Rooftop AC System: No in house air movement

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Old 08-19-13, 08:23 AM
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Rooftop AC System: No in house air movement

I came home at 11pm to find my house at 100F last night.

This is an all in one machine, everything on the roof. Carrier model: 585jj030075

Circuit breaker was tripped for the rooftop AC.
I reset the breaker, could hear the rooftop fan and compressor working, but zero air movement indoors.

Today:
I checked the breaker panel: All looks normal.
Visited rooftop unit: Fuses in service panel are good.
Turn on AC, reduce target temp to lower than house temp. Compressor on roof and fan on roof are audible (normal sounding). Zero air movement thru indoor ducts.
Visited rooftop unit: Large fan is running. Pulled service disconnect and could hear the coolant moving back down into the sump.
Reset service disconnect, returned indoors, still no movement.
Turned off temperature control. Unit turned off normally.
Set thermostat to fan only. No response of any kind.

Based on the above my theory is that I lost the circulation blower (correct term?).

Action theory: Remove side opposite the condenser coils, start tracing power.

Am I on the right track?
 
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Old 08-19-13, 08:57 AM
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Do you hear your fan running if you just put it in the on position at the stat? I'd say inspection of the blower and coil is the next step regardless. Insulation could have come off and blocked the coil if it does run or the motor could be down if it doesn't
 
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Old 08-19-13, 08:59 AM
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I just returned from the roof.
Removed two side panels.
One housed electrical across the top, and burners on the bottom.
Second contained a squirrel cage blower and a duct down into the attic.

Squirrel cage blower motor spins freely without noise.
 
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Old 08-19-13, 09:02 AM
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tinmantu: If I turn the fan to on using the thermostat (without selecting cool), there is zero response.
 
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Old 08-19-13, 09:03 AM
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If you have a service disconnect up there then set fan only up on stat and control the fan with the disconnect to test.
 
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Old 08-19-13, 09:05 AM
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Yes, there is a rooftop service disconnect.

I'll set the fan to 'on'.
Then head up and see if I can comprehend any of this wiring (I have minimal knowledge in this area, but I do have a basic volt meter)
 
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Old 08-19-13, 09:06 AM
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Time to dig out the volt meter and see if you have power to the motor, if you feel comfortable doing that.
 
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Old 08-19-13, 09:33 AM
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Progress report:

With the thermostat fan set to on (cooling not selected)
Went to roof, started looking for power using the volt meter.

Reference wiring photo posted previously:
Top right relay:
240V to white and black on right side of relay.
Zero V to left side of same relay.

Found 110V off lower leg of this relay, it goes down to the thermostat.
when I placed the Volt Meter probe in the white thermostat wire nut, and tried to follow power up to the relay it is connected to, I touched the orange wire at top right of said relay. Blower fan hummed but did not spin. I spun the fan manually and the FAN CAME ON SOLID. (this relay is top row, second item from left.)

Fan is now blowing (and I left it in the on position of the thermostat)
Cool air is now blowing (since I selected cool on the thermostat).

Thus I am temporarily in business for todays expected 107F.

Does this point to a bad blower capacitor and a bad relay?
 
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Old 08-19-13, 09:47 AM
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Considering you had to help it, I'd try the cap first. I see it's made in china and they aren't reliable. The relay isn't that expensive to replace if you still have problems.
 
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Old 08-20-13, 07:05 PM
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Replacement capacitor was $ 3.21.
Installed and system is functioning normally again.

Thank you for the assistance.
 
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Old 08-20-13, 07:32 PM
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Wow....what a bargain. Don't anticipate that capacitor to last too long either.
 
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Old 08-21-13, 05:49 AM
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Good to hear you are back up and running with minimal cost. Due to the high failure rate of the made in China run capacitors it is a good idea to have a spare one on hand for emergencies. Before installing a run capacitor you should always test it to make sure it is within specs, normally +/- 6% or +/- 10%. It should say on the label.
 
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Old 08-21-13, 06:36 AM
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The old capacitor was 24 years old.

Has quality control become so poor that they don't last these days?

New unit is a Titan Pro, Professional Grade. Yes, like everything it is made in China.
 
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Old 08-21-13, 11:05 AM
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Glad it worked out for you. From the looks of the motor, it appears to be a replacement, so that old cap may have been less than 24 yrs old. If you have another failure, consider getting same mfd in a 440 volt rating.
 
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Old 08-21-13, 11:17 AM
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No, that is the original motor. I've owned the house since it was 6 months old.

Replacement cap is:
Titan Pro, Professional Grade
Run Capacitor
5 MFD
440/370 VAC
TOCF5
Tolerance +- 5%
Protected 10,000 AFC
 
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Old 08-21-13, 11:26 AM
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Ok...just appeared to have reversing rotation leads that one doesn't see on a factory motor. As long as it works is all that counts.
 
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