CB780E/CB784E RELAY MODULES WITH VALVE PROVING
750-234 47 32-00150—03
Table 16. VPS Worksheet Example.
a
Divide inches w.c. by 27.7 to get psi.
b
Divide Btuh by 1000 to get cf/hr for natural gas or by 2550 to get cf/hr for LP gas.
Calculation of Valve Train Volume:
X = V1 + V2 + (A x L ÷ 144)
X = 0.0218 + 0.0238 + (3.356 x 1.75 ÷ 144) = 0.0864.
Calculation of Valve Proving Test Time:
Test Time = 187,000 x (P x X ÷ C)
Test Time = 187,000 x (2 x 0.0864 ÷ 2500) = 12.9 sec.
Round up to 13 seconds; enter 13 seconds into the VPS
Setup.
Table 20. VPS Worksheet.
a
Divide inches w.c. by 27.7 to get psi.
b
Divide Btuh by 1000 to get cf/hr for natural gas or by 2550 to get cf/hr for LP gas.
Item Description Information Lookup Table Results Formula Item
V1 Upstream Valve Volume 940-04544 17 0.0218 V1
V2 Downstream Valve Volume 940-04539 18 0.0238 V2
D Pipe Size NPT (in.) 2 in. NPT 19 3.356 A
L Pipe Length (ft) 1.75 ft — 1.75 L
P
Valve Inlet Pressure (psig)
a
2— 2P
C
Burner Maximum Firing (cf/hr)
b
2.5 mbtu — 2500 C
Table 17. V1 Upstream Volumes for Valves.
Models
Pipe Size NPT
(inches) Size
On/Off POC
940-04543 1-1/2 0.0218
940-04539 940-04544 2 0.0218
940-04540 940-04545 2-1/2 0.0227
940-04541 940-045262 3 0.0227
940-04409 940-04451 4 0.0779
Table 18. V2 Downstream Volumes for Valves.
Models
Pipe Size NPT
(inches) Size
On/Off POC
940-04543 1-1/2 0.0238
940-04539 940-04544 2 0.0238
940-04540 940-04545 2-1/2 0.0245
940-04541 940-045262 3 0.0245
940-04409 940-04451 4 0.0801
Table 19. Schedule 40 Pipe Internal Cross-Sectional
Area.
Pipe Size NPT
(Inches)
Cross-Sectional Area
(Sq. In.) “A”
1-1/4 1.498
1-1/2 2.036
23.356
2-1/2 4.788
37.393
4 12.730
Item Description Information Lookup Table Results Formula Item
V1 Upstream Valve Volume 17 V1
V2 Downstream Valve Volume 18 V2
D Pipe Size NPT (in.) 19 A
LPipe Length (ft) — L
P
Valve Inlet Pressure (psig)
a
—P
C
Burner Maximum Firing (cf/hr)
b
—C
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