Weil-McLain boiler serial numbers: where to find them and what they mean

Weil-McLain does not label its residential and commercial boilers with a generic serial number. The company's own lookup page calls the identifier the Consumer Protection CP/Serial Number, and that single number is what the manufacturer uses to tie a physical boiler to its production record, its registration and its warranty history. The letters CP stand for Consumer Protection, and the number that follows is the serial.

The number lives on the boiler jacket rather than on a paper document. The CGa Series 2 boiler manual instructs owners and technicians to have both the boiler model number from the rating label and the CP number from the boiler jacket before calling or writing about the boiler, and Weil-McLain publishes a CP Location Reference guide that shows, model by model, exactly where the number is printed on AquaBalance, CGa, CGi, ECO, ECO Tec, Evergreen, GV90+ and Ultra boilers.

The format is fixed and the manufacturer states it directly on the CP Lookup page: enter the seven-digit Consumer Protection CP number, beginning with the letters CP. The input field on the page shows the expected shape as CP1234567, and the live lookup only fires once the value matches CP followed by exactly seven digits.

The one documented variation is length. Weil-McLain says that if the CP number on the boiler includes only six digits, the person doing the lookup should enter a leading zero after the letters CP, giving a value such as CP0123456. The normalised nine-character form — two letters plus seven digits — is what the tool expects in every case.

The CP Lookup is not a simple age calculator; it is the manufacturer's product record for the boiler. When a number is found, the tool displays a description, the part number, the model name, the size, the manufacture date, the installation date and the product registration date. It also states when a product has already been registered, because registration is a one-time event and a second attempt is refused.

That output is why the CP number matters to more than the owner. A technician ordering a part can confirm the exact model and size the number belongs to before the order is placed. A homeowner planning a replacement can see the manufacture date without guessing from the appliance's appearance. And anyone checking a warranty question can see whether the boiler was registered and when it was installed, which is the evidence a claim is built on.

Weil-McLain also publishes a CP Date Ranges chart, revised for 2026, which maps CP number ranges to an approximate date of manufacture. The chart begins with 1988 and runs to 2026: for example, boilers with CP numbers from 1414001 to 1681500 are placed in 1988, and the 2026 row begins at 8278016. The chart is the fastest way to estimate a boiler's age when the exact record is not needed.

The chart carries two caveats in the manufacturer's own words. AquaBalance CP numbers are not sequential, so the chart may not be sufficient for that model, and the resulting date does not guarantee warranty coverage. Treat the chart as an approximate manufacturing window and the CP Lookup as the authoritative record.

Two documented situations produce no result. The lookup applies to boilers only — Weil-McLain states that it will not give manufacturing information for any other Weil-McLain product — and the company notes that no information is currently available for EG and EGH boilers. When a CP number cannot be found and the age of the unit is still needed, the lookup page directs the caller to the Weil-McLain Warranty department at 1-800-654-2109, option 4.

A missing number is also a reminder to record it. Photograph the rating label and the jacket stamp, write the CP number and model beside the service history, and keep the record with the boiler's documents. A boiler whose CP number is known is a boiler whose parts, age and registration status can be resolved in minutes rather than a service call.