2.6.6.1. Standard Units
This is set for the required heat input before despatch. In
the case of Hi/Lo and Modulating units both high and low
pressures are set. Pressures should be checked in the
following manner.
2.6.6.1.1. Standard Units
1. Set external controls to ensure that the main burner is
off.
Open the side access door. Connect a pressure gauge to
the burner pressure test point on the multifunctional
control.
2. Set external controls so as to turn on the main burner.
Compare the measured burner gas pressure to that
stated on the data plate. If necessary adjust the burner
gas pressure by turning the regulator screw anticlockwise
to decrease the pressure, or clockwise to increase the
pressure.
3. In addition it is advisable to check the gas rate using the
gas meter dial pointer. Ensure that no other appliances
supplied through the meter are in operation.
4. If required, after checking or setting the burner pres-
sures, the CO2 content in the flue gases can be checked
by sampling in the first section of flue fitted to the flue
outlet of the unit. Nominal CO2 values are given for guid-
ance in the Table at the bottom of the previous page.
5. Turn off the main burner and disconnect the pressure
gauge and replace the sealing screw. Turn on the main
burner as above and test for gas soundness around pres-
sure test joint using a leak detection fluid e.g. soap
solution.
Governor adjustment screw under cover cap (Honeywell
VK4105A1001B)
Fitted to the NVx 10 to 50
Governor adjustment screw under cover cap
(Honeywell VR4605AB1027)
Fitted to the NVx 60, 75, 90 and 90S
Governor adjustment screw under cover cap (Honeywell
VK425AB1007)
Fitted to the NVx 120 and 140
2.6.6.1.2. High/Lo Regulator
1. Set external controls to ensure the main burner is off.
Open the side access panel. Connect a pressure gauge to
the burner pressure test point on the multifunctional
control.
2. Set external controls to turn on the main burner and
maintain high fire. Compare the measured burner gas
pressure to that stated on the data plate. In addition it
is advisable to check the gas rate using the gas meter dial
pointer ensuring that no other appliances supplied
through the meter are in operation.
3. Repeat 2 above with external controls set to maintain
low fire.
4. If it is necessary to adjust either the high fire or low fire
pressures proceed as follows after levering off the plastic
cover from the Hi/Lo regulator.
Note: High fire setting must be adjusted first after
which the low fire setting can be set. Any adjust-
ment of the high fire setting alters the minimum
setting.
Maximum Setting
With the controls set to high fire use an adjustable or 8mm
spanner to turn the adjustment screw for high fire pres-
sure, clockwise to increase and counter-clockwise to
decrease, until the required pressure is obtained. Turn the
burner On and OFF several times to check the pressure
setting and then turn off.
Minimum Setting
Disconnect electrical connection of high/low regulator and
turn burners back on and wait until the burner pressure
has stabilized. Use a screwdriver to turn the slotted
adjustment screw for low fire pressure, clockwise to
increase and counter-clockwise to decrease, until the
required pressure is obtained. Reconnect high/low regu-
lator and check high fire pressure. Repeat both steps if
necessary and then replace cover cap.
5. Turn off the main burner, disconnect the pressure
gauge and replace the sealing screw. Turn on the main
burner and test for gas soundness around pressure test
joint using a leak detection fluid. Replace access panel.
2.6.6.1.3. Modulating Regulator
1. Set external controls to ensure that the main burner is
off. Open the side access panel. Connect a pressure
gauge to the burner pressure test point on the multifunc-
tional control.
2. Set external controls so as to turn on the main burner
and maintain high fire. Compare the measured burner gas
pressure to that stated on the data plate. In addition it is
advisable to check the gas rate using the gas meter dial
pointer ensuring that no other appliances supplied
through the meter are in operation.
3. Repeat 2 above with external controls set to maintain
low fire.
4. If it is necessary to adjust either the high fire or low fire
pressures proceed as follows after removing the plastic
cover from the Modulating regulator.
Note: Minimum fire setting must be adjusted first
after which the high fire setting can be set. Any
adjustment of the minimum fire setting alters the
maximum setting.
Minimum Setting
Disconnect electrical connection of modulating regulator
and turn burners back on and wait until the burner pres-
sure has stabilized. Turn 9mm adjustment nut for low fire
pressure clockwise to increase and counter-clockwise to
decrease until the required pressure is obtained. Recon-
nect modulating regulator and check high fire pressure,
readjust if necessary.
Maximum Setting
Disconnect electrical connection of modulating regulator
and turn burners back on and wait until the burner pres-
sure has stabilized. Push shaft gently downwards to the
maximum adjustment screw and hold there. Turn 7mm
adjustment nut for high fire pressure, clockwise to
increase and counter-clockwise to decrease, until the
required pressure is obtained. Release shaft. Repeat both
settings if necessary and then replace cover cap.
5. Turn off the main burner, disconnect the pressure
gauge and replace the sealing screw. Turn on the main
burner and test for gas soundness around pressure test
joint using a leak detection fluid. Replace access panel.
NVX Range Users, Instructions & Service Instructions Issue 5.5 August 2015 Page 25
2.6.6.2. Modulating Interface Board
Fig 8 Modulating Interface Board
The MIB interfaces between a 0-10VDC control signal
and the modulating regulator. The following are applicable
to this application.
1. The setting of the slide switches 1 & 2 should both be
to OFF.
2. Potentiometer P1 (Default setting 100%)
The control current of the V7335A is controlled by P1,
varying between 50% and 100% of the input signal.
E.g.
-When P1 is set at 100% (fully clockwise) maximum
power (165mA @ 22VDC) is provided to the modulation
coil with a 10VDC input control signal.
-When P1 is set at 50% (fully anticlockwise) maximum
power (165mA @ 22VDC) is provided to the modulation
coil with a 5VDC input control signal.
3. Potentiometer P2
Controls the minimum drop-out voltage between 0% and
40% E.g.
- When P2 is set at 0% the drop-out voltage with an input
control signal of 0-10V-DC is 0.3V-DC.
- When P2 is set at 40% the drop-out voltage with an input
control signal of 0-10V-DC is 4.0V-DC.
4. Potentiometer P3 (Default setting 100%)
Controls the maximum hold-in voltage. Its proportional
value is added to the P2 setting E.g.
- When P2 is set at 0% and P3 is set at 5%, the hold-in
voltage of the burner relay is adjustable between 5% and
100% of the input control signal. If the input control signal
is set at 0-10V-DC the hold-in voltage of the relay is
0.5V-DC.
- When P2 is set at 40% and P3 is set at 5%, the hold-in
voltage of the burner relay is adjustable between 45% and
100% of the input control signal. If the input control signal
is set at 0-10V-DC the hold-in voltage of the relay is
4.5V-DC.
The following table shows the relationship between P2
and P3 settings.
2.6.6.2. Flame Current
1. To measure the flame current connect a multimeter
capable of measuring micro amps as shown in the follow-
ing diagram.
2. Minimum current reading is 0.5mA and normal value
should be 1.5mA or higher.
Fig 8 Flame Current Measurement
2.6.6.3. Air Heater Controls
1. Close the gas service tap and ensure that the gas valve
is heard to close within 1 second and that the lockout light
is illuminated. Note that the heater may attempt five re-ig-
nitions before going to lockout. Open the gas service tap
and reset the unit from lockout.
2. Check that the room thermostat and all automatic
controls are operating satisfactorily.
2.6.7. Fan/Limit Thermostat
Thermostat settings:-
Fan Off
Fan On
Limit
NVx 10-140 86°F/30
o
C 122°F/50
o
C 212°F/100°C
Note: NVx 10 to NVx 75 units have one fan/limit
thermostat whereas NVx 90 to NVx 140 units
have two. The second thermostat is at the oppo-
site end of the heater to the burner/controls end.
The fan circuits are wired in parallel (either
thermostat will turn on the fan) and the limit
thermostats are wired in series (either thermostat
will shut down the burner)
2.6.8. Handing over the Air Heater
Hand these instructions to the user or purchaser for reten-
tion and instruct in the efficient and safe operation of the
air heater and associated controls. Adjust the automatic
controls to those values required by the User.
Finally, advise the user or purchaser that, for continued
efficient and safe operation of the air heater, it is important
that servicing is carried out annually.
In the event that the premises are not yet occupied turn
off the gas and electricity supplies and leave instructional
literature adjacent to gas meter.
Micro ammeter
J5
J6
A
I ion
DC
+
-
JT2
Ignition
Ionisation
JT1
