Trane Technologies CVHE - Page 29

Table 6. “C” values used to determine rupture disc vent line sizes
Evaporator
Size
(EVSZ)
(a)
Condenser
Size (CDSZ)
(b)
“C” Values for Unit Components
Total C val-
ue
Short H.R.
Condenser
Long H.R.
Condenser
Auxiliary
Condenser
With Free
Cooling
050 Short 050 Short 64.05
23.56 31.45 15.28 6.16050 Short 050 Long 71.94
050 Long 050 Long 83.02
080 Short 080 Short 86.28
29.06 38.80 15.28 5.87080 Short 080 Long 96.02
080 Long 080 Long 111.29
142 Extended 142 Long 142.20
N/A*
Design Special
15.28
Design Special
142M 142 Long 126.37
50.50
7.10
142 Long 142 Long 136.76
210 Long 210 Long 149.28 56.72
250 Extended 250 Long 173.33 62.12
Notes:
1. Rupture disc diameter is 3 inches (76 mm).
2. To determine the total “C” value for a specic unit, add the appropriate “C” values for the evaporator, standard condenser and economizer. If
the unit is equipped with any options (e.g., heat recovery, free cooling or an auxiliary condenser, add the applicable “C” values to this total.
With this new sum, refer to Figure 15, p. 30 to determine the vent line pipe diameter.
(a) EVSZ = Evaporator shell size
(b) CDSZ = Condenser shell size
For CenTraVacs using a rupture disc relief:
• L = equivalent length of discharge piping, ft (m)
• Cr = rated capacity as stamped on the relief device in lb/min (kg/s), or SCFM multiplied by 0.0764 lb/min (convert
multiplier in lb/min to kg/s for SI)
Cr = C value from Table 6, p. 29 (convert C in lb/min to kg/s for SI)
• f = Moody friction factor in fully turbulent flow
• d = inside diameter of pipe or tube, in (mm)
• ln = natural logarithm
• P2 = absolute pressure at outlet of discharge piping, psi (kPa)
• P0 = allowed back pressure (absolute) at the outlet of pressure relief device, psi (kPa)
P0 = (0.50 P ) + atmospheric pressure
Note: For rupture discs on CenTraVac chillers, P is 15 lb. Atmospheric pressure is at the elevation of the installation
above sea level; a default value is the atmospheric pressure at sea level, 14.7 psi (101.325 kPa).
TCVHE-SVX04D-EN 29
Vent Piping
RELEASED 10/Mar/2020 06:59:20 GMT