0108MLOOGBEN
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SECTION 6 ELECTRICAL CONNECTION
6.1 Electrical installation may only be carried out by
suitably qualified persons observing the rules in force.
6.2 Check that the electrical specification is in
accordance with the specified data on the air heater.
A unique appliance wiring diagram is supplied as a
separate document attached to this one, plus an
additional copy attached to the air heater.
6.3 These appliances must be earthed.
6.4 A separate key lockable electrical isolator for each
heater must be provided adjacent to the appliance
and in site of any person working on it. The isolator
must have a contact separation of at least 3.0 mm
on all poles.
6.5 Ancillary controls are required to provide timed heat
cycles, room comfort temperature level, frost
protection, override air circulation etc. These are not
included with the appliance and should be ordered
separately.
6.6 Ensure when planning the external appliance control
circuitry, that power will be supplied at all times to
the air heater, even when it is control switched in the
'heat-off' mode. This is necessary to ensure that the
fan can operate independent of the heating control.
Therefore, Never incorporate automatic controls that
electrically isolate the appliance.
NOTE:
ML SERIES AIR HEATERS ARE SUPPLIED WITH EXTERNAL CONTROL CIRCUITS
BRIDGED. THE AIR HEATERS WILL OPERATE CONTINUOUSLY UNLESS THESE ARE
REMOVED AND TIME AND TEMPERATURE CONTROLS SUBSTITUTED FOR THEM
SECTION 7 COMMISSIONING
7.1 Commissioning general:
Reznor ML series air heaters do not require
commissioning. Final testing during production
ensures that if a suitable gas and electrical service
and external controls have been connected to the
appliance strictly in accordance with the instructions
contained in this document then it is ready to be
taken into service. However, preliminary checks as
listed below are necessary to ensure safety and
correct operation.
Understand the controls lay-out figure 10 and how
the heater works text 7.2
- A test for earth continuity
- A test for resistance to earth
- Zero voltage neutral to earth
- Check phase 230/240V to correct input terminal
- Correct external controls connections. Check that
when external controls are operated that a
constant electrical supply to the air heater is
maintained when the controls are in the OFF mode.
This is necessary so that the air circulation fan
may operate at all times at the dictates of the
thermally activated fan switch.
7.2 Understanding how the ML series air heaters work.
7.2.1 Reznor ML series air heaters employ the direct
burner ignition principle i.e. a separate ignition
burner is not used to light the main burner. Flame
failure protection is by the ionisation principle i.e.
the ability of a suitable flame to pass an electrical
current between an electrode and the earthed
burner assembly.
7.2.2 At the dictates of the external controls an electrical
circuit is made to an electronic burner control The
burner control checks to ensure a safe start is
possible by ensuring that the combustion air
induced draught fan ("venter") is stationary as
monitored by a differential pressure switch. If no
air flow is proven, then the "venter" is switched on
and the proving switch moves from the no airflow
to the airflow position provided adequate airflow
exists. This safeguards a blocked flue, faulty flue
fan etc.
Once in the proved air flow condition the second
period of the ignition process commences this is
called the pre purge time and lasts for ± 18
seconds to ensure no unburnt gas is present in the
combustion chamber. If during this period, a flame
or simulated flame is detected, lockout will occur.
At the end of the pre purge period the ignition
sequence commences, a hot surface igniter heats
and glows, after a heating-up period of ± 23
seconds ignition temperature will have been
reached and the main gas valves will open and the
burner will light during a maximum time period not
exceeding 5.0 seconds. Provided the flame
remains adequate as sensed with a nominal flame
ionisation current of 1.5 - 3.2 µA the burner will
remain alight until the external controls are
satisfied.
7.2.3 Simultaneously to the ignition circuit and gas valve
circuit being energised as described above,
electrical power is supplied to an anticipator within
the air circulation thermal fan control. The
anticipator advances the warm up of the thermal
fan control thus ensuring that the air flow when
the fan is switched on is temperate at ± 45°C.
The air circulation fan will continue to run on after
the burner has switched off to cool the heat
exchanger.
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