IBC Technologies Inc.
28
VFC 15-150 and VFC 45-225
Prioritization value relative to the other
declared channels (e.g. moving the Load
3 preset value from 50 to 60 or reducing
another load’s value). Temperature
targets for the underserved load could
also be raised in this example. For
absolute priority, move the Load setting
above 90. This will eliminate Load
switching. Do not set each load to the
top value, and it is generally better to
avoid equal ratings. Note: the priority
scale values do not need to add up to
100 – they are relative only to each
other.
2.6.2 Reset Heating
The boiler offers Outdoor Reset control
as standard equipment; this coordinates
the control of boiler supply water
temperature for space heating with the
outdoor temperature. Outdoor Reset
offers enhanced home comfort and
efficiency by using variable water
temperatures to compensate for the
differing rates of heat loss that a
building faces as outdoor temperature
changes. At any outdoor temperature
above the coldest day expected, it
automatically uses lower heating
temperatures than would otherwise be
used. This saves energy without
sacrificing comfort. When applied
within a condensing boiler, outdoor
reset offers direct and significant
combustion efficiency benefits by
allowing generally lower circulating
water temperature. This provides cooler
return water to the boiler, promoting
more condensation (= energy capture).
Contacts are provided for connection of
an outdoor sensor (a
tekmar 070
or
similar sensor is shipped with each
boiler) to be placed in an appropriate
outdoor position. The temperature
management algorithm flexes the boiler
supply temperature according to
characterized heating curves that are
automatically called up through the load
declaration process. Curves are
provided for each of the radiation
terminal types offered - e.g. high or low
mass radiant floor, air handler, finned
tube baseboards etc.
Ch ar ac t er iz ed Cu r v es
7 0
8 0
9 0
1 0 0
1 1 0
1 2 0
1 3 0
1 4 0
1 5 0
1 6 0
1 7 0
-2 0
-1 0
0
1 0
2 0
3 0
4 0
5 0
6 0
7 0
Ou t d o o r Temper a t ur e
S
u
pp
l
y
W
a
t
e
r
T
e
m
per
a
t
u
r
e
Figure 11 – Outdoor Reset
In an “open loop” reset system, a room
or zone thermostat is used to send a call
for heat over a 24V
AC
lead; this opens
the respective zone valve, and signals
the boiler to fire using onward leads to
the boiler’s dry contacts (use one of the
pairs marked “Therm 1, 2 or 3” on the
orange connector terminal located on
the right edge of the controller). Gang
such leads in parallel from multiple
zone valves for single connection to the
boiler. Note that typical room
thermostats simply provide a call for
heat, they do not control the circulating
water temperature from the boiler in an
open loop reset system. Adjustment of a
room thermostat from 23°C to 30°C will
make no further difference to the
delivered temperature if the floor slab
has stabilized at the boiler temperature
served up by the reset curve.
Where Outdoor Reset is applied without
the indoor sensor feedback option, some
manual adjustment may be required to
1-
Baseboard
2-
IBC Air Handler
3-
CI Radiator
4-
LM Radiator
5-
HM Radiator
1
2
3
4
5
