A quotation that says “four-pole 1000 V DC solar isolator, 32 A, IP65” still leaves the most important purchase questions unanswered. The four poles may be arranged for one circuit or several circuits. The 32 A figure may apply at another voltage or utilization category. The switch may require a specific polarity or terminal sequence. IP65 may describe a complete factory enclosure, only the front of an open device, or a condition that depends on correctly fitted cable entries.
The fastest way to obtain comparable bids is to send a one-line circuit and an evidence matrix. State the maximum PV voltage and current conditions, grounding arrangement, number of independent circuits or MPPT inputs, required isolation points, intended load-breaking operation, conductor details, enclosure environment and applicable project rules. Require the supplier to map one exact manufacturer part number and wiring diagram to every input.
This guide does not select or approve a switch for a live project. The responsible electrical designer must apply the installation rules, product standard, inverter and module instructions, local requirements and expected fault conditions. The official IEC record for IEC 62548-1:2023, including its listed 2025 amendment places DC array wiring, electrical protection devices, switching and earthing provisions within PV array design. The official record for IEC 60364-7-712:2025 covers selection and application of equipment in PV electrical installations. Neither page certifies a quoted product.
Name the required function before naming a product
“Isolator” is often used commercially for several devices. In an RFQ, identify whether the project needs a switch, a disconnector, a switch-disconnector, a fuse-combination unit or another function. State whether the operator must open normal operating current, provide an isolation function for service, serve as an emergency control, or satisfy a particular inverter or installation requirement. One device can have more than one documented function, but the function must come from its exact technical record.
The current consolidated IEC 60947-3:2020 plus Amendment 1:2025 applies to switches, disconnectors, switch-disconnectors and fuse-combination units within its stated voltage scope, up to 1,000 V AC or 1,500 V DC. The official publication page says the fourth edition added critical-load-current tests for DC switches and conditional short-circuit-rating requirements for devices protected by circuit breakers. This scope and revision history explain useful evidence questions. They do not establish that an unnamed “solar isolator” complies, carries an isolation function or can break the project load.
Ask the bidder to state, for the offered part:
- manufacturer and complete order code;
- declared device function;
- applicable standard and edition in the supplied evidence;
- rated operational voltage and current at the exact utilization category;
- pole arrangement and manufacturer circuit or connection-diagram reference;
- permitted polarity, current direction and source/load terminal conditions;
- isolation and load-making/load-breaking characteristics claimed by the manufacturer;
- short-circuit withstand or conditional rating and required protective-device conditions;
- open-device or enclosed-device construction, with every required accessory.
Keep these rows separate. A product can have an adequate thermal current yet lack a declared operational current at the needed voltage and category. A switch can interrupt normal current yet not be the overcurrent protective device. A rotary handle can show OFF without establishing the isolation function or contact position required by the project.
Freeze the electrical operating envelope
Send the supplier a calculation sheet approved by the project engineer. It should include maximum open-circuit voltage at the minimum design temperature, maximum operating current, short-circuit current, possible reverse or backfeed current, number of paralleled strings, number of independent MPPT circuits, grounding arrangement and any source that can energize the device from either side. Identify whether the switch will be operated under current and how often.
Do not use module nominal voltage or inverter nominal DC voltage as the switch selection value. A cold array can have a higher open-circuit voltage than its STC value. The PV cold-weather Voc guide explains the data and calculation boundary. Put the resulting maximum voltage on the one-line diagram and require the bidder to show the exact product rating that covers it in the proposed topology.
Keep overcurrent protection separate. Parallel strings can create reverse-current conditions that affect conductors, fuses and switching duty. The PV string fuse guide covers the separate protection calculation. A switch-disconnector is not automatically a fuse or circuit breaker, and a normal-load rating is not an interrupting rating for every prospective fault.
Also identify energy on the inverter side. DC-link capacitance, another DC source, storage or an alternative converter architecture can affect the safe service procedure and the direction of possible current. Ask the inverter manufacturer and system designer to define the isolation scheme. Do not infer “source” and “load” solely from where the PV modules appear on a generic diagram.
Read utilization category together with voltage and current
A current number without its application category is incomplete. The category describes the switching use for which an operational rating is declared. The same device family can have different current values at DC-21A, DC-PV1 and DC-PV2. This makes category a commercial comparison field, not a footnote.
Eaton’s current official P-SOL/SOL brochure gives a concrete family-scoped example. For the two-pole P-SOL20 at 1,000 V DC, its table lists 20 A at DC-21A and DC-PV1 but 10 A at DC-PV2. P-SOL30 is listed at 26 A for DC-21A, 26 A with a conditional 30 A note for DC-PV1, and 10 A for DC-PV2. P-SOL60 is listed at 63 A in the three table rows. These values apply to the identified Eaton models and stated conditions; they are not generic derating ratios for other switches. Eaton P-SOL/SOL official brochure.
Eaton’s industrial-switchgear catalogue describes DC-PV1 as switching single PV string or strings without reverse and overcurrents, and DC-PV2 as switching several PV strings with reverse and overcurrents. Use that wording to understand the manufacturer’s selection tables, then have the designer apply the current IEC text and actual array architecture. Do not upgrade a DC-PV1 quotation to DC-PV2 by applying a personal margin. Eaton xEffect industrial switchgear catalogue.
Use one row per operating condition in the comparison:
On small screens, swipe or scroll sideways to read every column. Keyboard users can focus the table and use the arrow keys.
| Selection field | Buyer input | Supplier response required | Hold condition |
|---|---|---|---|
| Utilization category | Category selected from the actual PV circuit and governing design | Exact category printed in model technical data or scoped report | Only a generic “PV switch” statement |
| Operational voltage | Maximum design DC voltage, including cold-weather result | Rated operational voltage for the exact category and pole topology | Voltage taken from insulation rating or another wiring scheme |
| Operational current | Required design current and stated calculation basis | Rated operational current at that voltage and category | Catalogue headline current belongs to DC-21A or lower voltage |
| Reverse/overcurrent condition | Paralleled sources and possible backfeed identified | Manufacturer evidence covering the proposed condition | DC-PV1 offered where the design requires evidence for a different duty |
| Operating frequency and life | Expected switching sequence and service plan | Model-specific electrical/mechanical endurance and restrictions | Mechanical cycle figure presented as load-breaking endurance |
Do not confuse conventional free-air thermal current, rated insulation voltage or impulse withstand voltage with the operational voltage/current pair. For example, LOVATO Electric’s current page for the enclosed GAZ025DT2 lists 25 A conventional free-air thermal current and 1,500 V rated insulation voltage, while its DC-21A operational current is 16 A at 1,000 V. It lists DC-PV1 values at 600 and 800 V on that page, not a DC-PV1 value at 1,000 V. The page separately markets the exact product as a 16 A, 1,000 V enclosed PV switch-disconnector. A buyer should copy the applicable row, not combine the largest numbers from different rows. LOVATO GAZ025DT2 official product record.
Treat the pole diagram as part of the rating
Pole count does not fully describe the DC circuit. Two poles may switch positive and negative once each. Several poles may be connected in series within one polarity to achieve a particular voltage rating. Four or more poles may serve one circuit, two independent circuits, or a combined AC/DC arrangement. The only acceptable interpretation is the manufacturer’s diagram for the exact order code and rating row.
Put terminal numbers on the project one-line and ask the supplier to overlay its connection diagram. Show every factory link and every field link. Mark which contacts open each positive and negative conductor, which poles are series-connected, and whether circuits remain galvanically independent. Confirm conductor size, terminal type, stripping length, ferrule requirement, link orientation and torque from the model instructions.
The Socomec SIRCO MC PV 21PV4754 illustrates why the order code matters. Socomec’s official product page describes it as a four-pole, 40 A, 1,000 V DC photovoltaic load-break switch with 2P+2P- topology and says it is delivered without a handle. The associated manufacturer catalogue shows a single-PV-circuit connection for that reference. Nearby SIRCO MC PV references use different pole counts and arrangements, including products described as 3+3 or 4+4 poles for other circuits. A buyer cannot turn 21PV4754 into a two-MPPT switch merely because it has four physical poles. Socomec 21PV4754 product record; Socomec SIRCO MC PV IEC catalogue.
The LOVATO GAZ025DT2 provides a different model-scoped example. Its product record identifies two poles; its wiring diagram numbers one pole 1–2 and the other 3–4 and marks positive and negative paths. That drawing should travel with the exact quotation. It does not establish wiring for GAZ032DT3, GAZ040DT4 or another brand, and the polarity marks should not be converted into a claim about bidirectional operation without an explicit manufacturer statement.
The DC breaker pole-series guide addresses the same documentation discipline for circuit breakers. Do not transfer breaker diagrams or voltage-building assumptions into a switch-disconnector RFQ. The product types, tests and permitted connections must remain separate.
Distinguish polarity allocation, current direction and terminal side
Three questions often collapse into the phrase “non-polarized”:
- Which pole is assigned to positive and which to negative?
- Can current be interrupted safely in either direction under the declared rating?
- May the array and inverter be connected to either terminal side?
Ask all three. A manufacturer statement that no polarity is specified can be valuable, but it should be attached to the exact family, topology and instructions. It does not permit an undocumented series link or mixed circuit.
Eaton’s current P-SOL/SOL product page says no polarity is specified for those switch-disconnectors and describes their two-pole use in unearthed systems. The same page distinguishes the open P-SOL, intended for customer-specific enclosures or inverters, from the enclosed SOL. Apply that statement only to the identified Eaton products and current documentation. Eaton SOL/P-SOL product page.
Other manufacturers publish source/load or inverter/panel symbols on specific connection diagrams. Follow them unless the manufacturer documents alternatives. DC arc-control arrangements can depend on contact sequence, magnets, pole orientation or series connections that are not visible from the front. A symmetric-looking enclosure is not evidence that terminals are interchangeable.
If the project can reverse power flow, say so explicitly. Possible causes include multiple sources, storage, testing or an inverter architecture defined by its manufacturer. Request a written answer for the exact switch. The DC breaker polarity guide gives a useful terminology checklist, but breaker evidence still cannot certify a switch.
Define what “load break” means in the operating procedure
State the current the operator may interrupt, the expected voltage, the number of operations, ambient condition and circuit state. Identify whether switching is routine, occasional service isolation or emergency operation. Then ask the manufacturer to map that duty to its operational category and endurance data.
Do not use mechanical life as load-breaking life. The Eaton P-SOL table publishes both electrical and mechanical service information for its named models. The LOVATO page publishes a mechanical-life figure. These are useful only within each manufacturer’s definitions and test conditions. A high mechanical cycle number by itself does not show that the device can repeatedly interrupt the project’s DC load at maximum voltage.
Ask specifically about critical current. A DC switching device may face difficult interruption behavior at currents below its headline rated current. The IEC 60947-3 consolidated publication page identifies critical-load-current testing for DC switches as a change in the fourth edition. Request the exact model’s standard declaration and test-report scope where the project requires it. Do not invent a critical-current value or state that a product passed merely because its brochure cites IEC 60947-3.
Isolation and load breaking should appear as different acceptance rows. Require the manufacturer’s declared isolating characteristics, contact-position indication, handle behavior, padlocking provision and any door-interlock or defeater instructions. Then separately require the operational category and rated making/breaking evidence. A device with an OFF label is not automatically an isolation device; a load-break switch is not automatically suitable as the project’s lockout point.
Short-circuit conditions need another row. Ask for rated short-time withstand, making capacity or conditional rating as applicable, and name the upstream or downstream protective device required by the manufacturer. IEC’s current publication page highlights conditional short-circuit-rating requirements in the latest edition, but the project must still obtain the product-specific value and protection condition. Never present normal-load current as short-circuit interrupting capacity.
Select one circuit architecture before counting poles
Create a circuit schedule with one row per MPPT input or independent PV circuit. Record positive and negative conductor, maximum voltage, current condition, grounding arrangement and isolation requirement. If two inputs must remain independent, show that separation on both sides of the switch.
A four-pole device can fail the requirement in two opposite ways. It may use all four poles in series for a single high-voltage circuit, leaving no separate path for a second MPPT. Or it may be designed for multiple circuits at a lower voltage and lack the series topology used for the single-circuit rating. A supplier must return the exact diagram, not simply multiply or divide a pole count.
Do not perform your own “volts per pole” arithmetic. A 1,000 V four-pole rating does not mean every pole is a 250 V building block that can be rearranged freely. Contact timing, arc chambers, link arrangement, insulation and test circuit all belong to the documented topology. Likewise, placing contacts in parallel to gain current is not allowed without a manufacturer-rated diagram.
If an inverter has an integrated DC switch, ask whether the external device is still required by the applicable installation design, service access or local rule. Obtain the inverter maker’s switch scope and the system designer’s isolation plan. Do not add or delete an external switch on the strength of a sales description alone.
Integrate the open device and enclosure as one assembly
An open switch installed in a panel is not the same deliverable as a factory-enclosed isolator. The enclosure integration determines access, environmental protection, temperature, conductor routing, operating handle, shaft, interlock, glands, spacing and labels. Quote those parts and evidence as a controlled assembly.
Eaton explicitly describes P-SOL as an open switch-disconnector intended for customer-specific enclosures or inverters, with separate rotary handles and shaft extensions. It describes SOL as enclosed and pre-wired, with connector or metric-gland options and a stated IP65 enclosure in the official brochure. That distinction is a useful purchasing model: an open-device quote needs a panel-integration package, while an enclosed-device quote needs exact factory part identity and entry configuration. It does not make every SOL version suitable for every outdoor location.
The LOVATO GAZ025DT2 page identifies a specific 100 × 168 × 97 mm plastic enclosure with red/yellow handle, a two-pole switch, an IP65 degree of protection, M4 terminals, 1–10 mm² IEC conductor range and a 1.2–1.6 N·m terminal-torque range. Its drawing also identifies top and bottom knockouts. These figures belong to GAZ025DT2. If a bidder offers GAZ032DT3, GAZ040DT4 or a custom box, obtain that part’s own dimensions, entries, terminal data and ratings.
For every enclosure proposal, ask for:
- complete enclosure and internal-switch part numbers;
- enclosure material, dimensions, mounting orientation and environmental limits;
- ingress rating and the exact assembled configuration supporting it;
- cable-gland or connector make, model, thread and sealing range;
- number and location of entries, unused-opening plugs and drainage or pressure-equalization details;
- internal clearances, creepage, bend space, barriers and touch protection;
- switch power loss at the proposed current, enclosure temperature-rise evidence and any derating;
- handle, shaft, coupling, door interlock, padlocking and position-indication parts;
- terminal conductor type, size range, preparation, ferrule and torque;
- labels for PV DC voltage, circuit identity, polarity and isolation procedure as required by the project.
An IP code must be read with its tested configuration. Cutting a new hole, using the wrong cable diameter, omitting a plug or mounting an entry where water collects can change the finished protection. The IP67 versus IP68 guide explains how to request configuration-specific ingress evidence. It does not imply that IP67 or IP68 is required here; the project must define the correct enclosure condition.
Terminal and gland compatibility can also block assembly. Cable cross-sectional area does not determine outside diameter, and a conductor that fits electrically may not fit the terminal construction or gland. Use the cable conductor and terminal guide and the cable-gland sealing-range guide to define those separate interfaces.
Use a hypothetical screen without turning it into approval
Consider a hypothetical project, not a recommendation for any cited product. The approved electrical calculation gives 920 V maximum cold open-circuit voltage, 18 A required operational current, one floating PV circuit with both positive and negative conductors switched, and a condition involving paralleled strings for which the designer requires DC-PV2 evidence. The device will be in an outdoor enclosure.
Bid A states “25 A, 1,000 V PV isolator” but supplies only a DC-PV1 rating. Bid B offers an exact order code with 20 A at 1,000 V DC-PV2 in the manufacturer’s required two-conductor topology, plus the enclosure configuration and terminal schedule. Bid C offers a four-pole 32 A device but omits its wiring diagram and uses “four pole” as evidence for two independent circuits.
The first numerical screen for Bid B shows 80 V between its stated 1,000 V rating and the 920 V design maximum, and 2 A between 20 A and the 18 A requirement. Those subtractions are only a traceable comparison of supplied values. They do not establish adequate design margin, temperature performance, short-circuit behavior, isolation, code compliance or product approval. The engineer must confirm the required factors, manufacturer conditions and full design.
Bid A remains on hold because its category does not answer the stated duty. Bid C remains on hold because pole count cannot establish circuit topology. Bid B has the strongest paper response but still requires verification of model documents, polarity/direction, protective-device coordination, enclosure details and project rules.
For a second hypothetical topology check, suppose the inverter has two independent MPPT inputs that must remain isolated from each other. A four-pole switch wired as two series contacts in positive and two in negative for one circuit does not meet that architecture. A device with four poles assigned to two separate two-pole circuits might, but only if its exact model rating and diagram cover both circuits at their actual voltage and category. No amount of relabeling changes the manufacturer’s tested connection.
Compare quotations with a release table
On small screens, swipe or scroll sideways to read every column. Keyboard users can focus the table and use the arrow keys.
| RFQ decision | Evidence to request | Release condition | Reason to hold |
|---|---|---|---|
| Product identity | Manufacturer, full order code, revision and country/market variant | All returned documents refer to the same offered model | Family brochure only or altered suffix |
| Function | Declared switch/disconnector/switch-disconnector function | Function matches the approved operating and isolation plan | “Isolator” used without a technical declaration |
| Rating | Ue and Ie at exact category, topology and ambient conditions | Values cover the engineer’s requirements under documented conditions | Thermal current, Ui or another category substituted |
| Pole circuit | Manufacturer terminal and link diagram mapped to project one-line | Every conductor and MPPT remains in the intended circuit | Pole count offered without wiring evidence |
| Polarity/direction | Explicit manufacturer statements and terminal assignment | Proposed source/load and current directions are documented | Symmetry or a product photo used as proof |
| Load breaking | Category, endurance and critical-current evidence as required | Intended switching operation lies within exact model evidence | Mechanical life or OFF marking used alone |
| Short-circuit condition | Icw/Icm or conditional rating and specified protective device | Coordination is accepted by the responsible designer | Normal current mistaken for fault capability |
| Enclosure | Complete BOM, IP configuration, thermal, gland, spacing and handle evidence | Final assembly matches documented condition | IP claim belongs only to a component/front face |
| Production control | Sample, markings, test/inspection plan and change notice | Delivered item remains traceable to approved configuration | Silent substitution of switch, links, glands or enclosure |
Score missing evidence as unresolved rather than zero risk. Ask each bidder to cite the manufacturer document, page and table row. If a claimed certificate or declaration is important to the project, verify its exact legal entity, product codes, standard edition, scope and validity with the issuing source. A standards list on a product page is useful evidence, but it is not permission to infer every rating or market approval.
Build the purchase and verification sequence
1. Issue the one-line and duty schedule
Show array strings, combiners, fuses, inverter inputs, grounding arrangement, all possible sources and the proposed isolation boundary. Add maximum voltage/current conditions and required utilization category. Identify who operates the device and in what state.
2. Require a model-specific submittal
Ask for the product datasheet, installation instructions, connection diagram, declaration or certificate where required, dimensional drawing, enclosure details, accessory list and current revision. The supplier should highlight the exact rating row and diagram, not return an unmarked catalogue.
3. Approve a controlled configuration
Create one BOM for switch, links, terminals, handle, shaft, coupling, auxiliary contacts, enclosure, glands/connectors, plugs, labels and mounting hardware. Record any parts delivered separately. The Socomec 21PV4754 page, for example, says the switch is delivered without a handle; the RFQ must add the selected compatible operating part rather than discovering the omission during assembly.
4. Inspect a representative assembly
With safe, qualified procedures, verify model markings, terminal numbering, link placement, handle operation, conductor/gland fit, bend clearance, door or cover closure, labels and the specified torque process. This dimensional and assembly check does not create a load-breaking rating or prove compliance. Electrical testing, if required, must follow the applicable product/end-equipment procedure with defined equipment and acceptance criteria.
5. Control routine production and changes
At receipt or production, verify order code, rating label, pole/link configuration, enclosure and entry parts. Record torque or assembly checks under the agreed plan. Require advance notice before changing the internal switch, magnet/contact construction, links, terminal material, handle, enclosure, seal, gland, wiring or label. Decide which technical evidence must be reviewed again before accepting the change.
Send a complete PV DC isolator RFQ
Provide the approved one-line, maximum cold Voc, current and reverse-current conditions, utilization category, MPPT/circuit count, grounding arrangement, operation and isolation sequence, protective-device coordination inputs, conductor schedule, enclosure environment, applicable market rules and evidence matrix. Ask for exact model ratings and wiring diagrams, full enclosure BOM, sample terms, price, MOQ, lead time and deviations. Certification, stock, production capability, price, MOQ and lead time need written supplier confirmation for the exact order code; this article makes no such claim for SINAWATTS.
Buyer FAQ
Is a 32 A marking enough for an 18 A PV circuit?
No. Confirm what the 32 A represents and find the rated operational current at the required voltage, utilization category, topology and ambient condition. Thermal current or a rating at DC-21A, DC-PV1 or a lower voltage cannot be silently substituted for the required row.
Does four-pole mean the switch can isolate two MPPT inputs?
Not necessarily. Four poles may be series-connected for one positive/negative circuit or arranged for several circuits. Obtain the exact model’s connection diagram and ensure the rated topology preserves the required independence between MPPT inputs.
Can we reverse the array and inverter terminals on a DC switch?
Only when the manufacturer documents that connection for the exact model and rating. Ask separately about polarity allocation, current direction and source/load terminal side. A symmetric case or generic “non-polarized” description from another family is not sufficient.
Does DC-PV2 always have the same ampere rating as DC-PV1?
No. Eaton’s cited P-SOL table shows model-specific examples where the values differ and another where they are equal. Read the exact voltage/category row for the offered part. Do not create a generic conversion factor from those examples.
Does an IP65 enclosure make the isolator suitable for every outdoor location?
No. Verify the complete installed configuration, mounting, temperature, UV/corrosion exposure, cable entries, plugs, drainage and local rules. The IP evidence applies to its tested arrangement. Outdoor suitability and placement can include conditions beyond the IP code.
Is a switch-disconnector also the string overcurrent protective device?
Not automatically. Switching, isolation and overcurrent protection are separate functions. If a device integrates fuses or protection, obtain the exact combined-device ratings and fuse information. Otherwise coordinate separate protection through the approved system design.
What evidence is needed for load breaking at low current?
State the full operating duty and request the exact model’s IEC 60947-3 declaration and relevant critical-load-current test scope when required. The current IEC publication page says critical-load-current tests were added for DC switches, but only model-specific manufacturer or certification evidence can show what the offered product covers.
When should the isolator selection be reviewed again?
Review it after changes to string length, module, minimum temperature, parallel-string count, inverter or MPPT architecture, grounding, conductor, utilization category, protective device, pole wiring, switch order code, enclosure, gland or operating procedure. Each change can affect a different evidence row even if the front label still shows the same voltage and current.