A-102-1 Electric Duct Heater Brochure - Brasch

UL/NEC Requirements* (cont.)REQUIREMENTHEAT PUMPS AND AIR CONDITIONERSNEC Article 424-61:"Installation of Duct Heaters with Heat Pumps and Air Conditioners. Heat pumps and air conditionershaving duct heaters closer than 4 feet (1.22m) to the heat pump or air conditionershall have both the duct heater and the heat pump or air conditioner identified as suitablefor such installation and so marked."UL (Excerpt form Electrical Appliance and Utilization Equipment List Preface)Tests have indicated that no adverse thermal effects are obtained when duct heaters markedto indicated that they are suitable for use with heat pumps, or central cooling air conditionersand/or fan-coil units are installed with certain of these units (See Heat Pumps, CentralCooling Air Conditioners and Fan-Coil Units). provided the duct heater is used only in horizontalor upflow systems, and the duct heater is located downstream at least 4 ft. from thenearest surfaces of the heat pump, central cooling air conditioner, or fan-coil unit.FAN CIRCUIT INTERLOCKUL 1996, Paragraph 21.3"A heater that does not include a fan or blower motor but is intended to be used in conjunctionwith such motor, such as duct heater, shall be provided with terminals or leads for fieldconnection of an interlock circuit for such motor unless an airflow interlock is provided as anintegral part of the heater. The heater shall include the interlocking contacts or the power supply.It shall be so arranged that no heating element circuit can be energized unless the interlockingcontacts are closed or the interlocking power supply energized."NEC Article 424-63:"Fan Circuit Interlock. Means shall be provided to ensure that the fan circuit is energizedwhen any heater circuit is energized. However, time- or temperature-controlled delay inenergizing the fan motor shall be permitted."LOCATION OF DISCONNECTING MEANSNEC Article 424-19:"Disconnecting Means. Means shall be provided to disconnect the heater, motor controller(s),and supplementary overcurrent protective device(s) of all fixed electric space heatingequipment from all ungrounded conductors. Where heating equipment is supplied bymore than one source, the disconnecting means shall be grouped and identified.(a) Heating Equipment with Supplementary Overcurrent Protection. The disconnectingmeans for fixed electric space heating equipment with supplementary overcurrentprotection shall be within sight from the supplementary overcurrent protective device(s), onthe supply side of these devices, if fuses, and in addition shall comply with…(1) Heater Containing No Motor Rated Over 1/8 Horsepower. The above disconnectingmeans or unit switches complying with section 424-19(c) shall be permitted to serveas the required disconnecting means for both the motor controller(s) and heater under either(a) or (b) below.a. The disconnecting means provided is also within sight from the motor controller(s)and the heater; orb. The disconnecting means provided shall be capable of being locked in the openposition."HOW BRASCH MEETS REQUIREMENTAny UL Listed duct heater must be spaced at least 4 feet from a heat pump or air conditionerunless the combination (i.e., air conditioner with built-in heater) has been Listed byUL.Heaters are UL Listed for use with heat pumps or air conditioners (no closer than 4 feetbetween the two).Any one of the following methods of interlocking the heater with the fan will be providedin Brasch heaters:1. Built-in airflow switch (wired in series with elements or holding coils of contractors).2. Built-in fan relay to provide the interlocking contacts mentioned in Paragraph 18.3.3. Built-in power supply with control transformer primary wired to load size of fan starter.4. Built-in pneumatic-electric (PE) switch with fan interlocking contacts.NOTE: We recommend a built-in pressure differential airflow switch wherever practical(minimum total pressure differential in duct must be at least .05" WC). If a built-in airflowswitch cannot be used, we recommend a built-in fan relay or transformer interlock.To meet this requirement, Brasch heaters are available with built-in safety disconnectswitches (fused or unfused). These disconnects offer the additional advantage of havingan interlocking door handle which prevents terminal box door from being opened unlessswitch is in the off position. Additionally, switches installed in Brasch remote control panelscan be locked in the open position.NOTE: A combination door interlock switch and contactor can not serve as a disconnectingmeans since door interlock switches are nonindicating.NEC Article 424-64:"Location of Disconnecting Means. Duct heater controller equipment shall be accessiblewith the disconnecting means installed at or within sight from the controller."NEC Article 4234-21:"Switch and Circuit Breaker to Be Indicating. Switches and circuit breakers used as disconnectingmeans shall be of the indicating type."26 BRASCH MANUFACTURING