Burnham Apex APX399 Installation, Operating And Service Instructions page 62

Vii. gas Piping
2. For the low and high gas pressure switches proper
operation, the boiler inlet gas pressure must be
within 4.5" w.c. to 13.5" w.c range.
3. The gas pressure can be measured at the gas valve
inlet pressure port. Refer to Figure 42 "Gas Inlet
Pressure Tap and Pressure Switch Location ".
4. If either pressure switch is tripped, it must be
manually reset before the boiler can be restarted.
E.
Gas Piping for Multiple Boiler Installation
1. Individual module (boiler) gas pipe sizing specific
details - see Paragraph A.
2. Individual module (boiler) recommended gas piping
detail - see Figure 41.
OUTLET
TEST
PORT (P2)
LOW PRESSURE
SWITCH
MANUAL RESET
BUTTON
SIZE 500 ONLY
LEFT SIDE PANEL & BLOWER
OMITTED FOR CLARITY
MANUAL
GAS SHUTOFF
VALVE
62
(continued)
INLET
TEST
PORT (P1)
MANUAL RESET
BUTTON
HIGH PRESSURE
SWITCH
Figure 42: gas inlet Pressure Tap and Pressure Switch Location
3. An additional gas pressure regulator(s) may need to
be installed to properly regulate inlet gas pressure at
the smallest individual module (boiler).
if gas pressure in the building is above ½ psig,
an additional gas pressure regulator is required.
Using one additional regulator for multiple
boilers may result in unsafe boiler operation.
The additional regulator must be able to properly
regulate gas pressure at the input of the smallest
boiler. if the regulator cannot do this, two or
more additional regulators are required. Consult
regulator manufacturer and/or local gas supplier
for instructions and equipment ratings.
LOW PRESSURE
SWITCH
MANUAL RESET
BUTTON
6" LONG PIPE NIPPLE
(USED ON 500 ONLY)
PRESSURE SWITCH
ASSEMBLY
Warning
OUTLET
TEST
PORT (P2)
MANUAL RESET
BUTTON
SIZE 625 THRU 800
RIGHT SIDE PANEL & BLOWER
OMITTED FOR CLARITY
3
" NPT PIPE PLUG
4
(USED ON 625 THRU 800)
PART OF FACTORY
INSTALLED GAS TRAIN.
INLET
TEST
PORT (P1)
HIGH PRESSURE
SWITCH