Andrew Ian McLatchie, of Hull, pleaded guilty to seven breaches of Regulation 3 (3) of the Gas Safety (Installation and Use) Regulations 1998 and four breaches of the Trade Descriptions Act 1968.
The charges related to work undertaken at three properties in Hull while Mr McLatchie was not a registered gas fitter.
A joint investigation by Hull City Council Trading Standards and the Health and Safety Executive later discovered numerous defects in the work.
A spokesman for the HSE said: 'We urge homeowners to be on their guard when having gas work carried out at their properties and to always check the fitter is on the Gas Safe Register. In this instance Mr McLatchie installed gas appliances and gas pipework at three properties after falsely claiming he was registered.
'Mr McLatchie appeared in court for potentially putting lives at risk by carrying out defective gas work without the proper accreditation, and we will not hesitate to prosecute individuals who break the law and endanger others in this way.'