Modbus Instructions
5Unit Operation
DHW with remote control:
This installation may or may not have the hot water generator in close proximity to the boiler. Its sensors and thermostat values are only available through the Modbus communication bus.
To ensure that the SYNC boiler can properly respond to a call for hot water generation the following holding registers must be set in addition to other commands:
Holding Registers | Definition | Bit Value (HEX) | Action |
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40001 | Configuration | 00 4A | Set Configuration to read 40002, 4 & 5 |
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40002 | Coils | 00 08 | Enables Tank Tstat (00 00 disables unit) |
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40004 | Tank Setpoint | 0# ## | Sets Setpoint |
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40005 | Tank Temperature | 0# ## | Passes tank temp from remote sensor |
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NOTE: To ensure proper operation
For proper hexadecimal conversion of rate percentage, please refer to the Rate and Temperature Conversion section on page 17 of this manual.
Cascade
In order to operate the SYNC boiler in Cascade with Modbus communications, configure the leader boiler per the demand configurations in this manual. Connect the remaining boilers in the cascade through the normal cascade communications wiring. Cascade control can then be accomplished automatically through the leader boiler.
Please note that with Modbus communication connected to only the leader boiler, total Cascade information can be seen through the communications link. If you wish to see all the individual temperatures of each unit in the Cascade, each unit will have to have a Modbus communication board. However, each unit can be monitored without the need to control each one individually.
Monitoring Only
Any SYNC boiler can be equipped with the Modbus communication board and then be set up to operate with its own internal controls. If necessary, Modbus can be configured as a monitoring device by selecting demand configurations 1 - 3, and polling the Modbus board for the read only variables.
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