WW-F-2743A
flame failure or provide safe re-ignition in accordance with ANSI Z21.47. The timing for actuation of the gas safety shutoff device and automatic valves shall be as specified in ANSI Z21.47.
3.14.4.2 Group 3 units. The flame safeguard and programming control for group 3 units shall be of the electronic type employing flame detectors to monitor the presence of a flame. Flame sensing elements shall be limited to infrared, (lead-sulfide type) or ultraviolet photocells, except that flame rods may be used with gas flames. The programming control, in conjunction with the
flame safeguard circuit, shall provide the timed operational sequence in atmospheric gas burners in accordance with ANSI Z21.47, ANSI Z83.8 and UL 795 as applicable in power gas burners and oil burners in accordance with UL 296.
3.14.5 Oil delay valve. When specified (see 6.2), oil-fired units not equipped with programming controls shall be equipped with a delayed-opening oil shutoff valve. The valve shall automatically delay delivery of oil to the burner until such time as the combustion air fan and, when applicable, the induced draft fan are operating at rated speed.
3.15 Electrical requirements. Except as otherwise specified herein, all interconnecting wiring for motors, operating controls (thermostatic switches), limit controls, and programmers shall be furnished and installed. When components are shipped unmounted, interconnecting wiring shall be installed up to the location of the unmounted component and the terminals of the wires
identified to facilitate connection when the unmounted component is installed. All external wiring shall conform to and be installed in accordance with NFPA 70.
3.15.1 Motors. Motors shall be furnished and installed for the fans and blowers, the oil burner when applicable, and the induced draft fan, if furnished. Motors shall be rated and constructed in accordance with the applicable provisions of NEMA MG 1. Motors shall have the electrical characteristics as specified (see 6.2). The blower and fan motor horsepower (hp) (W) shall be sufficient to ensure compliance with the limits of motor winding temperature rise specified in
UL 727, UL 731, ANSI Z21.47 or ANSI Z83.8. When operating at the rated bonnet capacity the units shall not exceed the maximum air flow rate against the applicable esp specified in the referenced standards. Unless otherwise specified (see 6.2), motors shall have drip proof
enclosures in accordance with NEMA MG 1. Direct drive motors for group 1 units shall have not less than three rated speeds to cover the range of temperature rises specified in 3.8.4.
3.15.2 Magnetic starters. Integral hp motors shall be furnished with magnetic, across-the-line starters rated and constructed in accordance with NEMA ICS 1 and ICS 2. The starter shall provide thermal overload and under-voltage protection and shall include manual and automatic control stations. The overload protection shall include thermal cutouts in all three phases. Unless otherwise specified (see 6.2), enclosures for magnetic starters shall be NEMA type 1 in accordance with NEMA ICS 6.
3.15.3 Control panel. For group 3 units, the controls, including operating switches, indicating lights, alarms, motor starters, fuses, and circuit elements of the control systems shall be mounted and factory wired on a single control panel or cabinet insofar as practicable in order to centralize
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