Semi-Automatic Control with Manual Reset
Prefixed by DR, DRF, DRH, DRE, DRW - with suffix -L or -U. Example: Type DR-
21-2U. A single adjustment sets the operating point for automatic operation. A push-
button reset must be operated manually to restore the circuit to the original position
after automatic operation. Example: Type DA-21-2L. Circuit will open automatically
on a pressure rise to the pressure indicated by the pointer on the scale. No matter
how much the pressure drops, the circuit will not re-close until the reset button has
been operated. Suffix -L denotes control will operate automatically on an increase
in pressure. Suffix -U denotes control will operate automatically on a decrease in
pressure.
Manual Lock Type Reset Control
Operates automatically on a decrease of pressure with provision for man-ual reset
when pressure is below set point. Prefixed by DL, DLW, DLE, DLH. A single adjustment
sets the low pressure operating point of the control at any value on the scale range.
The control will operate automati-cally at the set point only on a drop in pressure. The
lock-type feature per-mits the circuit to be reset and locked in position when pressures
are below control setting. The lock remains in effect until the pressure has risen to a
value above the control setting. Lock then releases and the circuit is held in the reset
position due to the pressure rise. It will remain in the reset position until it is called on
to again operate automatically on a pressure drop to the select-ed setting.
Two-Stage Pressure Controls - Series D-400
Types DA, DAW, DAH, DAE - with suffixes 421, 423, 431, 433, etc., followed by
specification numbers 4122, 4123, 4129, 4132.
This series incorporates two single pole, single throw magnetic mercury switches,
actuated by the same Bourdon tube. The operating point of each switch is adjustable
through an outside adjustment.
The change in pressure which opens and closes each switch at its respective setting
is the switch’s fixed differential. The pressure represented by the difference between
the two adjustment pointers is the pressure “spread” between operation of the two
switches. Upper pointer “U” indicates the operating point of the HIGH pressure circuit.
Lower point “L” indicates the operating point of the low pressure circuit.
General Watertight or Weather-Resistant Types:
These controls are prefixed by
the letters DAW, DRW, DSW and DLW. They are supplied with flanged case, bottom
connection only, for surface mounting. Again, install firmly in a level position. Do not
mount the control by twisting the case; use a wrench on the square part of the 1/4˝
bottom pipe connection. Be sure pipe connection is in a vertical position. After cover is
properly attached, with the name plate on bottom of the cover, sight across the lower
end of the glass opening in the cover to see that the control is lined up vertically. Do
not use holes in case bottom for mounting.
Explosion-Proof Types:
Install controls prefixed by the letters DAH, DAHF, DRH,
DSH, DAE, DRE, DSE, firmly in a level position by means of mounting lugs attached
to the control housing. Line up horizontally by sighting across the left and right conduit
hubs.
Note:
Series D-30, D-230, D-430, D-530 (i.e., DA-31-3, etc.), when used for steam
with operating ranges of 35 psi or higher, must be siphoned to prevent live steam
from entering the Bourdon tube. With high pressure steam in excess of 100 psi, use
a remote connection.
Series D-20, D-220, D-420, D-520 (i.e., DA-21-2, etc.), when incorpo-rate an orifice as
standard in the bottom stem to dampen out surges or pul-sations.
WIRING
Wire in accordance with local electrical codes or equipment manufacturer’s instructions.
For general purpose controls, use a short piece of BX between the rigid conduit and
the control so that it will not be subjected to conduit expan-sion and contraction. Where
control is directly connected into load circuit, it should be connected into hot side of
line. For electrical rating, see name-plate attached to control case.
ADJUSTMENTS: How to Set Operating Point Double Adjustment Types - Fully
Automatic
Prefixed by DA, DAF, DAW, DAH, DAHF - provided with double adjustments. Adjust
the upper pointer “C” to set the HIGH PRESSURE POINT for switch operation. Adjust
the lower
pointer “U” to set the LOW U PRESSURE POINT. The differ-ence between the HIGH
and LOW pointers is the operating differential between “on-off” switch operation.
Single Adjustment Types - Fully Automatic
Prefixed by DS, DSE, DSF, DSH -equipped with a single adjustment. The single
pointer on the scale sets the pressure where switch operation occurs. Differential is
fixed (not adjustable). Example setting: Type DS-21-2, range 0-60 psi: circuit opens on
pressure rise. If pointer is set at 40 psi, the control will operate to OPEN circuit at 40
psi and RE-CLOSE circuit at the fixed differential of 4 psi.
C
Adjustment
Reset
Single
adjustment
Switch B high
U
Double adjustment types - Fully automatic
Semi-automatic control with manual reset
Manual lock type reset control
Single adjustment types - Fully automatic
Two-stage pressure controls Series 400
Adjustment
Reset
Upper
pointer U
Switch A low
Lower
pointer L
