Slant/Fin CHS-399 - Manual (Page 17)

CHS Series Controller and Display
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Slant Fin Corp.
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2.4.3 Lead Lag Config
The CHS boiler can be used as a stand-alone unit or as part of a cascaded arrangement with as many as 8 CHS
boilers. The Lead Lag Configuration parameters determine the boiler’s (or group of boilers) behavior during a
Lead Lag heat demand [i.e. CH2 (LL) heat input]. Only a demand on CH2 (LL) will initiate Lead-Lag, or
“staging”, of cascaded boilers. For stand-alone boilers, the CH2 (LL) demand simply behaves as a second heat
input (CH1 being the first). Note: a demand for central heat from CH1, takes priority over a demand for central
heat from CH2 (LL).
To enable, or allow the use of Lead-Lag function and the CH2 (LL) input, the “Lead Lag Master Config”
parameter “Master enable”, must be set to “Enable”; see Section 2.4.3.1 Lead Lag Master Config. In Lead Lag
cascade boiler arrangements, only one boiler has “Master enable” set to “Enable”, the others are set to “Disable”
(factory default).
Check List for Lead Lag Installation:
1. All Boilers in Cascade
a. Wire boilers together – Daisy-chain Data Communication wiring between boilers. See Installation and
Operating Instructions (Not applicable for stand-alone boiler applications).
b. Lead Lag Slave Configuration Settings (Optional) – Adjust the “Lead Lag Slave Config” setting “Slave
mode”, as desired. See Section 2.4.3.2.
c. MB2 Modbus address – set a unique “MB2 Modbus address” for each boiler. See Section 2.4.4.1 System
ID & Access.
2. Master Boiler in Cascade
a. Set “Master enable” to “Enable” – Select one boiler in the cascade to be Master; set its “Master enable”
setting to “Enable”. Other boilers are left as “Disable” (factory default). For stand-alone boilers the lone
boiler must have “Master enable” configured as “Enable”. See Section 2.4.3.1 Lead Lag Master Config.
b. Lead Lag Master Configuration Settings – Adjusted the “Lead Lag Master Config” and “Outdoor Reset”
settings to the desired values on the boiler with “Master enable” configured as “Enable”. No need to
adjust these settings on other boilers.
c. Heat Demand Input [CH2 (LL)] – Wire the head demand input to CH2 (LL) of the boiler with “Master
enable” configured as “Enable”.
d. System Sensor (Optional) – Wire the system (pipe) sensor to the boiler with “Master enable” configured
as “Enable”.
3. Any Boiler in Cascade
a. Outdoor Sensor (Optional) – Wire the outdoor sensor to any boiler within the cascade. Note: only one
outdoor sensor is required for a multiple boiler application.
b. System Pump Control (Optional) – With “CH pump use for LL master” set to “On”. The respective boiler
will operate the CH pump (Pump C) anytime there is a Lead Lag heat demand. See Section 2.4.4.2 Pump
Config.