Heat Pump turns off with FLO error (Water flow)

[hiddenoaks]

Hi all,
I'd appreciate some collective wisdom here with helping me understand what is going on. For context, I have a 20k gallon salt water pool, with a variable speed pump (newly installed this year) and a Hayward ACT-1250 heat pump. The newly installed VSP is running on lower speeds than my previous single speed pump, and over 2 weeks the heat pump has been turning off with FLO error, which is insufficient water flow error. However, the way it is happening is confusing me. Here's the scenario:

The pump runs at 1600RPM, heat pump works fine for a few days, then errors out with FLO error. I increase the pump RPM to 1800.
The heat pump starts working, and runs fine for a week or so. Then, errors out with FLO again. I increase the pump RPM to 2000, the heat pump starts working again.

I understand the heat pump needs a min 20gpm flow to work, and that may require tuning the pump RPM a bit, but why does it behave the way it has, with multiple turnoffs? Afaik, the filter should be clean (only opened pool about 3 weeks ago, I use skimmer socks to prevent some debris reaching the filter, use a robot to clean the pool, etc - the filter pressure has not climbed at all (maybe 1psi rise, not showing that its dirty). I dont think I have any clogs in my lines, flow works great when I run the pump at 3000RPM, zero issues then.

What exactly may be going on here?

 

[mknauss]

Do an Overnight Chlorine Loss Test. What you are seeing is a sign of algae in your pool water.

 

[ajw22]

Your filter can clog in a few days if you have algae.

What is your pump runtime?

Clean your filter.

Needing increasing RPMs for the same flow indicates a filter that is getting dirty.

 

[hiddenoaks]

Hmm, thanks - appreciate it, and will check today. Pump runtimes are 3k RPM for 1h, 10h at 1800RPM, then 1h for 3k again.
Just did a water test, zero combined chlorine and water is crystal clear - but will clean the filter to test this out!

 

[ajw22]

I see you are using Perlite in your DE filter.

When I tried that I found my DE filter was clogging too quickly with normal pool dirt and not algae and I had to backwash too often. I went back to using DE.

I think your Perlite is causing the problem.

 

[hiddenoaks]

yes Trying Perilite this year but if I have to backwash it 5 times more than DE, thats not really savings at all

 

[mknauss]

One of our members uses FiberClear instead of DE. Might look into that.

 

[hiddenoaks]

Quick update: everything back to normal, thanks to everyone in this thread for your knowledge and advice! It was indeed the filter being clogged, but not overly dirty - perhaps it was the Perilite that was causing the decrease in GPM flow that triggered the pump to shutdown.

What I did:
* disassembled the DE filter, cleaned it out, re-assembled
* charged it with 6lb DE, no more perilite experiment.
* Pump running at 1400RPM, filter pressure at 6PSI, and Heat Pump is working just fine - meaning flow is above the min 20GPM required for the Heat Pump.

Thanks all, and happy friday!