I recently drained down a friends heating system to enable the removal of 4 radiators for decorating purposes.They have a BOSCH WORCESTER GREENSTAR BOILER on refilling the system today I found that I was unable to get the boiler to run for more than about 3 minutes before it locked out.After turning the temperature control to reset the same thing constantly happened. I believe that I should vent the boiler by removing the casing and operating the vent. Am I correct please.
Thanks in advance for any advice.