Combiner Box Supplier: How to Choose a Reliable Manufacturer

Introduction: When Your Supplier Becomes Your Biggest Project Risk

A utility-scale solar developer in Texas learned a costly lesson in 2023. Six months into a 50MW project, their combiner boxes started failing—fuses blowing prematurely, terminals overheating, and enclosure seals letting in moisture. The root cause? A supplier who claimed UL 1741 certification but couldn’t provide verification evidence, used non-PV-rated protective devices, and had no temperature-rise verification for the assembled configurations. The result: three-month project delay, $280,000 in replacement costs, and strained relationships with the EPC contractor and asset owner.

Choosing a combiner box supplier isn’t about finding the lowest bid. It’s a strategic decision that affects project timelines, long-term system reliability, warranty exposure, and ultimately your reputation in the market. A reliable manufacturer delivers consistent product quality, maintains proper certifications, and stands behind their equipment when issues arise. An unreliable one creates cascading problems that cost far more than any initial savings.

This guide provides a practical framework for evaluating combiner box suppliers based on four critical pillars: technical capability, quality systems, business stability, and service support. Whether you’re a procurement manager at a solar EPC, a system integrator sourcing components for commercial projects, or an engineering firm specifying equipment for utility-scale installations, these criteria will help you separate genuinely capable manufacturers from those who simply claim expertise.

Why Supplier Selection Matters: The Hidden Costs of the Wrong Choice

The immediate cost difference between suppliers often obscures the total cost of ownership. A combiner box priced 15% below market might seem attractive on a spreadsheet, but that advantage evaporates quickly when hidden costs emerge.

Field Failure Impact: When a combiner box fails in the field, you’re not just replacing a $2,000 component. You’re paying for technician dispatch, site access coordination, system downtime (lost production revenue), warranty administration, and potentially damaged customer relationships. A single failure can cost $5,000-$8,000 in total impact. If your supplier has a 2% field failure rate instead of 0.2%, that cost multiplies across hundreds of units.

Project Delay Risk: Construction schedules build in equipment lead times based on supplier commitments. When a manufacturer ships late, delivers wrong configurations, or fails pre-installation testing, your project schedule slips. In utility-scale solar, schedule delays often trigger liquidated damages clauses, interconnection deadline penalties, or lost tax credit value. A two-month supplier delay on a 100MW project can cost millions.

Engineering Rework: Suppliers who can’t provide proper documentation—complete wiring diagrams, verified thermal ratings, accurate protective device coordination data—force your engineering team into rework cycles. This consumes internal resources, delays Authority Having Jurisdiction (AHJ) approvals, and increases the risk of design errors that surface during commissioning.

Reputation and Liability: Your company’s name goes on the project nameplate, not your supplier’s. When combiner boxes fail due to poor manufacturing quality or inadequate environmental protection, the customer holds you responsible. Repeated quality issues damage your market reputation and can jeopardize future bids or long-term service contracts.

The best suppliers reduce total project risk and lifecycle cost. They deliver on time, meet specifications consistently, provide complete technical documentation, maintain valid certifications, and resolve issues quickly when they arise. That reliability justifies a modest price premium—and saves money over the project lifecycle.

The Four-Pillar Supplier Evaluation Framework

Evaluating a combiner box manufacturer requires looking beyond marketing claims and price quotes. A systematic assessment across four dimensions gives you a complete picture of supplier capability and risk:

1. Technical Capability: Can they design and manufacture combiner boxes that meet PV system requirements? This covers engineering competence, production capacity, testing infrastructure, and ability to customize for specific project needs.

2. Quality Systems: Do they have processes to ensure consistent product quality batch after batch? This includes quality management certifications, incoming inspection protocols, production testing procedures, and traceability systems.

3. Business Stability: Will they be around in five years to honor warranties and support installed equipment? This examines financial health, operational history, facility ownership, customer references, and market reputation.

4. Service & Support: How well do they support customers throughout the equipment lifecycle? This covers pre-sales technical support, documentation quality, lead time reliability, after-sales service, and responsiveness to issues.

Each pillar matters. A manufacturer with excellent technical capability but poor business stability creates supply chain risk. One with strong quality systems but weak service support leaves you stranded when problems arise. The sections below detail what to look for in each area and red flags that should trigger deeper scrutiny or disqualification.

Technical Capability: Can They Manufacture to Specification?

Technical capability determines whether a supplier can actually deliver what your project requires. This goes beyond having a combiner box in their catalog—it’s about engineering depth, manufacturing infrastructure, and proven ability to meet PV-specific requirements.

Design Engineering Competence

Reliable manufacturers employ electrical engineers who understand PV array behavior, DC circuit protection, and thermal management in outdoor enclosures. Ask these questions:

• Can they explain their busbar sizing methodology and current-carrying capacity calculations?
• Do they understand NEC Article 690 requirements for string overcurrent protection and equipment grounding?
• Can they provide IEC 61439-2 verification evidence showing temperature-rise verification for the rated current and enclosure configuration?
• How do they handle internal separation and isolation requirements per IEC 62548-1?

Suppliers who struggle to answer technical questions or rely on generic “industry standard” responses lack the engineering depth to support complex projects or troubleshoot field issues.

Standards Compliance and Testing Infrastructure

A capable manufacturer maintains in-house or contracted testing facilities to verify product performance. Essential testing capabilities include:

• Dielectric withstand testing: Verifies insulation integrity at rated system voltage (600V, 1000V, 1500V DC)
• Temperature rise testing: Confirms that busbars, terminals, and connections stay within thermal limits at rated current under worst-case conditions
• Short-circuit testing: Validates that protective devices interrupt fault currents safely without enclosure rupture
• Essais environnementaux: IP rating verification, UV exposure, thermal cycling, and corrosion resistance for outdoor applications

Request test reports for the specific combiner box model you’re evaluating, not just generic capability statements. If a supplier can’t produce model-specific test data or refers you to component-level certifications only, they haven’t validated the assembled product.

Production Capacity and Scalability

Understand the manufacturer’s production infrastructure:

• Annual capacity: Can they handle your projected volume without straining resources?
• Manufacturing processes: Automated busbar fabrication, CNC enclosure machining, and consistent assembly procedures indicate mature production capability
• Approvisionnement en composants: Do they manufacture key components in-house or rely on outside suppliers? Multi-supplier dependency increases lead time variability
• Scaling ability: If your first project succeeds and you triple your order, can they ramp up without quality degradation?

A supplier operating at 95% capacity with limited automation poses delivery risk. Look for manufacturers with headroom to absorb demand fluctuations and proven track records scaling production for large projects.

Customization Capability

Standard catalog products don’t always match project-specific requirements. Assess the supplier’s flexibility:

• Can they accommodate custom string counts, voltage ratings, or protective device configurations?
• Do they offer rapid shutdown integration, arc fault detection, or monitoring system interfaces?
• How do they handle special environmental requirements—salt fog resistance for coastal sites, extended temperature ranges for desert installations, or seismic certification for high-risk zones?
• What’s their engineering change process, and how do modifications affect lead times and certifications?

The best manufacturers balance standardization (for cost and reliability) with thoughtful customization for legitimate technical requirements. Be wary of suppliers who either refuse any customization or agree to everything without discussing certification implications.

Quality Systems: How They Ensure Consistency

A single prototype that passes testing doesn’t guarantee reliable production. Quality systems determine whether a manufacturer delivers the same performance in unit 1 and unit 1,000. Look for documented processes that catch defects before products ship.

ISO 9001 and Quality Management Certification

ISO 9001 certification indicates that a manufacturer has implemented documented quality management processes covering design control, document management, purchasing controls, production processes, inspection procedures, corrective action systems, and internal audits. While not a product safety standard, ISO 9001 certification provides confidence in organizational consistency.

Verify that the certification covers the manufacturing facility producing your combiner boxes, not just a corporate headquarters or different product line. Request a copy of the certificate and confirm it’s current—ISO 9001 certificates require annual surveillance audits and three-year recertification.

Incoming Inspection and Component Qualification

Combiner box quality depends on the components inside—busbars, terminals, fuses, circuit breakers, surge protective devices, enclosures, and cable glands. Ask about the supplier’s component qualification process:

• Do they maintain approved vendor lists for critical components?
• What incoming inspection procedures verify component specifications before assembly?
• How do they handle component substitutions when primary suppliers have shortages?
• Do they require protective devices (fuses, breakers) to carry appropriate UL certifications for DC PV applications?

Manufacturers who accept components from multiple unqualified sources or skip incoming inspection introduce quality variability that surfaces as field failures.

Production Testing and Quality Control

Every combiner box should undergo production testing before it leaves the factory. Standard production tests include:

• Tests de continuité: Verifies all electrical connections are complete and correct
• Essai de résistance d'isolation: Confirms adequate isolation between circuits and to ground
• Dielectric withstand testing: Tests insulation integrity at above-rated voltage
• Tests fonctionnels: Validates that protective devices operate correctly and monitoring systems (if present) communicate properly
• Inspection visuelle: Checks for proper assembly, labeling, torque marks on connections, and cosmetic defects

Request the production test protocol and typical test records. Manufacturers with mature quality systems provide complete test documentation with each shipment, including test results for the specific serial numbers delivered.

Traceability and Serial Number Control

Traceability allows you to track a specific combiner box back to its production date, component batch numbers, test results, and inspector. This matters when field issues arise—you can quickly identify whether a problem affects a specific production batch or requires a broader investigation.

Look for suppliers who:

• Apply unique serial numbers to each combiner box
• Maintain electronic or physical records linking serial numbers to production data
• Can provide “birth certificates” or quality records for specific units
• Track which revision of drawings, bill of materials, and test procedures applied to each production batch

Manufacturers without traceability systems can’t support effective root cause analysis or targeted corrective actions when problems occur.

Certifications That Matter: UL 1741, IEC 62548, and Beyond

Certifications provide independent verification that a product meets safety and performance standards. But not all certifications carry equal weight, and some manufacturers claim certifications that don’t actually cover their combiner box products. Here’s what to verify.

UL 1741: The Essential Combiner Box Standard

UL 1741 is the Standard for Inverters, Converters, Controllers and Interconnection System Equipment for Use with Distributed Energy Resources. UL’s Balance of System (BOS) certification program explicitly identifies UL 1741 as the applicable standard for combiner boxes in PV systems.

When a supplier claims UL 1741 certification:

• Request the UL certificate or listing mark authorization
• Verify the specific product model and configuration in the UL Product iQ database (UL’s public certification directory)
• Confirm that the voltage rating, current rating, and string count match your project requirements
• Check that the certification covers the intended application—residential, commercial, or utility-scale

UL 1741 certification includes ongoing factory surveillance inspections, which means UL auditors periodically visit the manufacturing facility to verify continued compliance. This surveillance requirement differentiates genuine UL certification from one-time test reports.

IEC 61439-2: Assembly Design and Verification

IEC 61439-2 specifies requirements for low-voltage switchgear and controlgear assemblies, including power switchgear assemblies up to 1,500V DC. The 2020 edition includes PV-specific annexes and temperature-rise verification methods critical for outdoor combiner box applications.

Key elements to verify:

• Temperature-rise verification: The supplier must demonstrate that the assembled combiner box operates within thermal limits at rated current under worst-case ambient conditions. This requires either type-testing of the specific configuration or validated calculation methods
• Tenue aux courts-circuits: The assembly must withstand specified short-circuit currents without hazardous failure
• Internal separation forms: How circuits are separated within the enclosure affects safety during maintenance
• PV annex application: For PV use, confirm the manufacturer applied PV-specific design considerations from the standard’s annexes

Request the IEC 61439-2 verification report for the specific combiner box configuration. Generic claims of IEC 61439-2 compliance without configuration-specific verification evidence suggest incomplete application of the standard.

IEC 62548-1: PV Array Design Requirements

IEC 62548-1 (Design requirements for photovoltaic (PV) arrays) establishes requirements for PV array wiring, protective devices, switching and isolation means, earthing provisions, and protection against electric shock. Combiner boxes must integrate these requirements:

• DC wiring practices: Cable sizing, routing, and connection methods appropriate for PV DC circuits
• Protective devices: Overcurrent protection (fuses or circuit breakers) rated for DC PV application, including appropriate interrupt capacity
• Isolation means: Disconnect switches or other devices to isolate the combiner box from energy sources during maintenance
• Earthing: Equipment grounding conductors and bonding provisions
• Protection contre les chocs: For arrays directly connected to batteries, additional protection measures including insulation monitoring or residual current detection

Ask how the supplier’s combiner box design addresses IEC 62548-1 requirements. Suppliers with deep PV expertise can map their design features directly to standard requirements; those unfamiliar with the standard may struggle to explain compliance.

Component-Level Certifications

Beyond the assembly-level standards, individual components within the combiner box should carry appropriate certifications:

• DC circuit breakers: UL 489B or IEC 60947-2 for DC applications at the rated voltage
• Disconnect switches: UL 98B or IEC 60947-3 for isolation function
• Fusibles: UL 2579 for PV fuses or IEC 60269 for general-purpose fuses rated for DC
• Dispositifs de protection contre les surtensions: UL 1449 Type 1 or Type 2, or IEC 61643-11 for DC SPDs
• Enceintes: UL 50/50E or IEC 60529 for IP rating and environmental protection

A combiner box can only be as reliable as its components. Verify that protective devices carry DC ratings and PV-appropriate certifications—AC-rated devices may fail catastrophically in DC circuits due to sustained arcing.

Certification Red Flags

• Unverifiable claims: Certificates that can’t be confirmed in public databases or lack certificate numbers
• Test reports instead of certifications: A one-time test report isn’t equivalent to certification with ongoing surveillance
• Wrong standard scope: Claiming IEC 60947-1 (general rules) without IEC 61439-2 (assembly requirements) or UL 1741 (BOS equipment)
• Component-only certifications: Certified components don’t automatically certify the assembled product
• Expired or suspended listings: Check that certifications are current and haven’t been suspended due to non-compliance

When in doubt, verify certifications directly with the certification body. UL Product iQ, for example, is publicly searchable and provides official confirmation of what’s actually certified.

Business Stability: Will They Be Here in Five Years?

Combiner boxes carry 10-year or longer warranties, and your installed base creates ongoing service and replacement parts obligations. A supplier who exits the market, gets acquired and discontinued, or files bankruptcy leaves you with unsupported equipment and unenforceable warranties.

Financial Health Indicators

While private companies don’t publish detailed financials, you can assess stability through proxy indicators:

• Years in business: Startups and companies with less than 5 years operating history carry higher risk. Look for established manufacturers with 10+ year track records
• Facility ownership: Companies that own their manufacturing facilities have more capital stability than those operating from short-term leased spaces
• Investment in infrastructure: Recent capital investments in production equipment, testing labs, or facility expansions signal confidence and commitment
• Payment terms: Suppliers demanding 100% prepayment or offering unusually aggressive payment terms may be managing cash flow problems

Customer References and Market Reputation

Talk to other customers who’ve worked with the supplier:

• Request reference contacts from projects similar in scale and complexity to yours
• Ask about on-time delivery performance, quality consistency, and how the supplier handled issues
• Check online reviews, industry forums, and solar trade organization discussions
• Inquire with industry colleagues about their experiences

A pattern of delivery delays, quality complaints, or poor responsiveness across multiple customers indicates systemic problems, not one-off issues.

Market Presence and Scale

Suppliers with established market presence have more to lose from reputation damage:

• What’s their annual production volume and installed base?
• Do they serve multiple market segments (residential, commercial, utility) or depend on a single niche?
• Have they supplied major EPC firms or large solar developers with good reputations?
• Do they participate in industry associations, trade shows, or technical working groups?

A diversified customer base and visible market presence suggest stability. Suppliers operating in secrecy or serving only a handful of customers pose concentration risk.

Service & Support: Partnership Beyond the Purchase Order

The relationship with your combiner box supplier extends well beyond the initial purchase. Technical support quality, documentation completeness, lead time reliability, and after-sales responsiveness all impact your total cost of ownership.

Pre-Sales Technical Support

Before you place an order, assess the supplier’s technical support capability:

• Do they assign knowledgeable application engineers who understand PV system design?
• Can they help with product selection, configuration, and integration questions?
• How quickly do they respond to technical inquiries?
• Do they provide design tools, selection guides, or reference documentation?

Suppliers with strong pre-sales support save you engineering time and reduce specification errors that cause rework later.

Documentation Quality

Complete, accurate documentation reduces installation time, supports AHJ approvals, and enables proper maintenance. Evaluate:

• Installation manuals: Step-by-step procedures with torque specifications, wire sizing tables, and grounding requirements
• Wiring diagrams: Single-line and three-line diagrams showing internal connections, terminal designations, and protective device locations
• Certification documentation: Copies of UL certificates, IEC test reports, and declaration of conformity
• Specification sheets: Detailed ratings, dimensions, environmental limits, and materials of construction
• O&M documentation: Maintenance schedules, inspection checklists, and troubleshooting guidance

Poor documentation forces installers to reverse-engineer connections in the field, increasing installation time and error risk.

Lead Time Reliability

Quoted lead times mean nothing if the supplier routinely misses them. During initial discussions:

• Ask about current lead times and backlog status
• Request on-time delivery metrics from recent projects
• Understand their communication process if delays occur
• Clarify whether lead times include transit or start when goods leave the factory

Building a two-week buffer into your schedule doesn’t help if the supplier ships two months late.

After-Sales Service

Problems occasionally arise even with quality products. Assess how the supplier handles post-delivery support:

• Warranty terms: What’s covered, for how long, and what process do you follow to make claims?
• Disponibilité du support technique: Can you reach engineers who can help troubleshoot field issues?
• Replacement parts: Are common components (fuses, terminals, SPDs) available as spares?
• Field service: Do they provide on-site support for complex troubleshooting or repairs?
• Return and repair process: How do you handle warranty returns, and what’s the typical turnaround?

A supplier who’s responsive during sales but disappears after payment creates ongoing operational headaches.

Red Flags: Warning Signs to Walk Away

Some supplier issues are deal-breakers that should disqualify a manufacturer from consideration, no matter how attractive their pricing. Watch for these red flags during evaluation:

Certification and Compliance Red Flags

• No UL 1741 or equivalent certification for combiner boxes intended for U.S. projects
• Inability to provide certificate numbers or verification in public databases like UL Product iQ
• Test reports presented as certifications without ongoing surveillance programs
• Certification for different products (claiming terminal block certification covers combiner boxes)
• Expired or suspended listings that haven’t been renewed
• Refusal to provide IEC 61439-2 verification evidence for the specific configuration
• AC-rated protective devices in DC applications without DC ratings

Technical and Quality Red Flags

• No temperature-rise verification for the combiner box assembly at rated current
• Generic “industry standard” responses to specific technical questions about their design
• Inability to explain protective device coordination or short-circuit withstand ratings
• Missing or incomplete wiring diagrams and technical documentation
• No production testing protocol or willingness to share test records
• Lack of traceability systems or serial number control
• Reluctance to factory visits or audits, especially with vague excuses

Business and Service Red Flags

• Inconsistent or evasive communication during the evaluation process
• Pressure tactics demanding immediate commitment without adequate evaluation time
• Extremely low pricing (30%+ below market) with no clear explanation
• Payment terms requiring 100% prepayment with no history together
• No customer references or refusal to provide reference contacts
• Negative pattern in online reviews or industry reputation
• Recent company formation (less than 3 years) without experienced team or facility
• Frequent model changes or discontinuations suggesting poor product planning

Supply Chain Red Flags

• Unclear manufacturing location or frequent facility changes
• Inability to commit to delivery schedules or vague lead times
• History of missed commitments reported by other customers
• No buffer stock or finished goods inventory suggesting hand-to-mouth operation
• Single-source dependencies for critical components without backup plans

One or two minor concerns might be manageable. But multiple red flags, especially across different categories, indicate fundamental problems that will likely cause issues during and after your project. In those cases, move on to suppliers with more solid foundations—the risk isn’t worth any potential cost savings.

Cost vs. Quality: Finding the Right Balance

The lowest-priced supplier rarely delivers the lowest total cost. But that doesn’t mean you should automatically choose the most expensive option either. Smart procurement balances upfront cost against lifecycle value.

Understanding the Price Spectrum

Combiner box pricing typically falls into three tiers:

Budget Tier (Lowest 20% of market): Often lacks proper certifications, uses questionable components, provides minimal documentation, and offers limited support. Upfront savings of 15-30% disappear quickly through field failures, project delays, and engineering rework. Appropriate only for very small projects where risk exposure is minimal.

Mid-Market Tier (Middle 60%): Offers proper certifications, adequate quality systems, reasonable documentation, and acceptable support. Most reliable manufacturers operate in this tier. Price differences within this range often reflect scale, efficiency, and business model rather than quality gaps.

Premium Tier (Top 20%): Includes manufacturers with exceptional engineering depth, advanced monitoring features, premium materials and finishes, white-glove service, or specialized certifications. The premium may be justified for mission-critical applications, harsh environments, or projects where downtime costs are extreme.

For most commercial and utility-scale projects, the mid-market tier offers the best value. You get certified, quality products with adequate support at fair pricing.

Total Cost of Ownership Calculation

Evaluate suppliers on total cost, not just unit price:

Upfront Costs:

• Purchase price per unit
• Freight and logistics
• Engineering review of documentation
• Pre-installation testing or sample verification

Project Execution Costs:

• Installation labor (affected by documentation quality)
• Project delays from late delivery or non-conforming product
• AHJ approval delays from inadequate documentation

Coûts du cycle de vie:

• Expected field failure rate × cost per field service event
• Warranty administration effort
• Replacement parts availability and cost
• Technical support quality (reduces troubleshooting time)

A combiner box that costs $2,000 instead of $1,700 but has one-tenth the field failure rate saves money over a 10-year project lifecycle.

Value Indicators Beyond Price

When comparing similar-priced suppliers, these factors add value without necessarily increasing cost:

• Complete, accurate documentation that reduces installation time
• Responsive technical support that answers questions quickly
• Lead time reliability that protects project schedules
• Flexible configuration options that fit your exact requirements
• Strong warranty terms backed by financial stability
• Availability of replacement parts and consumables

A slightly higher price from a supplier who delivers consistently on time, provides excellent documentation, and responds to issues quickly often costs less than a cheaper supplier who creates project friction.

How VIOX Electric Meets the Reliability Standard

At VIOX Electric, we’ve built our combiner box manufacturing around the four pillars that matter to solar system integrators and EPC contractors.

Technical Capability: Our engineering team specializes in DC power distribution and PV system protection. We maintain in-house testing facilities for dielectric withstand, temperature rise, and short-circuit verification. All VIOX combiner box designs undergo IEC 61439-2 verification with documented temperature-rise analysis for each configuration we offer.

Quality Systems: VIOX operates under ISO 9001:2015 certified quality management covering our complete manufacturing facility. Every combiner box undergoes 100% production testing—continuity, insulation resistance, dielectric withstand, and functional verification—before shipping. We maintain full traceability with serial number control and documented test records available for every unit.

Certifications: Our combiner boxes carry UL 1741 certification verified in the UL Product iQ database, with configurations available for 600V, 1000V, and 1500V DC systems. We use only UL-listed protective devices rated for DC PV applications—UL 489B circuit breakers, UL 2579 PV fuses, and UL 1449 surge protective devices. Our enclosures meet IP65/IP66 environmental protection standards per IEC 60529.

Service & Support: We provide complete technical documentation with every order—installation manuals, wiring diagrams, certification packages, and specification sheets. Our application engineers support product selection and system integration questions. Standard lead times are clearly communicated and monitored, with proactive updates if any issues arise. Our 10-year warranty is backed by our facility ownership and 15+ year operating history in electrical components manufacturing.

We understand that choosing a supplier is choosing a partner. VIOX delivers the consistency, documentation, and support that keep solar projects on schedule and systems operating reliably for decades.

Conclusion: Your Supplier Evaluation Checklist

Choosing a combiner box supplier is one of the most consequential decisions in solar project procurement. The right manufacturer becomes a reliable partner who supports project success through quality products, complete documentation, and responsive service. The wrong one creates cascading problems that cost far more than any initial savings.

Use this checklist when evaluating potential suppliers:

Technical Capability

• ☐ Engineering team can explain design methodology and thermal analysis
• ☐ In-house or contracted testing facilities for type testing
• ☐ Production capacity adequate for project volume
• ☐ Customization capability for project-specific requirements

Quality Systems

• ☐ ISO 9001 certification covering manufacturing facility
• ☐ Documented incoming inspection and component qualification
• ☐ 100% production testing protocol with test records
• ☐ Serial number control and traceability systems

Certifications

• ☐ UL 1741 certification verified in UL Product iQ database
• ☐ IEC 61439-2 verification evidence for specific configuration
• ☐ IEC 62548-1 compliance for PV array design requirements
• ☐ UL-listed DC-rated protective devices (breakers, fuses, SPDs)
• ☐ IP65/IP66 enclosure rating per IEC 60529

Business Stability

• ☐ 10+ years operating history in electrical manufacturing
• ☐ Facility ownership and infrastructure investment
• ☐ Customer references from similar project scale
• ☐ Positive market reputation and industry presence

Service & Support

• ☐ Responsive pre-sales technical support
• ☐ Complete documentation package (manuals, diagrams, certificates)
• ☐ Committed lead times with on-time delivery track record
• ☐ Clear warranty terms and after-sales support process

Red Flag Screening

• ☐ No certification, compliance, or technical red flags identified
• ☐ No business or service red flags identified
• ☐ No supply chain reliability concerns

A supplier who meets most of these criteria offers the foundation for a successful long-term partnership. Those who fall short in multiple areas—especially certifications, technical capability, or business stability—pose risks that typically outweigh any cost advantages.

Take the time to evaluate thoroughly. The supplier you choose today determines whether your combiner boxes operate reliably for the next 25 years or become recurring problems that damage your reputation and profitability.