Hardy HI 3010 Filler/Dispenser Controller - Manual (Page 143)

127 CHAPTER 7
Troubleshooting
Step 5. Press the Exit button until you return to the Standby
Display.
Using Solid State Relays with Light Loads
(Optional Set Relays)
About Solid State Relays With Light Loads
There have been installations where solid state relays have
been used and failed to shut off a solenoid or relay when de-
energized. The actual problem comes from the internal snub-
bing network in parallel with the Silicon Controlled Rectifier
(SCR) which does the actual switching. This network pre-
sents an impedance of 30K ohms, which means with 120
volts across, it will pass 4mA of AC current.
FIG. 7-97 SCR SWITCHING LOAD CIRCUIT
1. The SCR itself presents no leakage
current. Some solid state relay manu-
factures specify 20mA minimum
load. This is based on the presumption
a relay or solenoid will drop out with
only 4mA through it, which is not
always true. That may not be true.
When switching a light load with a
solid state relay across the line, you
must look at the rated drop-out current
of the load, and if it is less than 4mA
it may not turn off. The solution is to
put a loading resistor in parallel with
the light load, to be sure leakage cur-
rent is sufficiently shunted away from
the coil.
2. Assume a load like a relay with a coil
of 15,000 ohms and of 5% of nominal
drop-out. When the solid state relay is
off, there will still be 1/3 of the line
voltages across the relay, so it will not
drop out. For the relay to have 5% of
the line across it, it and a parallel
shunt resistor must be 20 times less
resistance than the 30K snubbing net-
work, or 1.5K ohms. Use less than a
1.67K ohm parallel resistor and now
total load is below 1.5K ohm or
80mA.
System Integrity Check and Fault Determi-
nation From the Web Browser
Diagnostics
Diagnostics is used to troubleshoot the Filler/Dispenser. A
complete Troubleshooting Guide is available in the Service
Manual. What is important for Operational purposes is to be
able to see the information about this instrument. (See Fig. 7-
98)
Setting Default Settings is also useful to operators.
Step 1. Click on Diagnostics. The Diagnostics Page
appears. (See Fig. 7-98)
FIG. 7-98 OPERATION/DIAGNOSTICS
Step 2. Click on “Set Factory Defaults”. The Set Factory
Defaults page appears. (See Fig. 7-99)
FIG. 7-99 SET FACTORY DEFAULTS
WARNING: ANY AND ALL DATA WILL BE LOST IF FAC -
TORY DEFAULTS ARE INSTALLED . THIS , INCLUDES EVERY
PARAMETER THAT WAS CHANGED FOR INGREDIENTS , IP
SOLID
STATE
RELAY
HOT
NEEDED
SHUNT 15000 ohm
RELAY
COIL
NEUTRAL