Motor Ambient Rating - Short #241

HVAC School - For Techs, By Techs

Bryan Orr

Training, Careers, Airconditioning, Self-improvement, Hvac, Business, Education, Refrigeration, Heating, Ac, Apprenticeship

4.8 • 985 Ratings

🗓️ 20 May 2025

⏱️ 5 minutes

🔗️ Recording | iTunes | RSS

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Summary

In this short podcast episode, Bryan talks about what the ambient rating means on a motor. These ratings can be found on both condensing fan motors and blower motors. They have Cs in their rating, which represents the maximum ambient temperature the motor can handle in degrees Celsius (like 40C or 60C).

Heat and overvoltage kill motors, and motors with higher ratings can withstand higher temperatures and last longer in hot conditions. Be careful not to confuse this rating with the insulation class (which is classed by letters and corresponds to temperature limits). You could have a condition where you exceed the insulation's rating but not the ambient rating.

Air over operations (especially in the case of TEAO motors - totally enclosed air over motors) also play a role. The airflow helps cool the motor, and airflow restrictions like dirt and soil can create conditions that cause the motor to exceed its rating.

Motor bearings also matter. Ball bearings tend to last longer and withstand higher temperatures than sleeve bearings, but they are noisier. Many motors use sleeve bearings, and replacing a sleeve bearing motor with a motor that uses ball bearings may negatively affect the homeowner's comfort due to the noise, so that's a conversation you'll want to have with the customer and set realistic expectations.

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Transcript

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0:00.0	One, two, three, four, I declare an HVAC war.
0:08.0	No, I don't.
0:08.6	There's enough talk about war already.
0:11.0	This is the HVAC school podcast, and this is a short episode where we're going to talk
0:14.4	about ambient temperature ratings on motors.
0:17.2	But before we do that, we want to thank our great sponsors.
0:20.5	Copeland and their technician appreciation sweepstakes.
0:24.4	Carrier and Carrier.com?
0:26.5	Refrigeration Technologies at refrigetec.com.
0:30.2	The ESCO Institute, with over 200 HVACR training solutions, courses, webinars, and simulators,
0:37.0	find out more by going to
0:38.4	escowgroup.org.
0:42.2	All right, so ambient rating.
0:44.0	You've probably seen it.
0:45.7	Most commonly, you'll see, like, a lot of condensure fan motors, so I have a 60C,
0:49.6	60 degrees C rating.
0:51.3	Lowerers were sometimes even be lower than that, down to 40 degrees C in some cases.
0:56.4	But what does that mean?
0:57.4	So 60 degrees C, 60 degrees Celsius, is 140 degrees Fahrenheit.
1:01.8	Sometimes you'll see 70 degrees C, which is 158 degrees Fahrenheit.
1:05.5	And what is this ambient rating?
1:07.3	Well, that's just the maximum surrounding air temperature a motor can handle while running. So it's not coil temperature or case temperature or anything to do with the windings. It's just the air around it. It's the ambient temperature rating. So why does it matter? Well, you often not going to have like a lot of choice, but you're going to often see motors that are 60C,
	...

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