I'm not an expert, but I sure its gravity HW and a pumped CH system. Don't know anything about motorized valves, and I'm sure there isn't one. thanks brian108
thanks for your reply. it doesn't seem to boil, as the problem is only evident when the boiler first lights up. I was wondering if this could be caused by an indirect cylinder? brian108
Can anyone explain the cause of this problem?? We have a Baxi Bermuda boiler, gravity hot water and an indirect cylinder. There are seven radiators on a pumped circuit. On occasions, when the programmer switches on the hot water at 5 a.m. there is a large air pocket which leaves the...