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a very sunny day during which, however, the
outside air temperature is quite cool, EAT = 21°C.
However, with TAE>20°C, there will be no re-
quest of heating supply and the fresh air helps
to discharge the solar energy load picked up
into the walls.
EAT=21°C >20°C and ti = 25°C > EAT: the
external air can be used to cool the premises
for free.
FREE-HEATING CONDITION
EAT < t
cooling
and simultaneously ti < EAT
Example:
In a Mediterranean winter condition,
occasionally ti = 21°C, consistent
with operating setpoint theating = 20°C±2°C.
This condition may occur during the sunny
afternoon of a day characterised by a cold
morning. The outside air temperature heats up
and reaches the EAT value=23°C.
However, with TAE<26°C, there won't be a
cooling request and the fresh air helps to heat
the walls.
EAT=23°C <26°C and ti = 21°C < EAT: the
external air can be used to heat the premises
for free.
In all the remaining conditions it is convenient
to maintain the heat recovery active to save on
heating in the winter and on air conditioning in
the summer.
Operating logic with
post-treatment elements
Downstream of the heat recovery unit, on the
ambient air intake duct, it is possible to install
a postheating resistance or a post-heating
and/or cooling coil.
The machine controller can handle 230 volt
outputs for ON/OFF control of the resistance
or of the water shut-off valve feeding the
post-treatment coil. You can manage the
post-heating only or heating and/or cooling
function both in the 2 and 4 pipe configuration.
The control of the post-treatment elements
is managed according to the exhaust air
temperature.
MAIN OPERATING LOGIC
Antifreeze logic, electrical
pre-heating resistance
In the event of installation in cold climates
(indicatively with air temperatures below -5°
C) to prevent the formation of ice inside the
heat exchanger, you must install the electrical
resistance accessory (BEP). This is managed
automatically by the control board, mounted
on the machine, by means of a PWM signal in
order to optimise the electrical consumption
according to the real needs.
The controller actives the resistance below a
critical temperature of the external envi-
ronment for the formation of ice in the
heat exchanger and modulates the power
of the resistance to maintain the exhaust
air temperature above the freezing point.
With pre-heating heater at external tem-
perature below -20°C, the ENY-P units
get blocked because of frost emergency.
Antifreeze logic, without electrical
pre-heating resistance
Without electrical pre-heating heater at
external temperature below -5°C, the ENY-P
units are submitted every 10 min/h to defro-
sting cycles during which the fans work at a
minimum speed. Without the electric heater
the ENY-P units get blocked because of frost
emergency at -10°C.
Free-cooling / free-heating
management logic with by-pass
gate
The following indoor air setpoint temperatu-
res are defined managed by the air conditio-
ning system supplied by external suppliers:
t
heating
, normally 20°C
t
cooling
, normally
26°C
The following are also defined:
ti = internal air temperature (return air)
EAT = External air temperature
FREE-COOLING CONDITION
EAT > t
heating
and simultaneously t
i
> EAT
Example:
In the summer, occasionally ti = 25°C, con-
sistent with operating setpoint tcooling =
26°C±2°C.
This condition may occur during an evening of
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