Direct Venting; Removal Of Existing Furnaces From Common Vent Systems; Combustion-Air And Vent Piping - Carrier 58MXA Installation, Start-Up, And Operating Instructions Manual

Fig. 26—EAC Terminals on Control Center

DIRECT VENTING

The 58MXA Furnaces require a dedicated (one 58MXA furnace
only) direct vent system. In a direct vent system, all air for
combustion is taken directly from outside atmosphere, and all flue
products are discharged to outside atmosphere.
Step 1—Removal of Existing Furnaces from
Common Vent Systems
If furnace being replaced was connected to a common vent system
with other appliances, these steps shall be followed with each
appliance remaining connected to common vent system placed in
operation, while other appliances remaining connected to common
vent system are not in operation:
1. Seal any unused openings in common vent system.
2. Visually inspect vent system for proper size and horizontal
pitch. Determine there is no blockage or restriction, leakage,
corrosion, and other deficiencies which could cause an unsafe
condition.
3. Insofar as is practical, close all building doors and windows
and all doors between space in which appliances remaining
connected to common vent system are located and other
spaces of building. Turn on clothes dryers and any appliance
not connected to common vent system. Turn on any exhaust
fans, such as range hoods and bathroom exhausts, so they
operate at maximum speed. Do not operate a summer exhaust
fan. Close fireplace dampers.
4. Follow lighting instructions and place appliance in operation.
Adjust thermostat so appliance operates continuously.
5. Test for flue gas spillage at drafthood relief opening after 5
minutes of main burner operation. Use flame of a match or
candle, etc.
6. After it has been determined that each appliance remaining
connected to common vent system properly vents when tested
as above, return doors, windows, exhaust fans, fireplace
dampers, any other gas burning appliances to their previous
condition of use.
7. If improper venting is observed during any of above tests,
common vent system must be corrected. Vent system or vent
connectors may need to be resized. For any other appliances
when resizing vent systems or vent connectors, system or
connector must be sized to approach minimum size as
determined using appropriate table found in Part 11 of NFGC
or Section 5 of NSCNGPIC.
Step 2—Combustion-Air and Vent Piping
GENERAL
Combustion-air and vent pipe fittings must conform to American
National Standards Institute (ANSI) standards and American
Society for Testing and Materials (ASTM) standards D1785
(schedule-40 PVC), D2665 (PVC-DWV), D2241 (SDR-21 and
SDR-26 PVC), D2661 (ABS-DWV), F628 (schedule-40 ABS), or
F891 (PVC-DWV cellular core). Pipe cement and primer must
conform to ASTM standards D2564 (PVC) or D2235 (ABS). See
Table 5 for maximum pipe lengths and Fig. 31, 32, 33, 34, and 35
for exterior piping arrangements.
In Canada construct all combustion-air and vent pipes for this unit
of CSA or c-UL certified schedule-40 PVC, PVC-DWV or
ABS-DWV pipe and pipe cement. SDR pipe is NOT approved in
Canada.
A93053
NOTE: Furnace combustion-air and vent pipe connections are
sized for 2-in. pipe. Any pipe size change should be made outside
furnace casing in vertical pipe. (See Fig. 27.) This allows proper
drainage of vent condensate.
NOT IN
HORIZONTAL
SECTION
Fig. 27—Combustion-Air and Vent Pipe Diameter
Transition Location and Elbow Configuration
Combustion-air and vent pipes must terminate together in same
atmosphere pressure zone, either through roof or sidewall (roof
termination preferred), using accessory termination kit. See Table
4 for required clearances.
Furnace combustion-air and vent pipe connections must be at-
tached as shown in Fig. 28. Combustion-air intake plug fitting and
inducer housing alternate vent cap may need to be relocated in
some applications.
When combustion-air pipe is installed above a suspended
ceiling, pipe must be insulated with 3/8-in. thick Armaflex-
type insulation. Combustion-air pipe should also be insulated
when it passes through warm, humid space.
When vent pipe is exposed to temperatures below freezing,
such as when it passes through an unheated space or when a
chimney is used as a raceway, pipe must be insulated as
shown in Table 6 with Armaflex-type insulation.
20
FURNACE
PIPE DIAMETER
TRANSITION IN
VERTICAL SECTION
A93034