Trane Precedent Symbio units utilize EBM Pabst supply fan motors. These motors in most cases are equipped with onboard electronics that can communicate back to the Symbio unit controller via Modbus connection. There are a few exceptions that utilize a Mitsubishi VFD to control the supply fan motor. Anytime a supply fan ERM fault is reported, that fault is being communicated by the motor or the Mitsubishi VFD back to the Symbio controller.
A significant number of supply fan ERM faults stem from motor high voltage loss, often linked to connection issues. The photo below highlights the PPM/PPF151 and PPM/PPF161 black connectors. The white connectors are the Modbus harness. For supply fan ERM faults the focus should be on the high voltage connections.
Photo of the harness connectors PPM/PPF51 PPM/PPF61 leaving the high voltage control panel.
Recommendation is to check all connections highlighted below. It may be necessary to cutout the molex connectors if the connectors are damaged and/or cannot make a good connection. In this case the wiring can be directly spliced using the appropriately rated connectors. If the molex connectors have to be cutout it is recommended to order replacement harnesses and installing the new harnesses when available. The pigtail assembly for the fan motor can be ordered so the entire motor does not have to be replaced. The part number for the pig tail assembly is listed below.
EBM Motor pigtail: WIR14430
A supply fan ERM fault can also be caused by a voltage imbalance greater than 2% phase to phase. This is less common but has been found in areas where incoming power issues are known to be more problematic.
Voltage Imbalance
Three phase electrical power to the unit must meet stringent requirements for the unit to operate properly.
Measure each leg (phase-to-phase) of the power supply. Each reading must fall within the utilization ranged stamped on the unit nameplate. If any of the readings do not fall within the proper tolerances, notify the power company to correct this situation before operating the unit.
Excessive three phase voltage imbalance between phases will cause motors to overheat and eventually fail. The maximum allowable voltage imbalance is 2 percent.
Measure and record the voltage between phases 1, 2, and 3 and calculate the amout of impalance as follows:
% Voltage Imbalance = (100 × AV - VD)/AV
whereAV (Average Voltage) = Volt1 + Volt2 + Volt / 3
- V1, V2, V3 = Line Voltage Readings
VD = Line Voltage reading that deviated the farthest from the average voltage.
Example: If the voltage readings of the supply power measured 221, 230, 227, the average would be:
221 + 230 + 221 / 3 = 226 Avg.VD (reading farthest from average) = 221
The percentage of imbalance equals:
100 + 226 + 221 / 226 = 2.2%The 2.2 percent imbalance in this example exceeds the maximum allowable imbalance of 2.0 percent. This much imbalance between phases can equal as much as a 20 percent current imbalance with a resulting increase in motor winding temperatures that will decrease motor life.
- If the voltage imbalance is over 2 percent, notify the proper agencies to correct the voltage problem before operating this equipment.
WARNING:
Information in this article is intended for use by individuals possessing adequate backgrounds of electrical and mechanical experience and who comply with all federal, state, and local laws, rules, orders, or regulations related to the installation, service, or repair of a heating or central air conditioning product. Any attempt to install, service, or repair a heating or central air conditioning product may result in personal injury and/or property damage. The manufacturer or seller cannot be responsible for the interpretation of the information contained herein, nor can it assume any liability in connection with its use.