Trane RTHD series Installation, Operation And Maintanance page 68

Installation Electrical
D WARNING
Electrical Shock!
Contacting any of the motor terminals, even with the
motor off can cause a severe, potentially fatal, shock.
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.
IMPORTANT!
WHEN EVACUATING THE CHILLER'S
REFRIGERANT SYSTEM, ALWAYS HAVE
THE MAIN POWER DISCONNECT/ CIR-
CUIT BREAKER OPENED.
Even when the compressor is not running, voltage is
present at the compressor motor terminals, providing
the potential for current to flow through a low imped-
ance path.
When removing refrigerant for the chiller both the con-
denser and chilled water pump must be operating to
avoid freeze up.
Figure 34. Y-D Starter Panel Power Wire Routing
68
As the chiller is evacuated below atmospheric pressure,
the dielectric strength (resistance to arcing) of the gas-
eous atmosphere is significantly reduced. Because the
SCRs are connected "inside the delta, " three of the motor
terminals are connected directly to the line voltage. An
"arc over" can occur between motor terminals under
conditions seen in the evacuation process.
If this occurs the circuit breaker (or other external protec-
tive devices) will trip in response to high fault currents,
and motor damage may also occur.
This can be avoided through being certain that the
chiller is fully disconnected from all power sources
before beginning pumpdown or evacuation pro-
cedures, as well as guaranteeing that the disconnect
cannot be accidentally closed while the chiller is in a vac-
uum.
RTHD-SVX02H-EN