Smith Cast Iron Boilers GT Series Horizontal Direct Vent Systems, Vent Pipe To Boiler Attachment

GT INSTALLATION AND OPERATION INSTRUCTIONS Page 5

The GT condensing gas boiler is a high efficiency boiler utilizing induced power venting. It is designed to be vented directly to the outdoors using the venting methods and materials detailed in this section. The vent system must be both gas tight and watertight. All horizontal vent piping must be sloped back to the boiler a minimum of 1/4 in/ft, 21mm/m of vent.

NOTE: Steps must be taken to ensure that condensate does not collect in the venting system or the boiler will not operate properly.

This boiler may be vented using the following materials, but local codes must be followed:

•GT150 & 200: 3 in, 76 mm, PVC Sch.40 solid core pipe, CPVC Sch.40 pipe, AL29-4C Flex Stainless Vent or AL29-4C Rigid Stainless Vent.

•GT-400: 4 in, 102 mm or 6 in, 152 mm, PVC Sch.40 solid core pipe, CPVC Sch.40 pipe, AL29-4C Flex Stainless Vent or AL29-4C Rigid Stainless Vent.

CAUTION: All vent systems must be fully supported by the building structure. The vent connection and vent piping MUST be perfectly aligned to the boiler connection, Figure 3. It MUST NOT APPLY ANY WEIGHT OR LATERAL FORCE TO THE FLUE BOX or the flue box will be damaged voiding the warranty!

Appropriate adapters must be used to increase the 2 in, 51 mm vent collar to 3 in, 76 mm at the boiler, GT-150 & 200, Figure 3. On the GT-400 the 4 in, 102 mm long 4 inch diameter ABS pipe provided with the boiler must be inserted into the exhaust connection on the top of the boiler and tightened in place with the supplied clamp.

Figure 3- Vent Pipe To Boiler Attachment

The maximum combined equivalent vent and intake pipe lengths are listed in Table 2. The length specifi ed is the equivalent vent length added to the equivalent intake length.

Table 2 - Vent & Air Intake System Sizing

Model	Equivalent Combined Vent & Air Intake
Number	System Length (see note)
GT-150	105 ft, 32 m
GT-200	105 ft, 32 m
GT-400	4" - 30 ft, 9 m	6" - 65 ft, 20 m
PGT-150	50 ft, 15 m
PGT-200	50 ft, 15 m
PGT-400	4" - 30 ft, 9 m	6" - 65 ft, 20 m

Note: Subtract 5 ft, 1.5 m, for each 90° elbow except for the vent and air intake elbows. These don’t need to be considered. The length of the air inlet system must never exceed the length of the vent system. The vent system length may exceed the air inlet system length by no more than 20 equivalent ft, 6.1 equivalent m.

HORIZONTAL

DIRECT VENT SYSTEMS

Read the information in the GENERAL VENTING GUIDELINES section. It is recommended that two elbows be used, so that the 1/4 in/ft, 21mm/m slope of the horizontal vent system does not affect the vertical plumb of the pipe connected to the boiler, Figure 4.

Figure 4 - Vent System Attachment

When horizontal vent runs exceed 5 ft, 1.5m, they must be supported at 3 ft, 0.9 m, intervals with overhead hangers, 4 ft, 1.2 m for 6" pipe. The vent system must be pitched down, toward the boiler, 1/4 in/ft, 21mm/m. of vent. Structural penetrations must be made using approved thimbles.