Install Instructions

Page 40
LAARS Heating Systems
The DHW priority demand forces the control to operate to the
DHW setpoint, de-energizes the System pump and energizes
the DHW pump.
The domestic hot water temperature sensor or an aquastat
is used to monitor the DHW demand. The control uses the
DHW sensor to control the operation and modulation rate of
the appliance when there is a DHW demand.
Hydronic Heating Using Local Lead-Lag/Cascading
Feature with Indirect Hot Water -
(For a complete explanation of the Lead Lag system, see
Section 8.14.)
When using the Lead Lag boiler system to provide indirect
domestic hot water heating, the DHW demand should be
supplied to the Master boiler through the existing DHW
terminals. The Lead Lag system will change the operating
mode of just the Master boiler to supply water at the DHW
setpoint. The remaining boilers on the system will continue to
supply hydronic heating.
When the system is supplying both hydronic heat and
domestic hot water at the same time, both the System pump
and DHW pump contacts are closed, so special attention must
be paid to allow for proper operation. In applications serving
both hydronic and domestic heating, during a DHW call the
Boiler pump on the Master boiler may need to be turned
off. The DHW pump will provide ow through the boiler
and indirect tank when there is a DHW call. (This means the
DHW pump must be sized properly.) To turn off the boiler
pump in this application, the “boiler pump interrupt” jumper
must be installed. The terminal block location is terminal
block 5 (TB5) at the contacts labeled “boiler pump interrupt”
in the control panel.
Sensor Connection for Domestic Hot Water -
Connect the DHW sensor or aquastat.
If your system has just one boiler –
Connect the sensor across terminals 5 and 6 on TB6.
See Figure 31 on page 37.
If your system has more than one boiler, and is controlled
using the Lead/ Lag function –
On the unit used as the Lead/ Lag Master only, connect the
sensor across terminals 5 and 6 on TB6.
Domestic Hot Water Heating
Using External Modulation Control -
When the NeoTherm is used for DHW heating with external
modulation control, a call for heat must be supplied to the
“T-T or Interlock” terminal. By supplying a call to the “T-T
or interlock” terminal, the operating temperature setpoint
defaults to the hydronic heating setpoint, so all of the tem-
perature adjustments must be made to the hydronic setpoint.
When the unit receives the call, the control starts the Boiler
and System pumps and begins the ignition process. Once in
Run, the NeoTherm monitors the ame signal, call for heat,
safeties, and water temperatures. The heater setpoint is used
to limit the maximum water temperature leaving the boiler
only. The modulation rate is controlled by a 4-20mA signal
supplied by an external control. (This can also be 0-10Vdc us-
ing a converter.) When setting up a system using an external
control, take care to set Anti-Short Cycle feature to prevent
“hunting “ and possible premature component failure.
Boiler Pump Interrupt Function -
The Boiler pump interrupt feature is used in some applications
when the boiler is being used for both hydronic and domestic
hot water heating. The interrupt jumper is used to turn off
the boiler pump during a domestic hot water demand. For
this to work properly the system must be plumbed and
pumped to allow the DHW pump to supply the ow and head
requirements for both the boiler and indirect water heater. It is
not necessary to use the interrupt jumper in all applications.
To turn off the Boiler pump in this situation, the “boiler pump
interrupt” jumper should be installed between R1 and R2 on
TB5.
If your system includes several boilers, is controlled using the
Lead Lag system, and the indirect DHW tank is connected
to the boiler acting as the Lead Lag master, install the boiler
interrupt jumper on the Lead Lag master only.
WARNING
Failure to plumb, pump and install the appliance
correctly when using this feature may lead to reduced
or no water ow through the heat exchanger, causing
premature failure of the heat exchanger, personal
injury or death. Please consult the factory with any
questions regarding the use of this feature.
Setup for DHW Control Functions -
1. Set up the correct priority for the DHW function in relation
to Central Heat or Lead/ Lag demands. If a call for heat
and a DHW demand arrive at the same time, which will
have 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,” then
go to “DHW Conguration.” Select “DHW Priority vs
Central Heat.”
If your system has more than one boiler, and is controlled
using the Lead/ Lag function –
How to get there: On the unit used as the Lead Lag
Master, from the “Home” screen, press “I” to go to “Info/
Install.” Choose “Advanced Setup,” then go to “DHW
Conguration.” Select DHW Priority vs Lead Lag.”