Williamson-Thermoflo w 80, Information Manual

Installer’s Information Manual 

Page 15 

SECTION 8.  SIDEWALL VENTING 

In most cases, proper venting is achieved by using a 
conventional vertical vent or chimney.  However, it is not 
uncommon to have an installation where venting through a 
sidewall becomes necessary.  This section contains 
information on venting through a sidewall using a 
mechanical (power) venter.  A mechanical (power) venting 
system operates at negative pressure to draw the furnace 
flue products from the structure. 

This furnace must not be vented with high temperature 
plastic pipe. 

IN THE UNITED STATES 

Any mechanical (power) venting system is acceptable as 
long as it has been certified by a nationally recognized 
testing agency and meets all state and local codes.  The 
venter must be installed according to the mechanical 
(power) venter manufacturer’s installation instructions.  It 
must be sized appropriately for the furnace and be capable 
of maintaining a negative vent pressure of -0.1 to -0.5 
inches W.C. in the vent pipe leaving the furnace under all 
operating conditions.  Because this system operates at 
negative pressure, any single wall or Type B vent pipe may 
be used; however, Type B-1 pipe is recommended. 

In addition to the venter manufacturer’s instructions, the 
furnace manufacturer requires use of a secondary safety 
switch that will act to turn off the furnace in the event that 
the vent pressure becomes positive.  These devices are 
available through the mechanical (power) venter 
manufacturer. 

IN CANADA 

The mechanical (power) venter must be CGA certified for 
each furnace model.  At this time, there is one system 
approved for use on this furnace in Canada.  The system is 
manufactured by The Field Controls Company and 
includes: 

•

Power Venter model SWG-4HD 

•

Secondary Safety Switch model WMO-1 

•

Control Kit model CK-43 or 

•

Control Kit model CK-91 (for common venting with a 
water heater) 

The SWG-4HD is certified with this furnace for up to forty 
feet and four elbows of type B-1 vent pipe.  The venter must 
be installed according to the mechanical (power) venter 
manufacturer’s installation instructions.  Adjust the power 
venter to provide a negative pressure of -0.1 to -0.5 inches 
W.C. in the vent pipe leaving the furnace. 

SECTION 9.  INSTALLING GAS 
PIPING 

PREPARATION 

Refer to the current National Fuel Gas Code ANSI 
Z223.1/NFPA 54 and/or CAN/CGA B149 Installation Codes 
and local codes for gas piping requirements and sizing.  
Pipe size running to furnace depends on: 

•

Length of pipe 

•

Number of fittings 

•

Specific gravity of gas 

•

  Input requirements (Btu per hour) of all gas-fired 

appliances attached to same main supply line. 

Plan furnace gas supply piping so it will not interfere with 
removal of burner assembly, front door or blower door for 
servicing. 

Make sure gas piping is large enough for all appliances 
connected to it to operate at once without lowering gas 
supply pressure.  Failure to do so could cause lighting or 
burning problems on any of the appliances. 

Always use a pipe thread compound that is resistant to 
propane (LP) gas solvent action.  Sparingly apply thread 
compound to all joints on male threads only, starting two 
threads from the end. 

GAS ENTRY LOCATION 

Choose the best gas line entry location for your installation.  
This furnace has five possible gas entry locations. 

•

As shipped, 1/2” NPT pipe can be attached directly to 
the furnace gas control through the 1¼ by 2¾ inch 
opening on the top plate. 

•

Gas line entry may also be routed through the 1 ½ inch 
hole in the right side of the casing by positioning a 90 
degree street elbow (field supplied) on the gas valve as 
shown in Figure 20. 

•

For gas line entry through the knockout in the left side 
of the casing, position a 90 degree street elbow (field 
supplied) as shown in Figure 20.  ½” NPT pipe can 
now be attached to the furnace gas control from the left 
side. 

•

  For gas line entry through either of the upper 

knockouts located in the right and left sides of the 
casing, remove any attached street elbow from the gas 
valve, shown in Figure 20.  1/2" NPT pipe can now be 
routed directly to the furnace gas control. 

Some large electronic air cleaners will interfere with 
incoming gas line.  Install air cleaner on opposite furnace 
side from gas entry or route gas pipe over top of air cleaner 
through one of alternate knockouts.