Questions engineers actually ask
Certification, sizing, specification and ordering — answered with the same figures our engineering team quotes from.
Certification & compliance
- Are Rionex transformers UL listed?
- Yes, on three of the four product lines. Liquid-filled padmount transformers are UL Listed under file E526441. General-purpose dry-type units are UL Listed under file E539752 (UL 1561), and medium-voltage dry-type distribution units are UL Certified under file E545481 (UL 1562). Insulation systems are UL-Recognized under file E538000. Substation transformers and power-quality equipment are built to IEEE C57 or IEC standards and carry no UL file.
- How do I verify your UL certification?
- Search the file number on UL Product iQ at iq.ulprospector.com — E526441, E539752, E545481 or E538000. Each returns the certification scope and the holder. Certificate of Compliance PDFs are also downloadable directly from the certifications page, and a copy ships with every order for your submittal package.
- What is the difference between UL 1561 and UL 1562?
- UL 1561 covers general-purpose dry-type transformers, typically low-voltage distribution units in indoor electrical rooms. UL 1562 covers medium-voltage dry-type distribution transformers, where the primary is above 600 V. Rionex holds file E539752 for the UL 1561 line and file E545481 for the UL 1562 line, with primaries from 3.5 to 6.9 kV.
- Do you cover Canada?
- Yes. Padmount transformers carry CSA C227.4 and dry-type units carry CSA C22.2 No. 47. The same UL files list both US Listing and Canadian Certification, so a single certificate covers both markets.
- Is the factory audited?
- Yes. UL Follow-Up Services audits the manufacturing campus on an ongoing basis — the same production line, every production month. That is what keeps the UL files active rather than being a one-time test.
Sizing & product selection
- What kVA range do you offer?
- Three-phase padmount transformers run 45 to 4,000 kVA. Dry-type transformers run 30 to 3,000 kVA. Substation and power transformers are made to order, typically 2 to 60 MVA. Power-quality equipment covers reactors and filters up to 35 kV.
- How do I size a transformer for my load?
- Start from continuous load current and keep it at or below 80% of nameplate kVA, which leaves headroom for inrush and future growth. The kVA to amps calculator on this site does the conversion for single- and three-phase at a given voltage. Harmonic-rich loads such as VFDs and IT equipment usually need a K-factor rating rather than simply a larger unit. Final sizing must be confirmed by the engineer of record; a sizing review is included with every quote.
- What is the difference between cast coil and VPI dry-type transformers?
- Cast coil, also called cast resin, encapsulates the winding in epoxy under vacuum, giving a sealed surface that holds up in humid, dusty or corrosive environments. VPI, vacuum-pressure impregnation, impregnates the winding with resin under vacuum and pressure and then bakes it, which costs less and suits clean indoor rooms. Both are available across the 30 to 3,000 kVA dry-type line.
- Should I specify copper or aluminium windings?
- Padmount units are aluminium as standard, with copper available on request. Aluminium is lighter and lower cost at the same rating; copper gives a smaller footprint and lower losses per kVA, which matters when space is tight or when loss evaluation is part of the bid. If your specification does not call out a material, aluminium is quoted.
- When do I need a K-factor rated transformer?
- When the load produces significant harmonic current — variable frequency drives, UPS systems, LED lighting, IT and data-center equipment. Harmonics cause additional eddy-current heating that a standard transformer is not rated for. K-factor designs from K01 through K30 are available on the dry-type line; send the load list and the harmonic content and it gets sized as part of the quote.
- Do you supply single-phase padmount transformers?
- No. The padmount line is three-phase only, 45 to 4,000 kVA. Single-phase and pole-mounted units are not in the catalog.
Technical specification
- What is FR3 fluid and when should I specify it?
- FR3 is a less-flammable vegetable-ester insulating fluid with a much higher fire point than mineral oil, which is why fire codes and insurers often require it near buildings, in enclosed vaults, or on sites with occupancy above. It is also readily biodegradable, which helps near water. Padmount transformers are available with either conventional mineral oil at under 2 ppm PCB, or FR3-type vegetable oil.
- What BIL do your padmount transformers carry?
- BIL follows the voltage class and is confirmed at engineering review rather than fixed across the line. Padmount primaries run up to 24,940 GrdY/14,400 V across the 20.78, 22.86, 23, 23.9 and 24.94 kV classes. If your specification calls out a BIL, put it on the quote request; if you do not know it, leave it blank and the engineering review covers it.
- What impedance can I specify?
- Impedance is quoted against your specification, because it directly sets the available secondary fault current and therefore the interrupting rating of everything downstream. Standard values follow IEEE C57.12.00. AC reactors in the power-quality line are separately available at 1 to 6% impedance. State the required %Z on the quote request if the downstream equipment is already selected.
- What tap arrangement is standard?
- Padmount transformers ship with a ±2 x 2.5% de-energized high-voltage tap changer as standard, giving four tap positions above and below nominal. Substation and power transformers can be supplied with de-energized taps or a full on-load tap changer, specified per project.
- Can you meet IEEE 519 harmonic limits?
- Yes, through the power-quality line. Passive harmonic filters reach THDi below 5%, 8% or 12% depending on the design point, up to 415 V and 450 kW. Send the load list and single-line and the filter is sized as an application-engineering exercise, not an off-the-shelf pick.
- What testing is done before shipment?
- Every unit is 100% routine-tested: ratio, winding resistance, impedance, no-load and load losses, and applied and induced voltage, in a CNAS-accredited transformer test station. Medium-voltage units additionally go through a shielded partial-discharge test room. Test reports ship with the unit, and factory acceptance tests on substation transformers can be witnessed remotely.
Quoting & delivery
- How fast will I get a quote?
- Within one business day of submitting the quote form or emailing a spec sheet to support@rionexenergy.com. The quote comes back with unit pricing, lead time and freight, plus UL Certificates of Compliance and an engineering review of your one-line.
- What information do you need to quote?
- At minimum: product line, kVA rating, primary and secondary voltage, quantity, delivery location and required date. Helpful if you have them: BIL, phase, impedance %Z, enclosure or NEMA rating, taps, fusing, fluid type and K-factor. If those are not settled yet, leave them blank — the engineering review covers them rather than holding up the quote.
- What are your lead times?
- Both in-stock inventory and made-to-order factory production slots are available, so lead time depends on the unit and the current production schedule. It is confirmed in the written quote rather than quoted as a general figure. Note that the one-business-day commitment refers to the quote turnaround, not to equipment delivery.
- Does the price include freight?
- Quotes include freight to the delivery site. Give the delivery location on the quote request so freight can be priced into the total rather than added later.
- Where do you ship?
- The United States and Canada, matching the UL and CSA certification scope. Rionex Energy is based in Houston, Texas, and ships factory-direct from a UL-audited manufacturing partner.
Question not covered here? Send it with your quote request →
Still deciding on a specification?
Send the load list or one-line. Engineering review is part of every quote, and pricing comes back within one business day.