BS 5991:1983 download free.British Standard Specification for Indirect gas fired forced convection air heaters for space heating (60 kW up to 2 MW input): safety and performance requirements (excluding electrical requirements) (2nd family gases).
1. Scope
BS 5991 specifies detailed requirements, Including safety and performance requirements and methods of test, for indirect gas fired forced convection air heaters having heat Inputs from 60 kW up to 2 MW, Intended for Industrial and commercial applications.
The scope of BS 5991 includes indirect gas fired forced convection air heaters for use both with and without ducting, and intended primarily for space heating applications.
BS 5991 also specifies the requirements for indirect gas fired forced convection air heaters designed for permanent outdoor Installation.
It applies to appliances designed to operate on normal low pressure district supplies of 2nd family gas.
BS 5991 does not apply to portable and transportable Indirect gas fired forced convection air heaters.
NOTE. For appflanc.s fitted with gas boosters and/or flue dampers, additional requirements may apply.
2. References
The titles of the publications referred to In this standard are listed on the inside back cover.
3. DefInitions
For the purposes of BS 5991, the following definitions, together with those given in BS 1179 and the relevant installation standards and codes of practice, apply.
3.1 aIr temperature control. A temperature-actuated control intended to maintain the temperature of the discharged air, the return air to the heater, or the air In the heated space between specified limits. This is the normal means of air temperature control.
32 automatIc burner system. A burner system In which, when starting from the completely shut-down condition, the start-gas flame is established and the main gas valve(s) is actuated without manual Intervention. Automatic burners may have pilots that are interrupted or Intermittent.
NOTE. This definition differs from that given in BS 1179 : Part 6.
3.3 automatIc recycling. The automatic repetition of the starting-up sequence without manual intervention.
3.4 burner. A combustion system under the control of a single system of safety shut-off valves. An appliance may have more than one burner and a burner may comprise a number of separate nozzles or bars.
NOTE. This definition differs from that given in BS 1179: Part 8. 35 forced convection air heater. An appliance designed to provide space heating from a central source by distributing
7.1.20 Air outlets The air outlet(s) of a ductless heater shall be fitted with directional louvres that are capable of adjustment between horizontal discharge and discharge at an angle of at least 450 downwards from the horizontal. When the (ouvres are in the position of maximum closure, the minimum requirements for functional purposes shall be satisfied.
Ducted air heaters shall have air outlets equipped with flanges or spigots to facilitate connection of ductwork or flexible connectors.
7.1.21 FacilIty for remote control. Appliances shall be capable of being controlled remotely by means of thermostats and a time control.
7.1.22 Durability of protective finishes
7.1.22.1 Genera. Materials that are used for the construction of parts that are not normally subject to service and maintenance shall be adequately protected against corrosion.
7.1.22.2 Galvanized parts. Galvanized parts shall comply with the requirements of BS 729, BS 2989 or BS 4921 as appropriate.
Galvanized parts, or samples thereof, shall be subjected to nondestructive tests as specified In BS 1706 or other relevant standards and shall comply with the requirements of those standards.
7.1.22.3 Painted and plastics coated parts Painted or plastics coated surfaces shall comply with the following requirements.
(a) Resistance to heating. There shall be no appreciable change of colour on any part of the appliance, and the finish shall not become tacky or show other signs of deterioration at the end of the drying out period as specified In 6.2.
NOTE. This requirement does not apply to Parts that come Into direct contact with the flame.
(b) Resistance to abrasion. Surfaces shall be tested for resistance to scratching. The hardness shall be such that the protective film is not penetrated when subjected to the following test. The scratch shall not have a width greater than 1 mm at any point along its length. Method. Apply the apparatus (see figure 1) to the surface under test and move the ball, after loading with a force of 10 N, at 30 mm/s to 40 mm/s relative to the surface, If the indicator lamp lights, the surface is deemed to have been penetrated. A metallic paint applied directly to a metal surface will cause the lamp to light without penetration and, in this case, the paint surface should be visually examined for penetration. Clean the ball after each test and inspect It frequently to verify that it remains a 1 mm sphere.
7.1.22.4 Plated parts. Electroplated metal parts shall have a standard of adhesion and resistance to corrosion equivalent to the requirements of BS 1224 for service condition no. 2 (appliance designed for indoor installation) or service condition no. 3 (appliance designed for permanent outdoor installation), as appropriate.
7.1.23 NoIse. Noise emission shall not be excessive with regard to the application of the air heater.
Electrical components supplied for service replacement shall comply with the requirements of this clause.
22.6 Warning notices. Permanent warning notices shall be provided In a readily visible position on the appliance requiring the appliance to be switched off and the gas isolated before carrying out any service operation.
The warning notice shall be of red lettering on a white background. The minimum lettering size shall correspond to Helvetica Medium 12 point (3.0 mm) or any other comparable typeface.
The notices shall also draw attention to the need to replace any protective covers that give direct access to live components before the electrical supply Is restored. Removable panels covering live components shall be fitted with warning notices to that effect.
22.7 LIghting instructions. Lighting and shut-down instructions shall be affixed to the appliance in an accessible and readily visible position.
The minimum lettering size shall correspond to Helvetica Medium 10 point (2.5 mm) or any other comparable type. face.
The instructions shall be printed or marked on a matt surface and the contrast between the lettering and background shall be as great as possible.
23. Air handling
23.1 Air flow rate. The manufacturer shall specify the air flow rates and, In the case of ducted air heaters, the corresponding static pressures.
23.2 Air flow adjustment. When an air heater is designed for a range of heat outputs, means shall be provided for adjusting the air flow rate to give the required temperature rise through the appliance.
24. Combustion chamber pressure reliefs
24.1 The manufacturer shall certify that the appliance has been designed to withstand sudden internal pressure rises of up to 275 mbar without causing hazard to personnel in the vicinity of the appliance.
Means shall be provided to permit relief of the pressure In the combustion chamber. The manufacturer shall certify that the means of pressure relief has been designed such that no sudden pressure rise can exceed 275 mbar unless the manufacturer can provide evidence that the appliance will withstand such sudden internal pressure rises without causing hazard to personnel In the vicinity of the appliance.
24.2 The pressure relief shall have a mass per unit area not exceeding 24 kg/rn2 and shall easily be displaced or burst by the force of the expanding gases.
24.3 The pressure relief shall be capable of withstanding the temperature of the endosed combustion products.
24.4 The pressure relief shall be so designed that, in operation, it does not give rise to hazard to personnel.
24.5 Where the pressure relief is fitted on the same side of the appliance as any user-operated controls, means shall be provided to prevent hazard to personnel In the event of operation of the pressure relief. Shields or deflectors shall not interfere with the operation of the relief and the installation instructions shall draw attention to the location and free area required to provide safe operation.