Hayward H Series Heater Back Pressure

pickardc

Active member
Apr 4, 2020
27
Oakland, MI
I have a newly installed Hayward H Series heater. My PB was out with the Hayward rep and struggled to get it going. They were finally able to get it flowing by shutting the return jets 90% and diverting to the water slide which is a smaller diameter pipe. The tech said the reason was that the return jets are not creating enough back pressure for the heater and the LO sensor is tripping. They deferred to the PB to adjust the return eyelets.

Question I have is what exactly does the PB need to do. I have a 20,000 40 x 16 pool with 4 return jets and a VSP Max 500 pump. My equipment pad is also about 5 ft above the water line. Anyone seen this issue before?
 

JamesW

TFP Expert
Mar 2, 2011
19,427
My equipment pad is also about 5 ft above the water line.
That's the problem.

The heater pressure switch is not going to close unless the pump is on high speed and/or the returns are very restricted.

I would install a flow switch in the plumbing and connect it in place of the pressure switch.

Harwil makes the flow switch for the Hayward Aquarite.

You need a flow switch and T that's like the aquarite, but the activation flow rate needs to be higher than the Aquarite.

I would contact Harwil and ask them for the right model number.




 
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pickardc

Active member
Apr 4, 2020
27
Oakland, MI
thanks for the help. Waiting on my PB to come back with a solution before I suggest the change. He did good work on the install but there has been a number of smaller issues that have had to be run down. I know the pressure sensor is easy to swap and key is to get the desired state that no water = heater shuts off.
 

JamesW

TFP Expert
Mar 2, 2011
19,427
The pressure switch can be adjusted, but I would be cautious about adjusting it too much.

Do you have a picture of the whole system?

What is the btu/hr rating of the heater?
 

JamesW

TFP Expert
Mar 2, 2011
19,427
WATER PRESSURE SWITCH TEST / ADJUSTMENT PROCEDURE:

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 Table 14).

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 Table 14).

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.

Two-speed pump:

In a few cases the pressure from a two-speed pump is below the 1- pound minimum required to operate the water pressure switch on the heater.

This is apparent when the pressure switch cannot be further adjusted. In these cases the pump must be run at high speed to operate the heater. If the pump and piping arrangement are such that the re-quired 1-pound minimum pressure cannot be obtained, do not attempt to operate the heater. Correct the installation.
The 150,000 btu/hr heater requires a minimum of 20 gpm.

You can try to adjust the pressure switch as described in the manual.

In my opinion, a flow switch will be the best solution.

The Hayward aquarite flow switch turns on at 15 gpm and off at 12 gpm. It would work but I think that the flow is too low.

The 4S paddle turns on at 23 gpm and off at 18 gpm. So, that would work.

The 6M paddle turns on at 27 gpm and off at 22 gpm.
 

JamesW

TFP Expert
Mar 2, 2011
19,427
The flow switch is activated by the water velocity and not specifically the flow rate in gpm.

The Aquarite flow switch is activated by a water velocity of about 1.5 feet per second.

For 2" pvc, that's about 15 gpm.

However, if you used 2.5" pvc before and after the flow switch, the Aquarite flow switch would activate at about 23 gpm.

So, you would use a Lasco 402‐287 (2.5" slip x 2.5" slip x 1/2" female threads T) with some 2.5" pvc pipe before and after the flow switch.

Note: I'm not sure that the above T has a threaded 1/2" hole or if it's socket (slip). So, make sure that you get a T with the 1/2" hole threaded so that the flow switch will screw in as shown in the earlier picture.

There are some 4S flow switches available. So, that might be easier.
 
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JamesW

TFP Expert
Mar 2, 2011
19,427
If you adjust the pressure switch, make sure that the flow is at, or above, 20 gpm before adjusting the pressure switch.

In my opinion, the flow switch is the way to go.
 

pickardc

Active member
Apr 4, 2020
27
Oakland, MI
I’m holding off right now my PB is still working with Hayward. The changes the eyeballs to smaller ones and if you restrict the flow to the returns the heater runs. I’ve told my PB this isn’t acceptable and they need to correct the install. The other issue has been the salt cell will only run at 90% on the VSP perhaps this is normal but seems very high.

is it possible they have undersized the pump.
 

JamesW

TFP Expert
Mar 2, 2011
19,427
What is the exact model number of the pump?

Is it a SP23520VSP?

Is it wired 230 volts?

In my opinion, using a flow switch is the best option.

Restricting the returns is only going to cause you to have to run the pump at a much higher speed than necessary.

This will cost you money forever and it will cause you to have to listen to the pump noise.
 

JamesW

TFP Expert
Mar 2, 2011
19,427
The other issue has been the salt cell will only run at 90% on the VSP perhaps this is normal but seems very high.
The salt cell only requires about 15 to 20 gpm. Your pump should easily be able to do that at half speed. If you need to go to 90%, something is wrong. Is this with the returns open or severely restricted?

The heater requires about 20 to 25 gpm. That should be doable at half speed. The problem is that at 25 gpm, you're not going to generate enough back pressure to activate the pressure switch unless you run high speed and restrict the returns.

If you adjust the pressure switch or if you restrict the returns, it's important to make sure that the flow going to the heater is at or above 20 gpm.

You can't just close the valves going to the returns until the heater fires. Doing that without verifying the flow rate risks damaging the heater if the flow is below the 20 gpm minimum.

I would recommend a 2" T and a 4s switch or replumbing from the filter to the heater with 2.5" and using a Aquarite flow switch in a 2.5" T.

If you do the 2" plumbing, I recommend getting a flow meter as well to verify the actual flow rate.


 
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JamesW

TFP Expert
Mar 2, 2011
19,427
Has the builder tried to adjust the pressure switch?

Are they measuring the actual flow rate when trying to get the heater to start?
 

JamesW

TFP Expert
Mar 2, 2011
19,427
One way to estimate the flow rate is to check the heat rise from the heater inlet to the heater outlet.

The maximum temperature rise happens at the minimum flow rate of 20 gpm.

(150,000 x .84)÷(20 x 60 x 8.34) = 12.6 degrees.

So, you should not get more than about 12.6 degrees of temperature rise.

You have two sources of inlet temperature. The heater gives a water temperature and the automation gives a water temperature.

The cell is after the heater. So, the temperature reading from the Aquarite will be the outlet temperature.

When the heater is off, the inlet and outlet should be the same temperature.

Verify that all 3 temperature sensors are in agreement with the heater off.

When the heater is on, the cell temperature minus the inlet temperature is the temperature rise.

From the temperature rise, you can solve for the flow rate using the following formula.

Gpm = (150,000 x .84) ÷ (TR x 60 x 8.34)

Example:

(150,000x.84)÷(12.6x60x8.34) = 20 gpm

I would target a temperature rise of about 10 degrees, which would correspond to about 25 gpm.
 
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JamesW

TFP Expert
Mar 2, 2011
19,427
Here's a test that you can do. Get the pump running so that you have good flow through the heater. Try to estimate about 40 gpm.

Make sure that the returns are fully open.

Jump the pressure switch to make the heater start.

Check the temperature rise to estimate the flow. At 40 gpm, the temperature rise should be about 6.3 degrees.

Decrease the flow (rpm) in stages until the temperature rise is about 9 to 10 degrees.

Do not decrease the rpm too much. Make sure that you can verify good flow at all times.

Note the filter pressure, pump speed and power usage (watts) from the controller.

This is the optimum performance of the system.

You should not have to use more power or use a higher rpm than this.

Note: Only jump the pressure switch if you are sure about the flow through the heater.

Do not turn the pump off when the pressure switch is jumped.

Remove the jumper before you turn off the pump.

Only do this as a test while you are directly observing the heater and can shut it off.

Do not leave the pressure switch jumped.

Do not do this if you are unsure about it.

Do at your own risk and only if you're sure that you can do it safely.

If the builder's solution requires you to use a significantly higher rpm and power than optimum, I would consider it unacceptable.

Maybe have the service person do the test if you are unsure about it.
 
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Mayorb

In The Industry
Mar 16, 2010
160
I've gotten into the habit of installing a flow meter after the heater that takes all the math and guessing out of the true flow rate.
It also serves as a good indicator of when the filter needs cleaning. Even though the pressure gauge on top of the filter lets you know when psi is rising, I have found that an increase of just a few pounds can result in a drop of 5-10 gpms.
Flow meters should be standard equipment on all pool installs.
 
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