Pool Heater Low Flow

jkhamr · Aug 29, 2024

Hello, I have a Hayward W3HP21404T HeatPro 140K BTU, it has a minimum flow rate 30 gpm. My Hayward 2.25 HP varialble speed Super Pump XE at 100% is rated at 80 gpm. I run it 24/7 at 45% speed which maths out to 36 gpm. When I turn on the heater it flashes "Flo" meaning low flow rate, the heater won't actually kick on until I set the pump speed to at least 70% which is 56 gpm. Without an inline flow meter ahead of the heater, is there a way to check the actual flow rate? How sensitive is the flow sensor in the heater and is there one that can be swapped in to get the heater to opperate at a lower gpm? The heater works great and is awesome with the pump running faster, I just don't know that I'd want to leave the pump at 70% speed 24/7. TIA!

ajw22 · Aug 29, 2024

Pump speed rated flow of 80 GPM is a best case flow rate with no restrictions - no filter, no heater, etc.

Running your XE pump at 70% is around 2200 RPM which is what I would expect you would need to run that pump. And 70% is not flowing 56 GPM due to the filter and heater "head" or restrictions.

You are an example of why we recommend buying a 3HP pump that can be run at a lower RPM to save energy for the same flow rate.

jkhamr · Aug 29, 2024

ajw22 said:
Pump speed rated flow of 80 GPM is a best case flow rate with no restrictions - no filter, no heater, etc.

Running your XE pump at 70% is around 2200 RPM which is what I would expect you would need to run that pump. And 70% is not flowing 56 GPM due to the filter and heater "head" or restrictions.

You are an example of why we recommend buying a 3HP pump that can be run at a lower RPM to save energy for the same flow rate.

Thanks ajw22, I'll see how much difference running the pump at 70% makes on my electric bill heading into fall. I will definitely go with a bigger pump when this one fails, which may not be for many years. It's not a big issue, I'm just always wanting to learn as much as I can about the system. I appreciate the 411.

ChrisABS · Aug 29, 2024

Here is the pressure switch for the heater. That black nut can be adjusted. You have to chip away at the blue glue from the manufacturer to get it to spin. There’s a switch under the housing that closes when it contacts that nut/dial. I forget if it’s clockwise or counterclockwise to raise it up. You’ll have to tinker with it.

ChrisABS · Aug 29, 2024

If you look close to the picture you can see the little blue chips. Be careful and take a small flat head screwdriver to chip at it.

jkhamr · Aug 30, 2024

ChrisLPC said:
Here is the pressure switch for the heater. That black nut can be adjusted. You have to chip away at the blue glue from the manufacturer to get it to spin. There’s a switch under the housing that closes when it contacts that nut/dial. I forget if it’s clockwise or counterclockwise to raise it up. You’ll have to tinker with it.

ChrisLPC, thanks for the info and photo! I'll adjust the pressure switch and figure it out.

jkhamr · Aug 31, 2024

ChrisLPC said:
If you look close to the picture you can see the little blue chips. Be careful and take a small flat head screwdriver to chip at it.

I looked through the install/owner's manuals that came with the unit and I did not find any information about the pressure sensor switch. I did find this online on another pool equipment website:

Heat Pump Pressure Sensor Adjustment.png

I adjusted the knob as you said and as indicated above, now the heater kicks on with my pump set at 45%. The adjustment knob on my heater was not glued in at the factory setting, so didn't have to chip away the blue glue.
Thanks for all the help with this! As always, the folks on TFP are awesome!

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