INSTALLATION AND OPERATION INSTRUCTIONS
1-14
HC SERIES BOILERS HC 13-50, HC 23-84, HC 29-106, HC 33-124, HC 20-125, HC 33-160
1.4.7 “Direct Vent” Combustion Air Intake Piping
The boiler must always be installed as a Direct Vent venting system with the
combustion air piped directly from the outdoors to the boilers combustion air
connection. Provisions for combustion and ventilation air in accordance with
the section “Air for Combustion and Ventilation,” of the National Fuel Gas Code,
ANSI Z223.1/NFPA 54, or Clause 8.2, 8.3 or 8.4 of Natural Gas and Propane
Installation Code, CAN/CSA B149.1, or applicable provisions of the local building
codes.
For 3" Flexible PPs, up to 35 actual lineal feet are allowed in a nominally vertical
orientation (>45°). The equivalent length of 3" Flexible PPs shall be computed
using a multiple of 1.4:1, e.g. 35' x 1.4 = 49' equivalent. The balance of the
venting allowance is still available for use with rigid PPs piping material. 2"
Flexible PPs is not allowed.
INTAKE PIPE SIZE/FITTINGS MAXIMUM EQUIVALENT LENGTH
Schedule 40 CPVC or PPs – Allowances are for each side separately.
2" 35'
3" 120'
2" or 3" 90' Long Sweep Vent Elbow Allow 5 equivalent feet
2" or 3" 90' Short Sweep Vent Elbow Allow 8 equivalent feet
2" or 3" 45' Vent Elbow Allow 3 equivalent feet
PPS
PPs 87-90' Elbow Allow 8 equivalent feet
Flex PPS
3" PPs Flex 35 actual feet
Table 4: Maximum intake piping length.
Figure 15: Direct vent combustion air intake
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