Table of Contents
Advertisement
Service
The temperature controller and evaporator probe (NTC1) indicate when the refrigeration system is required to turn
on and off.
Plasma (PL) models are factory set with a -31.0 C (-23 F) set point. Lab (LB) models are factory set with a -24 C
(-11.2 F) set point.
The refrigeration system removes heat from the cabinet interior and rejects it to the surrounding room air. When
the evaporator probe temperature reaches -30.0 C (-22 F) on PL models, or -23 C (-9.4 F) on LB models, the
controller turns the refrigeration system on. The normally open controller contacts close and energize the slave
relay energizing the condenser fan motor and compressor. The compressor uses a potential relay and a starting
capacitor and run capacitor to start the compressor motor.
When the evaporator probe temperature reaches -32.0 C (-25.6 F) on PL models or -25 C (-13 F) on LB models,
the controller turns the refrigeration system off. The controller contacts reopen, which de-energizes the slave relay
and de-energizes the condenser fan motor and the compressor. The evaporator fan motor runs continuously when
the door is closed and the unit is not in defrost.
Refrigeration system
The FZR20/25 series refrigeration system is designed to give many years of trouble-free service. Except for
routine cleaning of the air-cooled condenser and related parts, the refrigeration system requires no service or
maintenance. The system uses a thermostatic expansion valve (TXV) metering device and is critically charged.
Access fittings are not provided. Temporary piercing valves are required to work on the refrigeration system. Follett
recommends that if hoses are ever connected to the refrigeration system for service, the refrigerant should be
recovered, permanent access valves should be installed and the system evacuated, and recharged by weighing in
the correct refrigerant charge (10.6 oz. (300g) R404a).
Note: Do not charge the system by pressures.
EVAPORATOR/DEFROST UNIT
Defrosting
The FZR20/25 series upright freezers control frost accumulation on the evaporator through automatic timed
defrost cycles. The evaporator defrosts automatically every 4 hours. The evaporator face mount heater, drain pan
heater, and condensate drain line heater energize and any accumulated ice on the evaporator and evaporator
drain pan melts and drains out the drain line to the condensate pan located under the compressor. Defrosting will
display on the main screen above the product temperature button. Defrost terminates when either 30 minutes has
elapsed or the evaporator temperature reading from the defrost probe (NTC2) reaches 5.0 C.
00981795R03 – FZR20/25 LB, PL
Low Psi
Vapor
Low Psi
TXV
Liquid
HIGH PRESSURE VAPOR
HIGH PRESSURE LIQUID
COMPRESSOR
ACCUMULATOR
HEAT EXCHANGE
DRYER
LOW PRESSURE LIQUID
H.P. SWITCH
475 PSIG cut-out
High Psi
Vapor
High Psi
Liquid
CONDENSING UNIT
LOW PRESSURE VAPOR
Service
23
Hide quick links:
Advertisement
Table of Contents
