Minimum RPM to run Heater without damaging it

Brian W

Bronze Supporter
Apr 25, 2020
27
Brea, California
Hi all,

First thanks for my first successful season as a pool owner with no major issues. I finally hooked up my Hayward heater to let my kids swim here in So Cal. I only have my SWG hooked up to my simple Intermatic timer. Primarily, I acted as my own pool builder during the pandemic. (I think ), I want to set my heater at a set 84 degrees and have the VS pump set at the lowest speed the heater will allow running 24/7 until summer heat kicks in. The heater manual says minimum 20 GPM but of course none of my equipment gives me GPM. I am running 2" pvc through everything except the 1 1/4 from the skimmer (why 1 1/4 and not 2"?)

So my questions. How do I figure out a reasonable speed to run the pump out w/o using all my brain cells for calculus, heat transfer, head, etc while not ruining my heater?

A related question, how does the water flow effect the SWG--- does a higher speed degrade the production--- seems like it must.

Thanks,

Brian
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
36,438
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Great job on putting everything together. How are you testing your pool water chemistry?

The heater has a pressure switch. So if there is not enough flow through it, it will not operate. At what rate do you normally run your VS pump? See if that is OK with the heater.

The SWCG could care less what flow rate you put through it. As long as the flow is enough to close the flow switch, it will generate the same amount of chlorine regardless of the flow rate.
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
24,025
Northern NJ
Pool Size
35000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
So my questions. How do I figure out a reasonable speed to run the pump out w/o using all my brain cells for calculus, heat transfer, head, etc while not ruining my heater?

Every pool is different. You have to find what pump RPM gives enough flow to satisfy the heater pressure switch. Probably between 1500-2000 rpm.

Once you get a flow that runs the heater put your hand on the heater output pipe flange. It should feel warm, not hot. If it feels hot increase the flow a bit until it just feels warm.

A related question, how does the water flow effect the SWG--- does a higher speed degrade the production--- seems like it must.

Water flow does not affect your SWG as long as it is sufficient to close the flow switch. If it is not sufficient for the flow switch your SWG turns off.
 

Brian W

Bronze Supporter
Apr 25, 2020
27
Brea, California
I appreciate the feedback. I'll try to play with the speeds in the next few days.
I won't burn anything permanently by invoking the heater's pressure switch?

I don't know if it's a "great job putting it together, but thanks to this forum it's level, clear, and my kids enjoy it. It was a lot of work. I think I did ok but won't be posting any pictures---- I am allergic to criticism.

Funny, I understand better why people use "pool professionals" because this stuff was intimidating at first!. Water chemistry, equipotential-bonding, solar covers not for generating heat, equipment size and usage, etc etc. That being said. because of you all- I also know now that ,with this forum, I won't need "pool professional" help either

I changed my signature to include the tft100 test kit. I just ordered the taylor k1766? salt test just because. My SWG hasn't complained. I, like most newbies, really can't figure out my CYA but I think it's between 50 & 60. Everything else seems fairly straight forward.

Last year I ran the vs pump at the factory settings-- 3450 rpm for an hour, 1400 rpm for 8 hours- with SWG , and 2200 rpm for two hours.
I was running it at 2900 rpm 24-7 to make sure the heater didn't burn.


--- I assumed that the flow could be too fast for the SWG--- my FC levels were low so I changed it to 100% for 6hours----might need to SLAM? Have to do an overnight test I think.

Here's my levels now--- swam with kids at end of swg day.

FC 2.5
CC 0.5
Ph 7.6
CH 225
TA 150 (tap is 170)
CYA 50
Temp 85
Salt 3900 (strip)

CSI -0.01