For a safety to be interrogated, both the associated sensor input and the lockout setpoint must be active. If a
safety trips, the alarm name will consist of the setpoint name plus a number indicating which condenser fan
tripped.
The following are a list of safeties that are incorporated in the MHRC control for heating stages. These safeties
are checked every second if the associated heating stage is on. Each heating stage is tested individually. If
a safety condition exists, action will be taken on that heating stage only, other heating stages will continue to
function normally.
HIGH HEAT AMP
High heating stage amps safety is based on the calculated value of the setpoint #89 “HI HEAT AMP” times the
value of the heating stage FLA setpoint #83 through #88. If the ampere raises above the calculated value and
it remains there for the time specifi ed in the safety time of setpoint #89, the heating stage safety will trip and a
“HI HEAT AMP#?” alarm will be generated. The heating stage is locked out and must be reset manual via the
LCD/Keypad or MCS-CONNECT.
LOW HEAT AMP
Low heating stage amps safety is based on the calculated value of the setpoint #90 “LO HEAT AMP” times
the value of the heating stage FLA setpoint #83 through #88. If the ampere raises above the calculated value
and it remains there for the time specifi ed in the safety time of setpoint #(), the heating stage safety will trip
and a “LO HEAT AMP#?” alarm will be generated. The heating stage is locked out and must be reset manual
via the LCD/Keypad or MCS-CONNECT.
HTR OFF AMP
The heating stage is off but the amp drawn sensor indicates current. This indicates a heater welded condition
FAN VFD ALM
Indicates a fault with the evaporator’s fan VFD
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21.7 Heating Stages Safeties
21.8 EVAPORATOR SAFETIES
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