Page 22
Venting Practices
* See Piping and Fittings Specifications table
Piping Suspension Guidelines
NOTE
- Isolate piping at the point where it exits the outside wall or
roof in order to prevent transmission of vibration to the structure.
SCHEDULE 40
PVC - 5'
all other pipe* - 3'
Wall
e
d
i
s
t
u
o
e
d
i
s
n
i
24” maximum
3/4” minimum
Wall Thickness Guidelines
FIGURE 21
If replacing a furnace which was
commonly vented with another gas appliance, the size
of the existing vent pipe for that gas appliance must be
checked. Without the heat of the original furnace flue
products, the existing vent pipe is probably oversized for
the single water heater or other appliance. The vent
should be checked for proper draw with the remaining
appliance.
REPLACING FURNACE THAT WAS PART OF A
COMMON VENT SYSTEM
CHIMNEY
OR GAS
VENT
(Check sizing
for water
heater only)
FURNACE
(Replaced)
WATER
HEATER
OPENINGS
(To Adjacent
Room)
FIGURE 22
1- In areas where piping penetrates joists or interiorwalls,
hole must be large enough to allow clearance on all
sides of pipe through center of hole using a hanger.
2 - When furnace is installed in a residence where unit
is shut down for an extended period of time, such
as a vacation home, make provisions for draining
condensate collection trap and lines.
Removal of the Furnace from Common Vent
In the event that an existing furnace is removed from a
venting system commonly run with separate gas applianc
-
es, the venting system is likely to be too large to properly
vent the remaining attached appliances. Conduct the fol
-
lowing test while each appliance is operating and the oth
-
er appliances (which are not operating) remain connected
to the common venting system. If the venting system has
been installed improperly, you must correct the system as
indicated in the general venting requirements section.
WARNING
CARBON MONOXIDE POISONING HAZARD
Failure to follow the steps outlined below for
each appliance connected to the venting system
being placed into operation could result in carbon
monoxide poisoning or death.
The following steps shall be followed for each
appliance connected to the venting system being
placed into operation, while all other appliances
connected to the venting system are not in operation:
1 -
Seal any unused openings in the common venting
system.
2 - Inspect the venting system for proper size and
horizontal pitch. Determine that there is no blockage,
restriction, leakage, corrosion, or other deficiencies
which could cause an unsafe condition.
3 - Close all building doors and windows and all
doors between the space in which the appliances
remaining connected to the common venting system
are located and other spaces of the building. Turn on
clothes dryers and any appliances not connected to
the common venting system. Turn on any exhaust
fans, such as range hoods and bathroom exhausts,
so they will operate at maximum speed. Do not
operate a summer exhaust fan. Close fireplace
dampers.
4 - Follow the lighting instructions. Turn on the appliance
that is being inspected. Adjust the thermostat so that
the appliance operates continuously.
5 - After the main burner has operated for 5 minutes,
test for leaks of flue gases at the draft hood relief
opening. Use the flame of a match or candle.
6 - After determining that each appliance connected to
the common venting system is venting properly, (step
3) return all doors, widows, exhaust fans, fireplace
dampers, and any other gas-burning appliances to
their previous mode of operation.
7 - If a venting problem is found during any of the
preceding tests, the common venting system must
be modified to correct the problem. Resize the
common venting system to the minimum vent pipe
size determined by using the appropriate tables in
Appendix G. (These are in the current standards of
the National Fuel Gas Code ANSI Z223.1.
