Combustion Air Source from Outdoors
1.Two permanent openings, one within 12” (30.5 cm) of the top and one within 12” (30.5 cm) of bottom of the confined space, Two per- manent openings, shall communicate directly or by means of ducts with the outdoors, crawl spaces or attic spaces.
2.One permanent openings, commencing within 12” (30.5 cm) of the top of the enclosure shall be permitted where the equipment has clearances of at least 1” (2.54 cm) from the sides and back and 6” (15.2 cm) from the front of the appliance. The opening shall com- municate directly with the outdoors and shall have a minimum free area of:
a.1 square inch per 3000 BTU per hour (322 cm2 per 0.879 kW) of the total input rating of all equipment located in the enclosure.
b.Not less than the sum of all vent connectors in the confined space.
3.The duct shall be least the same cross-sectional area as the free area of the air supply inlet opening to which it connects.
4.The blocking effects of louvers, grilles and screens must be given consideration in calculating free area. If the free area of a specific louver or grille is not known. Refer to Table 12.
Ventilated Combustion Air
The ventilated attic space or a crawl space from which the combustion air is taken must comply with the requirements specified in “AIR SOURCE FROM OUTDOORS” in this instruction or in Section 5.3, Air for Combustion and Ventilation of the National Fuel Gas Code, ANSI Z223.1 (latest edition). This type installation requires two properly sized pipes. One brings combustion air from a properly ventilated attic space or crawl space and a second pipe that extends from the furnace vent connection (top right of unit) to the exterior of the building. Refer to Table 8 for intake pipe sizing, allowable length and elbow usage. Follow all notes, procedures and required materials in the "COMBUSTION AIR/VENT PIPE SIZING" section in these instructions when installing the combustion air pipe from the unit and into a ventilated attic space or crawl space. DO NOT terminate vent pipe in an Attic or Crawl Space.
Ventilated Combustion Air Termination
Refer to Figure 38 for required attic termination for the combustion air intake pipe. For attic termination, use two 90 elbows with the open end in a downward position. Be sure to maintain 12” (30.5 cm) clearance above any insulation, flooring or other material.
A crawl space combustion air installation consists of a straight pipe from the PVC coupling on the burner box that extends into the crawl space and terminates with a 1/4” (6.4 mm) mesh screen and no elbows.
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- monxide 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.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
2.Close all building doors and windows and all doors.
3.Turn on clothes dryers and TURN ON any exhaust fans, such as range hoods and bathroom exhausts, so they shall operate at maximum speed. Open the fireplace dampers. Do not operate a summer exhaust fan.
4.Follow the lighting instructions. Place the appliance being inspected in operation. Adjust thermostat so the appliance shall operate contin- uously.
5.Test each appliance (such as a water heater) equipped with a draft hood for spillage (down-draft or no draft) at the draft hood relief opening after 5 minutes of main burner operation. Appliances that do not have draft hoods need to be checked at the vent pipe as close to the appliance as possible. Use a combustion analyzer to check the CO2 and CO levels of each appliance. Use a draft gauge to check for a downdraft or inadequate draft condition.
6.After it has been determined that each appliance properly vents when tested as outlined above, return doors, windows, exhaust fans, fire- place dampers and any other gas burning appliance to their normal condition.
7.If improper venting is observed during any of the above tests, a problem exists with either the venting system or the appliance does not have enough combustion air (Supply Air from outside) to complete combustion. This condition must be corrected before the appliance can function safely.
NOTE: An unsafe condition exists when the CO reading exceeds 40 ppm and the draft reading is not in excess of - 0.1” w.c. (-25 kPa) with all of the appliance(s) operating at the same time.
8.Any corrections to the venting system and / or to the supply (outside) air system must be in accordance with the National Fuel Gas Code Z223.1 or CAN/CGA B149.1 Natural Gas and Propane Installation Code (latest editions). If the vent system must be resized, follow the appropriate tables in Appendix G of the above codes or for this appliance.
12” minimum between bottom of air intake and any material below.
12” Min.
FIGURE 39: Attic and Crawl Space Combustion Air Termination
Specially Engineered Installations
The above requirements shall be permitted to be waived where special engineering, approved by the authority having jurisdiction, provides an adequate supply of air for combustion and ventilation.
Be sure to instruct the owner not to block this intake pipe.
VENT BLOWER ROTATION
For ease of venting, the vent blower may be rotated 90° in either direc- tion. For upflow installations the vent may exit through the top or either side of the cabinet. For downflow installations, the vent blower must be rotated so that the vent exits through either side of the cabinet. See Fig- ures 24-27 for details.
