Doug McEwen is warning consumers to be wary of fast-talking furnace salesmen after he says one company took advantage of his mother.

McEwen was visiting his 79-year-old mother, Rosemary, in her home in northeast Edmonton, when he noticed she had a new furnace.

"It absolutely did not need to be replaced. There was nothing wrong with it at all," McEwen said during a Friday morning interview on Edmonton AM.

"You're not going to get any benefit from a high-efficiency furnace in a home like that. Anyone who knows anything about furnaces, would know that."

McEwen said his mother was talked into renting the new heating system by Secure Home Services, even though her existing furnace was only 10 years old and in perfect working condition.

"She thought she was signing a contract to pay a furnace off over three years, and then she'd be done, but that's not what the contract says. The contract says it's for 10 years and it's a rental."

According to the contract, Rosemary, who lives on a secured pension, will be paying $94 per month over the next decade.

"So that adds up to over $11,000 for a furnace that is maybe worth $1,000," said McEwen.

Furthermore, McEwen, who used to work for a heating and cooling company doing installations and drawing up quotes, said they've had to pay to have the unit re-inspected twice, because it wasn't installed properly.

After calling the company call centre to complain, McEwan learned that the 30-day cancellation period had passed. Instead, $5,500 would have to paid, up front, to buy-out the contract.

McEwen said all that was buried in the fine print.

Service Alberta confirmed to CBC News it has received a number of complaints about Secure Home Services, and said it is investigating.

The Ontario-based company, which sells furnaces, hot water tanks and air conditioners door-to-door around Alberta, denies any wrongdoing.

"Secure trains its agents on the product knowledge of its equipment and to accurately and truthfully explain the program to consumers. Before Secure completes the consumer contract, it completes a verification call with the consumer to ensure that they understand the terms of the agreement," director of operations Gaetana Girardi said in a statement to CBC News. Girardi said the company is doing its best to resolve McEwen's concerns.

"Secure will continue to endeavour to reach an agreeable resolution with Rosemary."

In the meantime, McEwen said it's likely too late for his mother to get out of the deal, but he wants to warn other seniors, who may be taken advantage of by door-to-door salesmen.

"I don't know if she was targeted, but I certainly feel that way. People in that demographic are an easy hit."