1-19
INSTALLATION
TANKLESS WATER HEATER 199
Intake Pipe Sizing
For 3" Flexible PPs, you can use up to 35 actual linear feet in a nominally vertical
orientation (>45°). The equivalent length of 3" Flexible PPs must be calculated
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 PVC, ABS, CPVC or PPs – Allowances are for each side separately.
2"
65'
*
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 (Equivalent = Actual x 1.4)
Table 4: Maximum intake piping length.
* The input rate will derate as intake length increases. See table below for
approximate derate at 2" maximum intake length.
MAXIMUM FIRING RATE
APPROXIMATE DERATE
199,000
10 - 16%
For
inlet
air, you can use Schedule 40 PVC, CPVC, ABS or PPs piping of any
type. Use the same diameter as vent piping.
Insert combustion air piping directly into the 2" female plastic fitting on the top of
the unit, and run it horizontally or vertically to the outdoors. We recommend using
a bird screen of 1/4" stainless steel or plastic mesh (eg. IPEX System 636 drain
grate for CPVC systems) to guard against foreign objects.
Care must be taken to ensure adequate separation is maintained between the air
intake inlet and the vent termination. Refer to the vent termination configuration
drawings in the “Vent Termination” section above.
Support air intake and vent piping per local code and vent manufacturers
requirements. In the absence of support requirements, support the air intake and
vent piping at every vertical and horizontal transition as well as every 5’ of run.
1.4.8 “Indoor Air” Combustion Air Intake
The use of indoor air for combustion is prohibited. Combustion air must be
piped in from the outdoors and connected directly to the unit’s combustion air
connection
1.4.9 Closet Installations
For installations in a confined space (such as a closet), ventilation openings may
be needed through a door or wall to prevent build-up of excessive heat from
inside the space.
The unit must not be exposed to surrounding conditions above 122°F (50°C) or
below 32°F (0°C).