MVVS4.5 | Vacuum Switch 4.5, 435 PSI, 220V 16A

MVVS4.5 | Vacuum Switch 4.5, 435 PSI, 220V 16A

The MVVS4.5 Vacuum Switch is a safety-critical accessory designed
to protect high-flow, tank-fed pressure washer systems from
low-water and no-water conditions. Calibrated to close at approximately
4.5″ Hg of vacuum, this normally-open switch senses suction
at the pump inlet and only allows the burner or heating/control circuit to
energize when there is adequate water supply. When vacuum drops – because the
tank runs dry, a valve is closed, or the pump stops drawing water – the MVVS4.5
opens the circuit, helping prevent dry-running, overheating, and costly damage
to pumps, coils, seals, and heating components.

• Normally-open vacuum switch that closes on vacuum and opens on loss of vacuum.
• Set at approximately 4.5″ Hg – ideal for higher-flow tank-fed systems.
• Intended for pressure washers in the 4.5 GPM and up class (multiple-gun or high-output units).
• Provides automatic low-water protection for burners, solenoids, and heater controls.
• Compact body suitable for skid, trailer, and cabinet-style machine layouts.

How the MVVS4.5 Works

Mounted in the suction line between the bulk water tank and the pump, the
MVVS4.5 monitors inlet vacuum whenever the pump is running. As the pump draws
water, suction pulls on an internal diaphragm, overcoming the return spring and
closing the electrical contacts. This completes the safety loop
and allows power to flow to the burner control, fuel/gas solenoid, or other
controlled device. If the tank level drops too low, the inlet is blocked, or
flow is otherwise interrupted, vacuum collapses, the diaphragm relaxes, and the
contacts open, instantly removing power from the heating circuit.

Operating sequence

• Pump ON, water present: inlet vacuum reaches the 4.5″ Hg setpoint; contacts close and enable the burner or control circuit.
• Pump ON, water lost: vacuum disappears; spring returns the diaphragm; contacts open and shut the circuit down.
• Pump OFF: no vacuum; switch remains open by default.
• Automatic reset: when water supply is restored and vacuum returns to 4.5″ Hg, the switch recloses without manual intervention.

Construction and Ratings

The MVVS4.5 is built for the vibration, moisture, and temperature swings
typical of professional pressure washing and industrial cleaning equipment.
A vacuum-sensing diaphragm and mechanical return spring actuate a robust
contact set housed in a durable body. The hydraulic side connects via a
standard low-pressure port, while the electrical side offers simple
two-terminal wiring to tie into the safety chain.

• Vacuum setpoint: 4.5″ Hg (closes at setpoint, opens when vacuum falls below).
• Contact type: two-wire, normally open; closes on vacuum.
• Fluid connection: typically 1/4″ FPT or equivalent low-pressure vacuum port.
• Electrical rating: sized for typical burner primary controls, fuel solenoids, and control relays (check nameplate on your specific unit).
• Temperature capability: suitable for cold and warm inlet water within standard pressure-washer ranges (often up to about 131°F / 55°C in the suction line).

Design advantages

• Purely mechanical sensing – no electronics, logic boards, or software to fail.
• Clear on/off behavior makes troubleshooting and safety testing straightforward.
• Compact footprint fits in crowded engine decks, skids, and cabinet enclosures.
• Standard thread and two-wire connection simplify retrofits and replacements.

MVVS4.5 | Vacuum Switch 4.5, 435 PSI, 220V 16A

System Integration

The MVVS4.5 is tailored for larger tank-fed pressure washer systems –
particularly trailer rigs, multi-gun skids, and high-flow hot-water machines
where the pump’s inlet vacuum at higher GPM is more pronounced. It is normally
wired in series with other safety devices such as flow switches, pressure
switches, thermostats, low-fuel switches, and emergency stops to form a
complete safety loop controlling the burner or heating elements.

• Best suited to machines in the 4.5+ GPM range drawing from a bulk tank or tote.
• Installed in the suction line where vacuum reflects true water availability.
• Wired in series with flow, pressure, and temperature safeties for layered protection.
• Can switch burner primaries, gas/oil solenoids, contactor coils, or safety relays within rated load.

Typical wiring concept

• Line power is routed through emergency stop, pressure switch, flow switch, and MVVS vacuum switch in series.
• Only when all safety devices are closed (made) does power reach the burner or heater control.
• Loss of water (loss of vacuum) opens the MVVS4.5 immediately, disabling the burner circuit and protecting the pump and coil.

MVVS4.5 | Vacuum Switch 4.5, 435 PSI, 220V 16A

Typical Applications

Because of its higher vacuum setpoint, the MVVS4.5 is particularly well suited
to larger professional machines and multi-gun systems where flow rates are
higher and low-water risks are magnified. It adds an important low-water safety
layer in any system where the pump draws from a tank rather than direct city
pressure.

• Trailer and skid-mounted hot-water pressure washers feeding from large totes or saddle tanks.
• Multi-gun wash rigs serving two or more operators simultaneously.
• Industrial wash bays with high-flow cleaning systems and bulk storage tanks.
• Fleet and equipment wash centers where machines run long hours and water level can vary.
• Rental and contractor rigs where automatic low-water protection reduces pump failures and coil burnout.

Key Specifications – MVVS4.5 Vacuum Switch

• SKU: MVVS4.5
• Type: vacuum-actuated, normally-open safety switch.
• Vacuum setpoint: approximately 4.5″ Hg (closes on vacuum).
• Recommended flow range: designed for higher-flow tank-fed systems, typically 4.5 GPM and above.
• Connection: 1/4″ FPT (or equivalent) vacuum inlet / port.
• Electrical use: burner primary controls, fuel/gas solenoids, or control relay coils within rated load.
• Typical fluid: clean water or water/detergent mix on the suction side of the pump.
• Mounting: inline on suction line or on a dedicated vacuum tap from the inlet manifold.