New Vokera Compact 29a making squealing noise?

My vokera compact 29a boiler is only 3 months old. Recently it has started making loud squealing type noises when hot water is on/and or heating on. It doesn't always do it but when it does it can be very loud. Sometimes it makes the noise when only hot water is running and sometimes when heating is on and hot water running. It never makes the noise when just the heating is on. Any ideas please.