SS-APG010C-EN
9
Expansion Valves
Expansion valves meter refrigerant into the evaporator under controlled conditions. If there is too
much refrigerant, the refrigerant will not completely vaporize and the remaining liquid will slug the
compressor. If there is too little refrigerant, there may not be enough cooling for the compressor.
Table 4, p. 17, lists expansion valves. Each evaporator distributor requires a dedicated expansion
valve in order to maintain proper coil distribution. The expansion valve should be selected to match
the capacity of the coil that the distributor feeds.
Example: 10-ton coil with two equal distributors
10 / 2 = 5
Each TXV should be selected for 5 tons.
The proper balance for feeding refrigerant for a (4) TTA/TWA system is to provide 18°F of
superheat—the difference between the saturated and actual refrigerant temperature leaving the
evaporator. Expansion valve superheat is preset from the factory, but it isn’t set to 18°F. Use the
turns listed in Tab le 1 to adjust them to the correct 18°F superheat.
Table 1. Expansion valves
Sporlan
Standard off-the-shelf nominal valve settings (90 PSIG air test setting) Field adjust for 18°F
Valve Superheat, °F CW turns available CCW turns available
Superheat change
per turn
ERZE 12 4.5 4.5 2.4°F 2 1/2 CW
To Next Page
Loading...
