Robertshaw 9720 User Manual

Page 36

IMPORTANT SAFETY INFORMATION

WARNING:

■

Always turn off power at the main power source by unscrewing fuse or switching circuit breaker to the off position
before installing, removing, or cleaning this thermostat.

■

Read all of the information in this manual before programming this thermostat.

■

This is a 24V AC low-voltage thermostat. Do not install on voltages higher than 30V AC.

■

If you experience a loss of power, this thermostat will indicate “-AC” in the time field of the LCD display. This
means that your system’s 24V AC circuit is not receiving power or is not functioning correctly. The back-up
batteries provided in this thermostat will maintain the programming during the loss of power. However, the
thermostat requires 24V AC power and a functioning system for proper control.

■

All wiring must conform to local and national building and electrical codes and ordinances.

■

Do not short (jumper) across terminals on the gas valve or at the system control to test installation. This will
damage the thermostat and void the warranty.

■

This thermostat is equipped with automatic compressor protection to prevent potential damage due to short cycling or
extended power outages. The short cycle protection provides a 5-minute delay between heating or cooling cycles to
prevent compressor damage.

During extended power outages our thermostat provides an extra margin of compressor protection in the heat
mode by delaying the first stage of heating (heat pump) from engaging until the compressor crankcase oil has
been warmed. This will help avoid compressor damage due to improper oil circulation during cold weather
conditions. This important safeguard will delay the first stage of heating (heat pump) for 1 hour less than the
power outage, for up to 12 hours maximum. During this period the system will depend on the auxiliary stages of
heating to maintain the setpoint temperature.

Symptom

Remedy

Thermostat will not turn on heat pump

Compressor power outage safeguards may be in effect.

in heat mode. Uses auxiliary stages of

(See "COMPRESSOR PROTECTION.")

heating to control setpoint.

Heat turns on instead of cool and

Check wiring and system specifications.

vice versa.

Thermostat turns on and off too much.

Increase temperature differential setting. (See “PROGRAMMING.”)

Display is indicating “LO BATT.”

Replace back-up batteries soon. Be sure battery installation is correct.
(See “REPLACING THE BACK-UP BATTERIES.”)

Thermostat beeps once per minute

Back-up batteries low. Change batteries immediately. (See "REPLACING

and "LO BATT" is indicated in display.

THE BACK-UP BATTERIES".)

LCD display is blank.

Replace batteries to control system. (See "REPLACING THE BACK-UP
BATTERIES".)

Thermostat does not change when

SYSTEM button is in OFF or is in AUTO (changeover) position.

the

∨ or ∧ buttons are pressed.

Thermostat beeps and does not allow

Autochangeover "deadband" conflict (See "SELECTING AUTO

temperature changes when

∨ or ∧

CHANGEOVER".) or thermostat is locked.

buttons are pressed.