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California C4 Boiler, Hot Water Heating and Steam Fitting License
California has 692 active C4 Boiler, Hot Water Heating and Steam Fitting holders in the state file as of 2026-10-261, the 47th-largest of 64 classes with at least 200 holders. 22 of them expire by 2026-12-26.
- Active holders
- 692
- 0.3% of active California licenses
- Expiring by 2026-12-26
- 22
- 3.2% of holders
- Median bond on file
- $25,000
- 692 bonds
- Workers' comp exempt
- 15.0%
- of 692 with WC status
What does the California Boiler, Hot Water Heating and Steam Fitting license require?
C-20 Warm-Air Heating, Ventilating and Air-Conditioning Contractor. Related: C-4 Boiler/Hot Water Heating/Steam Fitting; C-43 Sheet Metal. Active C-20 must carry WC even with no employees. Refrigerant (EPA 608) not addressed on CSLB class page.2
Exam
Two exams: (1) Law & Business and (2) trade exam for the classification (no trade exam for C-61).3
Bond
$25,000 contractor bond (or $25,000 cashier's check).1
How many C4 contractors are exempt from workers' comp?
104 of 692 active C4 holders with a recorded status (15.0%) filed an exemption1, against 48.7% across all California classes.
How do you check a C4 license?
Search by license number or business name on the California license lookup, which reads the same state file.
Other California license classes
Sources
- CA CSLB License Master (cslb.ca.gov data portal) (cslb.ca.gov, 2026-10-26)
- Contractors State License Board (CSLB): classes (cslb.ca.gov)
- Contractors State License Board (CSLB): exam (cslb.ca.gov)