§ 27-893 Clearances.
AC § 27-893
(a)Minimum clearance. Minimum clearances at vent connectors to combustible materials shall not be less than those listed in table 15-10.
(b)Reduced clearances. These clearances may be reduced when the combustible construction is protected as provided in table 15-11. TABLE 15-10Vent Connector Clearance for Gas-Fired Equipment EquipmentMinimum Distances from Combustible Materials (in.)Type B Gas Vent MaterialOther Than Type B MaterialsBoilerAs required by Std. 6 Warm air furnaceAs required by Std. 6 Water heaterAs required by Std. 6 Room heaterAs required by Std. 6 Floor furnaceAs required by Std. 6 Conversion burner (with draft hood)6 9 Equipment with draft hoods6 9 Equipment without draft hoodsNot Permitted 18 TABLE 15-11Reduced Clearances for Vent Connectorswith Specified Forms of Protection a Specified Form of Protection b Reduced Clearances Where the Required Clearance with No Protection is:18 in. 9 in. 6 in. (a) 1/4 in. asbestos millboard spaced out 1 in.c 12 6 3 (b) 28 gauge sheet metal on 1/4 in. asbestos millboard 1242(c) 28 gauge sheet metal spaced out 1 in.c 9 42(d) 28 gauge sheet metal on 1/8 in. asbestos millboard spaced out 1 in.c 942(e) 1 1/2 in. asbestos cement covering on heating appliance 189 6 (f) 1/4 in. asbestos millboard on 1 in. mineral fiber bats reinforced with wire mesh or equivalent 642(g) 22 gauge sheet metal on 1 in. mineral fiber bats reinforced with wire or equivalent 3 22(h) 1/4 in. asbestos cement board or 1/4 in. asbestos millboard 18 94(i) 1/4 in. cellular asbestos 18 9 3 Notes for Table 15-11: a Except for the protection described in (e) above, all clearances should be measured from the outer surface of the appliance to the combustible material disregarding any intervening protection applied to the combustible material. b Applied to the combustible material unless otherwise specified and covering all surfaces within the distance specified as the required clearance with no protection. Thicknesses are minimum. c Spacers shall be on noncombustible material.
