Venting - A.O. Smith BTH 120 Service And Parts Manual

4-inch PVC may be used for a MAXIMUM intake of ONE HUNDRED TWENTY (120) EQUIVALENT FEET
and a MAXIMUM exhaust of ONE HUNDRED TWENTY (120) EQUIVALENT FEET. The maximum number
of 90° elbows with the 4-inch venting is six (6) on the intake and six (6) on the exhaust. A 90° elbow is equal
to five (5) equivalent feet of pipe. One (1) 90° elbow is equal to two (2) 45° elbows. Any venting configuration
using less than 50 equivalent feet should use 3-inch venting. See Vent Length Table.
The 3-inch venting terminals (provided) must be used with the 4-inch venting by adding 4 x 3 reducing
couplings at the venting terminals. A reducing coupling is also needed immediately after the condensate
elbow (exhaust) and immediately before the 3-inch blower adapter (intake) if direct venting is installed. See
Vent Length Table.
SUPPLY GAS
Minimum
Inches
Gas Type W.C.
Natural 5
Propane 11
NOTE: Pressure without capacity will result in
lockout. Follow the piping guidelines in the
instruction manual.
The supply gas pressure in normally measured
at the dirt leg or at the inlet gas pressure tapping
on the gas valve. This reading must be measured
with 'flowing' gas.
Regulated Gas Supply
Line
Main Gas Shutoff Valve
Dirt Leg Tee
Pipe Cap
A. O. Smith Water Products Company
Irving, Texas 2000©

VENTING

Equivalent Feet of Pipe Intake or Exhaust
VENT LENGTH TABLE
Number of 3" Minimum
90° Elbows Pipe (Feet)
One (1)
Two (2)
Three (3)
Four (4)
Five (5)
Six (6)
Maximum
Inches
W.C.
10.5
13.8
3" Maximum
Maximum Pipe
Pipe (Feet) (Feet)
7 45
7 40
7 35
7 30
--
7
--
7
MANIFOLD GAS
Minimum/Maximum
Gas Type Inches W.C.150/199
Natural 3.5
Propane 10
The manifold gas pressure is measured at the
manifold pressure tap of the gas valve when the
gas is flowing.
Pressure Regulator Adjustment
(Cover Screw)
Inlet Pressure Tap
Gas Inlet
The gas valves used on all BTH water heaters are
24 volt AC combination step opening gas valves.
They incorporate the main valve, and gas pressure
regulators into one body.
12
4"
115
110
105
100
95
90
Minimum/Maximum
Inches W.C. 120/250
10.0
Gas Valve On/Off
TH & TR Terminals
(Main Valve)
Service Handbook
Training Department
4.0
Manifold
Pressure Tap
Gas Outlet