Dunkirk 95M-200 Parameter Manual page 7

T1 Foot (Parameter 5) is the outlet water
temperature the boiler tries to maintain
whenever the outside temperature 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.
FIGURE 2 - TYPICAL RESET CURVES
Outdoor Reset Example A
210
M/R Limit
200
190
182 A/R Limit
T1 Top Set at 180°F
170
150
130
110
90
70
50
60 50
70
Outdoor Reset Example B
210
M/R Limit
200
195
A/R Limit
190
170
150
130
110
90
70
50
60 50
70
AUTOMATIC TEMPERATURE BOOST
• 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
application, use of setback thermostats or the need
for occasional 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 greater than the value of Parameter 4 (T1
Top). There is no concern that temperature boost
would supply water too hot for low-temperature
systems, such as slab-type radiant heating. On
7
T Blocking Set at 100°F
Boiler OFF
(T1 Set less than T Blocking)
T1 Foot Set at 60°F
10 0
40 30 20
Outside Temperature, °F
T Blocking Set at 40°F
T1 Foot Set at 60°F
40 20 10 0
30
Outside Temperature, °F
-20
-10
-20
-10