Greenheck Coils - Manual (Page 5)

Page 5 of 7 IOM, Rev. 2, November 2007
Copyright © Greenheck Fan Corporation
Refrigerant Coil Installation Recommendations
Refrigeration coils manufactured by Greenheck Coils are shipped with a small nitrogen holding charge.
Care should be taken when opening these coils for installation. DX coil distributors have caps installed
with soft silver solder. Once the cap is removed and if the TEV is to be installed using anything other than
soft solder, the distributor connection should be sufficiently cleaned with emery cloth to remove the soft
solder. Follow accepted refrigeration piping practices and safety precautions per Ashrae Standards. If
bends or 90's are necessary, long radius fittings must be used to keep the pressure drop through the
piping at a minimum. General recommendations for component selection and line sizing follow. Nitrogen
charged and capped piping is recommended.
A. Liquid Line Sizing
All compressors have a Refrigerant Charge Limit [RCL] that must not be exceeded. Since the RCL and
pressure drop are in direct conflict with each other, Greenheck Coils recommends that the liquid line be
sized as small as possible, while maintaining a low enough pressure drop to ensure 5°F of sub-cooling at
the expansion valve.
B. Liquid Line Components
Greenheck Coils recommends the use of a properly sized liquid line filter-drier, installed upstream from
the expansion valve and as close to the evaporator coil as possible. Filter-drier selection should be
based on a maximum pressure drop of 2 psi at the design condition.
A moisture indicator / sight glass should be installed between the expansion valve and filter-drier. The
moisture indicator / sight glass must be sized to match the size of the liquid line at the thermal expansion
valve.
A liquid line shut-off valve with an access port should be sized with the selected liquid line OD, and
installed close to the condenser.
The use of other valves, tube bends and reducers should be minimized, since these items tend to
increase pressure drop and to reduce sub-cooling at the expansion valve. Liquid line receivers, other than
those factory-installed, are not recommended.
The Thermal Expansion Valve [TEV] must be selected for proper size, capacity and refrigerant being
used. A slightly oversized valve will allow the unit to operate satisfactorily at low-load conditions. An
undersized valve should not be used at any time as this will starve the evaporator of refrigerant causing
insufficient air temperatures. The use of a hot gas bypass valve should also be considered when sizing
the TEV. Select expansion valves with external equalizer connections, and those designed to operate
against a backpressure of 20 pounds per square inch higher than actual evaporator pressure.
The TEV must be installed directly on the evaporator coil liquid line connection provided. The liquid
distributor must be in a vertical position. Insure that the distributor nozzle is installed in the distributor if
required and that the correct nozzle for the refrigerant being used is installed. Sensing bulbs must be
mounted on a clean horizontal suction line close to the evaporator outlet and insulated properly. The bulb
must be tight against the suction line at a 10 or 2 o'clock position, but take care not to over tighten and
cause damage to the sensing bulb. The bulb should not be mounted directly on top or bottom of the
suction line.