Under the Consumer Rights Act 2015, all products must be of satisfactory quality, fit for purpose and as described. You have a legal right to reject faulty goods and get a full refund – as long as you do this within 30 days of purchase. After that, you must give the retailer an opportunity to repair or replace the goods first. And if you do not make a claim within six months you may have to prove that the product was faulty when you bought it.
Since June 2014, buyers of items purchased on-line, by telephone or mail order have 14 days from the date of delivery/installation to assess the product and decide if they want to keep it. This has nothing to do with whether a product is faulty and is merely to allow consumers to assess a product in their own home as well as they would if buying a product in a face to face sale in a shop.
However, if you do have a problem with a new appliances you can instead choose to claim under the manufacturer’s guarantee. This does not offer an option to reject the goods but will normally include free repairs or replacement for a specified time.