Nortec AIRFOG Series - Manual (Page 15)

AirFog Installation Manual | 11
Vacuum Valve
The vacuum valve must be centrally located so there are approximately an equal number of
nozzles being fed from each of its two output ports (one on the left side and the other on the
right side). There is a mounting bracket supplied with each vacuum valve. Figure 9: Vacuum
Valve Interfaces illustrates the plumbing interface details. Elevation of the valve is very critical,
as is the positioning of the nozzles. The maximum height above the nozzle supply line the valve
should be installed is 12” (30 cm). Never install the vacuum valve lower than the nozzle water
feed lines.
The water flow rate through this valve is limited to 24 GPH, which limits the number of AFE
nozzles it can supply to 16. If more than 16 nozzles are to be installed, then the system must
be broken into zones using multiples of 16 (or less) nozzles with each zone controlled by its own
vacuum valve. One control panel can control multiple zones by “T” ing off the single control
panel air pilot output.
Air pressure from the control panel is used to open the water safety valve permitting water to
enter the vacuum valve, which controls the water feed to the nozzles. Figure 8: Vacuum Valve
Operation explains the operation of this water regulator. The vacuum valve assembly has three
sub-components. As illustrated in Figure 9: Vacuum Valve Interfaces. First, the safety valve
interfaces directly with the primary water supply to open or close on command from the control
panel. Loss of pilot air pressure (below 10 psig) will automatically close this valve to prevent
water proceeding beyond this point. In series with, and downstream of the safety valve, is the
water regulator. The water regulator is used as the first stage of water pressure reduction. The
water regulator reduces the supply water pressure to a range between 5 and 10 psig. This is
set manually at time of installation. Please note that system performance is not sensitive to the
exact setting as long as the pressure is within this range.
The second stage of water pressure reduction is the vacuum diaphragm, which drops the
pressure to ambient (0 psig). Output is through two exit ports on the underside of the vacuum
valve. This permits the nozzle to draw water from the supply as required rather than having
pressure force it into the nozzle. The siphoning action of the nozzle is controlled by the pilot
operated air regulator.
On top of the vacuum valve is a thumb wheel adjustment for adjustment of the AirFog droplet
size. The adjustment changes the volume of water to the nozzles. A reduction in available
water for a constant air flow results in smaller droplets and a finer spray. This adjustment can
be used to reduce the water throughput if there is a problem with water droplets reaching the
floor.
Pilot Operated Air Regulator
The pilot operated air regulator controls the air supply to the nozzles and is illustrated in Figure
10: Pilot Air Regulator. The pilot regulator is modulating flow controller rather than a simple
On/Off valve. The greater the pilot air pressure, the greater the air pressure fed to the nozzle
supply network. This means that the Control Panel is able to request a proportional opening of
the Air Regulator simply by varying the pilot pressure. There is a linear 1:1 relationship between
the pilot pressure and the output pressure drop. A pilot air pressure of 25 psig (172.5 kPa) will
drive the air regulator to have an output of 25 psig (172.5 kPa). A pilot pressure of 50 psig will
drive the air regulator to have an output of 50 psig. The pilot air pressure range is from 0 to 70
psig.