LAARS NeoTherm NTV (Sizes 150–850 MBTU/h) - Install and Operating Manual - Manual (Page 45)

Page 41 N eo T herm Boilers and Water heaters
DHW Temperature Setting -
Regardless of the type of DHW setup, the setpoint adjustment
is made the same way.
How to get there: From the “Home” screen, press “I” to
go to “Info/ Install.” Choose “Advanced Setup,” then go
to “DHW Setpoint.”
Hydronic Heating with
Domestic Hot Water (DHW) Priority -
When using the NeoTherm for hydronic heating with
domestic hot water priority, a call for heat must be supplied
to the “T-T or Interlock” terminal. Once the call is supplied,
the control starts the Boiler and System pumps and begins the
ignition process. Once in Run, the NeoTherm monitors the
flame signal, call for heat, safeties, and water temperatures
modulating as needed between 100% and 20% of rate to
satisfy the call for heat. When a DHW demand is applied
during a hydronic call for heat, the priority feature forces the
boiler to switch to the DHW demand for the priority time.
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.
Domestic Hot Water Demand - NTV only -
The “NTV” NeoTherm units are designed to provide “volume
water” DHW in conjunction with a storage tank. When the
NTV model NeoTherm is used in this application, a call for
heat must be supplied to the “DHW stat” terminal located on
terminal block 6 (TB6). The DHW heating call can be from
the supplied DHW sensor or from an aquastat. If the DHW
sensor is used, the heater operates to maintain the temperature
at the DHW sensor. (This may allow the actual heater outlet
water temperature to exceed the DHW sensor setpoint.) If
an aquastat is used to supply the DHW demand, the heater’s
firing rate is controlled by the DHW setpoint temperature and
the water temperature at the heat exchanger outlet.
When the unit receives the DHW call, the control starts the
Boiler and DHW pumps and begins the ignition process. Once
in Run, the NeoTherm monitors the flame signal, call for
heat, safeties, and water temperatures modulating as needed
between 100% and 20% of rate to satisfy the call for heat.
Hydronic Heating Using Local Lead-Lag/Cascading
Feature with Indirect Hot Water -
(For a complete explanation of the Lead/Lag system, see
Section 8C.8.)
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 flow 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.
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 flame 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.