DTH Electric Boilers
USE & CARE MANUAL
(Revision November/05)
, Page
9.
3.5.2 600Vac models
Line wiring must be from a 600 Volt ( 3 phase,
60 Hz) circuit protected by a properly sized
breaker. Wire gage (3 wires, ground) must be
properly sized. Consult the boiler rating plate to
select the proper breaker and wire gage.
3.6 PUMP POWER SUPPLY
3.6.1 240Vac models
Connect only a 120 Vac, 9 amp. (maximum)
pump to terminals C and C on the electric
pannel. Do not use a 600 Vac pump or one
drawing more than 9 amps. The logic circuit is
designed to activate the circulator based only on
demand by the thermostat after a time delay.
3.6.2 600Vac models
Use a relay (Honeywell #RA-889, RA-89A) or
the secondary contact of a zone valve (if the
heating system is zoned using 4-wire zone
valves). When a thermostat calls for heat: the
relay will power either the boiler pump or the
zone valve (the zone valve will power the boiler
pump upon opening fully). See figure 6 for more
details.
If the heating system is designed to use only a
single pump, then to minimize flow by gravity
and heat loss during non-draw periods,
a flow
check must be installed.
3.7 CONNECTING THE THERMOSTAT
3.7.1 For 240Vac model
3.7.1.1 Single heating zone
Connect a low voltage thermostat to terminals T
and T on the electric panel (
DO NOT apply any
power to these terminals!
).
3.7.1.2 Multiple heating zones
Connect the zone valve end switch to terminals
T and T on the electric pannel (
DO NOT apply
any power to these terminals!
). See figure 6.
3.7.2 For 600Vac model
3.7.2.1 Single heating zone
Connect the low voltage thermostat to a relay
(Honeywell #RA-889, RA-89A). See figure 6.
3.7.2.2 Multiple heating zones
Zone valve zoning
Connect the low voltage thermostat to the zone
valve. Components must be wired to ensure that
only the zone valve corresponding to the zone
calling for heat is actuated and that the circulator
is powered on a demand from any zone.The
transformer used to power the zone valves must
be sized for the load represented by all zone
valves in the heating system. See figure 6.
Circulator zoning
Connect the low voltage thermostat to the relay
(Honeywell #RA-889, RA-89A). Components
must be wired to ensure that only the circulator
corresponding to the zone calling for heat is
actuated. See figure 6.