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perature is less than t4 minimum (Parameter 6).
t1 Foot (Parameter 5) is the outlet water temperature
the boiler tries to maintain whenever the outside tem-
perature is higher than t4 maximum (Parameter 7).
When outside temperature is between t4 maximum
and t4 minimum, the control calculates a value for t1
Setpoint (t1 Set) between t1 Foot and t4 top.
•
the boiler may not operate all the way down to t1 foot.
Parameter 10 (t Blocking) sets a minimum operating
outlet water temperature. if the calculated setpoint, t1
set, is less than t blocking, the boiler shuts off.
•
Set Parameters 4 to 7 as needed for the desired reset
curve. make sure to set parameters 4 and 6 so the
outlet water temperature is at design water temperature
when outside temperature drops to the Odt (outdoor
design temperature).
Parameter 9 (T4 correction)
•
Location of the outdoor sensor may sometimes cause
the sensor to incorrectly detect outside temperature.
•
you can set Parameter 9 to correct for this difference
(up to 9° F more or less) if you believe boiler response
needs to be improved. Set a negative number to reduce
the outdoor temperature reading, a positive number to
increase the reading.
Parameter 10 (T blocking)
•
use this parameter to set a minimum operating boiler
outlet water set point temperature.
•
When calculated set point temperature, t set, is at or
below t blocking the boiler shuts down (after operating
a post pump cycle).
•
to deactivate this parameter, set the value to 32.
Suggested outdoor reset settings
•
t1 top: Set to the required supply water temperature
when outdoor temperature is at or below Odt .
•
t1 Foot: Set so the drop in supply water temperature
results in the best match of heating unit output to heat
loss as the outdoor temperature rises.
•
t4 maximum: Set to the balance point temperature for
the building (typically 65° F or lower).
•
t4 minimum: Set to Odt.
III - pARAMETER EXpLANATIONS
210
200
190
182
170
150
130
110
90
70
50
210
200
195
190
170
150
130
110
90
70
50
•
if the target temperature happens to be too low for the
heating units to supply sufficient heat within fifteen
minutes (default setting), the control "boosts" the target
temperature until the supply water meets the system's
needs.
•
even if the reset parameters are optimized for the ap-
plication, use of setback thermostats or the need for oc-
casional cold start operation will require faster recovery
than provided by the normal calculated supply water
temperature because the curve assumes steady-state
operation.
•
Boost will not call for supply water temperature setpoint
7
Figure #2
TypICAL RESET CURVES
Outdoor Reset Example A
M/R Limit
A/R Limit
T1 Top Set at 180°F
T Blocking Set at 100°F
Boiler OFF
(T1 Set less than T Blocking)
T1 Foot Set at 60°F
60
50
40
70
30
Outside Temperature, °F
Outdoor Reset Example B
M/R Limit
A/R Limit
T Blocking Set at 40°F
T1 Foot Set at 60°F
70
60
50
40
30
Outside Temperature, °F
AUTOMATIC TEMPERATURE BOOST
-20
20
10
0
-10
10
0
-10
-20
20
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