Re-plumb to improve flow rate?

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czb182 said:
Not sure if the issue , but there is some internal adjustment to pressure switch you are supposed to do for Jandy Jxi heater if equipment more than one foot above pool
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The pressure switches can sometimes be adjusted, but you need to be very careful about adjusting the switch.

You can install eyeballs in the returns to increase the back pressure. If that does not work, you can adjust the pressure switch as described in the manual.

In my opinion, the flow switch is a better choice.

The pressure switch is preset at the factory for most typical, deck level installations.

When the heater is located above or below the level of the pool or spa, the pressure switch may require adjustment to compensate for the change in static head pressure.

The following procedure is recommended when the switch needs adjustment and/or is replaced:

For Installations with Heater Above Water Level:

1. Be sure the filter is clean before making the adjustment.

2. Turn “ON” the filter pump and ensure all air is out of the water lines, and ensure water flow rate is at least the rated minimum (see Figure 10).

3. Turn “ON” the heater and adjust the thermostat to create a call for heat.

4. If the heater does not light, adjust the pressure switch by turning the adjustment knob on the pressure switch counter-clockwise, until the heater lights.

Turning the adjustment knob counterclockwise decreases the pressure needed to close the switch.

5. Check the function of the pressure switch by turning the filter pump on and off several times.

The pool heater should turn off immediately when the pump is turned off. Never allow the heater to operate with less than the minimum rated water flow rate.

For Installations with Heater Below Water Level:

1. Be sure the filter is clean before making the adjustment.

2. Turn “ON” the filter pump and ensure all air is out of the water lines, and ensure water flow rate is at least the rated minimum (see Figure 10).

3. Turn “ON” the heater and adjust the thermostat to create a call for heat.

4. Turn the adjustment knob on the pressure switch clockwise, until the heater turns off, then turn the knob ¼ turn counter-clockwise, so that the heater turns back on.

Turning the adjustment knob clockwise increases the pressure needed to close the switch.

5. Check the function of the pressure switch by turning the filter pump on and off several times.

The pool heater should turn off immediately when the pump is turned off.

Never allow the heater to operate with less than the minimum rated water flow rate.

Click to expand...
 
JamesW said:
The flow switch need to be set to trigger at about 10 gpm per 100,000 btu/hr of heater.

A 200,000 btu/hr needs 20 gpm.
a 400,000 btu/hr heater needs 40 gpm etc.

Contact Harwil for the right flow switch that will fit in the 2" T with a 1/2" female thread.

The Aquarite SWG flow switch triggers at about 15 to 20 gpm, so it won't be a good choice for a bigger heater like a 400,000 btu/hr.
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Looks like my heater is 250,000btu/hr. Think I could I get away with running an additional wire off the existing SWG flow switch to the heater?
 
To OP, I just redid my plumbing. Replaced a lot of the UV damaged flex PVC. If yours is exposed to sunlight be aware of cracking. Flex PVC is also hard to work with after it is weathered as it swells, making it difficult to couple due to not wanting to fit nicely with the fittings any longer.

But I did see increased flow rate due to the flex PVC being cracked. What didn't leak was sucking air.
 
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The problem with a pressure switch is that it does nothing to ensure that the flow is actually adequate.

Most likely, you are having to exceed the 25 gpm requirement just to create enough back pressure to close the pressure switch.

The big benefit of a 25 gpm flow switch is that it actually ensures that the flow is adequate without requiring excessive flow to trigger the switch.

With a 25 gpm flow switch, I would target about 30 gpm for a little bit of margin and that should work for you.
 
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JamesW said:
What is the filter pressure at full speed?

Is the pump wired to 115 or 230 volts?

If you can get a vacuum reading that would be helpful.

If you added a flow meter, that would help diagnose the issue.

If you can convert the filter pressure and vacuum pressure to feet of head, you can see what the expected flow rate is supposed to be at the below speeds.

For example, if the vacuum plus filter pressure is 20 psi, the total head is about 46.2 feet.

If we look at 46.2 feet of head and 115 volts, the flow is expected to be about 37 gpm.

If the pump is receiving 115 volts, the top speed is reduced to limit the maximum amps as shown in the black dotted line.

How far is the pump from the pool?
View attachment 337547
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I just added a FlowVis flow meter right after the pump, and am currently seeing about 69 GPM at full speed, with a filter pressure of about 9 PSI. Based on the chart above, TDH is about 32.

A 24/7 pump speed of 55% gives me 33GPM, which is spot on for 3 turnovers a day. TDH at this speed looks to be about 12. Even after fully adjusting the stock Hayward pressure switch (250k BTU heater), I still see a flow lockout code. Am I correct in assuming that the flow rate before and after the filter would be virtually the same, especially at lower speeds?
 

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The pressure switch is usually 2 or 3 psi and takes 3 or 4 psi to keep closed.

4 psi is 9.24 feet and 6.5 feet drop to the pool is 15.74 feet or 6.81 psi after the filter.

Assuming the filter is 1 psi of head loss, the filter pressure would need to be about 8 psi to keep the heater pressure switch closed.

Basically, you will have to run at full speed with a clean filter or get a flow switch.
 
I would estimate that you will need to have 60 gpm to keep the pressure switch closed.

60 gpm is going to take about 6 to 8 times more power than 30 gpm.

So, the power savings are definitely worthwhile, especially if the heater runs a lot.

60 gpm is about 3,000 rpm.

I think that 3,000 rpm is the slowest that you can run to keep the heater pressure switch happy and that is with a clean filter.

I would get a flow switch that closes at 25 gpm.

1624315251198.png
 
bjohannes said:
I find myself having to run the pump at 90% or more to keep the heater flow sensor happy.
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bjohannes said:
When the filter (DE4820) gets even a bit dirty, even 100% pump speed may not be enough to maintain the minimum flow rate for heating.
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90% is 3,100 rpm.

The pressure switch might be 2 or 3 psi from the factory.

My estimate is for 4 psi to keep the pressure switch securely closed and not chattering.

You might be able to get down to 2 or 3 psi.

If you adjust it down to 1 psi, you can make it work with lower flow, but you have to be careful not to make the heater run with no flow.

With a flow switch, the system can run at 25 to 30 gpm, which should be good for heating and efficiency.
 
bjohannes said:
2400RPM (40GPM) seems to keep the pressure switch happy.
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2,400 rpm crosses the system curve at about 48 gpm.

In any case the pressure switch can work if you adjust it and you keep the filter clean and you run the pump fast enough.

You're going to use more energy than necessary, but it will probably work.
 
If you are getting 40 gpm at 2,400 rpm, your system curve is a little bit steeper at about h = 0.0125F^2.

In any case, you can go with a flow switch or the pressure switch, whichever you want.
 
JamesW said:
90% is 3,100 rpm.

The pressure switch might be 2 or 3 psi from the factory.

My estimate is for 4 psi to keep the pressure switch securely closed and not chattering.

You might be able to get down to 2 or 3 psi.

If you adjust it down to 1 psi, you can make it work with lower flow, but you have to be careful not to make the heater run with no flow.

With a flow switch, the system can run at 25 to 30 gpm, which should be good for heating and efficiency.
Click to expand...
90% was needed before I adjusted the pressure switch. 70% does the trick now, but I had to adjust the switch to its minimum limit.
 
I would estimate the curve for everything after the filter at about y=0.004632x^2 - 6.5.

y=0.004632x^2 - 6.5, x = 0 to 80 - Wolfram|Alpha

Wolfram|Alpha brings expert-level knowledge and capabilities to the broadest possible range of people—spanning all professions and education levels.
www.wolframalpha.com www.wolframalpha.com

2.31 feet is 1 psi.

At about 45 gpm, the dynamic - static head is about 2.9 feet, which is just above the 1 psi estimated pressure switch close limit.

As you can see, at about 37.5 gpm, the pressure going into the heater is zero.

When the pump is off, the pressure in the filter is -6.5 feet (or the height of the gauge above the water surface).


1624373827462.png
 
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