Product Overview

The Danfoss KPI 35 stands as the most recognized and reliable pressure switch in the industrial automation sector, specifically engineered for the regulation, monitoring, and alarm systems of pumps and air compressors. This heavy-duty mechanical switch facilitates the automated start and stop cycles of water supply systems and industrial utility machinery with unmatched repeat accuracy. Unlike standard residential switches, the KPI 35 utilizes a high-performance bellows system that resists vibration and mechanical fatigue, ensuring thousands of stable switching cycles. Its robust design features a Single Pole Double Throw (SPDT) contact system, allowing it to function as both a controller and a high/low-pressure safety cutout. Whether managing a commercial booster set or an industrial cooling loop, the KPI 35 provides the mechanical certainty required to maintain optimal system pressure and protect expensive downstream assets.

Core Technical Advantages

High-Durability Bellows System

The KPI 35 employs a specialized metal bellows that translates fluid pressure into mechanical movement. This design offers superior resistance to pressure surges and vibrations compared to diaphragm-based alternatives. The bellows architecture ensures that the setpoint remains stable over years of continuous operation, even in systems subject to frequent pressure fluctuations.

Precise Differential Adjustment

The hardware incorporates two distinct adjustment scales: one for the main pressure setpoint and another for the differential (hysteresis). This allows engineers to fine-tune the gap between the "cut-in" and "cut-out" pressures, preventing rapid motor cycling (hunting) and significantly extending the lifespan of pump contactors and motors.

Industrial-Grade SPDT Contact System

The switch features a Single Pole Double Throw contact set rated for high inductive loads. These silver-plated contacts provide low electrical resistance and high arc resistance, making the KPI 35 capable of direct motor control in small systems or reliable signaling to a PLC in larger, more complex industrial networks.

Technical Specifications

Engineering Installation Guide

Setpoint Calibration

Adjust the range and differential scales using the internal setting screws located at the top of the switch. Always use a calibrated master gauge when setting the cut-in and cut-out points. Turn the range screw to set the high-pressure stop point, then adjust the differential screw to determine at what lower pressure the system should restart.

Wiring for Pump Control

Connect the power supply to the common terminal and utilize the "Normally Closed" (NC) contact for standard pump start/stop logic. When the pressure reaches the setpoint, the switch breaks the circuit to the contactor. Ensure all electrical connections utilize ferrules to prevent loose strands from causing short circuits within the compact enclosure.

Mechanical Mounting and Vibration

Install the KPI 35 on a vibration-dampened bracket if mounting near large reciprocating compressors. Utilize a flexible capillary tube or a "U" bend between the process line and the G 1/4 pressure connection. This prevents mechanical vibrations and thermal expansion from stressing the bellows, ensuring the calibration remains accurate over time.

Engineering Advantages

The KPI 35 excels in environments where reliability is the primary metric for success. Its simple, transparent scale allows maintenance personnel to verify system settings at a glance, while the manual trip function permits safe testing of the electrical loop without depressurizing the system. The switch’s ability to handle high ambient temperatures and its wide adjustment range make it a "universal" component for global B2B procurement, satisfying the requirements of various pump manufacturers and plant engineers alike. By standardizing on the KPI 35, facility managers reduce their spare parts inventory while gaining a proven safety layer that guards against both overpressure and dry-running conditions in essential fluid power systems.

Delivery & Logistics

Delivery Time: 3-5 days when payment finish.

Shipping Carriers: BY DHL/FEDEX/UPS.

Packaging: We utilize impact-resistant industrial packaging and original factory-sealed boxing. Each KPI 35 is shipped in anti-static materials to ensure the precision mechanical bellows and electrical contacts arrive in perfect industrial condition.

Technical FAQs

Q1: What is the difference between a KPI and a KP pressure switch?

A1: KPI switches are primarily used for liquid and air (non-aggressive media) in HVAC and industrial settings. The KP series is often specialized for refrigeration applications or heavy-duty industrial steam, though they share a similar mechanical architecture.

Q2: Does the KPI 35 support manual reset?

A2: The standard KPI 35 is an automatic reset switch. Once the pressure drops below the differential setting, the switch resets. For manual reset applications (safety cutouts), specialized variants within the KP/KPI family are required.

Q3: Can I use the KPI 35 for oil systems?

A3: Yes, the KPI 35 is compatible with neutral oils. However, always verify that the oil temperature and chemical composition are compatible with the metal bellows and G 1/4 connection materials.

Q4: How do I increase the IP rating of the switch?

A4: The KPI 35 comes as IP30. By installing the optional top cover and using a proper cable gland, the enclosure rating can be upgraded to IP44, providing protection against water splashes and solid objects larger than 1mm.