3.2　Heating Systems

3.2.1　Selection of heating systems should comply with the following provisions:

a）If hot water is served as the heating medium，single-pipe heating system should be used for multifloor buildings.

b）If steam is served as the heating medium，downfeed double-pipe heating system should be used.

3.2.2　Selection of radiators shall comply with the following provisions:

a）The radiators that are easy to be cleaned shall be used for the production buildings with relatively high requirement for dust dispersion or dust proof.

b）Corrosion resistant radiators shall be used in production buildings emitting corrosive gas or having higher relative humidity.

c）The radiators with a nice appearance should be used for the auxiliary buildings，laboratories，instrument control rooms，etc..

d）The steel-sheet pillar type，plate-type or flat-tubing type radiators shall not be used in the steam heating system.

3.2.3　Hot air heating shall be used when there is any of the following cases:

a）Radiators are not allowed due to the special requirements by a process.

b）The heating system can be combined with the mechanical air supply system.

c）All-fresh-air heating shall be used as required by fire protection，explosion protection and hygienics.

d）Due to large capacity of rooms，other heating modes cannot satisfy the requirements.

e）It is economic and rational to utilize recycle air for heating.

Circulating air heating shall also comply with the requirements of GBZ1 and Article 6.2.3 of this code.

3.2.4　For the plant buildings with hot air heating system，when the production is carried out intermittently and heating is required for standby heating，the combined heating should be adopted（i.e.hot air heating and heating by radiators）.

3.2.5　For the factory buildings in severe cold regions，e.g.the areas where the calculated outdoor temperature for ventilation in winter is lower than or equal to-10℃，at least，two systems or one system with two fans shall be provided for hot air heating with full fresh air.When either system or either fan in the system is in failure，the minimum capacity for fresh air and heating shall be maintained and the interior temperature shall not be lower than 5℃.

3.2.6　The capacity of unit heaters or air heaters shall have a safety coefficient of 1.2—1.3.

3.2.7　Air heating by unit heaters shall comply with the following provisions:

a）The quantity and location of unit heater are designed according to the geometric configuration inside the plant building，process equipment layout and air flow action range.

b）If steam is served as the heating medium，each unit heater shall be provided with individual valve and steam trap.

3.2.8　Hot air curtains should be provided for any one of the following cases:

a）If the exterior doors of production buildings located in cold or severe cold regions are frequently opened，but have no foyers and anterooms constructed.

b）If the room temperature in production buildings is not allowed to drop due to process requirements or provision of hot air curtains is techno-economically compared.

3.2.9　Electric heating may be used after the technical economical comparison when there is any of the following cases:

a）The zones with the special requirement in environmental protection.

b）Independent building far away from the central heat source.

c）The places with heat pump.

3.2.10　When the design is made for the up and down through heating for multi-storey production building，the hot air ascending effect shall be taken into account，and the vertical distribution of heat supply rate shall be descended from bottom to top.

Note:the installation openings with covers shall not be regarded as up and down through arrangement.

3.2.11　The metal radiation plates may be used for the local heating within the areas of plant buildings or for the local work place，meanwhile，when it is verified to be reasonable through economic and technical comparisons，it can be used for overall heating.The requirements on heat medium temperature are as follows:

a）If hot water is served as the heating medium，its average temperature should not be lower than 110℃.

b）If steam is served as the heating medium，its pressure shall not be lower than 0.2MPa.

c）The requirements defined in Article 6.1.1 of this Specification shall be met.

3.2.12　In the same building，hot water or steam piping for heating service shall be routed separately from that for process and living services.Piping for radiator heating systems should be routed separately from that for hot air heating systems or HVAC systems.

3.2.13　For the rooms with special corrosive gases，the corrosion protective measures shall be taken to protect the surfaces of piping and radiators.

3.2.14　Heating pipe shall be insulated for any of the following cases:

a）Heating pipe is routed in pipe trenches，enclosed roof space，non-heating rooms or locations prone to freezing.

b）Insulation is required for heating pipe that passes through the rooms or locations.

c）Useless heat loss from heating pipe is large.