The minimum vent diameter for the Category I venting system is as shown below:
MINIMUM VENT DIAMETER
MODEL | GUI* | GCI* |
45 | 3 Inch | 4 Inch |
70 | 4 Inch | 4 Inch |
90 | 4 Inch | 4 Inch |
115 | 5 Inch | 5 Inch |
140 | 5 Inch | 5 Inch |
Under some conditions, larger vents than those shown above may be required or allowed.
When an existing furnace is removed from a venting system serving other appliances, the venting system may be too large to properly vent the remaining attached appliances.
The following steps shall be followed with each appliance remaining connected to the common venting system placed in operation, while the other appliances remaining con- nected to the common venting system are not in operation.
(a)Seal any unused openings in the common venting system.
(b)Visually inspect the venting system for proper size and horizontal pitch as required in the National Fuel Gas Code, ANSI Z223.1, or the CAN/CGA B149 Installation Codes and these instructions. Determine there is no blockage or restriction, leakage, corrosion or other deficiencies which could cause an unsafe condition.
(c)Where practical, close all building doors, windows, and all doors between the space where the appliances remain connected to the common venting system are located and other spaces of the building. Turn on all gas appliances not connected to the common venting sys- tem and operate on high speed all exhaust fans (range hoods and bathroom), except summer exhaust fans. Close fireplace dampers.
(d)Following the lighting instructions, place the furnace being inspected in operation. Adjust thermostat so appliance will operate continuously.
(e)Test for spillage at the draft hood relief opening after 5 minutes of main burner operation. Use the flame of a match or candle, or smoke from a cigarette, cigar, or pipe.
(f)After it has been determined that each appliance re- maining connected to the common venting system properly vents when tested as outlined above, return doors, windows, exhaust fans, fireplace dampers and any other
(g)If improper venting is observed during any of the above tests, the common venting system must be corrected in accordance with the latest edition of the National Fuel Gas Code, ANSI Z223.1.
When resizing any portion of the common venting system, use the appropriate table in Appendix G in the latest edition of the National Fuel Gas Code, ANSI Z223.1.
Upflow or Horizontal units are shipped with the induced draft blower discharging from the top of the furnace. (“Top” is as viewed for an upflow installation.) The induced draft blower can be rotated 90 degrees counterclockwise for Category I venting, with the airflow horizontal left to right (Figure 5). For horizontal installations, a
1/2” beyond the furnace cabinet. Vent the furnace in accordance with the National Fuel Gas Code, NFPA54/ ANSI Z223.1 - latest edition. In Canada, vent the furnace in accordance with the National Standard of Canada, CAN/ CGA B149 - latest editions and amendments.
Figure 5
Upflow Rotated Induced Draft Blower
Counterflow units are shipped with the induced draft blower discharging from the top of the furnace. (“Top” as viewed for an counterflow installation.) The induced draft blower can be rotated 90 degrees counterclockwise for Category I venting, with the airflow horizontal right to left (Figure 6). For horizontal installations, a
Vent
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Figure 6
Counterflow Rotated Induced Draft Blower
To rotate the induced draft blower counterclockwise pro- ceed as follows:
1. Disconnect electrical power from furnace.
WARNING
To prevent death or personal injury due to electrical shock, disconnect electrical power.
2.Remove the round cutout from the side of the furnace.
Note: The assembly, starting from the outside, is induced draft blower, outer gasket, rotation plate, inner gasket, partition panel (See Figure 7).
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