111.5
Formula for temperature rise (Heater btu/hr X efficiency) ÷ (gpm X 60 X 8.33).
(400,000 X 0.84) ÷ (40 x 60 x 8.33) = 16.8.
GPM......Rise.......output
40.........16.8........120.8
50.........13.4........117.4
60........11.2.........115.5
70.........9.6..........113.6
80........8.4...........112.4
90.......7.5............111.5
Formula for temperature rise (Heater btu/hr X efficiency) ÷ (gpm X 60 X 8.33).
(400,000 X 0.84) ÷ (40 x 60 x 8.33) = 16.8.
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James, this is very helpful. I'm surprised that none of the experts working on this issue for us have mentioned this. Our GPM is about 40, so that's very much in line with your table. I'll experiment with increasing the flow rate. Thanks!
This is the pump performance curve.
Below is the estimated system curve superimposed on the performance curve.
Based on the heater exit temperature, the flow is estimated to be 60 gpm and the total head loss at 2300 rpm is estimated to be 35 feet.
Where the system curve crosses the pump curves are the estimated operating points.
Based on the estimated curve, the best you can do is about 90 gpm at 3,450 rpm, which will create an output temperature of 111.5 degrees Fahrenheit.
Below is the estimated system curve superimposed on the performance curve.
Based on the heater exit temperature, the flow is estimated to be 60 gpm and the total head loss at 2300 rpm is estimated to be 35 feet.
Where the system curve crosses the pump curves are the estimated operating points.
Based on the estimated curve, the best you can do is about 90 gpm at 3,450 rpm, which will create an output temperature of 111.5 degrees Fahrenheit.
Each component of the system will have it's own component curve to show how much head loss each component contributes to the total head loss.
For example, below are the head loss curves for the Clean and Clear Plus cartridge filter (black) (when clean) and the Clean and Clear cartridge filter (red).
Actually, the clean and clear plus cartridge filters have more surface area, but the head loss charts show that the clean and clear filters have lower head loss, which is the opposite of what you would expect.
I suspect that the charts are probably incorrect for some reason.
Maybe the Clean and Clear plus is supposed to be in feet instead of psi?
In any case, every component has its own curve.
If you check the head loss for each component separately, they should all add up to the total head loss.
I would have gone with a Clean and Clear Plus cartridge filter at 420 square feet instead of the Clean and Clear at 200 square feet.
You can add a 5 psi check valve bypass in parallel with the heater to reduce the heater head loss by allowing some water to bypass the heater.
I would have used a minimum of 3” pipe for the spa suction to reduce the suction side head loss.
Make sure that the cartridge is clean to reduce head loss.
www.inyopools.com
Do you have pictures of everything?
For example, below are the head loss curves for the Clean and Clear Plus cartridge filter (black) (when clean) and the Clean and Clear cartridge filter (red).
Actually, the clean and clear plus cartridge filters have more surface area, but the head loss charts show that the clean and clear filters have lower head loss, which is the opposite of what you would expect.
I suspect that the charts are probably incorrect for some reason.
Maybe the Clean and Clear plus is supposed to be in feet instead of psi?
In any case, every component has its own curve.
If you check the head loss for each component separately, they should all add up to the total head loss.
I would have gone with a Clean and Clear Plus cartridge filter at 420 square feet instead of the Clean and Clear at 200 square feet.
You can add a 5 psi check valve bypass in parallel with the heater to reduce the heater head loss by allowing some water to bypass the heater.
I would have used a minimum of 3” pipe for the spa suction to reduce the suction side head loss.
Make sure that the cartridge is clean to reduce head loss.
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Do you have pictures of everything?
Using the estimated system curve, the head loss at 90 gpm is about 80 feet. The filter should only be creating about 7 feet of head loss (assuming the component curve is correct).
Note: 2.31 feet of head = 1 psi.
That implies that everything else is creating about 73 feet of loss at 90 gpm, which is high.
Maybe the filter is dirty or the pipes are too small or possibly a different problem?
Can you run the pump at the following speeds and record the following information?
From the keypad, you can get the total system psi and gpm as shown in the below video.
RPM........Filter PSI......Pump PSI........Pump GPM
1,500........_______.........._______...........________
2,350........_______.........._______...........________
3,110........_______.........._______...........________
3,450........_______.........._______...........________
Note: 2.31 feet of head = 1 psi.
That implies that everything else is creating about 73 feet of loss at 90 gpm, which is high.
Maybe the filter is dirty or the pipes are too small or possibly a different problem?
Can you run the pump at the following speeds and record the following information?
From the keypad, you can get the total system psi and gpm as shown in the below video.
RPM........Filter PSI......Pump PSI........Pump GPM
1,500........_______.........._______...........________
2,350........_______.........._______...........________
3,110........_______.........._______...........________
3,450........_______.........._______...........________
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James, thank you very much for all of this additional information. I'll report back on how this goes with the adjustments.
This shows the estimated system curve and a second curve that I think probably could have been achieved with a better designed system.
This shows different system curves on a pump curve.
System Curve A is a typical curve, B is a poorly designed system and C is a well designed system
As you can see, a system curve like C is much more efficient because it allows for a slower pump speed to achieve a specific flow, which means less power and total energy costs over the pool lifetime.
https://aquamagazine.com/service/how-to-read-pump-system-curves.html
Your curve is a typical system curve.
This shows different system curves on a pump curve.
System Curve A is a typical curve, B is a poorly designed system and C is a well designed system
As you can see, a system curve like C is much more efficient because it allows for a slower pump speed to achieve a specific flow, which means less power and total energy costs over the pool lifetime.
https://aquamagazine.com/service/how-to-read-pump-system-curves.html
Your curve is a typical system curve.
James, at a first attempt, I can tell this will make a big difference. I couldn't quite figure out how to wake up the pump display. I was able to pull some numbers from the automation. For pump GPM, there are two numbers showing in the automation. I'm listing them both below.
RPM........Filter PSI......Pump PSI........Pump GPM
1,500........___15____.........._______...........____24/44____
2,350........___15____.........._______..........._____41/67___
3,110........___25____.........._______...........____59/91____
3,450........___25____.........._______...........____57/100____
RPM........Filter PSI......Pump PSI........Pump GPM
1,500........___15____.........._______...........____24/44____
2,350........___15____.........._______..........._____41/67___
3,110........___25____.........._______...........____59/91____
3,450........___25____.........._______...........____57/100____
15 psi X 2.31 = 34.6 feet, which is close to the estimated head loss of 35 feet, but it does not account for the suction head loss.
25 psi X 2.31 = 57.8 feet.
15 psi at 1,500 rpm or 2,350 rpm is too high.
Is the filter clean?
The filter pressure at two different speeds should be different.
57.8 feet at 3,450 rpm should be about 135 gpm, but that does not account for the suction head loss, which might be too high.
If we estimate 22.2 feet for the suction, the total head loss would be 80 feet and the estimated flow would be 90 gpm, which matches the estimated head loss curve.
What is the pipe size and length for the suction line from the spa?
Based on the numbers, the suction line is probably too small and there is excessive restriction on the return side as well.
A properly designed suction line will keep the velocity below 6 feet per second and the head loss will ideally be below 8 feet of head.
Maybe a dirty filter or some other issue.
I would clean the filter and make sure that the pump basket is clean.
Maybe consider putting a 5 psi check valve bypass on the heater to bypass excess water around the heater.
For suction, you want to keep the water velocity below 6 ft/sec. For returns, you want to keep the water velocity below 8 ft/sec.
Size.......6 ft/sec......8 ft/sec.
1.5"...........38...............51 gpm
2"..............63...............84 gpm
2.5............90.............119 gpm
3.0".........138.............184 gpm
4”...........234.............313 gpm
25 psi X 2.31 = 57.8 feet.
15 psi at 1,500 rpm or 2,350 rpm is too high.
Is the filter clean?
The filter pressure at two different speeds should be different.
57.8 feet at 3,450 rpm should be about 135 gpm, but that does not account for the suction head loss, which might be too high.
If we estimate 22.2 feet for the suction, the total head loss would be 80 feet and the estimated flow would be 90 gpm, which matches the estimated head loss curve.
What is the pipe size and length for the suction line from the spa?
Based on the numbers, the suction line is probably too small and there is excessive restriction on the return side as well.
A properly designed suction line will keep the velocity below 6 feet per second and the head loss will ideally be below 8 feet of head.
Maybe a dirty filter or some other issue.
I would clean the filter and make sure that the pump basket is clean.
Maybe consider putting a 5 psi check valve bypass on the heater to bypass excess water around the heater.
For suction, you want to keep the water velocity below 6 ft/sec. For returns, you want to keep the water velocity below 8 ft/sec.
Size.......6 ft/sec......8 ft/sec.
1.5"...........38...............51 gpm
2"..............63...............84 gpm
2.5............90.............119 gpm
3.0".........138.............184 gpm
4”...........234.............313 gpm
I tried that and still couldn't wake it up. I'll give that another shot tomorrow. I greatly appreciate your help on this.
Is the pump powered from the load side of the relay or the line side?
The pump should be powered from the line side of the relay so that it always has power.
Do you have a picture of the filter pump relay and wiring?
If you are in "Service" mode, you can press the Filter button on the main box to activate the pump display.
Turn the cell percentage to zero to make sure that it does not run during the tests.
The pump should be powered from the line side of the relay so that it always has power.
Do you have a picture of the filter pump relay and wiring?
If you are in "Service" mode, you can press the Filter button on the main box to activate the pump display.
Turn the cell percentage to zero to make sure that it does not run during the tests.
The filter and pump basket are clean. The pipe size for the suction line from the spa is 2" and the length is about 26'. I have a valve between the filter and the heater that I can manually adjust. It's inconvenient to change it between the times that I want the full heating capability and the lower temperature. Checking on the pump wiring now.
2" is too small. 2" pipe should not exceed about 63 gpm.
They should have used 3" pipe to allow up to 138 gpm without exceeding the recommended 6 feet per second.
2” pipe at 90 gpm is 8.77 feet per second and the head loss will probably be between 6 to 8 feet of head, which isn’t too horrible.
So, something is creating excessive head loss.
Do you have a picture of the system?
I would use a spring check valve.
A 5 psi spring check valve automatically opens to allow excess water to bypass the heater so you don't need to manually adjust anything.
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James, again thank you so much for your help. I am very grateful. I did get the readings, but they're for the pool not the spa. I think I needed to check spa relay on the service mode to get the spa readings? Would I need to check anything else there?
Here are the pool readings.
RPM........Filter PSI......Pump PSI........Pump GPM
1,500.............7 psi.............7 Psi................19 GPM
2,350........14psi .............17psi .............51 GPM
3,110...........22 psi .............29 psi ...........73 gpm
3,450........27 psi......................................82 gpm
I've got a commitment this evening, so I'm going to have to put this aside for now. I'll send pictures tomorrow. Thanks again.
--Lee
Here are the pool readings.
RPM........Filter PSI......Pump PSI........Pump GPM
1,500.............7 psi.............7 Psi................19 GPM
2,350........14psi .............17psi .............51 GPM
3,110...........22 psi .............29 psi ...........73 gpm
3,450........27 psi......................................82 gpm
I've got a commitment this evening, so I'm going to have to put this aside for now. I'll send pictures tomorrow. Thanks again.
--Lee
Ok, using the pump data, here is the updated system curve.
It is slightly worse than I originally estimated.
The curve indicates that the system is overly restrictive.
Once you show some pictures, I will look to see if there are any ways to improve the system curve to allow for better flow.
With the maximum flow at 82 gpm at 3,450 rpm, the temperature rise will be 8.2 degrees and an outlet temperature of 112.2 degrees.
Going to a 420 square foot filter would help.
Adding a 5 psi check valve bypass to the heater would help.
If you could get the suction pressure with a vacuum gauge, that would help diagnose the issues.
A flow meter would also help since the pump gpm flow-meter is only approximate.
It is slightly worse than I originally estimated.
The curve indicates that the system is overly restrictive.
Once you show some pictures, I will look to see if there are any ways to improve the system curve to allow for better flow.
With the maximum flow at 82 gpm at 3,450 rpm, the temperature rise will be 8.2 degrees and an outlet temperature of 112.2 degrees.
Going to a 420 square foot filter would help.
Adding a 5 psi check valve bypass to the heater would help.
If you could get the suction pressure with a vacuum gauge, that would help diagnose the issues.
A flow meter would also help since the pump gpm flow-meter is only approximate.
If we assume that the filter pressure is accurate for the return side and the pump pressure is the total pressure, that would leave 7 psi (7 X 2.31 = 16 feet of head loss) for the suction at 3,110 rpm and 73 gpm.
73 gpm going through 167 feet of 2" pipe would create 16 feet of head loss (7 psi).
Since the suction is only 26 feet long, there would seem to be an extra amount of resistance equal to 141 feet of 2" pipe.
The readings from the pump are not super accurate, so we can't rely on them too much.
Maybe there is a clog in the lines or possibly a clogged impeller?
Did you get a pump pressure at 3,450 rpm?
Based on the curve, I would estimate about 36 psi at 3,450 rpm and 82 gpm.
36 - 27 = 9 psi = 21 feet of head loss on the suction side at 82 gpm.
82 gpm going through 175 feet of 2" pipe would create 21 feet of head loss (9psi).
175 - 26 = the equivalent of an extra 149 feet of 2" pipe in resistance.
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