Presentation on theme: "GE - ECM Motor Technology and Troubleshooting"— Presentation transcript:
1 GE - ECM Motor Technology and Troubleshooting Presented by The RLCS Engineering Product Field Support
2 Airflow If SPEED is constant, CFM changes with Static Pressure To hold CFM constant, SPEED must change with Static PressureIf we can start out with this idea in mind, then proving that the ECM motor technology is superior will be much easier.If we take a PSC motor, whose speed is fairly constant (1075rpm), and we either add or take away static pressure, the CFM that the motor will deliver will vary.But, if we take an ECM motor, whose CFM is programmed to remain constant, then we can change the RPM of the motor to keep the CFM constant.Which would you rather have?
3 No System Balancing Required! 0.10.20.30.18.104.22.168.8130014001500160017001800190020002100220023002400Unregulated Versus Regulated AirflowPRESSUREAirflow (CFM)No System Balancing Required!Overblowing the systempoor moisture removalhigh power consumptionSystem airflow is starvedSet the airflow leveland go!
4 The ECM’s Benefits in HVAC ECM Airflow Control PSC Constant airflow over wide external pressure changesGreater customer comfort and satisfactionExternal pressure change causes:airflow variation as filter loadsreduced performancepoor latent/sensible capacity control
5 The highest efficiency motor there is! … A DC Motor What's an ECM ?The highest efficiency motor there is! … A DC MotorWithout mechanical Brushes and CommutatorPermanent Magnet RotorRotor losses are nearly zeroStator is driven from an Inverter which,in turn, is powered from the AC lineThe “Electronic Inverter”“Commutates” the stator magnetic fieldsSynchronous machineSpeed and torque controlledInterfaces to the HVAC controls
6 ECM Issues - Furnaces / Fan coils Prior to potted controls:Moisture was responsible for most failuresThe Power Transistors were the most common failureContaminants from the air, added to the moisture/condensation, were also a concernNow, most common failure:NO defects foundActually the most common failure is “NO FAULT FOUND”. That is why we have put this training program together. When we find a motor that has failed, the culprit is usually moisture. Water off fan coils are the biggest problem, followed by leaking A or N-coils sitting on top of furnaces. Water is rarely the cause of ECM blower failures in furnaces.Contaminants from the air , mixing with the moisture added to the problem.The solution...
7 ECM Potted ControlProduced in fan coils and Tyler products since October 1998Produced in furnaces since September 1999…ECM2.3!This motor is “potted” (dipped in goo) to prevent moisture from getting to the electronics. When this motor was subjected to a moisture and salt test, the bearing on the motor failed before the electronics did!This motor has been in production in our Fan Coils and Tyler Products since 10/98.Furnaces received this motor into production in September 1999.
8 Types of ECM Control Thermostatically Controlled Fan Coils / Non-condensing furnaces / Packaged UnitsPulse Width Modulation (PWM)Split systems (A/C & Heat Pump)Condensing FurnacesWhen we talk about ECM motors, there are two ways to control them;ThermostaticPulse Width Modulation.The Thermostatic control is most common. We will find this type of control in our Fan Coils, Non-Condensing Furnaces and our Tyler packaged Products.The Pulse Width Modulation (PWM) control is found in our Condensing Furnaces and our Split System -A/C & HP’s.We will now explain how each type of control works.
9 Thermostatically Control ECM logic for fan coils, non-condensing furnaces and Tyler productsUses Full, Half, Positive, Negative or No Sine waveBases CFM on predetermined CFM curvesModels programmed differentlyCFM is controlled by adjusting torque in response to RPMRPM is sensed by the motor’s “back EMF”Always uses the “highest CFM” of what is being called forThermostatic Controlled motors have pre-programmed parameters. The CFM desired is selected by “pins” that will send different signals to the motor. These signals are in “HALF-WAVE” form. Voltages of “0”v, -12vDC, +12vDC and 24vAC can be read with a volt meter. Each signal prompts the motor to run a different speed. Sometimes, combinations of signals are needed to have the motor run the requested speed (call for cooling; “Y” & “G”).The motor is a “constant volume” motor, in that it will constantly monitor the “back EMF” of the motor and adjust the RPM of the motor to provide a constant, predetermined CFM.If the motor receives more than one signal (“Y”- Heat Pump and Auxiliary Heat), the motor know to to run the higher of the two CFM’s to protect the equipment.
10 FAN COIL EASY SELECT BOARD DH - DehumidificationR - 24 VACW1 - 1st stage Elect HtW2 - 2nd stage Elect HtY1 - 1st stage CompressorYY/2 - 2nd stage Compressor or single stage CompressorG - FanO - Reversing Valve in ClgC - CommonHum - Humidifier (24VAC)AUX - Auxiliary (24VAC)EACThis is a typical control board (40FK/FK4C/FV4A) that will control the ECM motor. We will discuss how this is done later in the program.
11 Pulse Width Modulation PWM ECM LogicPulse WidthModulationPWMAnother other way to control an ECM motor is to send a PWM signal to the motor, receive a “Feedback” signal and then adjust the PWM to control it’s RPM.Split Systems or Variable Speed Furnace
12 Pulse Width Modulation (PWM) PWM is a simple way of commanding airflow (CFM), as defined from an external device (2 wire method)The variable speed circuit board supplies this signal to the motorsThis method is controlled by a two wire system, which is usually a control board(external device). Like in the condensing furnace, a “personality plug” is required to tell the circuit board what signals to send to the motor.
13 90% ECM MOTOR TECHNOLOGY “PWM” Pulse Width Modulation (PWM)Equation determines the slope of the curveBased on duty cycleCFM 2CFM 1Min PWM is Minimum torque and Max PWM is Maximum TorqueMinPWMMaxPWM
14 Duty Cycle The amount of “ON-TIME” per cycle PWM= A/B or PWM%= A/B% (a=b=full speed, emergency heat, sw 4 - on)AVoltage (dc)The signal sent to the motor would look very similar to the “square wave” above. The torque of the motor is determined by the width at which the “A”signal is sent to the motor electronics. The wider the signal (“B” is constant) the faster the motor will run. If A=B, the motor will run at 100% torque, which would be the maximum speed regardless of static situations or when setup switch #4 - Emergency Heat is activated.BTime
15 ECM logic for variable speed condensing gas furnaces Furnace control board sends a PWM signal to the motorControl logic is contained in the Furnace control boardAirflow is determined by the model or “personality plug” on furnace boardPWM can be read by an oscilloscopewill be seen as a square waveformThe signal could be viewed as a square-wave by an oscilloscope. Or you can use the troubleshooting guide to determine where to look for various voltages. There are a couple other methods available to help troubleshoot the ECM motor. We will discuss them in the troubleshooting section of this program.As mentioned before, the “personality plug” determines the signals needed to run the motor.
16 38TDA/YDA, 598W Condensing Units Uses logic in Circuit Board of outdoor unitControl Board sends a PWM signal to the motorSignal can be read with a “DC” volt meter, with motor at full speed (22º<OAT>90º) at PW1, PW216-20 VDC with motor connected20-40 VDC with motor DisconnectedIn the 38TDA/YDA, the condenser fan motor is controlled by the control board. The sixteen pin header is configured for each unit and the thermistors in the ambient air and on the coil help determine fan speed. Troubleshooting the fan motor can be found in the split system service manual.
17 Control Board SetupsThe following slides discuss the various control boards:Fan coils FK/FK4C/FV4ACondensing furnaces MVP / 355MAVNon-condensing furnaces - 58UHV / 333BAVSmall package products (SPP) SX / A (4 and 5 ton units ONLY)
18 FAN COIL EASY SELECT BOARD DH - DehumidificationR - 24 VACW1 - 1st stage Elect HtW2 - 2nd stage Elect HtY1 - 1st stage CompressorYY/2 - 2nd stage Compressor or single stage CompressorG - FanO - Reversing Valve in ClgC - CommonHum - Humidifier (24VAC)AUX - Auxiliary (24VAC)EACThis is the 40FK/FK4C/FV4 circuit board. To better explain the operation of the board, let’s pick an example.
19 FK4C Fan Coil Size 002 3 ton Heat Pump 15 KW electric Heat Setup We have selected a FK4C fan coil. We have matched it with an 3 ton Heat Pump and 15Kw of electric heat. We will also use the Comfort Heat Technology in the fan coil and the Thermidistat Control™.
20 If we look at the Product Data Sheet, we can determine the CFM’s that the fan coil will run under various conditions.When in cooling, the unit can run at 1050cfm under normal cooling and at 840cfm under a dehumidification callContinuous fan CFM will be at 525 because of the “LO” selection made.Electric Heat CFM will be at 980 because of the “LO” selection made.Remember that the higher CFM will always prevail, to protect the equipment.
21 Easy Select BoardThe violet wire determines the electric heater range. Below the selection is the CFM that the motor will run.The blue wire determines the size of the condensing unit.The orange wire begins to “massage” the CFM of the system. If “Heat Pump -Comfort’ is selected, the CFM in heating will be at 315 instead of the cooling CFM of 350.
22 Easy Select Board HP-COMFORT LO CFM ENH DELAY The black wire will adjust certain CFM’s either -10% or +15%.The white wire allows adjustment of the motor’s blower on/off delays. When this function is coupled with the Thermidistat Control™, the blower off delay in cooling can be eliminated be prevent re-evaporation of the water off the coil.The yellow wire allows 50, 66, and 100% of cooling speed for continuous fan.ENH DELAY
23 Easy Select Board Remove J1 jumper to activate dehumidify mode Remove J2 jumper to separate W1 & W2 (Intelligent Heat staging)J1 jumper allows the separation of the De-Hum signal from the “R” terminal. This will allow the control to slow the blower down 20% during certain operations.J2 allows the Electric Heat to be separated. W1 and W2 will only be activated with a call from the TSTAT or the outdoor unit (during defrost). When W1 is activated without W2, the motor will run at 75% of the W2 speed.
24 This is a wiring diagram of the FK4C/40FK/FV4A fan coil This is a wiring diagram of the FK4C/40FK/FV4A fan coil. If we look at the signals sent to the motor, we can see that the motor can run several different speeds. Troubleshooting the motor is not as bad at it would seem. We will show a detailed chart to help troubleshoot the motor and circuit board.
25 ECM setup for Variable Speed Condensing Gas Furnace 2 Sets of three (3) field selectable dip switch banks, Model Plug, and Thermostat inputs determine airflow.Status & Diagnosis LED’sContinuous Fan (CF)A/C SetupOnce the “personality plug” is installed, the installer must set the desired CFM for certain operations. The heating portion of the Infinity furnace is already pre-determined.We will discuss board setup in the Installation portion.Furnace Test, Blower, & DelayModel Plug
26 MVP furnace Board Setup (changes made in idle mode) The 58MVP circuit board has two different 3 switch dip switch banks to adjust blower CFM’s. The personality plug is critical in the operation of the board. Without it, the technician would need to jumper certain pins to tell the board what furnace it is trying to run.The red arrow shows the continuous fan “CF” setting. This would need to be adjusted for low speed operation of a two speed A/C or Heat pump or when more CFM is needed for Continuous Fan operation. This CFM can NEVER be higher than the A/C selection described next.The blue arrow shows where to adjust the A/C CFM. Some models are only capable of 1400CFM. Trying to adjust CFM higher than that will create a fault code and default to 1400 CFM.The green arrow show the 8 switch dip bank. Depending on what the system is, certain switches will need to be used (see description above).
27 80% Variable Speed Control Board From blower motorWhen dealing with the non-condensing furnace, we are using the similar setup of the FV4A fan coil(Thermostatic control).The yellow wire will determine the blower cooling CFM. You have to know which furnace blower drive you have to determine which pin to select.The blue wire allows us to use 315, 350 or 400CFM/ton for cooling.The orange wire is used if we have a straight A/C or dual fuel application.The red wire allows the adjustment of the Temperature rise range to be medium, medium-hi and high. Making sure the furnace is fired correctly is important before adjusting this option.The green wire will allow 50, 65 and 100% A/C CFM in the continuous fan operation.
28 Tyler Packaged UnitsThe Tyler Packaged products (48/50SX) also uses the Thermostatic Control type ECM motor. As you can see the adjustment are very similar to the fan coil and non-condensing furnaces.
30 ECM TroubleshootingAll troubleshooting information can be found in Service ManualsFan Coil (catalog# 03FA-5A0)Mid-efficiency furnace (catalog# )Infinity furnace (catalog# )ECM Troubleshooting Guide / Tyler products (catalog# )These are the current catalog numbers for the troubleshooting guides for the ECM motors.
31 All ECM MotorsSlight “cogging” or rocking is inherent to all ECM motorsmotor is finding its location between stator and rotor and is determining rotation“Rumbling” sound during startup and shutdownSystem mechanical resonance (approx rpm), three (3) permanent magnets (stators) cause the rotor to have a “rumble” during low RPM’s“Fixes”Don’t replace motor!Isolate sound: Canvas duct connectors, rubber grommets, etc.All ECM motors have inherent operating conditions that may seem troublesome to the untrained technician. As the ECM motor starts up, a slight “rocking” or “cogging” can occur. The motor may even run backwards for a brief second to find its’ location.In some situations, the motor may exhibit a rumbling sound during start up or shutdown. This is because of the three permanent magnets. If the rumble goes away once the motor comes up to speed, DO NOT change the motor. You need to isolate the sound to the fan coil or furnace. The noise was only noticeable on 1 hp motors in the MVP and has been resolved for several years. An older motor may have to be replaced along with the motor arms to resolve audible noise.
32 Power Plugs High Voltage Low Voltage 5 PIN CONNECTOR 16 PIN CONNECTOR When we begin to look at troubleshooting the motor electrically, we need to observe certain precautions. Here we show the High and Low voltage connections.
33 ECM Warning !!!NEVER remove or connect the 5 PIN HIGH VOLTAGE CONNECTOR of the motor, with the power ON !!- High Voltage is always present at the motor- Arcing could damage electronics.It is very important to remove power before we disconnect the High voltage power. Failure to do this could cause irreversible damage to the motor.
34 ECM warning!!! ECM motors should NOT be tested UNLESS under LOAD Erratic motor behavior could occur without a load (static pressure)
35 High Voltage Power Connector This is the description of the High voltage wires. Notice that the 230 Volt motor will NOT have the jumper between pins 1 & 2.
36 Troubleshooting ECM Motors Check HIGH VOLTAGE at motorPins 4, 5 of five pin connectorSHOULD ALWAYS HAVE HIGH VOLTAGE120 Volts for furnaces240 Volts for fan coils / Tyler productsWhat may seem unusual to an untrained technician, is that the motor will always have High voltage at the motor. It is up to the Low voltage to control the RPM’s of the motor.
37 Low Voltage ConnectorAll the ECM motor’s low voltage connections are like the picture above. What voltages appear may be different, but the terminal will stay the same. This picture really only applys to the 80v and the fan coil. The 58MVP uses different namings for the motor control inputs.
38 Troubleshooting ECM Motors Check LOW VOLTAGE at the motorPins 1(C), 12(R) of sixteen pin connectorSHOULD ALWAYS HAVE ~24VAC VOLTAGE AT THE MOTORIf not, check for voltage at circuit boardIf we looked at the previous slide, we could see that the motor should always have voltage at pins 1 & 12. These are the “R” and “C:” of the motor, similar to the “R” and “C” of a thermostat. This does not apply to the 58MVP.
39 ECM Motor shaft turns, but not smoothly If the shaft (with blower wheel disconnected) is difficult to turn with the motor control attached:- and turns freely with the control disconnected,then the control is damaged.- and does not turn free with the controldisconnected, then the motor is damaged. Verifycontinuity of windings (motor leads to unpaintedmotor end plate). They should be >100KW.What may appear to be a mechanical problem with the motor, may be an electrical problem. By verifying the above conditions, you may or may not have to continue with the electrical troubleshooting. In case it is an electrical problem, the following slides will show where to look for voltages.
40 ECM Motor won’t stop running Check for good ground betweenmotor groundtransformer common leadThermostat wiringControl BoardRemove 12 pin connector, if motor stops it’s control wiring.If it continues to run, motor is bad.This is another condition to check before going too deep into troubleshooting. It is still advisable to investigate the source of the problem and not just fix the symptom.
41 Replacement Issues Insert Blower motor as far into cradle as possible air over motor helps keep motor coolVerify proper installation of motor to prevent water entering pin connectionsDrip legs, proper positioningBeware of electronic thermostats (90% furnaces)units that notch the waveforms“Power-Stealing”If you have to replace the ECM blower motor, make sure that the blower motor is in as far as possible. It is important to get as much air as possible over the end bell of the motor. The furnace motors are designed with this in mind just note the belly band position and put it into this same position when replacing the motor. The comment above is a GE statement and is related to design and should not be over-ridden in the field.Make sure that the connections to the motor are in the 6 o’clock position and that a drip leg has been made with the wires. The statement above does not apply to multi-poise furnaces so be careful. It is mostly for upflows and fancoils.Also, in a retro-fit application, make sure that the thermostat is compatible with ECM motors. Thermostats that may notch the A/C waveform, may cause problems. Or thermostats that power-steal from especially the “W” signal, can cause problems. Avoid using cheap 3rd party thermostats with Deluxe products.
42 Notes on Mounting and Orientation A Few Factors Are Critical When mounting Motor/Control• Condensate or droplets can accumulate in harness• Orient connectors "down" whenever possible• "Drip Loops" are important!Motor Mounting to Blower Can Control Noise• Loose blower wheel on shaft can affect starting and will be noisy• Loose motor in mount or loose attachment to housing will cause noiseand poor starting
43 RCD - Fan Coil Replacement Modules Here is a list of Fan Coil Replacement Modules that are available from RCD. They are very competitive in cost to a PSC motor.
44 RCD - Furnace Replacements Module Here is the list of the Furnace Replacement Modules.
45 Pulse Width Modulation (PWM) Troubleshooting Troubleshooting the PWM motor is a little different because we have to make sure the motor and control board are talking to each other (remember we talked about a two wire system?).
46 Infinity Troubleshooting Guide Example: Inducer MotorUse Troubleshooting GuideCheck voltagesLine, PW and Feedback voltagesOne way to troubleshoot the 58MVP furnace is to use the service guide. This is a small portion of the guide, describing how to troubleshoot the ECM inducer motor. Even though we haven’t discussed the ECM inducer motor, it acts the very same way the blower motor does, except it is controlled at the correct speed based on the motor RPM when the pressure switches make. This is a very simple step-by-step approach to troubleshooting the motor. The next slide will show the wires attached to the ECM inducer.The most important thing to consider when using this guide is that, the voltages DO Not have to be exact. The most important thing is that you see a voltage change when there is to be a speed change from start to low or from low to high speed.
47 Infinity Inducer Motor Power / high voltagepins 6 & 12PW voltagepins 2 & 10Feedback voltagepins 2 & 1pin 4 /groundThe previous slide would have told you to look at various pins to determine if the fault lied in the circuit board or the ECM motor.
48 Advanced Product Monitor (APM) APM kit will help troubleshoot the furnace, including the ECM motorsRequires:LaptopSoftwareB&B RS485 AdapterAnother way to look at the 58MVP furnace, is by using a laptop and certain hardware described above. If you ever have to make a second service call on a Infinity furnace, this combination will pay for itself after one callback.
49 ECM Motor Simulator (for HK42FZ003 /012 Only) 1. Shut off power to the unit2. Disconnect PL13 and plug it into the ECM Motor Simulator3. Turn power on to unit4. Put setup switch SW-6 to the “ON” position5. Observe fault code displayedA third option will be a ECM Motor Simulator. By plugging this “blackbox” into the ECM motors, the fault code will tell whether the circuit board or ECM motor is at fault. This has been available on a limited basis for 1.5 years and will be available late 1999 from Finished Goods. This device has been received real well as an aid for troubleshooting.
50 Thermostatic ECM Troubleshooting The rest of the troubleshooting will deal with the Thermostatic Controlled motor.
51 Troubleshooting ECM Motors Call for Y/Y2, Check LOW VOLTAGEPins 1, 14 of sixteen pin connector(SHOULD HAVE ~ -12VDC)"DC" volts!For a Y/Y2 call, you would look for approximate -12vDC on pins 1 & 14. This does not apply to 58MVP.
52 Troubleshooting ECM Motors Call for W1, check LOW VOLTAGEpins 1, 2 of sixteen pin connectorCall for W2, check pins 1, 13(SHOULD HAVE ~24VAC)When looking for “W” signals, W1 would be at pins 1 & 2, while W2 wpould be on pins 1 &13.
53 Troubleshooting ECM Motors for Fan Coils Check LOW VOLTAGE at R and C, at the control boardPins 8, 9 of twelve pin connector(SHOULD HAVE ~24VAC)The fan coil control board will have 24vAC at pins 8 & 9.
54 FAN COIL PINS @ CIRCUIT BOARD CHECK W1, Y/Y2, Y1 (USES 24VAC)AUX/HEAT KW/CFM, AC/HP SIZE, SYSTEM TYPE, AC/HP ADJUST, ON/OFF DELAY, CONTINUOUS FAN (Uses Half Wave Signals)This chart will allow us to determine if the circuit board is sending the proper signal to the ECM motor. It is VERY important to understand how the fan coil is setup (possibly Comfort Heat), because two signals or the lack there of, can change the motor speed.
55 Newest FK4C installation instructions New instructions have more troubleshooting tables and examplesForm # IM-FK4C-07Catalog# 63FK-4C3
58 Other Contributing Factors Fan coils are a “DrawThru” designIf not properly trapped, the water will hold in drain panWater could drip on motor in downflow applicationMake trap IS DONE CORRECTLY!!
59 Troubleshooting ECM Motors for 80% two speed furnaces Check LOW VOLTAGE at R-C terminals, at the control boardPins 14, 9 of fourteen pin connectorSHOULD ALWAYS HAVE ~24VACThe first thing to check on the non-condensing furnace is that the circuit board is supplying 24vAc on pins 9 & 14.
60 80% 2 SPEED FURNACE PINS AT EASY SELECT CIRCUIT BOARD Check W1, W2, Y/Y2, Y1 (Uses 24VAC)AUX/HEAT KW/CFM, AC/HP SIZE, SYSTEM TYPE, AC/HP ADJUST, ON/OFF DELAY, CONTINUOUS FAN (Uses Half Wave Signals)Next, use the chart above to determine if the circuit board is supplying the proper voltage to the motor.(WITH 16 PIN MOTOR CONNECTOR DISCONNECTED)
61 Troubleshooting ECM Motors for Tyler Products CHECK LOW VOLTAGE R-C AT THE CONTROL BOARDPINS PL2-5, PL2-3 OF 7 PIN CONNECTORSHOULD ALWAYS HAVE ~24VACTyler Packaged Products are the same as the last two scenarios.
62 TYLER PRODUCT PINS AT CIRCUIT BOARD CHECK W1, G, Y/Y2, Y1 (USES 24VAC)AUX/HEAT KW/CFM, AC/HP SIZE, SYSTEM TYPE, AC/HP ADJUST, ON/OFF DELAY, CONTINUOUS FAN (Uses Half Wave Signals)Then use the chart to see if voltage is being supplied or not.(WITH 16 PIN MOTOR CONNECTOR DISCONNECTED)
63 Proper Ductwork Installation Check existing ductwork static pressureDetermine existing equipment CFMUse Product Data Sheet to determine that new equipment will work with existing ductwork or if it will require ductwork modificationsSee following examplesTrying to determine if an ECM product is “do-able” in an existing ductwork situation is simple enough, if you get the following numbers;Take a magnehelic or some type of device that will measure the external static of the furnace or fan coil.Next, determine the CFM of the current unit, one method is by using the “Temperature Rise” method.Next, take the two values and apply them to the Product Data sheet.
64 Condensing Furnace Fan Performance ECM Motor’s RPM range is rpmOutside of this range, a Status Code 44 will occurHigh fire will default to 1200rpmcooling- last valid PWMThis example shows a 58MVP furnace fan performance curve. If we had an old system that came up with a external static of 1100cfm, a Infinity furnace would work. If we needed 3.5 tons of cooling, we would get approximately 1350ccfm
65 Fan Coil Fan Performance Performance capable of 0.9” w.c. in some applicationsTorque”cad-back” will limit RPMOscillation can occur during high staticNominal 350cfm/tonAirflow can be adjusted + 15% or -10%Fan coil CFM performance is shown here...
66 Additional Fan Coil Consideration Return and Supply static must be in “white area” to prevent condensate removal from drain panWhen dealing with fan coils, additional considerations need to looked at. If the return static is too high, then water may be pulled out of the drain pan.Once again, this is why it is important to check external static pressures, whenever possible.
67 Other things to consider An ECM motor will out-perform a PSC motor in high static situationsCondensing furnace will display a fault code (above 1300rpm’s) but still provide more CFM than standard PSC motor at comparable external static pressureThermostatically Controlled motors will provide desired CFM in high static situationsIf you have ever put in an ECM motor and have had it fault due to high static situation, remember this;1) The furnace is just trying to tell you that the external static needs to be addressed, but it still outperform a PSC motor.2) In fan coil situations where the air noise is unacceptable, more than likely, this is the first time that the correct amount of air has ever moved through the ductwork.Corrections to the ductwork or external static pressure will quiet the air noise and/or eliminate any fault codes.
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