Hayward H400FDN Heater with S244T2 Heater - not firing up unless Speed 3 or higher?


Active member
Jun 13, 2015
Southborough, MA
Hi all- I have a 20x40 in ground with a Hayward Proseries High Rate Sand filter (S244T2) and an H400FDN nat gas heater. Since the initial opening last year, the heater has never fired up unless the pump speed is at least 3. On speed 2, I get a “Low flow” reading from the heater.

Does this sound right? Should the heater be firing up on Speed 2?


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LifeTime Supporter
TFP Guide
Jul 3, 2013
Fletcher, OK
I know they will not work without enough flow as it has a flow sensor so if it is saying low flow your going to have to use the higher speed... It is all about flow so with your piping it has to use speed 3 where another pool may only need speed 2... it just depends...
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CPS Reno

In The Industry
Feb 6, 2019
Reno, NV
Backflushing your filter MAY allow you to run at a lower speed, but ^^^ he's 100% correct. I have the exact same heater/filter combo with a MaxFlo VSP and my LO message usually needs 84% to 87% pump speed before it goes away.
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