Use Environments - Fujitsu UTZ-BD035B Technical Manual

4-4-3. USE ENVIRONMENTS

 DEW CONDENSATION PREVENTION
Our heat exchange unit has been confirmed not to cause dew
condensation water to drop under the following conditions.
If the unit is to be used in severer conditions than the following, dew
condensation water may drop.
JIS B 8628 Total Heat Exchanger Attachment 5 (Regulation) Dew
Condensation Test Methods
Indoor Conditions
Category
Dry-bulb Wet-bulb
temperature temperature
Cooling in Summer 22±1 17±2
Warming in Winter 20±1 14±2
Warming in Winter 20±1 14±2
In winter, the standard type should be used in the "Heat Exchange"
mode. If it is used in "Normal Ventilation" in winter while the heater
is on, the unit may develop dew condensation, resulting in the
condensation water on the ceiling, which will cause stains, short-
circuits in electric wiring, and fault current.
(Caution) Models designed for commercial use cannot be utilized for
residential use due to the different conditions these models
should satisfy. (Otherwise, dew condensation and serious
electric accidents may ensue. If such applications are
inevitable, please contact us in advance.)
(1) Prevention of Dew Condensation on Product Surfaces
 When the humidity and the temperature are high around the product under low
outdoor temperatures, dew may be condensed on the surface of the product.
 The following graph indicates marginal conditions for dew condensation on
product surfaces in terms of temperature and humidity around the product, and
outdoor temperature.
Preheat
 The product should be used in conditions not exceeding the relative humidity
around the product, as specified in the above graph.
Example 1 When the outdoor temperature is -10˚C and the ambient temperature
around the product is 20˚C, no dew will be condensed until the
ambient relative humidity around the product reaches 40%, as
indicated in the graph. However, when the ambient temperature
around the Product is 25˚C, the ambient humidity around the product
should be less than about 35%, as indicated in the graph.
Example 2 When the outdoor temperature is -10˚C and the ambient temperature
around the product is 20˚C, and if the ambient relative humidity
around the product may fluctuate between 40% and 50%, dew may
be condensed on the product surface. In this case, the outdoor
temperature needs to be preheated from -10˚C to -3˚C.
(2) Prevention of dew condensation on heat exchange
element
 As shown in the figure below, suppose a high temp absorbing air condition
A and a low temp absorbing air condition B are plotted on the air line figure,
then a high temp air A is heat-exchanged by the unit and goes out of the
saturation curve as shown by Point C. In this case, the unit will be dewed
or frosted. To avoid this, you are required to heat a low temp air B up to B'
so as to get C' below the saturation curve, before using the unit.
Dry-bulb temperature ( )
Outdoor Conditions
Operation Testing
Dry-bulb Wet-bulb
Conditions Time (h)
temperature temperature
35±1 29±2 On
-5±2 — On
-15±2 — Off
Relative Humidity
around Product
Outdoor Temperature ( )
Saturation
Curve
 PREVENTION OF INSECT INTRUSION
The heat exchange unit takes in fresh outdoor air. Thus, if there are
insects in the outdoor environment, they may be sucked in through
the external pipe hood.
Although the unit is equipped with a filter that can trap bigger dust
and dirt, small insects may not be captured by the filter and taken
into the room through the filter perimeters and the frame apertures.
In addition, when the unit is in the "Normal Ventilation" mode and the
nit:˚C
operation is stopped, the air course on the exhaust side and indoor
area is connected even though no wind is blowing. In this situation,
intrusion of insects may take place in very rare occasions.
As the emergence of insects may depend on various natural conditions,
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we recommend users to apply medium-performance filters (to be
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purchased separately) in environments where there are many insects
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or where insects are likely to swarm, as the exhaust/intake openings
are close to street lamps, etc. In addition, it is also recommended that
the unit should be turned off in the "Heat Exchange Ventilation" mode.
However, it is almost impossible to completely prevent intrusion of
extremely small insects. Users are thus advised to consider full-scale
insect prevention measures, such as installation of filter boxes (to be
separately purchased by the users) on the designing stage.
When the unit is in operation in the "Normal Ventilation" model, it
should be shifted to the "Heat Exchange Ventilation" mode first, and
then put to "Stop" after 30 seconds.
The medium-performance filters should be built in the unit, available for
the ceiling-mounted, the ceiling-mounted with a humidifier, and the ceiling-
suspension cassette types of the products, to be separately purchased.
Although these filters may be equipped after installation of the unit,
please be noted that the supply air volume may be reduced (about 10%).
(The filters are not available for specified and older models.)
 PREVENTION OF EXTERNAL
WIND INTRUSION
If the unit is turned off in the Normal Ventilation mode, the external
wind is likely to enter indoors. It is thus recommended to turn off the
unit in the Heat Exchange Ventilation mode.
In cold regions, or areas where frost damages may take place or
strong winds may blow, external winds may enter indoors when
the unit is turned off. In order to prevent these inconveniences, it
is recommended to install an "electric damper (to be separately
purchased by users)" on the side of the external duct.
For ducts with ø100 and ø150, please use the electronic dampers
(electric shutters) we provide; for ducts the diameter of which are
ø200 and ø250, please use those offered by PENTEK.
Contact: PENTEK. (TEL: 0568-81-0510)
 PREVENTION OF SALT EROSION
Our heat exchange ventilation units are not equipped with specific
countermeasures against salt erosion. The following measure may
be proposed, but should require thorough design planning about the
service life of the salt erosion prevention filters, etc.
() In case salt damages need to be prevented in seaside buildings, it is
recommended to install salt erosion prevention filters on the external intake
side (the OA side), which should be separately purchased by users. In this
case, it is necessary to confirm that the designed airflow can be secured,
as the intake airflow will be reduced by the filter. If it is found that sufficient
airflow cannot be obtained, further considerations will be required.
(As for the salt erosion prevention filters, please contact us separately.)
 INSTALLING THE UNIT UPSIDE DOWN
The ceiling-mounted model can be installed upside down. (The ceiling-
mounted model with humidifying and humidity-resistant types, as
well as the cassette types cannot be installed upside down. For more
details, please check the respective catalogs.)
 INSTALLATION LOCATIONS
Do not install the unit body and indoor intake openings in locations
where harmful or corrosive gasses may be present (e.g. acidic, alkali,
organic, solvent, paint gasses, etc. from machinery or chemical plants
and research laboratories, etc.).
(Installation in such a location could cause gas-poisoning, corrosive
deterioration within the unit, and a fire.)
 ODOR PREVENTION
 Water-soluble gasses cannot be used, as they may be freely ferred
with moist, inside the heat exchange element.
 Acid gasses cannot be used, as they may be accumulated within the
heat exchange element, and causing damages.
Bathroom (toilet) ventilation facilities should be separately installed.

Although the unit is designed to prevent mixture of fresh external air

and indoor air with packing and sealing materials, it is structurally
difficult to completely prevent such a mixture.
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