OPTIONAL FEATURES
HeatNet Control V3 3.x
Page 63
For
VFD driven
blowers, the minimum setting
of the boiler is calibrated so that the minimum
PWM signal to control the Blower motor is
20%. The VFD driven blower motor operates
with a control signal from 20% - 80% Pulse
Width Modulation. This PWM signal to the
VFD can be measured using a multimeter. It is
a 0–10volt square wave signal at 110 Hertz. A
20% modulation signal will read 2.0 VDC, and
an 80% modulation signal will read 8.0 VDC
on an RMS multimeter. See Figure 57, page 79.
For
Ametek
Blowers, the minimum signal to
control the blower will be less than 20%, but
the display % will be equal to the turndown %
of the boiler. Also, the signal sent to the
Ametek blower is twice that of non Ametek
blowers, so the VDC reading will need to be
divided by (2) to get the modulation % sent to
the Blower. The Ametek blower also has a
menu located at:
SETTINGS: BOILER:
BLOWER.
This menu allows the Acceleration,
Deceleration, and Soft Start Values to be set for
proper operation of the Blower.
For direct fire applications, the 0–10-volt
control signal is proportional to the output.
Such that: 1 volt will track linearly by 10%. So,
1v=10%, 2v=20%, 3v=30%, 4v=40%... The
control signal will still be limited by the
turndown and the 4-20mA INPUT menu. This
means that the 1v signal will have no effect on
a 5:1, 20% boiler. A ~2v signal will start the
5:1 boiler.
Setpoint Control
functionality can be implemented remotely
using the 4-20mA input. This function translates a 4 to 20mA
control signal to a setpoint mapped from 50F to 220F. The
feature is enabled in the SETPOINTS menu as:
SETTINGS:
SETPOINTS
:
SETPT SOURCE 4-20mA
.
SETTINGS: 4-20mA INPUT: CHANNEL MODE
. Also,
when selecting; SETUP: SETPOINTS: SETPT SOURCE and
selecting 4-20mA, the 4-20mA INPUT menu will be
automatically entered.
You may now select the current at which the boiler will start.
It is adjustable from 3.7mA to 5mA. Hysteresis of .1mA is
always in effect. So, if the starting mA = 4.10mA the boiler
will start when the control current applied achieves this value
of 4.10mA. The boiler must drop .1mA below this to turn
OFF, in this example 4.00mA. This hysteresis value is not
adjustable.
When using the 4-20mA setpoint control, a band may now be
set at which the 4-20mA signal will operate over. The lower
setpoint is defined as 4mA SETPOINT and the upper setpoint
is defined as 20mA SETPOINT. The 4mA SETPOINT is
linked to the BOILER START x.xxmA where this starting
current is the lower setpoint. So, if we set the 4mA
SETPOINT to 130F and the 20mA SETPOINT at 180F we
will have established the band. Once a starting control current
of BOILER START 4.1mA is applied, and the 4-20
REMOTE ENABLE INPUT is closed, the boiler will start and
the setpoint will be set to 130F. If a control current of 10mA
is applied the boiler will track on a linear slope towards the
20mA SETPOINT settling at a SETPOINT of ~149F. As the
current increases to 20mA, the SETPOINT will indicate 180F.
The Default setting is 4mA SETPOINT: 50F, and 20mA
SETPOINT 220F for backwards compatibility with the older
version.
Anytime a new firmware version is uploaded to
the control, these values return to these
defaults.
If using the direct modulation mode by applying a 4-20mA
current, only the BOILER START x.xx setting applies.
The 4-20 mA input can be set to HIGH PRIORITY. This is
done in menu:
SETTINGS: 4-20mA INPUT: CHANNEL
MODE
. This allows a MEMBER boiler to be taken offline
and directly modulated by an external control. If the
MASTER is using it for heating and the 4-20mA is set to
HIGH PRIORITY, an external control can now output a 4-
20mA signal which will take over the boiler’s fire rate. This is
typically used for DHW control.
Setpoint Priorities
Changing the setpoint can be done in many ways. If a higher
level setpoint control is lost, the next level setpoint control is
used until the System Setpoint is loaded. The setpoints are
prioritized in the following order:
1.
0-10V, 4-20mA setpoint Control
2.
BMS, MODBUS Setpoint
3.
Outdoor Reset Setpoint
4.
Menu’s System Setpoint
Any Setbacks that are active are then applied.