The QNET HVAC incorporates Microchip 2-Wire High-Accuracy Temperature Sensors model MCP9801.
The
complete specification sheet the temperature sensor can be found at
www.microchip.com/downloads/en/DeviceDoc/21909d.pdf
2.2.3 Power Amplifier
The QNET HVAC circuit board includes a PWM voltage-controlled power amplifier that is used to generate heat by
applying the input voltage to an array of resistors in parallel. It is capable of providing
2
A
peak current and
0
.
5
A
continuous current. The output voltage range to the load is between
0
V
and
24
V
.
2.2.4 Status LED
The QNET HVAC is fitted with a variety of safety measures that use the
Status LED
for feedback, see Figure 2.3. In
particular, two digital enable lines (one high, one low) are used to ensure proper system configuration. The system
states are displayed as in Table 2.2. Here, a
∗
indicates any state.
External Power (
24
V
)
Enable-
Fan Stall
Temperature
Status LED
Amplifier
0
∗
∗
∗
∗
Red
Disabled
∗
FALSE
∗
∗
∗
Red
Disabled
∗
∗
TRUE
∗
∗
Red
Disabled
∗
∗
∗
TRUE
∗
Red
Disabled
∗
∗
∗
∗
∗ ≥
90
degC
Red
Disabled
†
24
V
TRUE
FALSE
FALSE
∗
<
90
degC
Green
Enabled
†
: Re-enables amplifier when Temperature is
<
80
degC
Table 2.2: Status LED states of the QNET HVAC
2.3 Environmental
The QNET HVAC is designed to function under the following environmental conditions:
• Standard rating
• Indoor use only
• Temperature
5
◦
C
to
40
◦
C
.
• Altitude up to 2000m
• Maximum relative humidity of 80% up to 31
◦
C decreasing linearly to 50% relative humidity at 40
◦
C
• Pollution Degree 2
• Mains supply voltage fluctuations up to
±
10% of the nominal voltage
• Maximum transient overvoltage 2500V
• Marked degree of protection to IEC 60529: Ordinary Equipment (IPX0)
2.4 System Parameters
Table 2.3 lists and characterizes the main parameters associated with the QNET HVAC.
QNET HVAC - User Manual
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