Sometimes the problem can be a relay that has burnt contacts which result in the low voltage being supplied to the coil. Contactors can also chatter if they do not get the correct voltage. If the root cause of the failure of the motor is not solved when the new motor is installed then the new motor can also burn up as the old motor. The failure can be catastrophic requiring the motor to be replaced. A 277-volt motor that receives 200 volts will overheat and possibly fail. ![]() For example, a motor that requires 277 volts will need plus or minus 10% of 277 volts to properly function. The result is either a contactor or relay that sticks close or when it closes it passes the incorrect amount of voltage and current across the contacts which will cause severe issues with electrical components including motors and other devices in the chiller system. Old McQuay Chiller Control Panel | Proper Voltage ![]() Over time this arcing of the electrical contacts can cause the premature failure of the contactor or relay. The arc produces a tremendous amount of heat and the heat can cause the contact on the relay or contactor to melt or become softer. When the contact closes sometimes there is a small arc of electricity across the contacts. Burned contacts are the result of heat from arcing. Relays and contactors need to be checked for burned contacts that will stick and thereby fail to release when the contact is supposed to open. Even older panels require special attention to make sure the electrical connections are tight and that the electrical components are functioning properly. ![]() It is important that all the components in the chiller panel be checked for proper function along with all electrical connections being checked to make sure they are tight. This transformer provides single-phase voltage to other electro-mechanical controls (not pictured) which control the contactors shown in this picture. The final load which is fed from the main power is the step-down transformer. The fans have overload protection built into them in the condenser fan motors. There are eight three-phase fans for this chiller so there are eight separate contactors for each condenser fan.
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