page no. 4 of 44
NVx Range Users, Installation & Servicing Instructions issue 6.4 Aug 2017.
D) Description of Operation
Important: The heater must NOT be
controlled by switching ON and OFF the
main electrical supply to it.
1) Standard Units
The ignition sequence commences each time the external
controls e.g. Time clock, room thermostat etc. call for
heat. The internal exhaust fan will run and, when sufficient
combustion airflow is proved by the air pressure switch,
the ignition spark will be generated, the main gas valve
opens and the burners light. The green ‘ON’ indicator
will be illuminated. The heater fan will automatically start
approximately 2 minutes after the burners light. When the
external controls are satisfied the burners will be turned
off and approximately 2 - 3 minutes later the heater fan will
be automatically stopped. If the burners fail to light the
control box will make another four attempts at ignition.
2) High / Lo & Modulating Units
When the burners are alight, the heat output will be
controlled either to high fire or low fire or, in the case of
modulating units, to any point between high and low fire;
depending on the requirements of the space being heated
and the external controls fitted.
3) Summer / Winter Modes
Certain types of external controls will provide for two
modes of operation i.e.
Summer: The heater fan alone will run at the dictate of the
external controls to provide air movement.
Winter: The heater will operate normally.
4) Overheat Thermostat
This operates if high temperatures within the heater are
detected, the burners are turned off and a Red indicator
switch light on the front panel is illuminated. NVx15 - 75
units have the thermostat located inside the controls
section. NVx90SF - 140SF units have an additional
thermostat on the side of the unit at the opposite end to
the controls (either thermostat can go to limit and shut off
the burners). The fault condition must be identified and
rectified and the thermostat manually reset via the red
high limit reset switch. When the unit has cooled, push the
Red indicator switch inside the front panel to reset the limit
thermostat interlock relay, the red indicator light will go
out and the unit is operational again.
Note: The limit thermostat(s) can only be reset
once the unit has cooled down.
Unless the cause of the fault condition is
readily obvious, for example a power cut whilst
If the heater has not been left operational
proceed as follows.
A) Checks before lighting the Air Heater
The following preliminary checks should be made before
lighting the heater(s)
a) Ensure that the ELECTRICAL supply to the heater is
switched OFF.
b) Check that all warm air delivery outlets are open.
c) Check that the thermostat is set at MAX.
d) Check that the clock control is set to an ON period.
e) Check that any other controls are calling for heat.
B) Lighting the Air Heater
1. Switch on the electrical supply at the isolator
2. If the Limit indicator light comes on press the limit
interlock reset switch inside the heater.
3. The startup sequence will commence. After a short
delay the burners will light and the green ‘ON’ indicator on
the front of the heater will be illuminated.
4. If the burners fail to light the control box will
automatically restart the ignition sequence. If after 5
attempts at ignition the burners have still failed to light
the control box will go to lockout and the Amber lockout
light on the front of the heater (or on the low level remote
reset, MC200 or Powrtrol RR if fitted) will be illuminated. To
restart the ignition sequence depress the reset button on
the low level reset for about 1-2 seconds.
WARNING: If it is not possible to light the
heater after several attempts, contact the
installer or local service company.
C) To Shut Down the Air Heater
1) For Short Periods:
Turn the room thermostat to the OFF, or set to it’s lowest
setting.
2) For Long Periods:
Complete step 1 above. Wait for 5 minutes and then turn
OFF the electrical supply at the isolator.
User Instructions
