Key Takeaway
A DC disconnect switch is a mandatory safety device in any photovoltaic installation: it electrically isolates the solar panels from the rest of the circuit for maintenance or emergency interventions. Selection is based on 5 criteria: DC rated voltage (matched to the maximum string voltage), rated current (≥ Isc × 1.25), DC load-breaking capacity, IP protection rating (outdoor = IP65 minimum) and compliance with UTE C 15-712-1 and IEC 60947-3. Optim-Elec supplies Telergon DC disconnect switches suitable for all photovoltaic configurations.
Role of the DC Disconnect Switch in a Photovoltaic Installation
The DC (direct current) disconnect switch is a mandatory safety component in any photovoltaic installation. It fulfills two essential functions:
- Electrical isolation: it physically disconnects the solar panels from the inverter, allowing safe work on any component of the DC circuit.
- Load-breaking: unlike a simple isolator, a disconnect switch can break the current under load (energized and flowing) without the risk of a destructive arc flash.
Where to Install the DC Disconnect Switch
The UTE C 15-712-1 standard requires disconnect switches at two locations in a photovoltaic installation:
1DC Side (Between Panels and Inverter)
Installed in the DC protection enclosure (also called junction box or string combiner box), located between the solar panels and the inverter. It allows the DC supply to be disconnected before the inverter for maintenance, inverter replacement, or emergencies (fire, firefighter intervention).
2AC Side (Between Inverter and Grid)
An AC disconnect switch is installed downstream of the inverter to isolate PV production from the grid. This can be a standard AC disconnect switch.
⚠️ Safety Reminder
Before any work on the DC circuit of a PV installation, open the DC disconnect switch and verify the absence of voltage at the terminals with a DC-rated multimeter. Warning: even with the switch open, cables on the panel side remain energized as long as the panels are exposed to light.
5 Selection Criteria for a PV DC Disconnect Switch
1DC Rated Voltage
The disconnect switch must be rated for the maximum open-circuit voltage (Voc) of the panel string at the site's minimum temperature (Voc increases as temperature decreases). Common configurations are:
- 2 × 800 V DC: standard for residential and small commercial installations.
- 1,200 V DC: for longer strings (industrial installations or ground-mounted systems).
- 1,500 V DC: for large-scale PV plants (increasingly common IEC standard).
2Rated Current
The current rating must be ≥ Isc × 1.25 (string short-circuit current × 25% safety factor). For multi-string installations, account for the total current of all strings connected in parallel. Common ratings are 16 A, 25 A, 32 A and 63 A.
3DC Load-Breaking Capacity
Breaking a DC circuit is more difficult than breaking an AC circuit because direct current does not naturally pass through zero. The disconnect switch must be specifically designed and certified for DC breaking (category DC-PV1 or DC-PV2 per IEC 60947-3). An AC switch must never be used on a DC circuit.
4IP Protection Rating and Environment
The installation environment determines the required IP rating:
- IP20: indoor cabinet or enclosure mounting.
- IP65 minimum: outdoor mounting (weather and dust resistance).
Also consider the operating temperature range, especially in regions with wide temperature variations.
5Mounting Type and Accessories
Several mounting options exist depending on installation constraints:
- DIN rail with direct handle: quick enclosure mounting, minimal footprint.
- Door mounting with external handle: operation from outside the cabinet without opening the door.
- Lockable plastic enclosure: all-in-one solution for outdoor wall mounting with lockout capability (padlock).
Standards and Certifications
| Standard | Scope | Key Requirement |
|---|---|---|
| UTE C 15-712-1 | Grid-connected PV installations | Mandatory DC disconnect between panels and inverter |
| UTE C 15-712-2 | Standalone PV installations (off-grid) | DC-side and battery-side disconnection |
| IEC 60947-3 | Disconnect switches | DC-PV1 and DC-PV2 categories for PV use |
| IEC 62548 | PV installation design | DC sizing and protection requirements |
| NF C 15-100 | LV electrical installations | General protection and disconnection rules |
The Telergon F1 Range for Photovoltaics
Optim-Elec distributes DC disconnect switches from the Telergon F1 range, specifically designed for photovoltaic installations:
| Reference | Voltage | Current | Poles | Mounting |
|---|---|---|---|---|
| F1-00324P1DB | 2 × 800 V DC | 32 A | 4P | DIN rail — direct handle |
| F1-00324P3DC | 2 × 800 V DC | 32 A | 4P | Door mounting — external handle |
| F1-00324B3EP | 1,200 V DC | 32 A | 4P | Lockable plastic enclosure |
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Frequently Asked Questions — PV DC Disconnect Switch
Need help choosing your PV DC disconnect switch?
Our technical team supports you in sizing and selecting the right disconnect switch for your solar installation.
Contact our technical teamBy phone: 01 43 44 60 00 · By email: [email protected]
Key Takeaways
- A DC disconnect switch is mandatory in every PV installation — panels produce current as soon as they are illuminated.
- Install on the DC side (between panels and inverter) and a second on the AC side (between inverter and grid).
- Never use an AC switch on a DC circuit — risk of arc flash and fire.
- Size the voltage for the maximum Voc of the string at minimum temperature.
- Size the current at ≥ Isc × 1.25 — add Isc values for multi-string configurations.
- Choose the IP rating based on the environment: IP65 minimum outdoors.
- Optim-Elec supplies the Telergon F1 range in DIN rail, door mount, or lockable enclosure options.
