A solar DC disconnect — also called a DC isolator switch — is the device that safely cuts the direct-current side of a PV array for maintenance or an emergency. The two names describe the same job: a switch rated to break DC under load without sustaining a dangerous arc.
This guide covers what the switch does, how to size it by voltage, current, poles, IP rating and certification, and what to confirm when sourcing DC isolators and disconnects at project or distributor volume.
DC isolator vs DC disconnect — same device, different name
Across markets the terms are used interchangeably: "DC isolator" (AU / UK / EU) and "DC disconnect" (US) both mean a load-break switch on the DC side of the system. What matters is that it is a TRUE DC-rated switch — an AC switch of the same current rating is not interchangeable, because DC does not cross zero and the arc does not self-extinguish.
Why DC needs a special switch (the arc)
Alternating current naturally passes through zero 100–120 times a second, which helps an arc self-extinguish when a switch opens. Direct current is a continuous stream, so opening a live DC circuit creates a sustained arc that can damage equipment or start a fire. A true DC isolator uses arc-extinguishing contacts (often a magnetic blow-out) to break the arc in milliseconds — this is exactly why an AC switch cannot be substituted.
How to size a solar DC disconnect / isolator
Match four ratings to your array, then add the enclosure and certification your destination market requires.
- Voltage class: above the array maximum open-circuit voltage — commonly 600V, 1000V or 1500V DC
- Current rating: at least 1.25 × string Isc, checked per switched circuit (e.g. a 20A string pairs with a 25–32A switch)
- Utilisation category: DC-21B or the PV-specific DC-PV2 to IEC 60947-3
- Pole configuration: enough poles to break both the positive and negative of each string (a 2-string array often uses a 4-pole switch)
- Enclosure: IP66 / IP67 for outdoor rooftop use; lockable handle where lock-off is required
- Certification: the destination-market evidence (UL in the US, IEC 60947-3 internationally)
Where isolators are required — and where rules changed
Australia: AS/NZS 5033:2021 removed the blanket rooftop-isolator mandate, but a load-breaking PV array DC isolator at the inverter is still required, and many networks, insurers and EPC specs still include rooftop units. Isolators must carry RCM marking and AS 60947.3 compliance.
EU: IEC 60364-7-712 requires a DC disconnector that maintenance staff can reach. Most inverters have a built-in DC switch, so an external isolator is added where the inverter is far from the array or local rules ask for a separate device.
USA: NEC uses a different approach — rapid shutdown (NEC 690.12) plus a DC disconnect at the inverter. Australian-style rooftop isolators are not the norm, so confirm the design before copying a spec across markets.
What to put in the RFQ
State the DC voltage class, number of poles and how they are linked, rated current per circuit at DC-21B or DC-PV2, IP rating and enclosure material, glands (plate or pre-fitted), mounting style, certificates (IEC 60947-3 CB report, AS 60947.3 + RCM, TÜV or UL) and destination country. Ask for the derating at 60°C ambient — rooftop enclosures run hot, and the 40°C catalogue rating is not the operating rating.
Sourcing DC isolators and disconnects in bulk
For project and distributor volumes, confirm the certificate set and a sample before the order. A DC isolator is a high-failure-cost item if the arc rating or IP is wrong, so the evidence matters more than the unit price.
- True DC rating confirmed (not an AC switch relabelled)
- Voltage / current / pole rating matched to your array
- IP rating and lockable handle as required
- Certificate to IEC 60947-3 / UL with a verifiable number
- MC4 or terminal connection, and the enclosure / knockout layout
DC isolator / disconnect selection by system
| System | Voltage class | Typical switch | Notes |
|---|---|---|---|
| Residential / RV string | 600–1000V DC | 2–4 pole, 25–32A, IP66 | Lockable handle; one switch per array |
| Small C&I rooftop | 1000V DC | 4 pole, 32–63A, IP66 | Often at the combiner input; per-string isolation |
| Utility / large C&I | 1500V DC | Enclosed 63–250A+, IP66 | Higher breaking capacity; integrate with the combiner box |
OmniSol supplies DC isolators and disconnects rated to your array voltage and current from audited partner factories, with the IEC / UL certificate and a sample confirmed at the RFQ stage.
Procurement decision table
| Decision area | Buyer question | Procurement check | Risk control |
|---|---|---|---|
| Product scope | Which product families does this cover? | DC Isolator Switches, DC Protection (all), DC Circuit Breakers for Solar | Substituting an AC switch on the DC side |
| Specification input | What must be stated before comparing quotes? | Array max voltage (600 / 1000 / 1500V DC) | Use the same specification wording across supplier quotes. |
| Commercial input | What makes the quote operationally useful? | String operating current and switch rating | Tie quantity, packing and destination to the same RFQ line. |
| Quality gate | What should be checked before shipment? | DC Protection Selection Guide | Under-rating the voltage class for the array |
BOM and RFQ context
DC Isolator Switch for Solar: What It Does & How to Size It is most useful when it is read as a sourcing decision, not only an informational article. The affected product scope normally includes DC Isolator Switches, DC Protection (all), DC Circuit Breakers for Solar, DC SPD for Solar. A buyer should connect the answer to a live BOM, because cable size, connector rating, protection device choice, box configuration, storage accessories and export packing can change together.
For a procurement guide, the goal is to turn a broad buying question into a repeatable RFQ structure. The buyer should leave with the required product family, specification fields, quality checks and internal links needed to continue into the central products hub. In an RFQ, the minimum inputs should include Array max voltage (600 / 1000 / 1500V DC), String operating current and switch rating, Pole count (break + and − of each string), IP rating and lockable handle. These inputs let a sourcing team compare suppliers on the same basis instead of only comparing unit price.
The related follow-up content is DC Protection Selection Guide, DC MCB vs DC MCCB. Use those pages to validate standards, sizing, inspection and packing before sending a final quote request. The main risk to avoid is: Substituting an AC switch on the DC side Under-rating the voltage class for the array
FAQ
Do I need a DC isolator switch for a solar system?
In most markets yes — a DC isolator (DC disconnect) is required, and often mandated by code, so the DC side can be safely de-energised for maintenance or an emergency. Even where it is optional, it is strongly recommended because the DC side cannot otherwise be safely broken under load.
What is the difference between a DC isolator and a DC disconnect?
They are the same device — "DC isolator" is the AU / UK / EU term and "DC disconnect" is the US term for a load-break switch on the DC side of a PV system. Both must be true DC-rated with arc suppression; an AC switch of the same current is not a valid substitute.
How do I size a solar DC disconnect switch?
Choose a voltage class above your array open-circuit voltage (600V, 1000V or 1500V DC), a current rating above the string operating current (e.g. 32A for a 20A string), enough poles to break the positive and negative of each string, an IP66 / IP67 enclosure for outdoor use, and the certification your market requires (UL in the US, IEC 60947-3 internationally).
Are rooftop DC isolators still required in Australia?
AS/NZS 5033:2021 removed the mandatory rooftop (array-adjacent) isolator, but a load-breaking DC isolator at the inverter is still required, and many networks, insurers and EPC specifications still include rooftop units. If rooftop units are in the spec, insist on IP66 with properly fitted glands.
What is the difference between a DC isolator and a circuit breaker?
An isolator gives a visible, lockable break for safe maintenance and is operated by hand; it does not trip on a fault. A DC breaker adds automatic overcurrent protection. Many PV designs use fuses in the combiner box for overcurrent protection and an isolator for disconnection.
Can I use an AC isolator on the DC side of solar?
No. DC does not cross zero, so an AC switch will not extinguish the arc when it opens a live DC circuit, creating a fire risk. Use a switch specifically rated as a true DC isolator / disconnect with arc-suppression contacts.
Can I source DC isolators in bulk from China?
Yes. For project or distributor volumes, confirm the true DC rating, the voltage / current / pole match to your array, the IP rating, and an IEC 60947-3 or UL certificate with a verifiable number, and request a sample before the bulk order. OmniSol consolidates DC isolators with the rest of the DC protection BOM from audited partner factories into one shipment.