IBC Technologies Inc.
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VFC 15-150 and VFC 45-225
be provided to the power contacts on the
Pump/ Zone Valve Terminal Block. Use
a separate transformer – the 40VA unit
inside the wiring box is for internal
systems only. The individual load/zone
valves are then to be wired to their
associated contacts on the secondary
pump/zone valve connector. Do not
confuse such “load/zone valves” with
similar valves used to segregate a single
load type (e.g. those used on a zoned
radiant floor) – see next section.
1.7.4 Thermostat / Sensor Wiring
Dry contacts for thermostats for each of
3 loads are provided as marked on the
lower / orange connector strip (e.g.
“Therm 1”). Gang lines from a multiple-
zoned load (e.g. off the end-switches for
each radiant floor zone) to present a
common thermostat signal to the
controller. Ensure there are no disturbing
influences on the call-for-heat lines - e.g.
no coils to switch an air handler motor.
Where these zone valves are of a non-
isolated 3-wire configuration, the zone
valve end contacts must be isolated from
the load's controller thermostat terminal
using an appropriate relay.
1.7.5 Other wiring
Other optional low voltage connections
to the control board include:
•
two auxiliary interlocks - for external
safety devices as may be required by
some jurisdictions, such as a low gas
pressure cut-out (for off-grid
propane). A floor-protecting aquastat
can use one of these, to cause a full
boiler shutdown in the case of excess
floor temperature.
•
contacts for indoor and outdoor
temperatures sensors associated with
Reset Heating. A 10K ohm
thermister for outdoor reset sensing
is supplied with the boiler, to
encourage use of this temperature
compensating space heating
technique for improved comfort and
combustion efficiency.
•
one pair for a DHW tank sensor.
Connect to “DHW S” (not the
respective Therm 1,2,3 location) and
the boiler will automatically notice
and go to a smart DHW routine
•
one pair of contacts for remote
secondary loop temperature control.
•
One pair (marked
BoilerNet
) for
network connection – this is used for
connecting multiple VFC modulating
units for autonomous staging – see
separate Technical Memo for
guidance.
•
a final pair of contacts, to receive a
4-20 mA (default) or 0-10VDC signal
from an external boiler controller- for
direct throttle control. The boiler’s
own sensors act as high limits only.
User must enter maximum and
minimum boiler supply temperatures.
Note: all sensors connected to any
sensor input contacts must be of NTC
Thermister - type with a resistance of
10,000 ohms at 25°C and
β
= 3892.
1.7.6 Thermostat Heat Anticipator
An anticipator setting for the thermostat
is not applicable with the VFC
modulating series boilers. In the case of
a single temperature / heat load where
zone valves are used to manage
individual thermostatically controlled
zones, each room thermostat’s heat
anticipator should be adjusted to the
current draw of its associated zone
valve.