Yazaki AROACE CH-MG150, Installation Instructions Manual

Page: 23 / 28

23
Each chiller-heater has a junction box
located on the right side of the unit. This
junction box is a single point where all
electrical interface, be it high voltage or
controls, is intended to enter the unit.
High voltage connections should be
made to L1, L2, L3, and G. If the voltage
supply has a “wild leg” or “high leg”, that
leg should attach to L2. Be aware that
not all regions have high legs.
A rotation test must be performed as
well. Clockwise rotation
(lead end)
is
desired. If incorrect rotation is
discovered, swap L1 and L3 wires to
reverse the rotation. A rotation meter is
the only safe and reliable method to
determine rotation due to the use of a
VFD pump motor.
Figure 24
– Hioki Rotation Meter
The center section of the junction box
has the pump controls. Supply voltage is
provided from a field-supplied 24v
transformer that is connected to terminal
CM1. The unit will take that voltage and
route it to terminal P when there is a
chilled/hot water pump demand. It will
take that same voltage and route it to
terminal CP when there is a demand for
the cooling water pump. It will use that
same voltage to cycle the cooling tower
fan by applying that voltage to CTF when
the incoming cooling water is at 81.5°F
(27.5°C)
or greater, and taking it away
when the incoming cooling water drops
to 75.2°F
(24°C)
. This logic function of
cooling water temperature control is
provided for convenience, and is not
intended to supersede other, more
sophisticated controls such as VFD fan
controls, etc.
Terminals A through I in the upper
right section of the junction box are
intended for use with the optional Yazaki
Remote Control Panel. However, these
terminals can also be used to interface
with Building Management Systems.
When interfacing with a BMS, it is
recommended that two SPDT relays be
used and controlled by the BMS. Each
relay should have the E terminal
(which
supplies a DC voltage signal)
of the
junction box connected to its common
lead on the relay contacts. One of these
relays will be used to determine whether
the unit is in Heat or Cool mode. The
other will Enable or Disable the unit. For
the mode relay, designated ESC, the
normally closed contact should be
attached to the B terminal in the junction
box. The normally open contact should
be attached to the A terminal in the
junction box. For the Enable/Disable
relay, designated ESON, the normally
closed contact should be attached to the
D terminal in the junction box. The
normally
open contact should be
attached to the C terminal in the junction
box.
Finally, in the lower right section of the
junction box lies a terminal strip with
terminals 3, 4, 5, 6, and CM2. Terminal
CM2 supplies a DC voltage signal that
MUST return to terminals 3, 4, and 5.
Terminal 6 is not used in a CH-MG
chiller-heater. These are pump and
motor overload interlocks. Each starter
for the chilled/hot water pump, cooling
water pump, and cooling tower fan motor
should have a set of auxiliary contacts on
their overloads. Each starter should
receive the DC voltage from terminal
CM2 in the junction box and route it
through normally closed contacts to
return to the appropriate terminal. In this
way, the logic of the chiller-heater is
given information about the operational