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Smarty 4X V
www.salda.lt
1.32.1 Cold-Heat Recovery
Cold-heat recovery function is designed to control a heat exchanger. Its power is controlled by:
› Using plate heat exchanger - bypass damper. When it is closed, the heat exchanger is operating at full capacity. Its power is reduced by opening
the damper.
› Rotary heat exchanger power is controlled by changing its rotating speed or interval. When the rotor rotates at full speed, the heat exchanger is
used at full capacity. The power is reduced by slowing down the rotating speed or increasing the interval.
The heat exchanger can both heat and cool – it depends on air temperature. If it is colder outside than in the premises, the heat exchanger pre-heats
the outdoor air by using the room heat. If it is colder in the premises than outside, the heat exchanger cools down the outdoor air temperature by room
air. Its power is reduced to the minimum when the target supply air temperature is the same as outdoor one. The higher the difference between the
preferred and supply air temperatures, the higher heat exchanger power is used. When it is operating at maximum capacity, it is allowed to activate
other heating/cooling components.
For this function suitable heat exchanger type is indicated in the window SERVICE › HEAT EXCHANGER and PID controller coefficients – in the win
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dow ADJUSTER › PID CONTROLLERS ADJUSTING.
PID controller output limits are set for rotor or bypass damper, at which their operation starts.
› If rotor is controlled by 0..10 V signal, at low voltages it does not rotate, the motor heats up, thus the minimum control signal output is limited. If
On/Off rotary heat exchanger is used, PID percentage for activating the rotor is indicated in the window SERVICE › HEAT EXCHANGER.
› If the bypass damper opens only a few percent, noise can occur, thus the minimum its opening limit is limited, which also applies when coming
to the full opening. If the plate heat exchanger with a 3-way bypass damper is used, the opening time of the bypass damper is indicated in the window
SERVICE › HEAT EXCHANGER.
› If a plate heat exchanger with segment valves is controlled by an external controller is used, then the type of the bypass damper “REMOTE
CONTROLLER” is shown in the window “SERVICE › HEAT EXCHANGER”.
› If a plate heat exchanger with segment valves connected to a controller is used, then the type of the bypass damper is shown in the window
“Service › HEAT EXCHANGER” as either “2 SEGMENTS” or “3 SEGMENTS”. In the case of heat recovery control, segments are closed in sequence,
i.e. if heat recovery is not required, then all the segments are closed and the bypass damper is opened.
1.32.2 Heat Exchanger Frost Protection
This protection is designed to protect the heat exchanger from the formation of ice inside because ice formations can damage the structure of the heat
exchanger. The protection is configured in the service environment, in the window “SERVICE › HEAT EXCHANGER”.
The protection can be activated/deactivated according to the following:
• Specified outdoor air temperature
• Specified exhaust air temperature
• Specified exhaust air temperature difference compared to the calculated freezing temperature (this temperature is calculated according to
the outdoor air temperature, room air temperature and humidity)
• According to the pressure switch
Possible protection measures (to be carried out one by one as specified):
› Recirculation of outdoor and exhaust air
› Opening of the bypass damper or control of the segment valve, or slowing-down of the rotor
› Heating of outdoor air using a preheater
› Suspension of the supply air flow
› Shutting-down of the unit according to the low supply air temperature (by default, the limit is 5°C)
› Shutting-down of the unit if there are no protection measures activated (shut-down after 5 minutes)
› Shutting-down of the unit due to failure to reach the safe zone corresponding time interval (two cycles, by default, 60 minutes)
› Shutting-down of the unit according to the critical outdoor air temperature (to be shut down after 60 seconds)
The protection activation conditions and protection measures can be activate selectively. The protections are active only when the outdoor air tempera
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ture drops below the set limit, i.e. the protections will respond to the pressure switch only when the outdoor air temperature drops below the permissible
limit. For the anti-frost protection, the time interval after which the system switches from one protection measure to another is also specified (by default,
it is 30 minutes). If at least one of the activation conditions is satisfied, the protection becomes active and a message is shown. The initial protection
is recirculation, which is followed by the bypass damper or segment valve, then preheater and then, if the power is not sufficient, the supply air flow
is suspended. If the protection does not help within the specified time interval (by default, 30 minutes), the system switches to the following one. The
protections are switched from one to another in accordance with the sequence.
The recirculation of outdoor and exhaust air is an effective and cost-saving protection but it supplies exhaust air back to the supply air flow.
When using the bypass damper or segment valves, the supply air heater must be connected. By slightly opening the damper, the cold air flow through
the heat exchanger is reduced but supply air is cooled and must be heated using the supply air heater. This protection slowly opens the bypass
damper as long as the activation conditions are satisfied. When suitable conditions are reached, the damper is stopped for 5 minutes and then it is
slowly closed. If the outdoor air temperature drops below the permissible level (the heating power is not sufficient), then the damper is forcedly closed
according to the supply air temperature.
The bypass valve can also be with segment valves. In this case, the supply air temperature drops less than when using only the bypass damper. At
the time of deicing, segments are closed one by one in sequence, i.e. only one segment can be closed at a time and the bypass damper is opened. If
at least one segment is closed, then the bypass damper is opened; if all the segments are opened, then the bypass damper is closed.
For the protection with the preheater, the position of the outdoor air sensor in respect of the preheater is specified (upstream/downstream). If the sen
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sor is upstream the preheater, then the unit is not shut down if the required outdoor air temperature is not reached. At the beginning, the outdoor air
preheater is activated to the full capacity for a certain period of time, and that it begins maintaining the specified deactivation temperature (outdoor or
exhaust air temperature).
If the preheater capacity is not sufficient and the supply air flow reduction is permitted, then the supply air fan is periodically shut down and the heat
exchanger is deiced by heating it with exhaust air.
Recirculation, the bypass damper and supply air flow suspension operate in periodic cycles. The minimum deicing time is 5 minutes, and the minimum
time interval between deicing cycles changes depending on the outdoor air temperature (see the diagram), i.e. the lower the outdoor air temperature
