1.18.2 When in the heating mode of operation, the compressor (1) moves the refrigerant through the refrigeration system
by raising the pressure of the incoming gas from the outside coil (evaporator) (3) and discharging it as a high pressure
1.18.3 The high pressure gas passes through the reversing valve (7) that controls the refrigerant flow depending on the
operating mode. In this mode, the refrigerant is routed toward the inside coil (condenser) (2).
1.18.4 The high pressure gas enters the inside coil (2) where heat is released to the shelter air passing across the coil.
This will cause the high pressure gas to condense to a high pressure liquid.
1.18.5 The high pressure liquid reaches the inside expansion valve (10) outlet that will not allow flow in this direction. It
then passes through the inside check valve (13).
1.18.6 The outside check valve (13) will not allow flow in this mode of operation and the high pressure liquid is forced
through the filter drier (12) where any moisture that may be in the refrigerant is absorbed and any debris is removed.
1.18.7 The high pressure liquid then passes through the liquid indicator (15) where the condition of the refrigerant can be
1.18.8 The inside expansion valve (10) inlet and outlet pressures are equal in this mode of operation preventing flow
through it. The high pressure liquid will then pass through the outside expansion valve (10) which causes a pressure drop
and automatically meters the amount of liquid passing through it. The rapid drop in pressure causes the liquid to cool.
1.18.9 The cool, low pressure liquid passes through the outside coil (evaporator) (3) where heat is absorbed from the
relatively warmer outside ambient air passing across it causing the low pressure liquid to evaporate to a low pressure gas.
The low pressure gas then returns to the compressor (1) to begin the cycle again.
1.18.10 By lowering the temperature on the outside coil (evaporator) (3) to a point below freezing, any moisture that
accumulates on the outside coil (3) will freeze and prevent proper air circulation through the coil. The defrost cycle is
automatically controlled by an outside air temperature sensor and outside coil temperature sensor in the electrical system.
When an iced coil condition is sensed, the outside blower stops and the outside coil (3) is defrosted as high pressure gas
is sent from the compressor (1) into the coil (cooling mode). Supplemental electric resistance heat is energized to
compensate for the cooling of shelter air when in this mode. The defrost cycle will continue until the temperature sensors
1.18.11 If the outside ambient air temperature drops to 180 F -2 or below, the compressor (1) and outside blower will
be disabled and the FDECU will rely solely on supplemental electric resistance heat until the outside ambient temperature
rises above this point.
1.19.1 The power box (1) is where the incoming power supply is connected and distributed to the various components in
the FDECU. Power distribution is controlled by various relays and protective circuits.
1.19.2 The control box (2) contains the control circuit board as well as the unit mounted operator controls and indicators.
The control circuit board monitors the various sensors and operator controls in the FDECU and controls the power
distribution relays as necessary.
1.19.3 The remote box (3) duplicates the operator controls and indicators on the control box and can be remote mounted
within the limits of the attached 35 foot interconnecting cable.