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Transformer sizing
This tag page collects 2 TradesQuote articles related to Transformer sizing. Use it to browse contractor-focused guidance on sizing, code, cost, diagnostics, and estimating without hunting through the full blog archive.
Each post below is written for people who bid and run trade work — HVAC and electrical contractors, estimators, and technicians who need clear explanations they can apply on the next job. Skim the summaries, open the guides that match your question, then follow related calculator links when you need interactive numbers.
Featured reading in this collection includes: Transformer Sizing: kVA, Primary and Secondary OCPD (NEC 450.3); kVA vs kW: Power Factor, Apparent Power, and Why It Matters. Open any article for full detail, examples, and links to free tools that support faster estimating.
Looking for a broader topic? Browse all tags from the tags index, or jump to HVAC and electrical categories for curated topic hubs. TradesQuote also offers free calculators and an AI estimator when you are ready to turn a job description into a line-item quote.
Guides in this tag
- Transformer Sizing: kVA, Primary and Secondary OCPD (NEC 450.3)
The primary device may go to 250% of FLA - but only where the secondary is separately protected. Without it you're capped at 125%. And 450.3 protects the transformer, not the secondary conductors.
- kVA vs kW: Power Factor, Apparent Power, and Why It Matters
kW = kVA × power factor. At PF 0.8 the power triangle is a 3-4-5: 100 kVA is 80 kW and 60 kVAR - and the conductor is sized for the hypotenuse, not the base.
Related resources
- 04 Aug, 2026
Transformer Sizing: kVA, Primary and Secondary OCPD (NEC 450.3)
The primary device may go to 250% of FLA - but only where the secondary is separately protected. Without it you're capped at 125%. And 450.3 protects the transformer, not the secondary conductors.
- 04 Aug, 2026
kVA vs kW: Power Factor, Apparent Power, and Why It Matters
kW = kVA × power factor. At PF 0.8 the power triangle is a 3-4-5: 100 kVA is 80 kW and 60 kVAR - and the conductor is sized for the hypotenuse, not the base.
Frequently asked questions
Common questions about Transformer sizing guides on the TradesQuote blog.
What will I find under Transformer sizing?+
This tag lists 2 published guides tagged or categorized as Transformer sizing. Topics typically include sizing, cost estimating, diagnostics, and practical contractor workflows tied to that subject.
Are these articles a substitute for code or engineered design?+
No. TradesQuote guides explain concepts and estimating shortcuts so you can work faster and communicate clearly. Always follow applicable codes, manufacturer instructions, and professional engineering requirements for the job.
How do these pages relate to TradesQuote tools?+
Many articles link to free HVAC or electrical calculators and to TradesQuote estimating features. Use the guides to understand the topic, then use the tools to produce numbers for proposals and field checks.