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QUESTION:All the installation/tech docs for the Kenmore 90 furnace are generic,
with no manufacturer info. I'm guessing somebody else made the furnace,
and there may be alternate(cheaper) parts sources.
I asked in alt.hvac, but no response...
Kenmore 90 Furnace, 100,000 Btuh upflow, natural gas,
model # 867.769434 NUGK100DH05 Installed in late '88
Plastic impeller slipped down shaft in combustion blower and started
welding itself to the housing. It's only friction-fit, and some cracking
has loosened it. The motor is in great shape, and the housing is fine
despite some internal scratches. The problem is, only the whole
-combustion-blower-assembly- is listed in the tech reference sheet.
Can I get a new -impeller- ALONE, even though it's not listed?
What are the costs of the impeller and the whole blower?
One other thing: In operation, I get an air temp of about 150F +/- just
beyond the plenum. At about 152F, burner/c-blower cut-off. 10-15sec
cooldown to 140F or less, then they're on again. Main fan is always set
on, so it doesn't cycle. Limit is spec'd at 170F. Seems possible that
170F is happening down at the limit switch. I can either derate the
furnace down to 80,000 btuh using the #44 orifice x4, and see if that
fixes it and has enough capacity, or I can replace the limit switch and
hope that the new one will allow it to run somewhat hotter.
Ducts may be undersized, or the A-coil may be interfering, but I can't do
anything about that. Filter's clean and big, fan is at high tap.
Dampers wide open. House is heated well, with decent airflow. This cycling
problem has been there for years. BTW, all the other safety devices check
out ok.
ANSWER: I had a Tempstar dealer order that kit for me. Cost $40, which is $130
less than a new combustion blower! I'll be installing it in the next day
or so. I don't think the original impeller had a clip on it when I
did the emergency fix, nor do I remember a groove around the motor
shaft. This may be why the thing slipped down. It had developed tiny
stress cracks at the hub where the "split collar" part of the impeller is.
I might have to get out the moto-tool and grind a groove before
installing the new impeller, so it snaps in.
Have to pull the secondary exchanger to fix a small leak too. Longtime
problem -- I am hoping it's just the hose connection dripping to the
inside of the front panel. The leak is creeping out under that area,
and some of it gets into the main blower cabinet. A bit of rust, so I'm
going to sand and prime the areas affected before I put everything
back. Perhaps it won't require attention for a while then
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