Burnham Apex APX399 Installation, Operating And Service Instructions page 14

iii. Pre-installation and Boiler Mounting
b. Gas Piping - Follow instructions in Section
VII "Gas Piping" of the manual for sizing
and installation of an individual boiler. When
common gas piping is sized, insure it will have
adequate capacity for combined input (CFH
gas flow) of the selected stackable boiler
combination.
c. Water Piping and Trim - Follow instructions
in Section VI "Water Piping and Trim" of the
manual for system piping and boiler secondary
14
Figure 3: Stacking Boiler attachment Bracket Placement
G. General (continued)
piping selection/sizing based on combined
heating capacity and/or gross output of
the selected stackable boiler combination.
Follow instructions of Section VI "Water
Piping and Trim" for each individual boiler trim
installation.
d. Electrical - Follow instructions in Section VIII
"Electrical" of the manual to wire individual
boilers.