Dwyer A3000 User Manual
Page 3
ELECTRICAL CONNECTIONS
1. Cover: The amplifier-relay unit has an easy to remove housing.
Remove the three (3) screws as shown in Fig. G and slide the
housing off. Make all the electrical connections before reinstalling
and refastening the housing.
2. Conduit: Electrical access to the connection box portion of the
relay housing is by bottom opening for 3/4˝ conduit. Use of flexible
conduit is recommended. It should be supported from the panel or
other suitable surface to prevent the wiring system from exerting
undue strain on the instrument. See Fig. G.
3. Terminal or Connection Board Layout: In Fig. H “Terminal
Board,” Section A contains the connections for the load or slave
relay actuated by the high or right set point. This relay is a double
pole, double throw type. The two right connections are normally
closed, the two middle connections are normally open, and the left
connections are the common pair. The relay is in its normal or De-
Energized position when pressure is below the right hand set
point.
Section D is exactly the same as Section A except that its load
or slave relay is controlled by the low or left set point. The De-
Energized position is below the left hand pointer set point.
Section B contains the external connections to the holding coil
circuit for the high or right set point relay and Section C contains
similar connections for the low or left set point relay. The function
and use of these connections varies somewhat depending on the
circuit style of the instrument. See paragraphs 5 and 6 for details.
Section E contains the power connections for the control unit
transformer primary. The transformer in turn supplies reduced
voltage power for the LED, phototransistor, amplifier unit, and
load relay pull in and hold coils. Connections must always be made
to this section in order to put the unit in operation. Standard units
are designed for 120 VAC input to the transformer. Special units are
also available for other voltages.
Separate Ground Wire attachment is provided for by a No. 6-32
screw on the mounting bracket near the conduit opening. An addi-
tional ground wire connection is located on the side of the gage
body for use when the amplifier-relay unit is mounted remotely.
Single Set Point instruments are furnished with the right or high
set point components and circuitry in place. These are connected
to Sections A and B of the terminal board. The left or low set point
components are omitted.
4. Circuit Style: The PHOTOHELIC
®
SWITCH/GAGE is available
with several factory installed optional internal circuits. They are
identified as to style by a label shown in Fig. J. This label is mount-
ed prominently on the terminal board of each instrument. The letter
H denotes a circuit in which the relay can be made to latch or
remain energized after pressure increase to its set point.
The letter L denotes a circuit in which the relay can be made to
latch or remain de-energized after pressure decrease to its set
point. Two letters are required to fully identify a dual set point unit.
Thus, circuit style HH, which is standard, is a dual set point circuit
which has provisions for latching on pressure increase to either set
point. Single relay unit or L for the special low latch unit. Units for
use with other than standard 120 VAC will be so indicated on the
label.
5. Dual Set Point Automatic Reset: Circuit Style HH is used for
simple on-off switching applications. To place in service, connect
load circuits to the appropriate terminals in Section A (Fig. H) for the
right set point and Section D for the left set point. Note that the
N.O. contacts are open when the gage pressure pointer is to the
left of the set point pointers. No connections are necessary in
Sections B and C. Make external ground connections as required
and connect power to Section E for the control unit. To use circuit
style LL for automatic reset, a jumper wire must be installed
between the two terminals in Sections B and/or C.
6. Dual Set Point Manual Reset: Circuit Style HH may also be
used for manual reset applications where it is required to maintain
contact on either relay following pressure increase above its set
point. Load or signal connections are made to the appropriate ter-
minals in Sections A and D (as in paragraph 5 above). Connect ter-
minals in Sections B and C through normally closed switches or
push buttons as shown in Fig. K. Use of “dry-circuit” type switch-
es such as a Dwyer Part No. A-601 with paladium, gold, etc. or
rotary wiping action type contacts is recommended. Make external
ground connections as required and connect power to Section E
for the control unit.
COVER MOUNTING
SCREWS
4-3/8 [111.13]
CLEARANCE
FOR COVER REMOVAL
FLEXIBLE CONDUIT
SUPPORT CONDUIT
FROM PANEL
SECTION B
SECTION A
SECTION C
SECTION D
SECTION E
CAUTION: Do not apply electrical current
to terminals in Sections B and C.
Fig. H
Fig. J
Fig. G
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