Carrier 39LH Installation, Start-up And Service Instructions Manual

24Refrigerant Piping, Direct-Expansion (DX)Coils (Fig. 31) — Direct-expansion coils are divided into2 or 4 splits depending upon the unit size and coil circuiting.See Table 9 for coil circuiting data. Each split requires its owndistributor nozzle, expansion valve, and suction piping. Suctionconnections are on the air entering side when the coil is proper-ly installed. Matching distributor connections for each coil splitare on the air leaving side. See unit label or certified drawing toassure connection to matching suction and liquid connections.See Table 10 for distributor part numbers.27NOTES:1. Flange or union is located to facilitate coil removal.2. When control valve is omitted on multiple coils in parallel airflow.3. When a bypass with control is required.4. Coils with different pressure drops require individual traps.This is often caused by varying air velocities across thecoil bank.Fig. 29 — Multiple Coil Low PressurePiping Gravity ReturnNOTES:1. Flange or union is located to facilitate coil removal.2. To prevent water hammer, drain coil before admitting steam.3. Do not exceed one foot of lift between trap discharge andreturn main for each pound of pressure differential.4. Do not use this arrangement for units handling outside air.Fig. 30 — Condensate Lift to Overhead ReturnCAUTIONDirect-expansion coils are shipped pressurized with dry air.Release pressure from each coil split through valves in pro-tective caps before removing caps.Do not leave piping open to the atmosphere unnecessarily.Water and water vapor are detrimental to the refrigerantsystem. Until the piping is complete, recap the system andcharge with nitrogen at the end of each workday. Clean allpiping connections before soldering joints.The lower split of face split coils should be first on, last off.Row split coils utilize special intertwined circuits (asshown in Fig. 31); either split of these row split coils can befirst on, last off.Fig. 31 — Typical Direct-ExpansionRow Split Coil