Unit installation

IOMM ACZ/AGZ 15

With the minimum tons known, a smaller line size should be selected from ASHRAE Chapter 2,

Table 13 or 14 capable of entraining oil at the reduced tons. The smaller sized line should be the

one installed to be always active.

The net internal area of this smaller sized line (see Table 13 or 14) should be deducted from the area

of the size selected in paragraph 1) immediately above. The remainder represents the area of the

other riser. From Table 13 or 14, select a line size with an area equal, or close, to the calculated net

area. The combination of these two risers will provide the required performance at full circuit tons.

The line selected for the minimum load should always be active; and both lines should enter the

overhead horizontal line in a manner to prevent spillage of oil back down the other riser.

Underground Refrigerant Lines

McQuay does not recommend the installation of suction lines underground. If job conditions

require that they be located below ground, a suitable sized suction accumulator must be installed

ahead of the compressor to interrupt liquid refrigerant slugs at start-up.

Long Vertical Riser Installation

Where job conditions require refrigerant gas lifts of more than 25 feet, McQuay recommends the

installation of a short trap half-way up the riser or at not more than 20 feet intervals. These traps

are required to capture and hold small quantities of oil during off cycles.

Figure 8, DX Coil Piping

Condensing Unit Above Coil Condensing Unit Below Coil

EXPANSION VALVE

CONTROL BULB

STRAP TO LINE

AND INSULATE

SUCTION TRAP

SHORT AS

FITTINGS PERMIT

LIQUID TO

COIL

LIQUID