A DC circuit breaker should be selected from the actual DC voltage, continuous current, prospective fault level, pole and polarity requirements, and the system’s isolation arrangement. For solar strings, batteries, and DC distribution, the selected model must be rated for the circuit rather than assumed equivalent to an AC breaker.
This checklist helps solar EPC teams, panel builders, and OEM buyers prepare a usable RFQ. Start with the CHAC DC circuit-breaker category and use the final model documentation to confirm ratings and installation instructions.
Part 1. What does a DC circuit breaker do in a solar or DC system?
A DC circuit breaker protects a DC branch against overload and fault conditions within its declared ratings and can provide an operational switching function where the selected device is designed for it. It belongs in a wider protection architecture that may also include fuses, surge protection, disconnectors, contactors, and monitoring.
| System area | Typical concern | Selection input |
|---|---|---|
| PV string or combiner | DC voltage and reverse-current conditions | Maximum system voltage and string architecture |
| Battery branch | Continuous current and available fault energy | Battery data and protection study |
| DC control circuit | Low current with frequent switching | Voltage, load type, wiring method |
| DC distribution output | Selectivity with downstream equipment | Fault level and coordination plan |
IEC 60947-2 provides the general circuit-breaker framework. The project engineer must still determine whether a breaker, fuse, disconnector, or combination is appropriate for each location.
Part 2. Which voltage, current, and fault inputs must be confirmed first?
The voltage value should be the maximum DC voltage that can appear at the breaker terminals, including the project conditions that affect it. Current should be based on the design operating current and the applicable engineering margin, not only on a module or battery label.
| RFQ input | Why it matters | Do not assume |
|---|---|---|
| Maximum DC voltage | Determines voltage class | AC voltage rating applies to DC |
| Continuous current | Determines thermal loading | Nameplate current alone covers all duty |
| Prospective fault current | Determines interrupting-duty review | All DC sources have the same fault behavior |
| Pole count | Defines circuit opening arrangement | One pole is always sufficient |
| Grounding scheme | Affects architecture and protection review | PV and battery schemes are identical |
| Enclosure and ambient | Affects installation conditions | Indoor catalog conditions apply outdoors |
Record these inputs before requesting a quote. If the source is a PV array, battery, rectifier, or DC bus, identify it explicitly because fault behavior and operating patterns differ.
Part 3. Why can’t buyers assume an AC breaker is suitable for a DC circuit?
DC interruption has no natural current zero crossing in the way an AC waveform does. A device intended for a DC circuit therefore needs a published DC switching and interruption capability for the project conditions.
| Check | DC-specific question |
|---|---|
| Voltage rating | Is the model explicitly rated for the maximum DC voltage? |
| Pole arrangement | Does the model documentation require poles in series for this voltage? |
| Polarity | Are terminal markings or wiring directions specified? |
| Interrupting duty | Is the declared DC fault capacity suitable for the project study? |
| Load type | Is the circuit PV, battery, control, or another DC source? |
Do not select from an AC MCB label alone. Review the data sheet and installation manual for the exact model and wiring arrangement.
Part 4. How do poles, polarity, and isolator requirements affect selection?
Pole count is an engineering decision that follows the circuit topology, required disconnection, and the selected breaker instructions. Some DC designs use more than one pole to achieve a particular voltage or opening arrangement; the model documentation controls the permitted configuration.
| Device role | Primary purpose | Selection boundary |
|---|---|---|
| DC circuit breaker | Overload and fault protection within rating | Must be specified for DC duty |
| Isolator / disconnector | Isolation for maintenance when applicable | Does not automatically provide protective interruption |
| Fuse | Current-limiting protection in defined applications | Requires coordinated holder and replacement process |
| DC contactor | Remote switching in control architecture | Does not replace upstream fault protection by itself |
IEC 60947-3 distinguishes switching and disconnecting roles. Ask the project engineer whether visible isolation, lockout provisions, or a separate maintenance disconnector is required instead of treating every breaker as an interchangeable isolator.
Part 5. What should solar and battery-system RFQs include?
An RFQ should make the circuit condition reviewable by both the panel engineer and the product manufacturer.
Minimum DC breaker RFQ checklist
- Source type: PV string, battery, rectifier, control supply, or DC distribution bus.
- Maximum DC voltage and normal operating current.
- Prospective fault current or the protection-study reference.
- Required pole count, grounding scheme, and proposed wiring direction.
- Installation location, enclosure, ambient conditions, and altitude if relevant.
- Required isolation, locking, accessory, labeling, and target-market documentation.
For product-line orientation, see terminal electrical appliances. For customization requests, include the requested branding and packaging alongside the circuit inputs at terminal electrical customization.
Part 6. Which CHAC routes support DC circuit-breaker programs?
Product recommendation
CHAC publishes several DC circuit-breaker routes. Use the listed products as a starting point after completing the RFQ checklist, then validate the exact product data against the circuit.
| Buyer route | CHAC starting point | RFQ focus |
|---|---|---|
| DC miniature breaker evaluation | PXB6HDC-63 DC miniature circuit breaker | Voltage, poles, polarity instructions |
| Alternative DC MCB route | PXB6DC-63 DC miniature circuit breaker | Product data and installation arrangement |
| DC breaker program | CQB7DC-63 series DC miniature circuit breakers | Source type and accessory needs |
| OEM/ODM program | Terminal electrical products customization | Branding, packaging, regional documentation |
Submit maximum voltage, current, pole arrangement, fault-duty requirement, and target market through Contact CHAC Electric to route the inquiry correctly.
Part 7. What are the fit boundaries for this checklist?
This article is a procurement and pre-selection checklist for low-voltage DC breaker routes. It does not replace:
- Project short-circuit and selectivity calculations
- PV or battery design approval
- Live work, commissioning, or wiring instructions
- Medium-voltage protection selection
- Compliance approval for a specific country or installation
When maximum voltage, fault level, or model-specific polarity data is missing, do not freeze the breaker selection. Request the project engineer and product documentation to review the final circuit.
FAQ
What is a DC circuit breaker?
A DC circuit breaker is a protective switching device selected for a DC circuit within its declared voltage, current, and interrupting-duty ratings. It is used as part of a coordinated DC protection architecture.
Can an AC breaker be used for DC?
Not by assumption. The selected device must have a published DC rating and approved wiring arrangement for the actual circuit. Check the exact model data sheet and manual.
How do I size a solar DC breaker?
Start with maximum DC voltage, operating current, prospective fault current, poles, grounding scheme, and installation environment. Then select a model whose published DC ratings and instructions match those inputs.
What data should be included in a DC breaker RFQ?
Provide source type, maximum voltage, operating current, fault-duty requirement, pole arrangement, enclosure conditions, isolation requirement, target market, and OEM labeling needs.
Does a DC circuit breaker replace an isolator?
Not automatically. A breaker provides protection within its rating; a disconnector or isolator serves an isolation function. The system design and the selected device documentation determine whether separate isolation is required.
Why do polarity and pole count matter in DC circuits?
Some DC breaker designs specify terminal polarity or use a defined pole arrangement to achieve their stated DC duty. Follow the exact model’s wiring instructions rather than generalizing from another breaker.
