Rheem 3204-80 blower removal

[SteveHogan]

My ancient Rheem 3204-80 furnace started putting out "something electrical is burning" smell last night.  This AM I reach into the blower opening to see if it is turning freely and the  squirrel cage is hitting the housing.  Obviously bearings are shot and the blower stalled and ??.

The blower is mounted to a sheet metal "drawer" that looks like it is supposed to just slide out.  I cannot budge it.  Can someone tell me where the secret decoder ring is to let the blower assembly slide out so I can figure out how screwed I am?

Thanks,

[dkpd1581]

Check around and see if there are two or more 1/4  or 5/16 sheet metal screws holding it to the case....possibly attaching to the back bulhead of the unit

[SteveHogan]

Bingo!

2  phil pan sheet metal screws in the apron beneath  the burner air intake manifolds prevented the blower frame from sliding out.

Having now extracted the blower and the motor, it appears that the squirrel cage hub setscrew had vibrated loose over the years and the cage slipped sideways, hitting the housing and stalling the motor.

The windings are blackened and fried in the motor.  The externally mounted Variable Speed control module which appears to be a small rectangular autoformer (variac) is also fried.

The motor appears to be a standard sized induction motor.  (No motor caps) --

Redmond Model AY 5027,   115 V , 60 cycle, 5 Amps,  no rpm, no hp rating on nameplate.  Mounts on circular rubber motor mounts like an appliance motor. The shaft appears to be 1/2" in diameter with a flat for a setscrew.

I'm guessing that I can find a replacement blower motor cheaper than a new furnace, and at the same time I can probably get more horsepower in the same frame size drawing less current. (maybe a multiple speed).  Maybe even with permantly lubricated ball bearings, although that doesn't seem to be the main problem since the shaft still turns freely.

Advice freely accepted on replacement options.

Thanks

[RegUS_PatOff]

is this the one?

 this page says it  = Miller 326 = 301543

http://www.aqua-man.com/TechTips/motorManDetails.asp?mfg_number=AY5027&motorID=20676

http://www.electricmotorwarehouse.com/aosmith/page114.pdf

replacement motor at cshincorporated

 

 

[SteveHogan]

I have studied up on HVAC motors all day, and I know a lot more about them tonight than I did this morning.

I have determined that the old motor has a 48 Y frame.  The length of the motor from end cap to end cap (not including the bolts and  the rubber rings) is 4". The rubber rings are 2.5" in diameter. The center to center distance of the mounting rings is 4.75".

Based on the 5.0 amp consumption of the old induction motor, it was probably 1050 RPM and about 1/8 to 1/7 HP.  The motor you discovered was about right in hp but not in size.  It is smaller than the original so it won't fit the old mounting bracket.

My choice for a replacement motor (subject to correction by more enlightened folks) is the A. O. Smith model 134.   If I am reading the catalog info correctly it matches exaclty the size of my old motor (4" long body, 5 5/8" diameter, 2.5" diameter rubber ring mounts)  This motor is a PSC instead of an induction Split Pole motor, so it is much more efficient than the old motor.  It is a 1050 RPM 3 speeds, 1/3, 1/4, 1/6 hp.

I know I need the extra HP if I add a AC coil to the top of the furnace -- the 1/8 HP motor won't be enough for sure.  Is the extra moxie on the 3-speed motor going to cause me grief or will it be OK?  I suspect that I will end up strapping it permanently at low speed for heat only use, especially since the old motor had a variac-type speed control that had the single speed motor cranked down a bit.

The 134 also seems to be very cheap at just under $60 + a $5  7.5uF cap from CSH.

Is the A. O. Smith brand OK? I'm guessing that it may be Chinese based on the low price, but then again look how old the furnace is -- maybe not worthy of a more expensive solution.

Is CSH an ok place to buy from?  Since I don't buy HVAC stuff on a regular basis, I don't know them as a vender.   I am interested in a real bargain -- quality stuff at a low price.

My only concern is that I know I should probably just replace the furnace due to its age and the possibility of the heat exchanger being cracked.  I have a carbon monoxide detector in the hallway.  Being a newbee, I don't really know how to test the furnace for a cracked heat exchanger.  I'm not sure it can be tested without a working blower.

A decent furnace is probably going to cost me $500 to $1000 and I can fix the blower for less than $100.   I just don't want to have a dangerous situation.

Thanks for your advice.

 

 

 

 

 

 

[dkpd1581]

With the blower assembly out is a perfect time to do a visual inspection of the the exchanger.  Crawl underneath with a good light and inspection mirror and check all that you can reasonably get to.  If you are really motivated you can check from the top by reoving the supply plenum.  If you are truely motivated and have a little time, take apart the whole furnace section and check each exchanger plate. 

Having a monoxide detector is a good move; however, it may be useless in checking for a cracked exchanger.  If you do have a crack or fissure and you have good combustion, you may not necessarily have CO.  CO is only the product of incomplete combustion.  It is possible to have both complete combustion and a bad exchanger with not alarm from the detector

Another way to check the exchanger with the motor in is to observe the flames before and after the blower comes on.  If the flame stands tall and strong before the blower and begins to get lazy, float around, or try to make its way out when the blower engages, then you have a crack.  You are pressurizing the cabinet and the air is affecting the flame.  You can put the blower on high speed and pressurize the cabinet to the max ability of the motor and check for the same.  I have had low speed not show indications while high speed did.

As to the motor, lets not over engineer this and call the local Rheem dealer.  They will tell you all you want to know about the motor.  Make sure to have your model serial - obviously.  I highly suggest getting a new wheel as well so make sure to add this cost in.  If the Rheem guys are less than friendly, call tell them your name and say you work for whatever big company.  They usually do not like to deal with resident/homeowners but will entertain technicians all day long.  They wont know you but will recognize the big name company.  Since the big companies have boat loads of techs, they wont think twice.

Getting a motor that is too small (overloaded) or too large (underloaded) will defeat your best efforts and will prematurely kill the motor.  Go with exactly what the Rheem guys suggest.  I would strongly discourage guessing at the HP or going to a higher HP without justification.

[RegUS_PatOff]

more info

 

AOSmith 134 

http://www.aosmithmotors.com/pdf/brochures/3200hvacr.pdf