1. (a) The heater shall be:

   1. (1) Hot water combustion type;
   2. (2) Electric heating element; or
   3. (3) Heat pump.
2. (b) If only one (1) heater is used, it shall be fresh-air or combination fresh-air and recirculation type.
3. (c) If more than one (1) heater is used, additional heaters may be recirculating air type.
4. (d) The heating system shall be capable of maintaining bus interior temperatures, as specified in test procedure SAE International J2233.

5. (e) Auxiliary fuel-fired heating systems are permitted, provided they comply with the following:

   1. (1) The auxiliary heating system shall utilize the same type fuel as specified for the vehicle engine;

   2. (2) The heater or heaters may be:

      1. (A) Direct;
      2. (B) Hot air-type; or
      3. (C) Connected to the engine coolant system;

   3. (3) An auxiliary heating system, when connected to the engine coolant system, may be used to:

      1. (A) Preheat the engine coolant; or
      2. (B) Preheat and add supplementary heat to the heating system;
   4. (4) Auxiliary heating systems must be installed pursuant to the manufacturer’s recommendations and shall not direct exhaust in such a manner that will endanger bus passengers;
   5. (5) All combustion heaters shall be in compliance with current Federal Motor Carrier Safety Regulations;

   6. (6)

      1. (A) The auxiliary heating system shall require low voltage.
      2. (B) Auxiliary heating systems shall comply with FMVSS No. 301, Fuel System Integrity, and all other applicable FMVSS, as well as with SAE International test procedures;

   7. (7)

      1. (A) All forced-air heaters installed by body manufacturers shall bear a name plate that indicates the heater rating in accordance with SBMTC-001, Standard Code for Testing and Rating Automotive Bus Hot Water Heating and Ventilating Equipment.
      2. (B) The plate shall be affixed by the heater manufacturer and shall constitute certification that the heater performance is as shown on the plate;

   8. (8)

      1. (A) Heater hoses shall be adequately supported to guard against excessive wear due to vibration.
      2. (B) The hoses shall not:

6. (i) Dangle or rub against the chassis or any sharp edges; and

   1. (ii) Interfere with or restrict the operation of any engine function.

      1. (C) Heater hoses shall conform to SAE International J20c, Coolant System Hoses.
      2. (D) Heater lines, cores, and elements on the interior of the bus shall be shielded to prevent scalding or burning of the driver or passengers;
   2. (9) Each hot water system installed by a body manufacturer shall include one (1) shut-off valve in the pressure line and one (1) shut-off valve in the return line, with both valves at the engine in an accessible location, except that on Type A and Type B buses, the valves may be installed in another accessible location;

   3. (10)

      1. (A) All heaters of hot water type in the passenger compartment shall be equipped with a device installed in the hot water pressure line which regulates the water flow to all passenger heaters.
      2. (B) The device shall be conveniently operated by the driver while seated.
      3. (C) The driver and passenger heaters may operate independently of each other for maximum comfort;
   4. (11) On hot water-type systems, accessible bleeder valves for removing air from the heater shall be installed in an appropriate place in the return lines of body company-installed heater; and

   5. (12)

      1. (A) Access panels shall be provided to make heater motors, cores, elements, and fans readily accessible for service.
      2. (B) An exterior access panel to the driver’s heater may be provided.

Codification Notes: “FMVSS” means Federal Motor Vehicle Safety Standards. "SMBTC" means School Bus Manufacturers Technical Committee.