Thermo Pride Gas/Propane Furnace Premiere Series 2-Stage CHX3 - Manual (Page 16)

All installations and services must be performed by qualified service personnel.
10
Horizontal runs of air intake pipe shall slope downward at least ¼ inch per foot from the outlet of
the last elbow or last horizontal run, before exiting the wall, to the intake termination beyond the
outside wall. This slope will permit proper drainage of any precipitation that enters the intake pipe.
6. The exhaust vent pipe shall be supported at every joint (no more than 4-feet between supports) to
prevent pipe blockage due to condensate trapped at a local low point, or sag, in the vent system.
7. The maximum permissible length of piping (consisting of a combination of straight pipe and a
corresponding number of elbows) permitted is:
•
75 equivalent feet, for the exhaust vent system, and
•
70 equivalent feet, for the combustion air intake system.
8. The maximum quantity of Schedule 40 series, type DWV thermoplastic pipe elbows allowed in
each system is listed in Table 2. When counting pipe elbows, all elbows used in the exhaust vent
or combustion air intake systems must be considered. This includes all elbows, or equivalent pipe
fittings, used inside the furnace jacket in addition to those used to construct the termination.
Furthermore, a credit of 5-feet of straight pipe may be taken for each elbow, up to maximum of
three (3) elbows, which is dropped from the maximum permissible number for each system.
Table 2: Maximum Permissible Exhaust Vent and Combustion Air Intake Lengths When Using the
Maximum Quantity of Elbows
Thermoplastic
Pipe Vent Size
(Nominal)
2 in. Diameter IPS 3 in. Diameter IPS
Furnace Model Exhaust or
Intake
Straight Pipe
Length (ft.) Maximum Qty.
of Exhaust
Elbows
1, 2
Maximum
Qty. of Intake
Elbows
2
Exhaust or
Intake
Straight Pipe
Length (ft.) Maximum Qty.
of Exhaust
Elbows
1, 2
Maximum
Qty. of Intake
Elbows
2
CHX3 / CDX3-75 35 8 7 - - -
CHX3 / CDX3-100 Not Permitted 35 8 7
CHX3 / CDX3-125
Superscripts:
1
The drain tee supplied with the model series CHX3 / CDX3 furnaces is considered
equivalent to one (1), 90° elbow.
2
Two (2) 45° elbows can be substituted for one (1), 90° elbow.
Care should be taken to design the shortest possible intake and exhaust systems. Each system
should contain as few elbows as possible to insure the satisfactory operation of the furnace.
However, system length should never be less than 8 ft of pipe with two (2), 90 deg. elbows.
For best overall operation of the combustion system, we recommend the actual equivalent lengths
for both the constructed intake and the exhaust systems have approximately the same value.
9. Use a saw designed to cut thermoplastic pipe. All cuts should be made at right angles to the pipe
wall. Smooth jagged edges and remove all burrs and strings. All pipe joints must utilize
standard PVC Schedule 40 series, DWV type elbows, couplings, and fittings. Clean all pipe
surfaces at connections using a fine abrasive material or approved PVC cleaner (primer). Secure
all pipe joints using suitable permanent PVC pipe solvent cement. Joints are NOT to be made by
simply gluing raw edges of butted together vent pipe.
The piping joints inside the furnace vestibule should be sealed with a silicone caulk, rather than
pipe cement, to allow for disassembly and removal of piping, if necessary, during maintenance.