8
9
4.4
Outside air version
In outside air version the unit is used to distribute air to which more than 25% outside air is added. However, in the unit no
special regulators are installed to keep the air temperature constant. If you want to use the unit as an outside air unit, we suggest
that you:
•
If you want to use the unit as an outside air unit, we suggest that you add thermal insulation to the front fan access panel
to prevent condensation. Multicalor has a range of suitable acoustic and thermal insulating materials in stock.
4.5
Downflow versions
The Multicalor O–series units are supplied in an UPFLOW version. Downflow versions are available on request.
4.6
Installing the ducting system
4.6.1 Installing the return air ducts
Noise problems are often created if air heaters are used with very short and/or undersized return air ducts. These problems can
be avoided by:
•
insulating the return air ducts by means of an acoustic liner;
•
installing a sound damper in the return air ducts;
•
making sure the that there are at least 2 generously sized 90° turns in the ducting system;
•
Increasing both diameter and length of the return air ducts.
You can connect the return air duct to the left, right or the bottom of the unit. We strongly suggest using only the bottom return
air opening (please remove the cut-out when commissioning). If possible, install the unit on an insulated plenum, on which
side return ducts can be connected. If you do not have sufficient free space to use an insulated return air plenum, it is possible
to install an optional side filter frame. However, in doing so, a large part of the acoustic insulation is lost. Always use a return
air duct and return air from OUTSIDE of the combustion compartment. If you do wish to apply an open return, make sure that
the unit is used as a space heater (the unit is ONLY heating the room where it is installed).
ATTENTION:
•
Do not forget to remove the cut-out under the unit when using a bottom return (or a side return with bottom plenum).
4.6.2 Supply air ductwork
Fit a matching supply air on the unit. The height of the plenum should be at least as high as the width of the unit. The supply
air plenum should, like the supply ducting system, be thermally insulated. The supply air duct should be of a sufficient size to
permit air displacement with normal speeds and pressure losses.
4.7
Commissioning the burner
Please refer to the installation instructions from the burner manufacturer. First set the desired air speed, then select a nozzle
that has an air temperature of about 65°C (Delta t of 40 to 45°C) after 15 minutes of continuous use. Make sure that the fan
compartment is CLOSED when doing this test.
4.8
Fan and limit controller
The Honeywell fan and limit control is used to switch the fan on and off. The FLC also shuts down the burner if the air
temperature is too high (e.g. when the fan fails to start). This is a safety feature.
4.8.1
Switching the fan on and off
ON:
When the air temperature in the heat exchanger compartment
is higher than the set value (e.g. 50°C), the fan is switched ON.
OFF:
When the air temperature in the heat exchanger compartment
is lower than the set value (e.g. 30°C) the fan is switched OFF.
This means that the burner is NOT controlled by the fan and limit controller,
but only by the thermostat.
4.8.2
Interrupting the combustion process when the air
temperature in the heat exchanger compartment is too high
STB: When the air temperature in the heat exchanger compartment is higher
than the set maximum temperature (e.g. 90°C) the electrical supply to the
burner is cut. THIS IS A SAFETY FEATURE! The safety needs manual re-
arming by pushing the red button.
The STB safety only trips when one of the following conditions is true:
1 Air flow too low:
increase air flow
