Short answer - Found most A082 - 7021-xxxx .95A 3000rpm 70-75 cfm Fasco replacement combustion blowers have an insufficiently sized impeller.
Background..
Had my Invincible T since '95
2 1/3 ton year, always well maintained and produced a nice light, fluffy grey ash.
Last season my combustion blower finally seized after 18 seasons.
Had ordered a replacement from an online vendor that indicated this unit was a match for this suffix motor.
Seemed to work ok but about that time the auger feed tube had developed a crack, and was altering the airflow as well, but the extra air was at least getting a complete burn.
This season pulled and welded the weldment's feeder tube that had worn and fatigued due to some seasons with a mildly compromised hopper door gasket and hopper door misalignment (one can hear the leaking airflow with ones ear up to the seal)
Upon reassembly and startup, flame was somewhat lazy , more especially after some dark ash developed in the burn pot.
Dark smelly ash coated the heat exchanger very quickly, a touch goey near the combustion blower.
Went all thought the structure and cleaning and looking for air leaks, door was excellent as were all other seals, burnpot, blower, etc.
I had on-hand a replacement combustion impeller but hadn't installed it in the replacement blower, just used the one that came with it installed..
After fighting this for a few weeks this season, compared the impellers, and they are indeed sized differently.
The Harman part indicated is almost 4.94" vs 4.67, a healthy 1/8" longer blades. There was my missing cfm.
Attaching images in case this help others solve these typically robust stoves.
Background..
Had my Invincible T since '95
2 1/3 ton year, always well maintained and produced a nice light, fluffy grey ash.
Last season my combustion blower finally seized after 18 seasons.
Had ordered a replacement from an online vendor that indicated this unit was a match for this suffix motor.
Seemed to work ok but about that time the auger feed tube had developed a crack, and was altering the airflow as well, but the extra air was at least getting a complete burn.
This season pulled and welded the weldment's feeder tube that had worn and fatigued due to some seasons with a mildly compromised hopper door gasket and hopper door misalignment (one can hear the leaking airflow with ones ear up to the seal)
Upon reassembly and startup, flame was somewhat lazy , more especially after some dark ash developed in the burn pot.
Dark smelly ash coated the heat exchanger very quickly, a touch goey near the combustion blower.
Went all thought the structure and cleaning and looking for air leaks, door was excellent as were all other seals, burnpot, blower, etc.
I had on-hand a replacement combustion impeller but hadn't installed it in the replacement blower, just used the one that came with it installed..
After fighting this for a few weeks this season, compared the impellers, and they are indeed sized differently.
The Harman part indicated is almost 4.94" vs 4.67, a healthy 1/8" longer blades. There was my missing cfm.
Attaching images in case this help others solve these typically robust stoves.
