Laars Rheos RHCH, Installation And Operation Instructions Manual, Page: 21 / 60

Rheos Boiler and Water Heater
Page 21
SECTION 5.
Electrical Connections
WARNING
The appliance must be electrically grounded in
accordance with the requirements of the authority
having jurisdiction or, in the absence of such
requirements, with the latest edition of the National
Electrical Code, ANSI/NFPA 70, in the U.S. and
with latest edition of CSA C22.1 Canadian Electrical
Code, Part 1, in Canada. Do not rely on the gas
or water piping to ground the metal parts of the
boiler. Plastic pipe or dielectric unions may isolate
the boiler electrically. Service and maintenance
personnel, who work on or around the boiler, may
be standing on wet floors and could be electrocuted
by an ungrounded boiler. Electrocution can result in
severe injury or death.
Single pole switches, including those of safety
controls and protective devices must not be wired in a
grounded line.
All electrical connections are made in the field
wiring box that is located inside the appliance.
NOTE: All internal electrical components have been
prewired. No attempt should be made to connect
electrical wires to any other location except the wiring
box.
Wiring connections are shown in Figures 18
through 33.
5.1 Main Power
Connect a properly sized and fused, 120-volt
supply to the main power switch (hot leg is connected
directly to switch). Neutral leg is connected directly to
the white wire. Ground wire can be connected to the
grounding screw in the box or on the switch.
5.2 Pump Connections
The pump time delay relay will call the pump
to be energized upon a call for heat, and will keep the
pump energized for a delay period after the call for
heat has ended. The delay period is adjustable from
0.1 to 10 minutes.
Pump-mounted Rheos units have pumps that are
wired at the factory to the pump time delay through a
relay. Wiring to a separate 230V single phase circuit,
per the wiring diagrams in Figures 18 through 33 is
necessary.
Rheos units without the factory-mounted pump
also have the pump time delay relay. A 120V single
phase pump, which is no larger than 1hP, or 230V
single phase pump no higher than 3/4hP, can be wired
directly to pump time delay relay, as shown in the
unit’s wiring diagram (120V hot connection on the
pump to terminal 2 on the pump delay relay, and 120V
neutral to the 120V neutral circuit of the unit.)
If the pump is 3-phase, higher voltage than 120V,
or higher horsepower than 1hP, the pump’s starter
or a separate relay can be connected to the unit’s
pump time delay relay, and the pump can be driven
indirectly.
Contact the factory if there are questions about
connecting a pump to the Rheos’ pump time delay
relay.
5.3 Temperature Control — Boiler
Connect boiler T-T wires to isolated contacts on
zone valves, circulator relays, sequencing controls
(multiple appliance applications) or other temperature
controlled devices. The Rheos boiler temperature
control measures temperature on the boiler inlet. Set
the temperature control such that the setpoint plus
the boiler temperature rise equals the desired boiler
outlet temperature. Also set the manual reset high limit
20°F above the outlet temperature to avoid nuisance
lockouts.
Example, Imperial units: If the desired outlet
temperature is 180°F, and the boiler temperature rise is
25°F, then set the boiler temperature at 155°F (180°F
– 25°F). Lastly, set the manual reset high limit to
200°F (180°F + 20°F).
Example, Metric units: If the desired outlet
temperature is 82°C, and the boiler temperature rise is
14°C, then set the boiler temperature at 68°C (82°C-
14°C). Lastly, set the manual reset high limit to 93°C
(82°C+11°C).
5.4 Temperature Control — Water Heater
5.4.1 Remote Water Heater
Temperature Control
The Rheos water heater can be used with a field-
supplied tank aquastat, sequencing control, or other
temperature control device, which will call the unit for
heat when the temperature goes below the controller’s
setpoint. For the most efficient setting, set the tank
temperature at the lowest possible setting for adequate
hot water in the application.
Caution
If the tank temperature control is set too high, a
potential for hot water scalding may exist.
After a setting has been chosen for the tank
temperature control, set the heater temperature control
10°F (6°C) higher. The heater’s temperature control
senses the inlet water temperature to the heater. The
heater’s manual reset high limit senses heater outlet
temperature, and should be set 20°F (11°C) above the
outlet temperature to avoid nuisance lockouts.
Example, Imperial units: If the tank temperature
is set to 140°F, set the heater’s temperature control to
150°F (140°F+10°F). Further, if the temperature rise