Application - PENN Controls - LIT-121116 - A70AA - A70BA - A70GA - A70HA - Electromechanical Temperature Control - A70 and A72 Temperature Control

A70 Series Low Temperature Cutout Thermostat Line Voltage Technical Bulletin

Product name
A70 and A72 Temperature Control
Document type
Technical Bulletin
Document number
LIT-121116
Document revision
H
Revision date
2019-03-12

The A70 low temperature cutout thermostats have electrical contacts operated by a temperature sensing element. The switching mechanism on the single-pole, single-throw (SPST) 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.

Figure 1. Electric thermostat shown with manual reset.