⭐ Product Overview (This vs That)

This – 356922Z Variable Speed & Flow Drive (VSF)

The 356922Z is the dedicated drive for IntelliFlo VSF pumps. It controls both motor speed and actual water flow using Pentair’s flow-calibration system. It’s the “smart” drive that maintains precise flow rates for heaters, water features, spas, and advanced pool automation.

That – 356879Z Variable Speed Drive (VS)

The 356879Z is a standard Variable Speed drive used on IntelliFlo VS and VST pumps. It controls only motor RPM. It does not measure or maintain flow — it simply runs the motor at programmed speeds.

Pros & Cons

356922Z – VSF Drive (This)

Pros

• Controls speed and flow

• Works with advanced pool automation

• Ideal for systems with heaters, spas, water features

• Protects equipment by maintaining proper flow

• Highest efficiency and performance

Cons

• More expensive

• ONLY fits VSF motors (not VS motors)

356879Z – VS Drive (That)

Pros

• Reliable speed control

• Excellent energy savings

• Ideal for standard pools without advanced features

• Lower cost than VSF drives

Cons

• Does NOT control flow

• Not compatible with VSF motors

• Less precise for systems needing exact flow rates

❗ Why You CANNOT put a VS Drive on a VSF Pump/Motor

This is the key piece customers always ask about — and here is the simple, correct explanation:

1. The Motors Are Different

• VSF motors contain additional internal flow-sensing electronics.

• VS motors do not have this hardware.

A VS drive (356879Z) cannot communicate with or control the flow-measurement system built into a VSF motor.

2. The Software Is Completely Different

• The VSF drive (356922Z) runs firmware designed to read, calculate, and regulate flow.

• The VS drive (356879Z) has firmware for RPM control only.

When you put a VS drive on a VSF motor:

• The motor and drive cannot “handshake”

• The system cannot calibrate

• The pump will fail to start or show drive/motor errors

3. It Can Damage the Motor

Running a VSF motor using a drive that doesn’t speak the same “language” can:

• Break communication between the drive and motor electronics

• Cause improper amperage draw

• Stress the motor windings

• Lead to early drive or motor failure

4. The Pump Will NOT Control Flow

VSF pumps are designed to maintain a flow rate (GPM).
If you remove the VSF drive:

• The pump loses flow control

• Heaters may shut off

• SWGs may not get enough flow

• Water features may surge or starve

This can cause:

• Heater damage

• SWG low-flow errors

• Poor filtration

• Warranty issues

5. Pentair Firmware Checks for Correct Drive Type

Pentair builds in a compatibility lock-out.

A VSF pump will not accept a VS-only drive because:

• The drive identifies itself to the motor

• The pump checks for correct VSF firmware

• If incorrect, it will not operate

This ensures the pump cannot be configured incorrectly.