IBC Technologies Inc.
33
VFC 15-150 and VFC 45-225
use the
Summer Shutdown
field to
enter a threshold temperature for the
avoidance of heating during warmer
times. This is typically set at 60° to
65°F so as to eliminate excessive
boiler cycling in marginal heating
conditions.
Use the
Minimum Temp
. field to
optimize boiler run times on low
mass loads. Finned tube baseboards
sink very little heat when operated
below 100°F; application of a “full
reset curve” (e.g. 160°F right down
to a 70°F room target) would cause
boiler cycling in light-to-moderate
heating conditions. Set baseboard
minimums at 100-120°F and aim for
4 or less cycles/hr. A minimum
setting can also be used to enhance
home comfort with single or
excessive speed air handlers to
avoid the cool blast effect. Set the
lowest possible level for combustion
efficiency. IBC’s high efficiency
fully modulating air handlers (AH60
or CAF60) can use a minimum as
low as 100°F to achieve up to 95%
efficiency when combined with the
VFC modulating boiler’s wide
throttle turndown.
10.
For all loads, select and enter a
Maximum
allowable temperature
and on/off
Supply Differential Temp.
Note these values must be input;
they are not automatically assigned
as done within some boiler controls.
Ensure the Maximum takes account
of the construction and safety
requirements of each application –
e.g., 140°F max. for typical in-slab
radiant floor, for avoidance of
thermal stress. The Differential shall
be set to offer a reasonable
temperature control range
(suggested values: 22°F for high
mass radiant // 40°F for low mass
baseboards // 30°F for DHW).
Ensure that the spread between the
Target
and
Maximum
temps is
greater than one half of the
Differential
(e.g. for a radiant floor
Design Supply Temperature
of
125°F and a
Maximum
of 140°F, a
differential of 22°F (half of which is
11°F) fits nicely.
11.
Avoid situations where the
Maximum
is close or below the
potential Target, or the boiler will
cycle off its (software) water high
limit.
12.
Priority:- where more than one load
is present, it is critical that a value
be entered to allow reasonable load
scheduling (see Section 2.7.1)
13.
At the lower end of the Load 1-2-3
setup screen, there are 4 lines
available for “mapping” of sensor
inputs.. For example, “
Indoor Temp.
from
…..
Indoor
” indicates that the
boiler will look for a signal from an
indoor sensor on the Indoor Sensor
wiring contacts. Failing a valid
signal, the screen will display
“
Indoor Temp. …..Open
”, and there
will be no effective indoor trim of
the reset curve. These lines do not
