Worcester Negative Fan Pressure decrease after cleaning heat exchanger

[DRAGONEXPRESS]

Hi, I am new gas safe registered. I serviced a old worcester R28 HE Z7-28 system Boiler. found negative fan pressure -3.95mb lower than MI's -4.2mb, Gas rate is 2.82 m3/h, little bit lower than MI'S 2.9M3/H, so clean heat exchanger very well. after that check fan negative pressure, -3.11mb, later check again-3.22mb working through 10minutes at Max Rate. Gas rate 2.61m3/h, just same as -10% of 2.9m3/h. Curiously, I check the heat exchanger again, totally clean, and wash through by 4 litre water, it is totally clean, never see any heat exchanger clean then this. I don't know why the pressure is lower after cleaning heat exchanger. Cheers

 

[Allgoode]

might be a weak fan taking into account boiler age & or check connections as through ageing can have leakage thus giving you issues.
Thats the problem with older boilers, wear & tear, if rest of readings check out then you will be fine,
cheers,
Andy

 

[DRAGONEXPRESS]

might be a weak fan taking into account boiler age & or check connections as through ageing can have leakage thus giving you issues.
Thats the problem with older boilers, wear & tear, if rest of readings check out then you will be fine,
cheers,
Andy

Man thanks Andy hope that explains

 

[Last Plumber]

Did you check the fan blades and check the air intake, flue exhaust and sump?