KLook wrote:Looking at that picture, I would check the holes in the grates.
I think we have a Bingo!
I'll bet a bucket of coal that either A: the blades of the fan are clogged (dust, car hair, UFO exhaust leak) You need to take extra care when looking at the fan blades. They can look OK at a quick glance, but close inspection will reveal a thin yet complete coating of crappola. or B: the holes in the grate are plugged. (Rust, dust, fine bits of coal) It's very difficult to see each hole. Shut down, remove the grate, find the right size drill & bore yourself to death by counting the holes as you drill them clean.
I'd have added debris under the burn plate but you said you just cleaned that.
I guess also...anything being possible... you say it hasn't worked well from day one.... perhaps fan air is leaking somehow...missing gasket? Something misaligned? And yes, open a window in the boiler room a crack.