LAARS Rheos+ RHHV - Install and Operating Manual - Manual (Page 30)

Rheos+ Boiler and Water Heater Page 29
The second menu “Add” has to do with the N2
address. Pressing enter when “Add” is displayed will
display “255”, which stands for 255 unique addresses.
The up and down arrows change this value, and enter
saves the value if it is changed.
Changing the “Add” value will have no affect
on the Rheos+, unless a communications card as
been built onto the unit. If a Rheos+ unit has been
ordered with an optional communications card,
more menus will be active, and the unit will come
with separate instructions.
5.7 External Control Connections
Rheos+ units are built with a selector switch and
a terminal strip to allow the Rheos+ to receive a
0-10VDC signal from an external controller (such as a
building automation system or multiple boiler control).
When the selector switch is in the “Rheos+
Control” position, the Rheos+ will be modulated by
the unit’s factory-mounted modulating control.
When the switch is in the “External Control”
position, the unit look for a 0-10VDC signal from an
external (field-supplied) controller.
To interlock the external boiler control with the
Rheos+, the call for heat signal MUST be connected
to the field interlock terminal strip on the Rheos+
(shown in Figure 29). Be sure to remove the factory-
installed jumper between the field interlock terminals.
The 0-10VDC modulating signal MUST be connected
to external control terminal strip, located to the right
of, and behind the front panel. The terminal strip is
labeled “0-10VDC +” and 0-10VDC –” to indicate
which terminal received the hot signal (+) and which
terminal receives the common signal (-) from the
controller.
The Rheos+ unit will modulate between 2.23V
and 10V (for 25% and 100%, respectively). Anything
less than 2.23 volts will result in 25% of full fire.
For the external control to modulate the Rheos+,
the selector switch on the front panel must be in the
“External Control” position.
Important Note: DO NOT MAKE/BREAK RHEOS+
LINE VOLTAGE TO SIGNAL CALL FOR HEAT. A
“call for heat / end call for heat” MUST be connected
to the field interlock terminals. The Rheos+ does not
recognize 0 volts as a signal to shut off. If the call
for heat is not connected between the field interlock
terminals, the Rheos+ will remain in low fire when it
sees 0 volts as a modulating signal.
Caution
Rheos+ supply voltage must not be disengaged,
except for service or isolation, or unless otherwise
instructed by procedures outlined in this manual. To
signal a call for heat, use the 24V field-interlock, as
shown in the wiring diagram(s).
Some Rheos+ components are designed to have
constant voltage during normal operation. If Rheos+
supply voltage is toggled as a call for heat signal,
premature failure of these components may result.
5.8 Wiring Diagrams
Caution
Label all wires prior to disconnection when servicing controls. Wiring errors can cause improper and dangerous
operation. Verify proper operation after servicing.