Ruud EMC Condenser Fan Motor conversion to PSC


Old 06-10-18, 12:49 AM
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Join Date: Jun 2018
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Ruud EMC Condenser Fan Motor conversion to PSC

Ruud (UAPM-030-JEZ) EMC Condenser Fan Motor conversion to PSC

Here is what lead to the conversion, skip ahead to see how it was done. A tenant called Saturday afternoon saying no heat on a June day in Austin, Tx. The HVAC Dealer I bought it from said this eight year old system was under warranty but it would take “five business days” (one week) to get in the replacement EMC motor and it might not be available. They made me promise, before they would order it, that I would pay them $50 for shipping and $400 labor to install the motor. Seven days in the Tx heat is an eternity so I needed another solution. I contacted a HVAC guy on Craigslist, a guy that works for himself. He took out the EMC motor and put in a PSC motor. Parts and labor cost me $250. The tech said the motor was $127 and the relay was $14, the capacitor was around $15. Compare $250 for a working system to the $450 (labor and shipping) that the Dealer wanted just to install a warranty motor that might not be available.

The tech bought a PSC manufacturer’s motor from a HVAC supply store (see photo), it will mount without modification in my system. This motor matched closely the RPMs of the defective ECM motor. It also came with a white connector that can be easily reverse the direction of the motor. The amps were almost double the EMC motor and the Horse Power was 1/4 compared to 1/5 for the EMC motor. But I am trading off the efficiency of the EMC motor for the reliability of the PSC motor. He also bought a 5 MFD 370 V capacitor that the motor calls for and is written on the motor box. He also bought a C130A single pole relay (photo).

After I took some pictures he pulled the old motor out, The points of contact for the four wires from the old EMC motor will no longer be used, the new motor does not use the old motor points of contact. He mounted the new motor and ran the wires. The motor came with a wiring diagram (picture). He used the middle diagram (4). Why? I am not sure why he chose diagram 4 over diagram 3. The diagram shows the White and Black wires coming from the motor going to 240 VAC (on one side of the new relay), and the Brown and Brown/White wires coming off the motor going to the new 5 MFD capacitor. The ground is self explanatory. The third diagram (photo) shows how you can reverse the direction of the motor with a connector.

He mounted the new relay to the outside of the Circuit Board enclosure (no room inside) and connected the motor’s White and Black wires to one side of the relay. He connected the motor’s Brown and Brown/White wires to the new capacitor and mounted the capacitor inside the Circuit Board enclosure.

Then he added two new wires that go from the other side of the new relay to “Line In” (240 VAC). The best place to tap into 240 VAC was from the lug screws on the Printed Circuit Board labeled “Line In”. Now we have a path for 240 VAC to get to the new motor.

Next he added a new wire to the relay coil to ground, it goes anywhere on frame ground. The other side of the Relay coil goes to the 24 vac line coming from the furnace that demands cold air, Y1 (pretty sure). You may watch a volt meter to see the 24 vac drop out with the cycling of the thermostat to make sure you have the correct wire. The tech just took off the wire nut and added the wire from the Relay coil.

We tested and it worked fine. I noticed the coil fan motor comes on first, then the compressor kicks in a few minutes later. Previously, the compressor kicked in first and a few minutes later the coil fan motor kicked in. Obviously an electrical saving feature which I now forfeit. I understand there is a ICM 251B relay control that we might add in the future. The best part is the tenant is not complaining about no AC.
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Old 06-10-18, 01:14 AM
Gunguy45's Avatar
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Is there a question here or forthcoming? If not, this will be moved to General Chats and Discussions. Sorry, these areas are not for "chat room" usage.
Old 06-11-18, 08:26 AM
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Join Date: Jun 2018
Location: usa
Posts: 2
Sorry, I thought my question was implied. Here’s the question, did this Tech follow best practices for this install as I described it?

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