Suntree PV Disconnect 1000VDC 32A 4-Pole (SISP40)
The Suntree PV Disconnect SISP40 is a DIN rail-mounted DC isolating switch designed specifically for photovoltaic solar systems. Rated at 32 Amps and 1000 VDC, it provides a code-compliant, manually operated means of isolating a solar array from its connected load — whether that is a charge controller, inverter, or DC distribution cabinet. The 4-pole configuration simultaneously disconnects all four conductors in a single operation, eliminating the risk of leaving a live conductor in circuit during maintenance or emergency shutdown.
Across Kenya’s growing rooftop and ground-mounted solar market, the Suntree SISP40 is used at the critical disconnect point between the PV array output and the inverter DC input. It is equally applicable in combiner box assemblies, battery system disconnect applications, and any DC circuit requiring a lockable isolation point.
Switch Mechanism and Contact Design
The SISP40 operates as a rotary DC isolating switch — the handle turns to open and close the circuit. This rotary mechanism is a deliberate engineering choice for DC applications. Unlike toggle or push-button designs, a rotary isolator separates contacts with a physical arc-stretching motion that is controlled and repeatable.
Inside the switch, the contacts are silver-plated to industry-leading thickness standards. Silver plating directly reduces contact resistance at the point of connection. Lower contact resistance means less heat generated during continuous current flow. In turn, this extends the operational life of the switch and prevents the gradual thermal degradation that affects lower-quality contacts over time.
The SISP40 achieves an arcing time of approximately 2 milliseconds during disconnection. This is a critically short arc duration for a DC switch. Unlike AC circuits, which pass through a natural zero-crossing point 50 times per second and self-extinguish the arc, DC circuits sustain arcs until the contacts physically separate far enough to quench them. A 2 ms arc time reflects the speed and travel distance of the contact separation mechanism, and directly determines how long the switch and the connected system are exposed to potentially damaging arc energy.
Additionally, the switch is polarity-independent — it operates correctly regardless of which terminal the positive or negative conductor is connected to. This reduces wiring errors during installation.
4-Pole Configuration
The SISP40’s 4-pole layout is its most operationally significant feature for solar PV applications. In a standard solar DC circuit, two conductors carry current — a positive and a negative. A 4-pole switch, however, provides two poles per conductor, meaning it interrupts each of the two live conductors at two separate contact points simultaneously.
This double-break configuration produces two key safety outcomes:
- Doubled arc voltage withstand per pole — each pole only needs to withstand half the total circuit voltage during arc interruption, reducing stress on the contact mechanism
- Simultaneous complete isolation — all four poles open and close together via a single handle rotation, ensuring no conductor remains live after the operator turns the switch to OFF
As a result, the 4-pole design is considered standard for 1000 VDC solar applications and is explicitly referenced in IEC 60947-3, the standard the SISP40 is designed and certified to.
DIN Rail Mounting
The SISP40 is designed for 35 mm standard DIN rail mounting inside electrical enclosures. This distinguishes it from the enclosed SISO-40 variant, which is a wall-mounted standalone unit with its own IP66 housing. The SISP40 is intended for installation inside combiner boxes, distribution enclosures, or dedicated solar switchboards where the installer populates the enclosure with individual components.
DIN rail mounting provides several practical advantages:
- Compact footprint — components mount in a row on a single rail, minimising enclosure size
- No separate fasteners — the DIN clip secures the switch directly to the rail with a snap-fit
- Easy removal — the switch can be unclipped and replaced without disturbing adjacent components
- Modular pairing — the SISP40 can sit directly alongside Suntree DC MCBs, SPDs, and fuse holders on the same rail within an IP66 combiner enclosure
Safety Features
Beyond the core isolation function, the SISP40 incorporates several safety features directly relevant to solar installation practice in Kenya:
- Lockable in the OFF position — a padlock can be fitted through the handle boss when the switch is open. This implements Lock-Out/Tag-Out (LOTO) procedure, preventing the circuit from being accidentally re-energised while maintenance work is in progress on the connected array or inverter
- UV-resistant, V0 flame-retardant housing material — the switch body uses a V0-rated polymer, meaning the material self-extinguishes in under 10 seconds when exposed to flame. Suntree’s in-house testing confirms extinguishment in under 5 seconds — well below the IEC-mandated 10-second maximum
- Rational operational design — the handle mechanism physically prevents reverse or incorrect rotation, eliminating misoperation during emergency switching
- Earth terminal — an integrated earth terminal allows the enclosure earth conductor to be terminated directly at the switch body
Standards and Certifications
The Suntree SISP40 PV Disconnect is certified to:
- IEC/EN 60947-3 — Switches, disconnectors, switch-disconnectors, and fuse-combination units
- IEC/EN 60947-1 — General rules for low voltage switchgear
- AS/NZS 60947.3 — Australian and New Zealand equivalent standard
- DC-PV1 / DC-PV2 / DC-21B — DC switching duty categories under IEC 60947-3
- CE, CB, TUV, SAA, IEC — Multi-market international product certifications
