HydroTherm KN SERIES, Control Manual

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P/N 42-9452 8/08 Copyright Hydrotherm
KN USER’S CONTROL MANUAL
Method 2: HeatNet modulation – BMS control
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Table 3 Modbus holding (read/write) registers
Address
Data
Type Description Valid Values/
Range
40001 Unsigned Boiler/System Enable/Disable 0 = Disabled/Off
1 = Enabled/On
40002 Unsigned System Setpoint Timer (1) 0 – 65535 seconds
40003 Unsigned System Setpoint (1) 40°F – 220 °F
40004 Unsigned Outdoor Air Reset Enable/Disable 0 = Disabled/Off
1 = Enabled/On
40005 Unsigned Outdoor Air Setpoint 40°F -100 °F
40006 Unsigned Water Temperature at High Outside Air 60°F -150 °F
40007 Unsigned High Outside Air Temperature 50°F -90 °F
40008 Unsigned Water Temperature at Low Outside Air 70°F -220 °F
40009 Signed Low Outside Air Temperature -35°F -40 °F
40010 Unsigned Set Clock – Month (2) 0 – 11
40011 Unsigned Set Clock – Day of Month (2) 1 – 31
40012 Unsigned Set Clock – Year (2) 0 – 99
40013 Unsigned Set Clock – Hours (2) 0 – 23
40014 Unsigned Set Clock – Minutes (2) 0 – 59
40015 Unsigned Set Clock – Seconds (2) 0 – 59
40016 Unsigned Set Clock – Day of Week (2) 1 – Monday 7
– Sunday
40017 Unsigned Set Clock – After the Set Clock Registers listed
above have been written, a 1 must be written to
this location to set the clock. (2)
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Table 4 Boiler status fl ags
Bit Description Bit Description
0 Disabled 16 Pilot Valve
1 Local Override 17 Blower
2 Alarm 18 Ignition Alarm
3 Failed 19 Valve Alarm
4 Member Error 20 High Limit
5 Boiler Running 21 Air Prove Switch
6 Pump Running 22 XS Factory
7 Spare 3 Interlock 23 Software Operator
8 LWCO Interlock 24 Header Sensor not Present
9 VFD Interlock 25 Supply Sensor not Present
10 Gas Prove 26 Return Sensor not Present
11 Spare 4 27 Outside Air Sensor not Present
12 Operator Interlock 28 — —
13 Water Prove (Flow) Interlock 29 — —
14 Air Prove UV Sensor Interlock 30 Master Boiler
15 Main Valve 31 Present (Boiler Detected)
Overview
Th is method uses an RS485 digital communications cable
with the Modbus protocol to control a boiler or HeatNet net-
work.
Th e boiler or boiler network will operate as in the HeatNet lo-
cal control method (Section 1 of this manual). But, instead of
the HEAT DEMAND input, a soft ware form of the HEAT
DEMAND input is used (address 40001 — Boiler/System
Enable/Disable).
Th e System Setpoint Timer needs to be loaded periodically
to allow the HeatNet system to revert to local control from
the master boiler in the event communications is lost.
Th e Modbus protocol allows writing and reading registers
using Modbus commands. An optional BACnet or LonWorks
bridge module can be used to connect the Modbus net-
work to a BACnet or LonWorks network.
Th is method allows enabling and disabling the boiler or
HeatNet system; changing setpoints; and reading boiler
status or temperatures remotely, using digital commands
from a Building Management System.
Th e master boiler assumes the role of MEMBER, RTU, 192Kb,
8 bits, Even Parity, 1 stop bit, when connected to a BMS.
Th e Member Boilers should not be connected to a BMS
system other than to view read-only addresses.
MODBUS registers
See Table 3, page 14; Table 4, page 14; and Table 5, page 15
for register requirements.
Th e system setpoint timer and system setpoint work in tan-
dem to externally control the operating setpoint.
Th e setpoint (countdown) timer should be loaded with a
timeout value (in seconds) prior to writing the system set-
point.
When the timer reaches zero, the control assumes that the
BMS is no longer operating and the local setpoint (saved on
the master control) is reloaded.
Th is is a fail-safe feature used to help safeguard the system in
case of BMS failure.
If the setpoint timer is not writt en, a default timeout value of
60 seconds is assumed.
To write the system clock, registers 40009 – 40015 must
fi rst be loaded with the correct date and time. Th en, a 1
must be writt en to register 16 to write the date and time to
the system clock.
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