RPM to activate Hayward Heater

afliime · Apr 22, 2022

Moved from here.. VS Hayward pump rpm to activate Hayward Heater flow switch

If my pump runs below 2750rpm. the heater will turn off (LO). From my research I think I can alter the rpm by playing with the pressure switch inside the heater to allow a lower rpm setting to run the heater?

1poolman1 · Apr 22, 2022

Do Not adjust the pressure switch. They are one of the most important safety devices in a pool heater. If you have a 1hp VSP, 2750 just may not be enough flow to safely operate the heater. They require a minimum flow to be safe, set at the factory and can't be changed. Go below this, fire the heater, and a damaged heater may be the least of your problems.

BMerrill · Apr 22, 2022

On a Hayward heater the pressure switch is preset for the heater intakes to be level with the pool. If the heater is higher or lower than the water, the pressure switch can be adjusted. How to do so are in the manual for your heater. As posted above, this is a safety device. Though it works off of pressure, the heater has also has a minimum flow rate GPM requirement. This you must not go below and it’s best to add 5-10 GPM to this number. My H400 requires a minimum of 35 GPM and it’s above the pool water line by 18”. This would be a pump rpm of 1000 for 35 Gpm, but the pressure is to low to close the switch. Mine required 2400 rpm’s (80 gpm) to close the switch. After a minor tweak, got the rpm to 1800 with a flow rate of 60 GPM.

afliime · Apr 23, 2022

Thanks for the feedback. My neighbour has the exact same setup as mine (exact same equipment, pool design, pipe materials/size, layout) and his heater shouts off is his pumps goes below 1900 rpm. So I was wondering if it had to do with the programming of the Prologic automation?

afliime · Apr 23, 2022

After coming across this thread Heater only fires up well above minimum 25gpm and seeing that the issue may be the check valve, that may be my issue as I have one as well. When I open up the pool I'll temporarily remove the flap and see if that makes a difference.

BMerrill · Apr 23, 2022

Issue has nothing to do with the Prologic automation. When heat is called for, the controller sends 24 volts to the heater to close a relay. It is the heaters fail safe features that determines if the the heater will fire. The pressure switch is one of these. If you have a flow meter in your system you could adjust the pressure switch. If not, then leave it alone or call the pool company. The pump is using about 1.2 kw per hour. At 15¢ an hour its minor compared to the amount of gas it’s using.

afliime · Apr 24, 2022

thanks for the responses.