Tag: ecm

First, let’s cover the basics. X13 is a brand name for the Regal Beloit / Genteq brand of constant torque motors, there are other manufacturers who make them but the term “X13” has become pretty much synonymous for the fractional horsepower HVAC constant torque motor.

Also, this article is specifically discussing the common residential/light commercial motors. There are other types of variable and constant torque motors and equipment not being addressed here.

Both variable speed and X13 motors are ECM or “Electronically Commutated Motors”, This just means the DC power that drives them is electronically switched from positive to negative. Both are more efficient than the typical PSC motor with ECM motors commonly being about 80% efficient and PSC being about 60%.

Both X13 and variable speed motors are DC, 3 phase, permanent magnet rotor motors that use back EMF to determine motor torque and adjust to load conditions.

The primary difference is the type of inputs to the motor control. A variable speed motor is programmed for a specific piece of equipment to produce a set amount of airflow based on the particular static pressure profile of that system as well as based on the inputs from the air handler circuit board or system controller. In other words, a variable speed motor can ramp up down based on the static pressure as well as the staging of the equipment, pin/dip switch or controller settings for desired airflow output and “comfort profiles” that can be setup to allow the blower to ramp up or down for enhanced dehumidification and comfort.

An X13 motor is programmed to produce a set motor torque based on which input it is receiving 24v. This means that while an X13 motor is more efficient than a PSC motor and does a better job of ramping up to overcome static pressure increase it does not have the level of control that a variable speed has and it also does not produce an exact airflow output across the full range of static pressure.

This is why when you check the blower charts on a unit with a variable speed motor the CFM will remain the same over a wide range of static points but when you look at an X13 system the CFM will drop as the static pressure increases.

— Bryan

Ever since Nikola Tesla invented the modern induction motor we have been struggling with varying the speed of motors in an efficient and reliable way. The trouble in the HVAC industry is that there are several different types of technologies in play and they can easily get confused.

ECM (electronically commutated motor)

In residential and light commercial HVAC we have seen ECM (Variable Speed / X13) motors for years, primarily in blower motors but sometimes even in condenser fan motors. The first thing to know is that an ECM motor is “Brushless” DC motor. Most traditional DC motors require brushes to provide power to the motor rotor (spinning part). Brushes are notorious for wearing out over time making DC motors unreliable in constant duty applications. An ECM motor uses a permanent magnet rotor which eliminates the need for power to be fed to the rotor through brushes.

An ECM motor is a DC 3 phase motor with a permanent magnet rotor where the cycle rate is controlled by the motor module. Here is a great video on how they work.

 


VFD (Variable Frequency Drive) 

For existing A.C. (Alternating Current)  3 phase motors the only way to change the speed reliably and efficiently is the alter the “frequency” of the power applied to the motor to something other than 60 hz (60 cycles per second). A VFD intercepts the power applied to a motor, changes it to DC power with a bank of diodes (rectifier) also called a CONVERTER. It then smooths out the power using capacitors before feeding that power to a bank of transistors called an INVERTER which is constantly switching the power from DC back to a form of power called PWM (Pulse Width Modulation) which replicates frequency change to the motor. The drive needs to be able to provide this PWM power at the correct voltage and current in order to control a 3 phase motor properly.


Inverter / Inverter Drive

Many A/C systems are coming with Converters, Capacitor Smoothing (Intermediate Circuit) and then the Inverter all built in to the equipment itself to drive a compressor or compressors. This inverter technology is essentially an intelligent and specifically designed VFD built into the equipment itself. The Carrier Infinity system is one of many systems that utilize inverters.

These technologies are constantly evolving and changing and while they may be similar, the different names describe different types and applications of technology all designed with e end goal of making motors go more than one speed with the best efficiency and reliability.

— Bryan

This question was submitted on the site in response to the recent GFCI tip. It’s a good question with several possible answers. What do you think?


Hey Bryan,

I have had a few instances where we are firing off a furnace in a new build with a temporary power pole outside with gfci outlets installed that are tripping the gfci on blower motor start up. (In order to get temporary heat for drywall, we run an extension cord to the gfci pigtailed to the furnace). I’ve never had issues doing this with PSC motors, but everytime I’ve tried to use a gfci with a variable speed or true ECM motor, it trips the gfci. I’ve tried multiple motors, different furnaces.

What gives?

Sincerely,
Frustrated in Fort Collins


Howdy Frustrated (This feels like a Dear Abby article but I’m just gonna roll with it),

I haven’t tried this so I haven’t experienced it (No big call for temporary heat in Florida) but it does make some sense. The GFCI is just watching for a difference in current on hot and neutral. When you add in a variable frequency drive (Which is essentially all an ECM or X13 motor is) the circuitry / housing is exposed to a lot of “induced” electromagnetic fields due to the varying frequency / harmonics. Some of this induction (Magnetic Flux) may be routed to ground causing a tiny imbalance. Here is a thread in my buddy Mike Holt’s forum that talks about this very phenomenon HERE

Thanks for participating. Great stuff!

— Bryan

P.S. – What do you think is going on?

Scroll to top
Translate »

Daily Tech Tip

Subscribe to our daily tech tip to receive daily tips and advice!
Email address
Name