Watlow QPAC-01 - Page 23

Starting Out
23
QPAC User's Manual
How to Install and Wire the QPAC, Chapter 2
Input Wiring
Figure 32
Single and Three
Phase Wiring
① NOTE:
Interstage
transformers (16-
0176) required for
units 75 amps and
above.
Operation
The DH card uses a CT to monitor the load current and also detects when a firing
pulse is sent to the SCR's. The load current must be set by the pot on the DH board
(P1). If there is load current and no pulses to turn on the SCR's, the "Shorted SCR"
LED will be lit. The opto triac (U4) closes 3 or 4 seconds later and energizes an
external alarm relay. If part of the load opens (20% or more), and there are SCR
pulses, the "Open Htr" LED is lit and 3 to 4 seconds later, the alarm relay energizes.
This board only operates with the zero cross firing cards. For three phase, the CT's
go in T1 and T3 lines.
Setup Procedure
1. With the DH card installed and the temperature control wired to the SCR
power control, set the temperature control output to "full on" (20mA for 4-
20mA output, or 5 volts for 0 to 5 volt output).
2. Adjust P1 until the open heater light on the DH card is full on. No
intermittent cycling.
3. Slowly adjust P1 until the open heater light just turns full off. No
intermittent cycling.
If you are getting false alarms, adjustment is probably set too sensitive and
should be readjusted towards the off condition of the open heater light.
A shorted SCR will energize the shorted SCR light.
Load Number of Passes of Load Wire
Current Thru Current Transformer
2 to 3 Amps 5
3 to 4 Amps 4
4 to 5 Amps 3
5 to 10 Amps 2
10 to 40 Amps 1
Single and Three Phase DH Option
Open Heater or Shorted SCR Detector
①
Table 7-
Load Wire Passes
Thru Current
Transformer
①
①
Motherboard
Connector
1
2
J2
DH
08-5405
120 VAC
To Alarm
or Contactor
Customer Supplied Relay
(Philips ECG PIY 1055 or equivalent)
N.C.
Momentary
Reset
Switch
U4
P1
Open heater
when lit
Shorted SCR
when lit
2.20"
(56 mm)
1.20"
(30 mm)
2.70"
(69 mm)
Interstage transformer
16-0176 for 75 amps
and above
J3J3
CT
T1
Load Wire
Single Phase
T1
T3
Three Phase
J3
Load Wires
T1
T3
Three Phase
J3
Load Wires
Interstage transformer
16-0176 for 75 amps
and above
(Without
Interstage
Transformer)
ç
CAUTION:
The shorted SCR
detector feature will
not work with the
manual control
input;