2
A70, A72 Technical Bulletin
7. Take the following steps
when mounting a control
with a vapor-pressure
sensing element. (See
Fig. 9.)
a. Mount the control with
the power element
down.
b. Mount the control and
bulb at approximately
the same level.
c.
Mount the bulb with the
free (sealed) end lower
than the capillary end.
Note
: On cross
ambient models the
side of the bulb marked
“TOP” should always
be up.
!
CAUTION: Do not dent or
deform the sensitive bulb of
this control. A dent or
deformation will change the
calibration and cause the
control to cycle at a
temperature lower than the
dial setting. When a bulb
mounting clip is used to
mount the bulb near the
refrigerant tubing, be sure
the sheet metal screw does
not pierce the tubing.
Wiring
!
CAUTION: Disconnect the
power supply before the
wiring connections are
made to avoid possible
electrical shock or damage
to the equipment. On
multiple circuit units, more
than one circuit may have
to be disconnected.
Make all wiring connections
using copper conductors only,
and in accordance with the
National Electrical Code and
local regulations. For maximum
electrical rating of the control,
see the electrical rating shown
on the inside cover label of the
control.
The contacts on the single-pole
A70 controls with main and
auxiliary contacts are identified
on the contact block. The main
contacts are LINE-M2 and the
auxiliary contacts are LINE-M1.
The action of the main contacts
are shown on the cover label.
Figure 6 shows a typical wiring
hookup.
Where it is desirable for the user to
increase or decrease the DIFFERENTIAL
ONLY, external adjusting knob is supplied
on differential screw as shown in Fig. 4.
Knob is provided with stops and factory
assembled to permit change only within a
specified range.
External adjusting knob may be placed on range
screw, as shown in Fig. 5, where it is necessary
for the user to raise or lower both CUT-IN and
CUT-OUT points (differential remains constant).
Knob is provided with stops and factory
assembled to permit adjustments within a
specified range.
NOTE: Knob is usually factory assembled in
either position as shown in Figs. 4 or 5 above,
depending upon specifications of original buyer.
However, knob may be changed in the field
from the differential to the range screw or vice
versa by loosening set screw and removing
knob and indicator plate and reversing their
positions. Assuming that knob is factory
assembled on range screw (Fig. 5) and set to
restrict adjustment to 10F
°
(5.6C
°
), adjustment
will be restricted to approximately 5F
°
(2.8C
°
) if
knob is placed on differential screw
(Fig. 4).
MANUAL RESET
BUTTON
Manual button shown in
Fig. 3, left, when
supplied provides
MANUAL START only.
Button must be pushed
and released to restart
after lockout occurs.
Fig. 7 -- Interior view of “Open Low”
temperature control showing how to adjust
the set point and differential.
Fig. 8 -- Interior view of “Open High”
temperature control showing how to adjust
the set point and differential.
