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MINI ULTRA ELECTRIC BOILERS Installation and operating manual (Revision: May 2015)
10
3.5.4 Thermostat(s) and pump(s)
connections
Thermostat: Use a low voltage 24Vac thermostat
designed for central heating system (do not use a
240Vac thermostat designed for electric
baseboards).
Some thermostats are equipped with a
temperature sensor for radiant floor application.
The purpose of the thermostat is to give a signal
to the boiler that there is a demand for heat. When
the boiler will receive this signal, it will control the
activation of the heating elements.
A two stage thermostat can be installed to activate
the BOOST mode as shown in section 4.8.2.
Heating systems equipped with one
thermostat and one pump:
With an 18gauge cable, connect the room
thermostat directly to the following boiler
terminals.
Two wire thermostat: Terminals “R” and “W”
Three wire thermostat: Terminals “C”, “R” and “W”
Using 14 gauge wires, connect the circulating
pump directly on terminals “P” and “P
N.B. The amperage of the pump and 120Vac
accessories must not exceed 5A or 1/6HP
Multiple pumps zoning applications
Components shall be connected in such a way
that when a thermostat is generating a heat
demand, only the corresponding pump be
operated and that this heat demand is brought to
the boiler in order to activate the elements.
To do so, you will need relays as illustrated below.
Boiler terminals P-P will not be used.
Figure 5 : Zoning with Multiple pumps
Zoning applications with motorized valves
Connect the end switch contact of all motorized
valve to terminals R & W on the boiler.
Connect the circulator to terminals “P” and “P”- in
the boiler.
The connection of the thermostats to their
corresponding zone valve shall be done according
to the zone valve manufacturer’s instructions. See
on fig.5 below a typical example.
The R & C terminals on the boiler can be used to
supply 24Vac to the zone valves if the
corresponding load does not exceed 25VA.
Otherwise an external transformer will be
required.
Voltage at the outlet of the transformer shall never
be under 24Vac.
Figure 6 : Zoning with Motorized valves
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