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Benchmark 750-3000 Boiler Installation & Startup Manual
SECTION 5 – SAFETY DEVICE TESTING
LOW Gas Pressure Test Instructions: BMK 750 – 2500
MANUAL
SHUT-OFF
VALVE
Figure 5-1c: BMK 2500 LOW Gas Pressure Test Components
5.2.2 LOW GAS PRESSURE TEST: BMK 3000 Only
To simulate a low gas pressure fault on BMK 3000 units, refer to Figure 5-2, below, and perform
the following steps:
LOW Gas Pressure Test Instructions: BMK 3000 ONLY
1. Close the external gas supply ball valve (not shown) upstream of the unit.
2. Locate the port on the top of the Low Gas Pressure switch (see Figure 5-2, below) and
loosen the screw inside a few turns to open it. Do not remove this screw completely.
Alternatively, you can remove the 1/4 inch plug shown in Figure 5-2 and install a hose
barb fitting in that location.
3. Attach one end of the plastic tubing to the port or barb fitting and the other end to a 16"
W.C. (0 – 4.0 kPa) manometer.
4. Apply the reading of the manifold pressure taken in Step 15 of section 4.4.1 (natural gas
units) or Step 15 of section 4.4.2 (propane units) and plug it into the following formula,
which calculates the minimum allowable gas pressure:
•
FM Natural Gas pressure ____ x 0.5 + 0.7 = ______ min gas pressure
•
DBB Natural Gas pressure ____ x 0.5 + 1.6 = ______ min gas pressure
•
Propane Gas pressure
5. Remove the cover from the Low Gas Pressure switch and set the dial indicator to 2 (the
minimum).
6. Open the external gas supply ball valve (not shown) upstream of the unit.
OMM-0121_D • GF-205 • 5/9/2019
HIGH GAS PRESSURE
SWITCH
TO
AIR/FUEL
VALVE
LOW GAS BALL VALVE
____ x 0.5 + 0.6 = ______ min gas pressure
Technical Support • (800) 526-0288 • Mon-Fri, 8 am - 5 pm EST
NATURAL
GAS INLET
SSOV
LOW GAS
PRESSURE
SWITCH
1/4" NPT PLUG
Install manometer
here for LOW gas
pressure fault test.
Page 80 of 122
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