new , aps, venturi, thremistors.
all terminals clean and sound.
fan runs ! how do you check speed is ok seems, its running etc.
does the main board adjust speed.
boiler runs ok with inner cover off.
runs ok with cap on top off.
what next !!!!!!

steve, March 2008

there is a restrictor on the flue as it leaves the boiler this may be incorrect all depending on the flue length you may say its not that but when the fan is new it is more efficient this i guarantee is your fault if you replace the fan it will work however when that fan is not as efficient you will be back to square one better to change a restrictor costing 1.5o than changing a fan at 1oo pounds

ricky, March 2008

whats the boiler make/model?

sounds to me like, whit the cover on, its not getting enough air,
therefore the venturi is not making the aps......with the cover off its taking the air from the room.....

You sure there is no obstruction in the flue, both exaust and outer ring...for combustion air.......

Look at your terminal carefully, could it be recycling the flue gases when the cover is on...? (ie...gases out the centre of the flue being take back in the freah air port)

With it running witht he cover off ok, youd have to be looking at flue outle/intake possiblilities, as its working with cover off you can effectively rule out most of the other devices...

Let me know how you get on.......

T, March 2008