Hayward VSP pump is pulsating

[JamesW]

The suction line at a single 2" line is too small, which might be causing cavitation.

As you can see, the flow can get to about 175 gpm at full speed and low head loss.

The suction should have been at least 3" and probably 4" depending on the total flow required.

You want to keep the water velocity below 6 ft/sec on the suction and below 8 ft/sec on the pressure side of the pump.[7]

At 138 GPM, the head loss would be 35.2 feet and the velocity would be 14.1 feet per second for 2" PVC pipe.

Once the head loss exceeds 17 feet, the pump is in danger of cavitating.

Any flow over 100 GPM in 2" suction pipe risks cavitation.

If they had used 3" PVC pipe, the head loss would be only 6.2 feet at 175 GPM.

Pipe Size	6 ft/sec	8 ft/sec
1.5"	38 GPM	51 GPM
2"	63 GPM	84 GPM
2.5	90 GPM	119 GPM
3.0"	138 GPM	184 GPM
4.0"	235 GPM	312 GPM

Hazen-Williams Water Flow Formula: Head Loss, Data, Charts & Calculator

Friction head loss (<i>ft_H2O per 100 ft pipe</i>) in water pipes can be estimated with the empirical Hazen-Williams equation.

www.engineeringtoolbox.com

PVC Pipes Schedule 40 - Friction Loss vs. Water Flow

Water flow in thermoplastic PVC and CPVC pipes Schedule 40 - friction loss <i>(ft/100 ft, psi/100 ft)</i> and flow velocities at dimensions ranging 1/2 to 16 inches.

www.engineeringtoolbox.com

 

[JamesW]

Check the vacuum pressure.

15 inches of mercury is 17 feet of head loss.

If the vacuum pressure is greater than 15" Hg, then the pump might be cavitating.

 

[Cole johnstone]

Can you show these stickers?

View attachment 481452

It seems to start at around 95% or 96%..so around 3,300 RPMS

 

[JamesW]

Here is the model number:

Hayward - W3SP3206VSP TriStar Variable Speed Pool Pump, 2.7 THP

Can you check the voltage, current and power at different speeds?

https://hayward-pool-assets.com/assets/documents/pools/pdf/manuals/tristarvs-IS32950VS.pdf

Can you check the wattage, voltage, current, return pressure and suction pressure at these speeds?

3,450, 3,000, 2,400, 1,725, 1,000 RPM.

 

[JamesW]

Can you make a video of the pump running well and then transitioning to poor as the speed is increased?

 

[JamesW]

It doesn't really sound like cavitation, but the drive might be reacting to some measured parameter and adjusting the speed accordingly.

Maybe the power is being limited?

Maybe the drive is defective?

In any case, the suction line is too small and that will be very difficult to fix if you need to do that.

See what the builder is able to figure out.