A70HA-1 GA-1 Instruction Manual

Installation Sheets Manual 121
Temperature Controls Section
Technical Bulletin A70
Issue Date 0492
A70 Series Low Temperature
Cutout Thermostat Line Voltage
Application
The A70 low temperature cutout
thermostats have electrical
contacts operated by a
temperature sensing element.
The switching mechanism on the
single-pole, single-throw models
opens the circuit on a drop in
temperature. On the 4-wire,
two-circuit models the main load
contacts (LINE-M2) open on a
temperature drop and
simultaneously the auxiliary or
alarm contacts (LINE-M1) close.
The thermostat is used as a low
temperature cutout device on
heating and cooling coils or other
applications where there is a
possibility of air being stratified.
It responds only to the lowest
temperature along the 20 feet of
the sensing element. The
sensing element is usually
located on the downstream side
of the coil. When the
temperature at any point along
the sensing element reaches the
set point, the thermostat will stop
the fan. The outdoor damper is
installed to close when the fan
stops.
The thermostats with manual
reset will lock out when the
sensed temperature drops below
the set point. The reset must be
pushed and released before the
contacts can be reclosed.
All Series A70 thermostats are
designed for use only as
operating controls. Where an
operating control failure
would result in personal injury
and/or loss of property, it is
the responsibility of the
installer to add devices
(safety, limit controls) that
protect against, or systems
(alarm, supervisory systems)
that warn of, control failure.
The thermostat may be mounted
Installation
Mounting
! CAUTION: Locate the
thermostat case and
bellows where the ambient
temperature is always
warmer than the set point.
The thermostat operates
only from the lowest
temperature along the
entire 20 foot sensing
element. Avoid sharp
bends or kinks in the
sensing elements.
Fig. 1 -- Electric thermostat
shown with manual reset.
to a wall surface or panel board
using the two mounting holes
provided in the back of the case.
The desired mounting position is
with the element bellows pointing
down.
For accurate thermostat
operation, the sensing element
should be horizontally
serpentined across the face of
the coil to sense temperature in
all areas.
Specifications
© 1992 Johnson Controls, Inc.
Code No. LIT-121116
Part No. 997-742
1
Wiring
! WARNING: Disconnect
the power supply before
wiring connections are
made to avoid possible
electrical shock or
damage to the equipment.
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
thermostat, see the label on the
inside of the thermostat cover.
Loads exceeding the rating of
the thermostat can be handled
with a relay or motor starter.
Checkout Procedure
The operating point of the
thermostat should be confirmed
by an accurate thermometer.
Before leaving the installation,
observe at least three complete
operating cycles to be sure that
all components are functioning
correctly.
Repairs and Replacement
Field repairs must not be made.
For a replacement thermostat,
contact the nearest Johnson
Controls distributor.
! CAUTION: Use terminal
screws furnished in the
switch (8-32 × 1/4 in.).
Longer terminal screws can
interfere with the switch
mechanism and damage
the switch.
Controls Group
507 E. Michigan Street
P.O. Box 423
Milwaukee, WI 53202
2 A70 Technical Bulletin
Printed in U.S.A.