EC Indoor Blower Motors, Resistance is Futile

Part one of this three-part series on indoor blower ECMs provides information on power connections and airflow adjustment.

Thirty-two years after ECM (electronically commutated motor) technology was introduced to the residential and light commercial HVAC industry, the indoor blower motor segment of this industry is now almost completely converted from PSC to ECM. Interestingly enough, the first application for ECM in the HVAC industry was also the indoor blower motor. The constant airflow “variable speed” indoor blower motor was introduced by GE* in 1987.

This motor is primarily applied to top tier multi-stage or modulating HVAC equipment. By 2005, approximate 15% of all new HVAC equipment was built with this motor. However, in 2006, there was a major shift in this segment driven by the 13 SEER regulation. At the same time this regulation was being developed, Regal Beloit Corp. (“Regal”)1 was developing a new type of ECM for indoor blower motor applications called “constant torque.” This technology would provide the same electrical efficiency as the constant airflow ECM but with fewer features and a lower cost.

The constant torque ECMs would be utilized by almost all HVAC OEM in the majority of their air handlers and package systems that moved from 10 SEER to 13 SEER in 2006. By the end of 2006 over 50% of new HVAC equipment was built with an ECM indoor blower motor. In 2019, another regulation focused on the electrical efficiency of fossil fuel appliances has again caused a major shift in this segment. Due to the Fan Energy Rating (FER) regulation that went into effect July 2019, the vast majority of furnaces that were still being built with PSC motors, are now built with constant torque ECMs.

So, it seems like now would be a good time for a refresher course on these two types of motors. Even though they are both built with ECM technology, they are very different in almost every aspect. This article will cover the basic design, input connections and airflow adjustment of each type of motor.

Constant airflow ECMs

Let’s start with the constant airflow (often referred to as “variable speed”) ECMs. I refer to these motors as “communicated ECMs.” The term “communicated” here refers to any type of communication between the HVACR system control and the motor control that meets the following criteria:

  • The connections are fixed at both ends (typically with plug connections), meaning that they are not adjusted from one position to another to modify the operation of the ECM.
  • Airflow adjustments related to the output of the motor are selected at the HVACR system control or user interface.
  • The line-voltage inputs are separate from the communication inputs and are powered continuously from the HVAC system.

Figure 1 shows the type of plug connections used by Genteq® constant airflow ECMs.

The 5-pin plug is populated with the line voltage and ground inputs. The 16 and 4-pin plugs are used for communication. The 16-pin plug represents a communication style that was developed in the 1990s but is still used today. The 4-pin plug represents the latest communication style called digital serial communication (DSI) or simply “serial communication.”

When HVAC systems that use constant airflow ECMs are installed, there are numerous “setup” options related to all of the motors’ features and benefits. At a minimum, the factory default airflow settings should be checked to make sure that they match the capacity of the heating and/or cooling systems. However, most systems also allow for “fine tuning” of the heating and cooling airflow to maximize system performance and comfort. There are humidity control and continuous fan selections that can be tailored to the customer’s preferences as well. Because they can be directly related to various operational issues (or even component failures), these settings should always be checked—and adjusted, if needed—at the time of installation or commissioning. The installation manual should always be stored near the unit for future reference.

The two most common means for adjusting these settings are DIP switches or jumper pins located on the HVAC system control board. Both provide the same basic function. The position of the switch or jumper on the control board determines the selection of a particular feature or function and the output communication to the ECM.


Communicated ECMs


Figure 1: Communicated ECMs


The HVAC system manufacturer provides charts (often labeled as “set-up” or “airflow” or “comfort” settings) that relate the position of each switch or jumper to its corresponding setting. In some cases, charts may be located on stickers on the HVAC unit itself, or they may be part of the schematic. Information may even be printed right on the control board, near the selections. The charts and complete instructions about each setting and how it affects the operation of the HVAC system are always found in the installation and/or service manual. Most HVAC system manufacturers create one manual for each model line they produce, and that manual contains all of the charts for every unit in that model line. There- fore, it is important to find the chart or charts that match the precise model number for the system on which you are working.

Please note the following:

  • Many HVAC system control boards are manufactured with multiple sets of DIP switches or groups of jumper pins for the selection of additional features, such as time delays, thermostat choice, staging control, or built-in diagnostics. Some of these settings are not only imperative to the proper operation of the system, but also affect comfort and noise levels.
  • Even though systems that utilize constant-airflow ECMs are predominantly multistage or modulating systems, there is typically one airflow selection that adjusts the heating or cooling airflow for all stages or operating points.

Figure 3 is an excerpt from the installation manual for a residential gas furnace.

Jumper pins typically are arranged in groups of columns or rows on the control board. Each group is labeled on the control board to identify its purpose. Each pin or pin set is labeled on the circuit board with a letter, word, abbreviation, or value.

The charts provided by the HVAC system manufacturer relate the position of the jumper in each group to a corresponding airflow value, comfort selection, or other feature (see Figure 4). The type of control board illustrated in this example from York® 2 requires the user to move a jumper or plug from one position to another (across two pins) to change selections.

Compared to jumper pins, DIP (dual in-line package) switches are smaller in size. Each switch is labeled with a number. The positions of the switch may be labeled as follows: on and off; or 1 and 0; or on with an arrow (see Figure 2 on pg. 23).

The switch numbers and position labels are very small. Depending on its orientation in the unit, the control board may appear upside down or sideways.

This can make it easy for a service technician to set a switch in the wrong position if he or she is not paying close attention. The charts provided by the HVAC system manufacturer relate the position of the switch to a corresponding airflow value, comfort selection, or other feature (see Figures 5 and 6).


Dip Switches


Figure 2: DIP switches (Trane® UY080R9V3W). Image courtesy of Trane®



Furnace contro board schematic


Figure 3: Furnace control board schematic (York® TM9v)


Most fossil fuel heating systems have the heating airflow preset at the factory to operate with a temperature rise that is within a few degrees of the midpoint of the temperature rise range specified on the unit rating (data) plate. However, the technician should always measure the temperature rise and compare it to the information on the unit rating plate. There are several ways to modify the heating airflow if the temperature rise does not meet the specified range, or if adjustments are needed to improve airflow or register temperature.

The chart shown in Figure 5 (this time from Trane® 3) provides detailed temperature rise, airflow, and power values related to a pair of switch settings. Note that the factory default setting is identified as “Normal.” Also, notice that even though the values for first-stage and second-stage heat are given, there is only one selection that modifies the airflow for both stages.



HIGH / LOW SPEED COOLING AND HEAT PUMP CFM
060B12 080B12 Jumper Settings
High Low High Low COOL Tap ADJ Tap*
1343 865 1320 882 A B
1116 727 1093 755 B B
1235 791 1203 810 A A
1026 661 1001 693 B A
1079 709 1080 730 A C
889 590 880 641 C B
900 599 910 642 B C
787 531 803 585 D B
814 542 836 597 C A
712 490 738 557 D A
725 499 749 561 C C
641 456 682 529 D C
HIGH / LOW HEAT CFM
060B12 080B12 Jumper Settings
High Low High Low HEAT Tap ADJ Tap*
1364 843 1433 945 A Any
1253 745 1320 887 B Any
1102 660 1223 840 C Any
1014 607 1134 768 D Any

Figure 4: Airflow data (York® TM9V)



For most systems, the cooling air ow is also the heat pump heating air ow. Most units designed to be used in split systems are capable of operating with multiple sizes (capacities) of A/C or heat pump systems. Therefore, the factory default selection always must be checked and adjusted to match the installation.

Figure 6 shows an example of a chart from Trane that allows for the selection of cooling air ow by unit capacity (tonnage) and the ability to set the air ow at 350, 400, or 450 cfm per ton for more or less latent heat removal (dehumidification). In this example, four switches must be adjusted to achieve the proper selection.

These are just few examples of how different manufactures provide charts and functions for selecting air ow. Constant air ow driven systems also have many other options for selecting comfort features such as improved dehumidification and continuous fan. While many are similar, it’s important to be familiar with and follow the instructions provide for each individual HVAC system.

Many HVAC manufacturers also now offer communicating thermostats with on-screen menus. These menus may include some or all of the air ow and comfort selections previously discussed, as well as advanced diagnostic features and real-time operational values, such as cfm and TESP (total external static pressure). If the HVAC system control board utilizes DIP switches or jumper pins, their settings may be superseded by the communicating thermostat menu selections. Again, be sure to check the HVAC manufacturer’s literature for information related to these advanced thermostats.



AIRFLOW SETTING DIP SWITCH SETTING EXTERNAL STATIC PRESSURE
SW 7 SW 8 0.1 0.3 0.5 0.7 0.9
HEATING
1ST
STAGE
Low ON ON CFM
TEMP.
RISE WATTS
800
56
105
800
56
140
800
56
180
800
56
220
800
56
265
MEDIUM LOW OFF ON CFM
TEMP. RISE
WATTS
860
52
115
880
51
165
890
50
215
920
48
265
910
49
320
NORMAL ** ON OFF CFM
TEMP. RISE
WATTS
960
46
150
990
45
200
1000
44
230
1020
44
310
1010
44
350
HIGH OFF OFF CFM TEMP. RISE WATTS 1080
41
195
1110
40
255
1120
40
315
1120
40
365
1080
41
390
HEATING
2ND
STAGE
LOW ON ON CFM
TEMP. RISE
WATTS
1100
62
205
1100
62
260
1120
61
320
1120
61
370
1090
63
400
MEDIUM LOW OFF ON CFM
TEMP. RISE
WATTS
1210
57
265
1240
55
340
1260
54
410
1260
54
470
1130
61
430
NORMAL ** ON OFF CFM
TEMP. RISE
WATTS
1360
50
365
1390
49
445
1400
49
500
1360
50
535
1210
57
475
HIGH OFF OFF CFM
TEMP. RISE
WATTS
1360
50
355
1390
49
450
1400
49
520
1350
51
535
1180
58
465
NOTES:
* First letter may be “A” or “T”
** Factory setting
1st Stage Capacity = 49,000
2nd Stage Capacity = 73,000

Figure 5: Heating airflow (cfm) and power (watts) vs. external static pressure with filter for gas furnace (Trane UY080RV3W)





OUTDOOR
UNIT SIZE
(TONS)
AIRFLOW
SETTING
DIP SWITCH SETTING EXTERNAL STATIC PRESSURE
SW 1 SW 2 SW 3 SW 4 0.1 0.3 0.5 0.7 0.9
2.0 LOW
(350 CFM/TON)
ON ON OFF ON CFM
WATTS
750
84
750
122
750
154
720
185
710
221
NORMAL
(400 CFM/TON)
ON ON OFF OFF CFM
WATTS
840
109
840
146
840
181
840
226
820
264
HIGH
(450 CFM/TON)
ON ON ON OFF CFM
WATTS
940
136
940
177
940
215
940
274
940
318
2.5 LOW
(350 CFM/TON)
OFF ON OFF ON CFM
WATTS
850
113
850
150
870
200
890
250
890
295
NORMAL
(400 CFM/TON)
OFF ON OFF OFF CFM
WATTS
960
150
990
200
1000
230
1020
305
1010
350
HIGH
(450 CFM/TON)
OFF ON ON OFF CFM
WATTS
1080
195
1110
255
1120
315
1120
365
1080
390
3.0 LOW
(350 CFM/TON)
ON OFF OFF ON CFM
WATTS
1020
175
1020
225
1040
280
1050
330
1050
375
NORMAL
(400 CFM/TON)
ON OFF OFF OFF CFM
WATTS
1170
240
1180
300
1200
365
1200
415
1130
420
HIGH
(450 CFM/TON)
ON OFF ON OFF CFM
WATTS
1290
310
1320
410
1350
470
1340
520
1150
440
3.5 LOW
(350 CFM/TON)
OFF OFF OFF ON CFM
WATTS
1170
250
1190
315
1210
370
1210
435
1100
405
NORMAL
(400 CFM/TON)
OFF OFF OFF OFF CFM
WATTS
1360
365
1390
445
1400
500
1360
535
1210
475
HIGH
(450 CFM/TON)
OFF OFF ON OFF CFM
WATTS
1360
355
1390
450
1400
520
1350
535
1180
460

NOTES: * First letter may be “A” or “T”

  1. At continuous fan setting: Heating or Cooling airflows are approximately 50% of selected cooling value.
  2. LOW airflow (350 cfm/ton) is COMFORT & HUMID CLIMATE setting;
    NORMAL airflow (400 cfm/ton) is typical setting;
    HIGH airflow (450 cfm/ton) is DRY CLIMATE setting.

Figure 6: Cooling airflow (cfm) and power (watts) vs. external pressure with filter for gas furnace (Trane UY080RV3W)

Constant torque ECMs

Constant-torque ECMs are most commonly built using a multi-tap design similar to that of a PSC induction motor. Each tap (usually called a “speed tap”) is actually programmed with a torque value. The torque value for each tap is stored in the motor control. When the tap is energized, the motor control operates the motor at that value. This is also very similar to an induction motor in which the motor winding is tapped to create multiple speeds based on the torque created by each tap. However, that is where the similarities end. The Genteq® model Endura® Pro motor is an example of a multi-tap constant-torque ECM (see Figure 7).

The motor control is powered with continuous line voltage when the HVAC system’s disconnect is closed. The high-voltage terminals on the connection block of all Endura® Pro motor controls, regardless of the rated voltage, are labeled “L” (Line 1), “G” (ground), and “N” (neutral). The “N” terminal is connected to the neutral line on 15-V ac and 277-V ac systems, or to Line 2 on 208-/230-V ac and 460-V ac systems. Each model is built to operate at a single voltage source.

The five speed taps can be energized with 24 V ac or 15–33 V dc. By far the most commonly used input voltage is 24 V ac. The connection block is always labeled “C” for 24 V ac common and 1–5 for the speed taps. The ECM turns on and off when the speed taps are energized and de-energized (see Figure 7 on pg. 25).

To select the correct tap for heating and cooling airflow with constant-torque ECM- driven systems, follow the same criteria as those used with induction motor systems. The air- flow of any given tap is affected by the TESP (see Figure 9). Temperature rise on fossil fuel systems and airflow for cooling or heap pump systems should be measured to ensure accuracy. Always measure the TESP and verify that it is as close to the HVAC system manufacturer’s recommendation as possible. If the TESP is higher than recommended when the system is new and clean, it may be prone to nuisance failures and inadequate performance due to filter loading and/or the closing or blocking of registers and grilles by customers.

The schematic provided by the HVAC system manufacturer typically includes a leg- end that correlates the speed tap designation (lo, hi, heat, cool, fan, etc.) to the wire color, tap number, or both. There may also be a chart and/or notes related to suggested tap usage (see Figure 8).

The factory-selected heating tap speed (in fossil fuel systems) typically provides a temperature rise within a few degrees of the midpoint of the temperature rise range specified on the unit’s data plate at the recommended TESP (typically 0.5 in. w.c.). If the measured temperature rise at this speed does not fall within the required range, the TESP should be improved or a higher speed tap should be selected (if applicable). Before changing the factory-selected heating tap, always consult the airflow table in the installation manual and read all applicable notes related to adjusting the blower speed for heating mode operation.

The factory-selected cooling or heat pump tap speed is typically the highest speed (unless that is required for the heating tap). Most fossil fuel furnaces and air handlers are capable of operating with multiple sizes of connected A/C or heat pump systems.

The factory-selected cooling speed tap may need to be adjusted to match the installed system’s airflow requirement. Before changing the factory-selected cooling tap, always consult the airflow table in the installation manual. Such tables provide rated cfm values for each tap relative to the TESP (see Figure 9) and can be used to adjust airflow accurately for proper performance.

In this article, I referenced Genteq® motors as the examples for each ECM type. While there are other manufacturers of ECMs many use the same plug connections and methodology described here. If you follow the HVAC manufacturers literature related to a given type of ECM, the information provided here should serve as a good basis of understanding for all ECM driven systems.

Watch for Part 2 of this article series coming in the August 2020 issue of RSES Journal, where we will discuss the airflow performance characteristics of these motors related to Total External Static Pressure and their unique operating programs. In the third article (in the October 2020 issue of RSES Journal), we will discuss diagnostics and replacement.


Electrical Connection Details


Figure 7: Electrical connection details



Example-of-wiring-diagram


Figure 8: Example of wiring diagram (partial) for single-stage gas furnace



FURNACE AIRFLOW (CFM) VS. STATIC PRESSURE (in.w.g.)
MODEL SPEED TAP 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
*UXIB060A9H31B 4 - HIGH - Black
3 - MED-HIGH - Blue
2 - MED-LOW - Yellow
1 - LOW - Red
1358
1196
1025
863
1327
1166
1000
830
1296
1135
975
797
1272
1109
943
762
1248
1082
910
726
1215
1053
878
687
1182
1023
845
648
1122
939
813
601
1061
955
780
554

Figure 9: Example of airflow table (partial) for single-stage gas furnace



*“GE” is believed to be a trademark or trade name of the General Electric Co. 1 Regal, Regal Beloit, Genteq® are trademarks or trade names of Regal Beloit Corp. or one of its affiliated companies.

2 York is believed to be owned by Johnson Controls International plc or one of its affiliated companies. 3 Trane is a subsidiary of Trane Technologies.



Christopher Mohalley is the Training Manager for Regal. He has applied his 25+ years of HVAC field experience, instruction and extensive product training to create a nationally-recognized ECM training program. He serves as a NATE Technical Committee SME, is a member of RSES and is NATE certified in all HVAC disciplines.

Interested in reading more about this topic? Check out Mohalley’s book Understanding Electronically Commutated Motors (SKU 200-523x), published as a part of the RSES Sustainability Series at www.rses.org/store. Use promo code ECM2020 and get 10% off the purchase price.



"EC Indoor Blower Motors, Resistance is Futile", by Christopher Mohalley. June 2020 feature reposted with permission from RSES Journal, www.rsesjournal.com.

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