Setpoint Priorities - HydroTherm HeatNet KN -6 User Information

Kn series gas-fired direct vent cast iron boilers

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OPTIONAL FEATURES

For non Ametek blowers, the minimum setting

of the boiler is calibrated so that the minimum

PWM signal to control the Blower motor is

20%. The VFD to 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 36, page 56.

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: ADVANCED

SETUP:BLOWER SETTINGS. 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: SETUP:

SETPOINTS:SETPT SOURCE 4-20ma.

ADVANCED SETUP: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. NOTE: anytime a new firmware version is uploaded

to the control, these values return these defaults.

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: ADVANCED SETUP: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.