Hammond Power Transformer Serial Number Lookup & Decoder Guide - Power Transformer Technical Guide & Educational Resources

Written by Tan, Electrical Engineer @ Transformer4U | Last Updated: January 2026 | Reading Time: ~5 minutes

This guide explains how to decode Hammond Power transformer serial numbers to determine
manufacturing date, year, and equipment specifications.

⚡ Quick Answer: Hammond Power Serial Number Format

Format: WWYY

Year Position: Characters 3-4

Example: 4223 → Week 42
2023

1. Hammond Power Serial Number Format

Hammond Power uses the following serial number format for transformers:

Date Code Format

Pattern: WWYY

Element	Position	Meaning
Year Code	Position 3-4	Manufacturing year (2 digits or letter code)
Month/Week Code	Position 1-2 (week)	Manufacturing month or week
Sequential Number	Remaining digits	Unique unit identifier

Notes: WW=Week YY=Year. Applied directly to transformer

2. How to Decode Your Hammond Power Serial Number

📋 Step-by-Step Decoding

Locate the Nameplate
- Padmount: Inside cabinet door
- Substation: Tank exterior near control cabinet
- Dry-type: Enclosure frame
Find the Serial Number – Look for “S/N”, “Serial No.”, or “Serial Number” field
Identify Year Code – Characters at position 3-4
Decode Manufacturing Date – Use the format table above
Contact Hammond Power if Needed – https://www.hammondpowersolutions.com/

📐 Decoding Example

Serial Number: 4223

Manufacturing Date: Week 42 2023

Professional technical diagram showing Hammond Power transformer date code format 4223 with annotation — **Figure:** Hammond Power WWYY date code format – Week 42, 2023

3. Source Reliability

Source Type: ✅ Official Manufacturer Documentation

This format is based on official documentation from Hammond Power.

4. Why Serial Numbers Matter

Use Case	Why Serial Number is Critical
Warranty Claims	Hammond Power needs serial number to verify purchase date and coverage
Replacement Parts	Serial number links to specific winding configuration and tap settings
Age Assessment	Determines remaining life expectancy (transformer life: 25-40 years)
PCB Testing	Pre-1979 transformers may contain PCBs requiring special handling (EPA regulations)

5. Frequently Asked Questions

❓ How do I decode a Hammond Power transformer serial number?

Locate the serial number on the nameplate, then use the format guide on this page to identify the manufacturing
date. The year is typically at position 3-4. If the format doesn’t match, contact Hammond Power directly.

❓ Where is the serial number on a Hammond Power transformer?

The serial number is located on the nameplate—typically a metal or durable plastic plate
affixed to the transformer. On padmount units, it’s inside the cabinet door. On dry-type units, check the
enclosure frame.

❓ Can Hammond Power provide manufacturing date from serial number?

Yes, Hammond Power maintains production records for decades. Contact their customer support at https://www.hammondpowersolutions.com/ with the complete serial number to obtain the exact
manufacturing date and specifications.

6. Related Resources

🔍 Complete Serial Number Guide
All manufacturers + decoding methods

📋 Transformer Nameplate Guide
How to read every nameplate detail

📏 Transformer Sizing Chart
Complete kVA selection guide

📝 About This Guide

This Hammond Power serial number decoding guide is authored by Tan, Electrical Engineer at Transformer4U.

Serial number formats may vary by product line or manufacturing era. For authoritative
decoding, contact Hammond Power directly at https://www.hammondpowersolutions.com/.

Disclaimer: Serial number formats may vary by product
line, manufacturing plant, and era. This guide provides general decoding information. For authoritative
manufacturing dates, contact Hammond Power directly.