Built-In Self Test - Hoffman Controls 890-DSQ Series Complete Installation & Operating Instructions

Installation Con't
Figure 6
Liquid Line Temperature Sensor Mounting
b. Fasten sensor firmly, only using tape provided. Make sure
the metal tab "heat sink" on the sensor makes firm contact
with the liquid line tubing. NOTE: Using hose clamps or tie
wraps to secure the sensor's metal tab to the liquid line will
break the sensor's internal resistor. Use only the provided
waterproof tape to secure the sensor to the liquid line.
5) Refer to Figure 7, 890-DSQ Wiring Diagram 2, (on
page 14) for applications using staged relay outputs with pres-
sure transducer inputs.
6) Refer to Figure 8, 890-DSQ Wiring Diagram 3, (on
page 15) for applications using Modbus, secondary set points,
the 0-10 VDC input, and/or variable stage (VS) EC motors and
SCRs.
7)
When using variable speed EC motors, within a bank of 6
PSC condenser fan motors, the least time consuming way to
replace two of the PSC motors, is with 2 variable speed EC
motors, that have the same horsepower, line voltage, frame
size and airflow as the replaced PSC motors.
8) When using SCRs to continuously modulate the current
in a heating system, insert an SCR with twice the current
capability that the heating element to be modulated has.
9) Install and wire the variable speed EC motors or SCRs per
the manufacturers's instructions.
10) Wire the 890-DSQ Sequencer per the wiring diagrams
appropriate for this installation. More then one wiring dia-
gram's information may be used, depending upon the applica-
NOTE:
tion. Temperature sensors and pressure transducers
can not be used together, as inputs, on the same sequencer.
11) The 890-DSQ Sequencer is designed for low voltage (24
VAC) operation, including the 24 VAC relay stage output
loads.
When additional cable is required —
12)
a. Always use 22 AWG (minimum) stranded, twisted pair cable
properly insulated for outdoor applications.
b. Sensor or transducer cables, 0–10 VDC input wires,
Modbus wires, and VDC / PWM output wires should not
run in proximity, or be attached, to conduit carrying line
voltage power wires.
13)
This completes the 890-DSQ Sequencer's installation.
Initial Sequencer Checkout
• Verify all wire connections are complete and correct for this appli-
cation.
• Apply 24 VAC power to the 890-DSQ Sequencer.
• Perform all Built-In Self Test instructions (below).

Built-In Self Test

The Built-In Self Test function can only be operated in manual
mode, and only simulates the value of a temperature sensor or
pressure transducer or a voltage depending on the input mode cur-
rently selected. The Built-In Self Test allows the installer to use the
sequencer's UP and DOWN buttons to simulate the input value.
For the rest of this section, the simulated input will be assumed
to be temperature.
To begin, press and hold the UP and EXIT buttons down simul-
taneously for about one (1) second. While continuing to hold both
buttons down, press the ENTER button and then release all three
buttons at once. The 890's LCD will display what appears to be
the Home Screen (Figure 1, page 3) and the relays stages may start
turning on, depending on the sequencer's selected set point values.
However, the installer can now change the simulated temperature
shown on the LCD screen's bottom line. Each press of an UP or
DOWN button will raise or lower the LCD temperature by 1.0 °F
The 890-DSQ's operation can be verified by observing each fixed
stage's turn on and turn off temperature, displayed on the LCD's
screen and indicated by each stage's LED. When selected, the VS
(variable stage's) operation can also be verified.
When using the Built-In Self Test function:
1) Verify the fixed relay stages turn on and off at the correct
temperatures, for the application, by observing the LCD
screen's displayed temperature along with each stage's
indicator LED.
2) If selected, verify the 2nd set of set points work cor-
rectly.
3) If selected, verify the VS (variable stage) EC motors (or
SCRs) turn on and reach full speed (or full current) at
the correct temperatures.
4) To exit the Built-in-Self Test function, press the MODE
button and then the EXIT button.
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