Laars NEOTHERM NTH Installation And Operation Instructions Manual

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Page 42LAARS Heating SystemsBoiler Pump Interrupt Function -The Boiler pump interrupt feature is used in some applicationswhen the boiler is being used for both hydronic and domestichot water heating. The interrupt jumper is used to turn offthe boiler pump during a domestic hot water demand. Forthis to work properly the system must be plumbed andpumped to allow the DHW pump to supply the flow and headrequirements for both the boiler and indirect water heater. It isnot necessary to use the interrupt jumper in all applications.To turn off the Boiler pump in this situation, the “boiler pumpinterrupt” jumper should be installed between R1 and R2 onTB5.If your system includes several boilers, is controlled using theLead/Lag system, and the indirect DHW tank is connectedto the boiler acting as the Lead/Lag master, install the boilerinterrupt jumper on the Lead/Lag master only.WARNINGFailure to plumb, pump and install the appliancecorrectly when using this feature may lead to reducedor no water flow through the heat exchanger, causingpremature failure of the heat exchanger, personalinjury or death. Please consult the factory with anyquestions regarding the use of this feature.Setup for DHW Control Functions -1. Set up the correct priority for the DHW function in relationto Central Heat or Lead/ Lag demands. If a call for heatand a DHW demand arrive at the same time, which willhave the higher priority?If your system has just one boiler –How to get there: From the “Home” screen, press “I”to go to “Info/ Install.” Choose “Advanced Setup,” thengo to “DHW Configuration.” Select “DHW Priority vsCentral Heat.”If your system has more than one boiler, and is controlledusing the Lead/ Lag function –How to get there: On the unit used as the Lead/LagMaster, from the “Home” screen, press “I” to go to “Info/Install.” Choose “Advanced Setup,” then go to “DHWConfiguration.” Select DHW Priority vs Lead/Lag.”2. Set the setpoint for the DHW function.If your system has just one boiler –How to get there: From the “Home” screen, press “I” togo to “Info/ Install.” Choose “Advanced Setup,” then goto “DHW Configuration.” Select “DHW Setpoint.”If your system has more than one boiler, and is controlledusing the Lead/ Lag function –How to get there: On the unit used as the Lead/LagMaster, from the “Home” screen, press “I” to go to “Info/Install.” Choose “Advanced Setup,” then go to “DHWConfiguration.” Select “DHW Setpoint.”3. Set the DHW priority time. If the DHW function has thepriority, the priority will continue during the priority time.If your system has just one boiler –How to get there: From the “Home” screen, press “I” togo to “Info/ Install.” Choose “Advanced Setup,” then goto “DHW Configuration.” Select “DHW Priority Time.”If your system has more than one boiler, and is controlledusing the Lead/ Lag function –How to get there: On the unit used as the Lead/LagMaster, from the “Home” screen, press “I” to go to “Info/Install.” Choose “Advanced Setup,” then go to “DHWConfiguration.” Select “DHW Priority Time.”8C.8 Cascading Lead/Lag OperationAbout Lead/Lag Operation -If an installation includes two or more boilers, they may beset up for “Lead/Lag” operation. One boiler will be set up asthe “Master”, and the others will operate as “Slaves.” Figure38 shows an installation with four boilers. (A Lead/Lagsystem can include up to eight boilers.) The boiler controllersare connected in a “daisy chain” using a Modbus connection.See Fig. 40.A single System sensor is used to monitor the demandfor heat. The input from this sensor is used by the Mastercontroller to control the modulation rates of all of theoperating boilers.Lead/Lag Modulation Cycle -Note - We will explain the modulation cycle here, in caseyou need to understand how the Lead/Lag system actuallyoperates. If you are installing the unit(s) and want to skip thissection, just remember that, as the heating demand increases,the Lead/Lag system puts more boilers on-line. As theheating demand is reduced, the Lead/Lag system shuts offsome of the boilers.The signal from the System sensor is sent to the unitoperating as the Lead/Lag Master. A Run sequence isinitiated when the system temperature falls to the Lead/LagCentral Heat setpoint. (Actually this is the LL CH setpointless the On Hysteresis value. The default setting for OnHysteresis is 5°F, but this is adjustable.)NOTE: If your NeoTherms are Lead / Lag configured,you will find it very useful to customize your HomeDisplay to show LL Operating Temp and LL SetpointTemp.Please refer to Section 7.5 to learn how to customizeyour Home Display. Various parameters can be displayedon the Home Display to suit your needs.