VS Hayward pump rpm to activate Hayward Heater flow switch

[Sunfire67]

We just moved into a new house with a Hayward Tristar VS pump and a Hayward H150FD heater. I'm trying to figure out the proper rpm for the pump to allow the flow switch to activate and turn on the heater. I've done a few trials at 1600rpm, 1750rpm, 1850rpm and 2000rpm at the 1750 and 1850 the pump stayed on for quite sometime and then after I went in about 30mins to 1hr later I checked the heater and it shutoff due to low flow. I left it on 2000rpm and the heater continued until the pump setting changed to the lower rpm. So my question is 2000rpm pretty high or should I be able to get it lower?

My pool is approx. 16 x 30, shallow end 3 1/2' deep, deep end 8' deep

 

[Matt_S]

I have the same problem (same pump and heater) - My first thought is that the filter is too small and can't flow fast enough, but I'm waiting for the experts to chime in. What filter do you have?

 

[Sunfire67]

I have Hayward SM250 Sand Filter. I backwashed the filter today and set the pump to 1750rpm's and was able to activate the flow switch for the heater.

 

[GaryT58]

Yes, cleaning your filter can definitely help. The flow switch is measure the flow rate (i.e. gallons per minute GPM). The RPM of a variable speed pump does not directly correspond to a flow rate as things, like valve settings and filters can affect it. For myself, my salt water chlorine generator (SWG) I will run at 800 RPM as the lowest, as this seems to work well, even when my sand filter is dirty. When clean, I can run as low as 650 RPM. There are variable flow pumps which you set the flow rate, and it will adjust the speed automatically to maintain the flow.