Checkout Procedure For The Slide Valve And Load-Unload Solenoids - Trane RTHD Troubleshooting Manual

WARNING
Live Electrical
Components!

Checkout procedure for the Slide Valve and Load-Unload Solenoids

WARNING
Hazardous
Voltage!
RLC-SVD05A-EN
Compressor Capacity - RTHD
fails open), look like it was stuck "on" when using a voltmeter to test it. Thus it is
important to verify that the solenoid coil is continuous and providing a normal
load or to connect a known good load, such as a low wattage 115 Volt lamp, to the
terminals when testing the outputs. Refer to the wiring diagrams in the control
panel for the following procedure.
During installation, testing, servicing and troubleshooting of this product, it may
be necessary to work with live electrical components. Have a qualified licensed
electrician or other individual who has been properly trained in handling live
electrical components perform these tasks. Failure to follow all electrical safety
precautions when exposed to live electrical components could result in death or
serious injury.
With a particular compressor running, the triacs may be checked by measuring
voltage from terminal J3-1(load) and J2-1 (unload) to neutral. The triacs operate
in the high side and switch 115 VAC power to J3-1 (load solenoid) or J2-1 (unload
solenoid) to move the slide valve in the appropriate direction. Except during
compressor starts and stops, in normal operation, the solenoid valves can only
be energized for a period of between 40 and 400 milliseconds once every 6
seconds. Often, if the chilled water setpoint is being met under steady state
conditions, they may not be energized at all. To assure loading and unloading is
occurring it may be necessary to make slight adjustments to the chilled water
setpoint to force the action. As the pulsed on-time is potentially short it may be
difficult to see, especially if using a meter movement type voltmeter. Use of a low
wattage 115 VAC lamp may be of some help for a visual indication of output triac
operation.
When a triac is off, about 3 VAC or less should be measured on its terminal with
the solenoid load connected. When it is on, the voltage should be close to 115
VAC (the drop across the triac is about 1-2 volts).
The best time to check the unload solenoid is immediately after the compressor
starts. For the first 45 seconds (30 seconds in ice making) after the start the
unload solenoid should be energized continuously.
Checking the load solenoid is more difficult. 45 seconds after the start, the
compressor will usually start to load until the water temperature is satisfied.
Remember however, that certain limit conditions may prevent the compressor
from loading even if the chilled water setpoint is not satisfied.
Make sure unit is off and there is no power in the control panel before beginning
this procedure.
Disconnect all electric power, including remote disconnects before servicing.
Follow proper lockout/tagout procedures to ensure the power can not be
inadvertently energized. Failure to disconnect power before servicing could
result in death or serious injury.
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