Smith Cast Iron Boilers GB300 Combustion AIR & Ventilation, All Air From Inside The Building, 500

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GB300 BOILER INSTALLATION AND OPERATION INSTRUCTIONS

COMBUSTION AIR & VENTILATION

WARNING: This boiler must be supplied with combustion air in accordance with Section 5.3, Air for Combustion & Ventilation, of the latest revision of the National Fuel Gas Code, ANSI Z223.1/NFPA 54 and all applicable local building codes. Canadian installations must comply with CAN/CGA B149.1 or .2 Installation Code. Failure to provide adequate combustion air for this boiler can result in excessive levels of carbon monoxide which can result in severe personal injury or death!

WARNING: Never operate a GB300 in an environment subjected to a negative pressure unless it is Direct Vented. Failure to comply with this warning can result in excessive levels of carbon monoxide causing severe personal injury or death!

To operate properly and safely this boiler requires a continuous supply of air for combustion. Oxygen is used by the boiler burners to burn the gas. NEVER store objects on or around the boiler. In addition, air is also used to assist in the safe disposal of the products of combustion. This air is known as dilution air and mixes with the products of combustion to assist in their exit through the flue pipe and chimney. An adequate supply of air must be available to replace the air used by these processes.

Older buildings often have enough natural infiltration to provide an adequate amount of combustion air provided that the demand for combustion air is not too great.

Buildings that are relatively new or “tight” will most likely require the installation of a fresh air duct or other means of providing make-up air. Any building utilizing other gas burning appliances, a fireplace, wood stove or any type of exhaust fan must be checked for adequate combustion air when all of these devices are in operation at one time. Sizing of an outside air duct must be done to meet the requirements of all such devices.

All Air From Inside The Building

If the boiler is to be located in a confined space minimum clearances of 2 ft, 0.61 m must be maintained between the boiler and any adjacent construction. When installed in a confined space two permanent openings communicating with an additional room(s) are required. The combined volume of these spaces must have sufficient volume to meet the criteria for an unconfined space. The total air requirements of all gas utilization equipment, fireplaces, wood stoves or any type of exhaust fan must be considered when making this determination.

Each opening must have a minimum free area of

1in2/1000 Btu/hr, 2200 mm2/kW based on the total input rating of ALL gas utilization equipment in the confined area. Each opening must be no less than

100in2, 64,516 mm2 in size. The upper opening must be within 12 in, 300 mm of, but not less than 3 in, 80 mm from, the top of the enclosure. The bottom opening must be within 12 in, 300 mm of, but not less than 3 in, 80 mm from, the bottom of the enclosure.

All Air From Outside The Building

When installed in a confined space two permanent openings communicating directly with, or by ducts to, the outdoors or spaces that freely communicate with the outdoors must be present. The upper opening must be within 12 in, 300 mm of, but not less than 3 in, 80 mm from, the top of the enclosure. The bottom opening must be within 12 in, 300 mm of, but not less than 3 in, 80 mm from, the bottom of the enclosure.

Where directly communicating with the outdoors or communicating with the outdoors through vertical ducts, each opening shall have a minimum free area of 1 in2/4000 Btu/hr, 550 mm2/kW of the total input rating of all of the equipment in the enclosure.

Where communicating with the outdoors through horizontal ducts, each opening shall have a minimum free area of 1 in2/2000 Btu/hr, 1100 mm2/kW of the total input rating of all of the equipment in the enclosure.

When ducts are used, they must have the same cross- sectional area as the free area of the opening to which they connect.

When calculating the free area necessary to meet the make-up air requirements of the enclosure, consideration must be given to the blockage effects of louvers, grills and screens. Screens must have a minimum mesh size of 1/4 in, 6.4 mm. If the free area through a louver or grill is not known ducts should be sized per Table 1 below.

Table 1 Make-up Air Duct Sizing

	Required Cross Sectional Duct Area
Input	1/4 in, 6.4 mm		Metal		Wooden
(MBH)	Wire Screen		Louvers		Louvers
	in2	cm2	in2	cm2	in2	cm2
400	100	645	133	858	400	2581
600	150	968	200	1290	600	3871
800	200	1290	267	1723	800	5161
1000	250	1613	333	2148	1000	6452
1200	300	1935	400	2581	1200	7742
1400	350	2258	467	3013	1400	9032
1600	400	2581	533	3439	1600	10,323
1800	450	2903	600	3871	1800	11,613
2000	500	3226	667	4303	2000	12,904