19
OPTIONAL CONTROLS & WIRING
phase 2 conTrols:
This system consists of multiple outdoor thermo-
stats with settings spaced at increments to actuate
the number of modules necessary to match the heat
load based on outdoor temperature. The heating
modules are cycled as a group by an indoor-outdoor
reset controller with temperature bulbs connected
by capillary tubes. This system provides low cost
control for small and medium heating systems of
two to five modules where it is desired to control
the supply water temperature in relation to outdoor
temperature. Ratio and temperature range are
adjustable. Control capillary tube length places
some limitations on this system. Module location
in relation to outside wall is important and should
be checked before selecting this system. See
figure #12
.
operaTion:
When the outdoor temperature drops below set
point of the main outdoor thermostat, the circulator
is turned on. The indoor-outdoor control regulates
the supply water temperature. Individual outdoor
thermostats turn on more modules as the outdoor
temperature falls below their set points.
phase 6 conTrols
Consist of a microprocessor control (W7100J)
capable of sequentially step firing up to 6 heating
modules necessary to match the heat load based
on outdoor and/or indoor air temperature. The
C7031G outdoor air sensor and C7170A discharge
water temperature sensor work in unison to adjust
the system water temperature corresponding to the
heat load demand. This system utilizes lead lag
operation to equalize the on time of each module.
Separate control band, reset ratio, and setpoint
control settings allows customizing of any modular
heating system. See
figure #13
.
operaTion:
When the indoor air temperature drops below the
thermostat setpoint, the system is energized. The
first module will fire and the remaining ones will
follow at one minute increments. Once the setpoint
limits plus the control band setting is reached, the
first module will cut out. If the system water tem-
perature remains above the control band setting
the remaining modules will begin to cut out. If the
system water temperature drops below the lower
control band setting, the next module in sequence
will fire. This process of sequencing will continue
until the heat load is satisfied.
Summary of Contents for SFM24150W
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