The National Electrical Code (NEC 725.136A) specifically excludes any low voltage wiring from being installed in an electric panel, raceway, or box used for high voltage (120/240V) circuits. Electricians know better, but we regularly find homeowner-installed doorbell transformers sitting loose in the bottom of an electric panel, like in the photo above. This particular homeowner also attached flammable paper tags to the wiring to each breaker to identify the circuits—another no-no.
It is acceptable, however, to mount the doorbell transformer to the exterior of a surface mounted electric panel, and is usually done at the top of the panel.
While we hope you find this series of articles about home inspection helpful, they should not be considered an alternative to an actual home inspection by a local inspector. Also, construction standards vary in different parts of the country and it is possible that important issues related to your area may not be covered here.
© McGarry and Madsen Inspection
