The 54-year-old from North Devon was found guilty of three fraud charged and three consumer protection offences after two-week trial.
A plumbing and heating engineer from Instow has been found guilty of fraud.
Gary Henry, 54, was found guilty of three charges of fraud and three of contravening professional diligence under the consumer protection legislation, following a two week trial.
Before the trial at Exeter Crown Court, Henry pleaded guilty to two consumer protection matters relating to falsely advertising trade association membership.
He was acquitted of two further Fraud Act offences and two further consumer protection charges.
The court heard how Mr Henry had traded under the names of Barnstaple Plumbing and Heating, and Gary Henry Ltd.
He told the court that he had been a plumber for 30 years, alongside his job as a professional firefighter for Devon and Somerset Fire and Rescue.
After receiving complaints about his work, Devon and Somerset Trading Standards discovered that in 2011 and 2012 Mr Henry carried out work for several customers, some of which was of poor standard, and vastly overpriced.
The level of over-pricing for parts and labour were so high in fact that the court found him guilty of fraud in relation to three out of four of the complainant’s cases .
The quality of some of the work was so poor that experts expressed serious safety concerns.
One elderly customer was charged more than £25,000 for the replacement of an oil-fired system, which when inspected by an expert was found to have numerous faults.
Apart from the trade association issues, Mr Henry had denied all the charges.
The judge said there was ‘serious dishonesty’ involved and he will be sentenced after probation reports and a financial investigation.
Mr Henry had also invoiced customers for work that had not been done, and falsely claimed in advertisements and on documentation that he was registered with OFTEC, the main trade association of technicians working with oil fired heating and cooking systems, when he was not.
According to experts, Mr Henry’s invoices and work were exorbitant and excessive.
Two elderly customers, both recovering from illnesses, were over-charged thousands of pound for appliances, materials and labour.
A boiler, bought for £1,699, was itemised on an invoice as £3,860. On that occasion, work charged for was not done, and a flue pipe costing £87 was itemised on the invoice at £870.
The amount charged for labour on invoices was vastly inflated with hugely expensive hourly rates.
The number of hours charged-for was excessive in relation to the hours actually put in.
Councillor Roger Croad, Devon County Council’s cabinet member with responsibility for the Trading Standards service, said: “Although Devon and Somerset Trading Standards has brought this case, the quality of this trader’s work is so poor that we are recommending anyone who thinks they have had an oil fired applience installed by Mr Henry, should not only check whether their local district council building control has been notified of the installation, but also get the appliance checked by a properly qualified and registered oil fired appliance technician to ensure that it is correctly installed and safe to use.
“I’m pleased that we have been able to bring this case to court, which is partly down to the readiness of several elderly customers to give evidence.
“The fact that it was a fireman who introduced the fire risks to their homes makes his offences all the more despicable.”
Devon and Somerset Trading Standards Service runs the Buy With Confidence Scheme to promote the highest standards of trading across the two counties, for the benefit of both consumers and businesses.
Businesses who become members of the scheme undertake to operate their company in a legal, honest and fair way.
You can search for a member near you at https://www.buywithconfidence.gov.uk/
Anyone with concerns, or who would like advice about their rights, should telephone The Citizens Advice Consumer Service on 0345 0404 506 or visit www.adviceguide.org.uk
Businesses can also find advice from Devon and Somerset Trading Standards website, www.devonsomersettradingstandards.gov.uk, or call 01392 381381.