Gas boilers installed at a hotel put the lives of staff and guests at risk, a court was told.
A court heard the system could have exploded, caught fire or leaked deadly carbon monoxide.
The boilers were installed during 2009 at the Glendower Hotel, North Promenade, St Annes.
Before Blackpool Magistrates was the plumbing company involved Derby-based North West Mechanicals, which has since gone bankrupt.
Also in the dock was its local worker in the Lancashire area, 68-year-old David Hamner, of Magdelen Avenue, Cleveleys.
Hamner, who was said by magistrates to have acted with a level of deception, was given an eight week jail term, suspended for a year.
He will also have to pay £8,965 costs.
The company was said to have made significant profit on the work done but their work fell well below the standards required and did not take any notice when a fitter pointed out problems.
The company was fined a total of £20,000.
The company was found guilty in its absence to two offences brought by the Health and Safety at Work Act of a breach of its duty to the hotel by exposing staff and guests to danger.
It was also found guilty of allowing an employee – Lee Reeve – to carry out work at the hotel which he was not approved or trained to do.
Hamner pleaded guilty to the same offences.
The court heard how mistakes in the fitting of the boilers were discovered during an annual service which found them faulty and a risk to life and property. Hamner had been removed from the CORGI gas fitting register in 2008 following an HSE investigation and was not on the register when he began work on the Glendower project.
Alan Godwin, for Hamner, said his client was self-employed at the time being paid an hourly rate.
He worked for North West Mechanicals for the bulk of the time and when the job at the hotel came up both he and the company put in estimates knowing one of them would succeed. Mr Godwin said his client only worked for a short time on the boilers and did not sign the system off
“That was done by one of the two anonymous people from the company who have not attended proceedings,” he added.
Andrew Howarth, managing director of the Glendower Hotel, said: “We want to thank the Health and Safety Executive for their hard work and the fact their have managed to bring a successful prosecution.
“Obviously it was very upsetting for us as a business and we wanted to make sure they (the company and Hamner) were not able to do this to anyone else.”