Thermo Products COMBOMAX Models from 8 kW to 24 kW : 240 Volts ( single phase ) - Manual (Page 8)

COMBOMAX MC Electric boiler Set-up, use and care guide (revised January 2006) , Page 8.
cold water supply line between the
COMBOMAX
MC unit and flow check valve.
Contact your installing contractor, water
supplier, local plumbing inspector or plumbing
supply house for assistance.
3.6.3 Recirculation line (if applicable)
If a recirculation line is installed, the return
connection should be made to a tee close to the
inlet connection on the water heater. A check
valve should always be installed in the
recirculation line to prevent cold water from
entering.
3.6.4 Domestic hot water temperature
and pressure relief valve
An automatic temperature and pressure relief
valve must be installed at set-up time. No valve
of any type should be placed between the safety
relief valve and the water heater. Use a tee to
set the relief valve onto the hot water outlet. The
pressure rating of the relief valve must not
exceed 150 psi.
The BTU per hour rating of the relief valve must
equal or exceed the BTU per hour input of the
boiler(s) or heat source(s) as recorded on the
boiler(s) rating plate. For a circulating tank
installation, the separate storage tank(s) must
have similar protection.
Connect the outlet of the relief valve to a
suitable open drain, with the discharge at most
6” above the floor, far from any live electrical
parts. The discharge line must pitch downward
from the valve to allow complete draining and be
no smaller than the outlet of the valve. The end
of the discharge line should not be threaded or
concealed and should be protected from
freezing. No valve of any type, restriction or
reducer coupling should be installed in the
discharge line. Local codes shall govern the
installation of relief valves.
3.6.5 Thermostatically controlled mixing
valve (included)
For general-purpose hot water requirements in a
domestic environment, a thermostatically
controlled mixing valve is recommended to
reduce the risk of scald injury. Contact a
licensed plumber or the local plumbing authority
for further information. Adjust the mixing valve to
the lowest required temperature setting.
3.7 BOILER WIRING
The boiler cabling and grounding must conform
to local codes or, in their absence, to the
National Electrical Code.
Power must be provided by a 120/240 volt
(single phase, 60 Hz) circuit, appropriately fused
and with 3-wire plus ground cabling of sufficient
gage. The fuse and cabling gauge may be
determined from the boiler rating plate.
3.8 CIRCULATOR WIRING
The COMBOMAX
MC
heating pump (120 Vac,
1/25 Hp) is connected to the C&C terminals on
the boiler electrical panel. The control circuit is
designed to start the pump upon receiving a
heating signal from the thermostat or priority
aquastat.
3.9 CONNECTING THE THERMOSTAT
3.9.1 240V models
3.9.1.1 Single heating zone
Connect the low-voltage thermostat to the T&T
terminals on the COMBOMAX
MC
electrical panel
(DO NOT apply current to these terminals).
(see figure 10).
3.9.1.2 Zone valve zoning
Connect the low-voltage thermostat to the zone
valve. The components must wired such that,
upon a heating signal from a thermostat, only
the corresponding zone valve will be actuated
and will in turn activate the COMBOMAX
MC
circulator relay. Connect the zone valve switch
to the T&T terminals on the COMBOMAX
MC
electrical panel (DO NOT apply current to
these terminals). See figures 9 and 10.
The transformer used to power the zone valves
must be of sufficient capacity to handle the load
represented by all zone valves.
3.9.1.3 Multiple circulator zoning
Connect the low-voltage thermostat to the relay
(Honeywell #RA-889, RA-89A). The components
must wired such that, upon a heating signal from
a thermostat, only the corresponding circulator
will be activated. See figure 9.
3.10 PRIORITIZING TERMINAL POST
The K&K terminals on the electrical panel create
a dry contact when the domestic hot water
priority aquastat contact closes.