If the flue is actually sitting correctly then it could be the following:
If a fan is mounted over to the right-hand side on the top external vent it can draw air up past the boiler on the right and actually cool the boiler as well as the top condenser fins.
I had the same problem. Ended up installing just one fan and mounted it as far to the left as possible. Heat from the flue then returned to normal.
cheers
Mike
Hi Mike
@mikerezny , I took your advice when you were up here and looking at my van set up with fans. As you know, I have two powerful fans in the vents for my 3 way fridge - bottom one pulling cool air in and the top one pulling the hot air out. After having to remove fridge owing problems with sooting ( undetected partial chimney obstruction) and poor operation, (see earlier post) I decided not to move fan further along the vent and away from boiler, and instead, using the same sheet aluminium, put a metal partition all the way up beside the boiler , right to the top and exhaust point. Would only have been able to do this with the fridge out, but very effective now. Very little if any of the fan forced air injected from the bottom fan can interfere with the heating of the boiler and the exhaust at the top is unhindered too. Have done some exacting tests under 240 volt power and gas with temps and times from start up to full cooling which I will provide for the 3 way fridge followers when I get back from a 5 day trip to a nearby State Forest Park. Very hot up here in Brisbane for the last few days and more to come too. Getting ready to depart Sunday, fridge fully loaded is maintaining 5C in ambient temp of 34C during day and 23C at night (inside
open van temperature) - a lot hotter in the sun and van is in full sun too. Should be a good test again after more insulation and better mods. The proper and accurate recordings I will provide make interesting reading. Available after I return on Saturday.