lp-548 Rev. 000 Rel. 004 Date 1.11.19
10
For example: Send a setpoint of 110
o
F. The formula to use for the interpolation is:
Voltage to be applied = (Desired setpoint – BMS temp at low analog input) (High voltage – low voltage) + Low voltage
(BMS temp at high analog input – BMS temp at low analog input)
From the default values:
Desired setpoint = 110
BMS temp at low analog input = 68
BMS temp at high analog input = 180
High voltage = 10
Low voltage = 1.6
[(110 - 68)(10-1.6)/(180 - 68)] + 1.6 = 4.75 volts
(4.75/10) x 100 = 47.5
48 = 30 Hexadecimal
A value of [00] [30] in hexadecimal would be written to holding register 40003/AV2 to issue a command for a 110
o
F setpoint.
NOTE:
If your particular BMS supports DECIMAL inputs, then the desired voltage level can be sent directly. In the above example, you would
send 48 (4.8v) to 40003/AV2.
The holding registers need to be set as follows:
Holding Registers
Definition
Decimal Value
HEX Value
Action
40001 / AV0
Configuration
4
04
Set configuration to read 40002
40003 / AV2
Setpoint
0-100
00-64
Enables CH Demand (00 00 disables demand)
Table 14 - Setting Holding Registers for Setpoint
Register 40003/AV2 needs to receive the
setpoint command as follows: Acceptable
range is 0 to 100. Value needs to be greater
than 15 for the appliance to fire.
When the command is 16, the appliance will
run with the setpoint controlled by the 925
menu parameter I12 (MIN BOILER TEMP).
When the command is 100 the appliance
will run with the setpoint controlled by the
600 menu parameter CENTRAL HEAT on
appliances or the PHOENIX setting in the
water heater user menu.
If the command value is anywhere between
16 and 100, the appliance will run at a setpoint
proportional to the command sent between
minimum and maximum setpoints.
NOTE:
To ensure proper operation, resend
the configuration bits to holding register
40001 / AV0 prior to issuing a command.
Figure 5 - Setpoint Curve
In this configuration, the appliance is controlled by setting the modulation from 0 – 100%. Rate command will be 0 – 100% of the modulation
range. All sensors and limiting devices (excluding the 0 – 10 Vdc signal, which will be sent to the MODBUS/BACnet adapter) should be
hardwired to the correct locations on the appliance.
For this command to function, configure the appliance according to the corresponding row in the following table.
2. Send Firing Rate Command from BMS to Appliance
Appliance
Parameter I16
Parameter I17
Phoenix, Munchkin, MODCON rev2 and earlier
2
2
Elite, Elite Premier, EnduroTi
0-10 Volt
Fan Speed
Table 15 - Send Firing Rate from BMS to Appliance
The holding registers need to be set as follows:
Holding Registers
Definition
Decimal Value
HEX Value
Action
40001 / AV0
Configuration
4
04
Set configuration to read 40003
40003 / AV2
Rate Command
0-100
00-64
Sets Modulation %
Table 16 - Setting Holding Registers for Firing Rate
Parameter
Default Values
Default
Deg C
Deg F
Voltages
Appliance temperature setpoint at low analog input
21
68
1.6
Appliance temperature setpoint at high analog input
82
180
10
Table 13 - 0-10 Volt Temperature Values for Setpoint
