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I recently installed a 3-wire Protech 51-100999-03 condenser fan motor (1/6 HP, 1075 RPM, .73 A, CCW rotation) and a 24" dual blade, 28 degree pitch, CCW fan blade. New motor has same specs as old motor (TradePro TP-C16-1SP2 6-wire motor) except old motor was rated at 1.2 A.

In addition, I installed a Protech 50 + 3 μF dual run capacitor and a Protactor single-pole contactor.

To wire the circuit, I wired:

enter image description here

(pictured)

  • line voltage wire (white) on L1
  • line voltage wire (black) on L2
  • 24v wire (yellow) on coil of contactor
  • 24v wire (black) on other coil of contactor
  • red wire from compressor on T1
  • black wire from compressor on T2
  • orange jumper wire on T1 (and on Com terminal of capacitor)

(not pictured)

  • purple compressor wire on Herm terminal of capacitor
  • ground wire attached to ground strip on condenser assembly
  • orange jumper wire on T1 and on Com terminal of capacitor
  • orange wire from condenser fan motor on Com terminal of capacitor
  • black wire from condenser fan motor on T2
  • brown wire from condenser fan motor on Fan terminal of capacitor

Problem

The condenser fan motor will run for perhaps 30 minutes and then it noticeably overheats (burning hot) and stops.

Tested Capacitor

I tested the capacitor using Fluke DMM. Herm-Com tested at 50.2 μF and Fan-Com tested at 3.2 μF. The old wiring configuration used two capacitors: one for the condenser fan motor and another for the compressor. I decided just to use a dual run capacitor.

Fan Blade

I warped the old fan blade while removing it from old condenser fan motor. I had it on the new motor for an hour or two. It was moving air, but I could see a slightly wobble at the shaft. Not extreme, but noticeable. So, after the condenser fan motor overheated the first time, I turned the power off at sub-panel. I bought a new blade yesterday (24" dual blade, CCW rotation, 28 deg. pitch). The same overheating problem occurs before and after the fan blade replacement.

While it ran with the new blade, it was pushing a good amount of air out the top of the assembly. No air coming out from the sides, so I suspect the blade is located properly on the shaft.

Cleaned Coils

I disassembled the entire cage for the condenser to paint it. While I had it diassembled, I cleaned the coils. The overheating problem occurred before and after I cleaned the coils.

Now, I have no idea what could be causing the overheating except for a faulty motor. Any other ideas?

  • Your picture shows L2 has a white wire not black as in your description. – Ken Sep 6 '17 at 3:56
  • What voltage do yo measure across L1, L2 and also from each to ground or neutral? It sounds like you could be under or over voltage. Your original was reversible (you have the correct direction CCW/CW ?). The new motor seems to be really efficient in comparison to the old one 1/6HP @.73 Amps - perfect efficiency would be around .5Amp (124 Watts)/220V – Ken Sep 6 '17 at 4:31
  • @Ken—I will measure in the morning. Mosquitoes have been fierce lately at night. Current (new) motor is CCW and the current (new) blade is CCW. Old motor was also spinning CCW. – user56530 Sep 6 '17 at 6:39
  • @Ken—It looks white because it has some sort of film or coating on it. – user56530 Sep 6 '17 at 6:41
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Is this condenser fan motor for a split system with the condensing unit outside? Can you check the running amperage of the new motor to make sure it is not running in an overloaded state? Are you sure that the new motor is the same H.P. as the old motor? Did you check the old and new motors to make sure that the input voltage and RPM are the same? There has to be a good reason for the new motor to overheat.

  • The condenser and compressor are both outside. I have no means to check amperage; I don't have an ammeter clamp. The motors are indeed same HP, but different amperage (new rated .73 A; old rated 1.2 A). I had made another thread on this a week or so ago (but it was about selecting the proper capacitor). RPM is theoretically the same (1075 RPM). I don't know how to determine actual RPM. I did not check input voltage. I will read up on that. – user56530 Sep 5 '17 at 19:55
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    Years ago when we replaced motors on fans and the like we would increase the horse power i step. When replacing small motors we would assume that the newer motors were made slightly cheaper and provided less power, which many times turned out to be true. By increasing the motor HP. we would always have a satisfied customer on the first call. – d.george Sep 7 '17 at 16:20
  • d.george-Sounds reasonable. I did buy another motor, this time 1/3 HP, 825 RPM. We'll see what happens when it gets here. – user56530 Sep 7 '17 at 20:32
  • Turns out the 1/6 HP motor was too weak. I replaced it with a 1/3 HP motor which is running flawlessly (50 + 5 μF cap instead of 50 + 3 cap μF). – user56530 Sep 9 '17 at 1:46
  • The 825 RPM may be too slow to provide the needed air flow for the condensing unit during peak operating conditions. Not enough air flow will result in the high side refrigerant pressure exceeding it's rated limits. This will also cause a greatly reduced operating efficiency. I have been retired for 10+ years but I do not think that things have changed that much in the industry except for the types of refrigerant used. I was weaned on R-12, R-22, ans R-500. To get the rated air flow you will need the original RPM of 1075. Hopefully, the younger people will also share their comments. – d.george Sep 9 '17 at 9:38
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Aloha. I recently had this problem on a Rheem condenser. I replaced the 1/5 hp mtr with a 1/3 hp mtr. Original two blades blade. Same result the mtr would run 1 amp above the rated spec of the mtr. All factory replacement parts. Changed the fan blade from a two blade to a three blade and adjusted the pitch. Problem solved. Perfect amps on mtr. Head pressure right where we like it. I hope this helped.

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