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SKP25U.. Pressure Regulating Gas Valve Actuators Technical Instructions
Document Number 155-752
July 9, 2014
Siemens Building Technologies, Inc. Page 5
Regulating Function,
Continued
The SKP25.0 models may be applied as a 1:1 air/gas proportionator or as a zero
governor. For either application, the standard spring has to be replaced with AGA28
spring, which allows sdjusting the bias between + 0.6" to –0.6" WC.
For proportionator operation, the air pressure sensing line must be connected to the
port marked “AIR".
High bias model SKP25.611U1 is a 1:1 air/gas proportionator with a factory installed
spring for 0” to -4.0” WC bias.
NOTES: 1. To avoid oscillation, do not oversize the VG valve body. (See
Technical Instructions, P/N 155-512P25.)
2. SKP25.4 models must not be used as proportionators.
Installation
• Personal injury or loss of life may occur if procedures are not followed
as specified.
• All installations must be performed by qualified personnel only.
• Do not pull the actuator shaft.
• If minimum gas pressure detection is required, the pressure switch must
be mounted upstream of the regulating gas valve to ensure sufficient
gas pressure before starting the burner. If maximum gas pressure
detection is required the pressure switch must be mounted downstream.
• The AGA66 gasket must be installed between the actuator and the gas
valve body to provide NEMA 3, 3R, and 4 protection rating for VGG
and VGD valves.
• The gas pressure sensing line must be at least 1/4-inch inside diameter.
• The gas pressure sensing line connection must be flush with the inner
wall of the gas pipe in order to sense turbulence free pressure. The gas
sensing line connection should be located at least five pipe diameters
downstream of the valve, elbow, coupling, or other flow disturbing fitting.
Do not use the taps on the valve body for the gas sensing line
connection since these locations typically have strong turbulence.
The pressure connection pipe should be as short as possible to allow
the regulator to react to sudden changes.
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