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Old 11-17-2012, 09:37 AM   #16
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furnace wont stay on


New member---please don't start duplicate threads on the same subject---I merger two threads of yours---

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Old 11-17-2012, 02:43 PM   #17
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update - I just spent about an hour looking for a crack in the exchanger. I pulled out the blower so I could get my upper body in there to look. I could see 99% of the exchanger and used my inspection camera for what I count not see.

I can not find a crack, I did find the blades to the draft fan all over the place. So I know I need to change that. but my question is would you change the whole draft assembly or just the blades. I did not spent a lot of time on the fan but it looks like I have to pull out the board and the burners and everything.

Has anyone ever worked on this model before 48gs-030060301
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Old 11-17-2012, 02:51 PM   #18
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The squirrel cage on the inducer rusts and falls apart on those units.
It doesn't have a pressure switch. It is one of those centrifugal switches.
It is satisfied as long as the motor spins and will not know the squirrel cage is practically gone. The roll out switch catches that.

You can remove two 5/16 inch screws on the 90 degree elbow on the unit to see the squirrel cage. Checking the heat exchanger before replacing the inducer (if it is that) wouldn't be a bad idea though...
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Old 11-17-2012, 02:52 PM   #19
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You beat me to the punch. I've seen the inducer do this at least a dozen times...
Carrier FAD since 1991.
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Old 11-17-2012, 10:42 PM   #20
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The middle wire is the 24v hot leg and the other 2 are HOT or COLD
this is a flame sensor like the mercury flame sensors we used to have but Carrer uses a bimetal that expands/contracts to switch from spark ignition to main burners and gas valve. very common. the induced draft provbing switch will also be suspect as will the pressure switches tubings orifices upon which it connects.
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Old 11-18-2012, 09:26 AM   #21
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It doesn't have a pressure switch.

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Old 11-18-2012, 09:42 AM   #22
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Had to rewire a Trane rooftop unit in 1980 that got all the wiring burnt from a centrifugal switch that failed and had a major rollout. Froze my butt for 2 days on that rooftop. Coleman had some of those too and it is a BAD idea/method.
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Old 11-18-2012, 09:56 AM   #23
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Yeah, I've also had to rewire a commercial Carrier RTU that had the roll out switch fail to lockout the unit when the inducer wheel corroded away.

I've seen this hall effect on Trane units as well.

I would prefer to see pressure switches. I suspect they are used because of the environment on rooftops but have never asked in Carrier or Trane class.
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Old 11-18-2012, 10:15 AM   #24
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Rollout switches are not the fastest responding devices are they? They are cheap, small bimetal switches and they can get corroded in an outdoor environment. Now we should talk about fireyes in commercial boilers, now thats fun and fast response and foolproof.
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Old 11-18-2012, 07:25 PM   #25
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. .. . So has anyone changd one of these out? Can I just change the blades or do I need to change the whole assembly? Do I have to take out the control board to get to the screws for the draft housing.
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Old 11-18-2012, 07:32 PM   #26
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if the wheel comes off and its available change the wheel...I would personally change it all....
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Old 11-19-2012, 07:52 PM   #27
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I usually replace the whole inducer assembly unless it isn't very corroded.
Take a look at the set screw on the inducer wheel and inspect the motor shaft. Can you take it apart?

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