Heater only fires up well above minimum 25gpm

[Weasel2017]

Hayward Universal H series 250k btu shows a minimum flow rate of 25gpm. My flow meter is right after the heater and unless I get the flow up to 35 to 40 gpm the heater shows a low flow warning. I read about adjusting the pressure switch whether the pool is above or below the water level. Mine is likely 2ft below. Anyone else come across this issue? Would be nice to get it to engage at a lower pump rpm if possible.

 

[ajw22]

What flow meter do you have?

Where is the flow meter positioned in your plumbing?

What rpm are you running your pump for 25 and 40 gpm?

I would just run your pump at a speed that makes the heater happy.

 

[Weasel2017]

I have a FlowVis flow meter which is doubling as my check valve between heater and salt. 1350 rpm will get me 25 and 2100 gets me 40. I think I have found a soft spot around 1700 rpm that will keep the salt generator and the heater happy. I don't mind running at higher rpm just made me wonder why the heater wouldn't even come close to starting at its min gpm.

Thanks

 

[PoolGate]

+1 don't worry about what your meter reads run what makes your heater happy. Heaters are more efficient when they run faster.

 

[ajw22]

I question the gpm accuracy of your flowvis.

1700-2000 rpm is what I would expect for a gas heater SWG setup.

 

[jseyfert3]

What particular model FloVis do you have, and how much straight section it pipe do you have in front of it? Some models require a minimum section of straight piping before the meter for an accurate reading.

 

[Weasel2017]

It is the FV-2 model which says zero required in front. I likely have 6" before the valve. I played with it a bit this weekend and 1650 rpm shows 32gpm which seems to make everything happy so not a far cry from the 25gpm minimum stated in the heater manual. Not sure if that is an accurate reading or not but it works. This is my first time installing any sort of check valve but definitely was concerned by the amount of pressure the springs were under to open the valve. That could be totally normal though as I have no experience with them but I was concerned how it may restrict flow.

 

[mknauss]

Remove the check valve (it is not needed) and see if your RPM lowers for the heater to operate.

 

[Weasel2017]

Interesting. When I was planning everything out I had read that a check valve between the SWG and Heater was a good idea.

 

[mknauss]

I had read that a check valve between the SWG and Heater was a good idea.

That is a carryover from the check valve between a trichlor erosion device and the heater. It is not the chlorine that is the issue with a heater, it is the acid. Trichlor is very acidic.

If you can remove the flapper you may find you can run your pump at a lower rate.