I have a Baxi Bermuda 552 back boiler with LFE3 Super fire front. I've had it for about 17 years. The other day I was standing next to it, the fire front was not on, but the boiler had fired up, and I felt a steady flow of warm air coming out of the grill at the top of the fire front. I had never noticed this before, but had perhaps never stood right close to it before! Can anyone please tell me if this is normal?