11984 Rev 01 Page 6 of 8
1.3 Requirements
This pressure drop is a function of the piping diameter and configuration, the
presence or absence of a condenser and, most importantly, the Flow rate (SLM)
through the exhaust line. Pressure drop is increased by long pipe lengths and
elbows in the pipe. If a physical measurement of this pressure drop cannot be
made, within Zone B on Figure 1-3 is a graph which indicates typical pressure
drops as a function of Flow. It should be noted that flow is calculated as the
combination of Total flow through all MFC’s as well as Flow through any gaps should
the furnace not be completely sealed!
P
Controller
: Pressure Drop across Controller
This is also a simple calculation. As in the case of all piping, the Sentry 1510 will
also have a resistance or pressure drop which is dependent upon flow. Located
within Zone C on Figure 1-3 is a chart which indicates pressure drop as a function
of flow. (This pressure drop is inclusive of the PTI-patented N
2
bias flow through
the Sentry 1510).
P
Facility
: Pressure Drop between Sentry Exit Port and House Exhaust
Finally, there exists a pressure drop between the exit of the Sentry controller and
the main house exhaust duct. This pressure drop must also be accounted for if
house exhaust is determined at the main duct.
Example
Using the above calculation with a negative process pressure, taking into account
Zones A,B,C & D, determining the minimum house exhaust to achieve a process
pressure of -5mm with a flow of 20 SLM and a 1 mm drop between controller exit
and House exhaust (Zone D) would be calculated as follows:
P
Sense
(-5) - [P
Exit
(3) + P
Controller
(7) + P
Facility
(1) ]= -16mm H
2
O Minimum H.E.
Electrical Components
The Automated SENTRY 1510 is outfitted with an electrical package consisting of
a Supervisor with LCD display, a pressure transducer, a stepper motor and
cabling. Power is supplied to the Supervisor, which conditions and supplies power
to the Supervisor electronics, as well as to the stepper motor and the pressure
transducer on the SENTRY 1510 controller. The on/off switch within the Supervisor
acts as a safety cut-off device in the event of an overcurrent situation. The
pressure transducer has a measurement range of 0-50.80 mm (0-1 inch) of water
column. The SENTRY 1510 will operate in the range of 5 to 46 mm water column.
For negative pressure operation, the operating range is a negative differential
pressure relative to ambient (-5 to -46 mm) of water column. The operating range
for a positive differential pressure control configuration is +5 to +46 mm of water
column.
To Next Page
Loading...
Need help?
General