Heater cycles on/off without heating

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Pentair has a formula and graph for the power at different speeds and flow rates.

So, if you know the speed and the power usage, then you can determine the flow and the total head loss.

For example, if the speed is 3,450 rpm and the power usage is about 1,938 watts, then the flow is about 40 gpm and the head loss is about 92 feet of head.

If the power usage was 2,775 watts, then the flow would be about 100 gpm and the head loss would be about 76 feet of head.

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Hi
I removed the filter cartridges which seem to be quite old and that let's me get up to 76 GPM @3450 RPM. The pressure gauge shows 19 PSI. Still not great, but maybe ok??

Intake restriction is a bit unlikely as I also don't get more GPM when I am taking water from SPA. That would mean both intakes are clogged. The input manifold is right before the pump
 
That's still about 84 feet of head loss or 36.8 psi, which is excessive.

That puts the system model at about head loss = 0.014543(gpm^2), which is excessively restrictive.

What is the system pressure reading from the keypad?

What is the filter pressure when the keypad system pressure is 36 psi?
 
What is the filter pressure when the keypad system pressure is 36 psi?

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Your system models at about 1 when it should model closer to 2.

The head loss at each flow rate is about 1.8 times higher than it should be.
 

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36 - 17 = 19 psi.

The 17 is only the return pressure.

The 36 represents the total system pressure, which is the suction plus the return.

So, that implies that the suction might be 19 psi, but that is not possible because the maximum suction can only be 14.7 psi and the suction will start cavitating before it ever hits 14.7 psi.

Maybe there is some sort of restriction in the suction line or maybe a clogged impeller?
 
ajw22 said:
Do you have a Heater Bypass - Further Reading ?
Click to expand...
I do not
JamesW said:
36 - 17 = 19 psi.

The 17 is only the return pressure.

The 36 represents the total system pressure, which is the suction plus the return.

So, that implies that the suction might be 19 psi, but that is not possible because the maximum suction can only be 14.7 psi and the suction will start cavitating before it ever hits 14.7 psi.

Maybe there is some sort of restriction in the suction line or maybe a clogged impeller?
Click to expand...
When you say suction of 19 PSI is impossible does it mean the small snake part between the pump and filter is blocked?
 

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Kill the power and open the pump lid remove basket and reach around the impeller with some tweezers. See if you feel anything. Open cell and inspect at the same time that would be the easiest. Than I would do what James explained above while in service mode with spa mode on and see if there is a difference.
 
For the SPA flow is generally limited to less than 47 GPM but the numbers look a bit different:
3000RPM, 1370 Watt, 40 GPM, 30 PSI at the pump, 21 PSI at the filter or
2500RPM, 814 Watt, 33 GPM, 21 PSI at pump, 16 PSI at filter

what is your reading of this? Is the SPA doing better? The watt/PSI is less but 46GPM@3450RPM looks weak too.





 
ratzfatz said:
When the keypad pressure is 36PSI (at 3450RPM) the filter pressure gauge shows 17 PSI.
Click to expand...

I get the following though my pool:

1700 rpm - 24 gpm - 273 watts - 9 psi pump - 7 psi filter - 2 psi diff
2450 rpm - 46 gpm - 842 watts - 19 psi pump - 16 psi filter - 3 psi diff
3450 rpm - 69 gpm - 2390 watts - 37 psi pump - 30 psi filter - 7 psi diff
 

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