system
air
55
Connection
• The indirect gas heating coil section must always be located in the positive pressure part of the air handling unit –
downstream from the supply fan, to prevent the mixing of supply air and flue gases in the event of a heat exchanger
defect.
• The heat exchanger is installed into its casing on guide rails that facilitate its sliding out from the section in the event
of defect or damage. For this purpose, provide a clearance space on the unit service side of a width equal to or
greater than the external width of the air handling unit.
•
Upstream and downstream of the gas heater section, the installation of empty sections is specifiedplanned, with a
modular length of min. 600 mm, with access into the interior to enable checking the condition of the gas heater.
• Discharge from the pan must be led through the section bottom into a siphon and acid neutralisation unit into the
sewage system.
•
The condensate drain connection, located in the inspection opening at the bottom back part of the tube register
collector, must be led through the back wall of the section casing.
• The safety pressure switch, the safety thermostat, the temperature limiter and the operating thermostat must be
installed outside the section casing. In the case of an outdoor unit, protect these elements, as well as the burner, by
installing them in a waterproof and thermally insulated protection chamber.
•
The gas burner must be fixed to the combustion chamber rim from the outer side of the section casing. For this
purpose, apply flanges adapted to the size and type of gas burner.
•
In the case of indoor air handling units, make the necessary provisions for adequate inflow of combustion air, natural
ventilation of the room and extraction of flue gases.
• In the case of outdoor units that are exposed to weather elements (wind, rain, snow, etc.), the gas burner must be
installed in a waterproof and thermally insulated protection chamber, which, on its bottom side, must be fitted with
an opening to freely supply combustion air. The protection chamber must be large enough to also accommodate the
safety pressure switch, the safety thermostat, the temperature limiter and the operating thermostat. The chamber
must have enough capacity (to the left and to the right of the gas burner) to allow the installation of the gas supply
train.
•
In designing the method for the extraction of flue gases, consult a competent chimney-sweeping service. Where
the supply of a section with a stack is ordered, the stack must be sized and constructed in accordance with the
applicable regulations, laws and standards. To facilitate obtaining consent from a chimney-sweep service, design
documents should be drawn up for the stack, including the solutions for the extraction and neutralisation of the flue
gas condensate.
•
Connect the gas heater to the stack in accordance with the requirements applicable to stacks for gas-fired
installations. The joint between the stack connection and the stack tube must be waterproof to prevent uncontrolled
discharge of condensate in the event of flue gas condensation.
•
The gas heater stack connection does not need to maintain a natural draft.
• Electric cables must not be run inside the section casing. In the case of an outdoor unit, a gas burner protection
chamber may be utilised to accommodate cables, provided that the cables do not obstruct the servicing of the
equipment; alternatively, cables may run on the free outer surfaces of the casing (back wall, bottom, etc.), in
agreement with the designer or the customer.
• The gas supply line must be arranged so as not to obstruct the servicing of the unit’s functional sections and to allow
any functional element to be slid out of the casing of the air handling unit as necessary.
• In the gas heating coil section design, the free circulation of air must be ensured between the unit interior and the
environment, for cooling purposes. Fit the opening in the ceiling or on the side with a spring-driven damper and
install a duct leading from the damper to the open air. The damper and the duct must be thermally insulated; the
insulation material must be non-combustible. In the event of power supply failure or any other fault that may result
in the abrupt failure of unit interior cooling or its overheating, the damper must open and allow natural cooling of the
gas heating coil.
• The sealing between the casing frame and the panels of the left and right adjacent sections and the sealing of the
joints between the left and right sections and the gas heating coil must be provided by means of a ceramic fibre
sealing tape 19 x 5 mm, resistant to temperatures in a range from –20 to +1200°C. In the case of putty sealing, apply
a high resistance grade glue-sealing paste, stable at temperatures in a range from –40 to +250 °C, and, on a short-
term basis, to +300°C.
• All the electric cables, cable glands and protection tubes installed inside the casings of the left and right sections
adjacent to the gas heating coil section must have insulation resistant to high temperatures.
•
For the purposes of filtering air immediately upstream of the gas heating coil, apply a metal filter with no EPDM
sealing tape and with no bottom pan (unless greases are to be filtered out).
