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In the on-off mode, the function switch provides a
choice of manual or automatic contact operation, and
manual override of the timer program as follows:
1. Contact open—burner off.
2. Standby.
3. Contact closed—burner on.
4. Automatic—normal operating position, allowing the
timer/programmer to switch between occupied and
unoccupied settings.
5. Continuous occupied setting—overrides setback,
providing constant comfort discharge water tem¬
perature.
6. Continuous unoccupied setting—overrides tim¬
er/programmer, providing constant setback discharge
water temperature.
RESET RATIO
The reset ratio is the ratio of outdoor temperature
change to the resulting change in discharge water
temperature. Reset automatically adjusts the boiler dis¬
charge water temperature in response to changes in
outdoor temperature. When outdoor temperature rises,
water temperature is automatically lowered, and when
outdoor temperature falls, water temperature is raised.
This saves energy by reducing transmission losses,
stack losses, and heat losses resulting from open
window control.
The W964F provides continuously adjustable reset
ratios from 1:3 to 2.5:1. The 1:3 ratio has the greatest
resetting effect on water temperature in that a 1 degree
change in outdoor temperature causes a 3 degree
change in water temperature. The 2.5:1 ratio has the least
resetting effect since it requires a 2.5 degree outdoor
temperature change to produce 1 degree change in
water temperature. Note on the ratio graph (behind ratio
dial) that the curve with the 1:3 ratio has the steepest
slope, while the 2.5:1 ratio has the shallowest slope.
Reset is adjusted by means of the front panel ratio dial.
The ratios marked on the dial are shown as curves on the
graph behind the dial. However, the dial can be set
between marked numbers and those ratios must be
interpolated between curves on the graph. Suggested
ratios for several different heating systems and design
temperatures are shown in Table 2.
PARALLEL SHIFT
Parallel shift provides fine tuning of reset by creating a
reset ratio curve parallel to the curve originally deter¬
mined by the selected reset ratio. The amount of parallel
shift is adjustable ±35 F [±19 C].
With the parallel shift set at 0 F, all reset ratio curves
relate to an initial set point of 70 F for both outdoor
temperature and discharge temperature. The parallel
shift setting allows the initial control point of the dis¬
charge temperature (70 F) to be shifted by a maximum of
±35 F [±19 C]. For example, with the parallel shift setting
at +10 F, the initial control point of the discharge
temperature would be 80 F (refer to chart on ratio
adjustment dial on face of W964F).
Suggested values of parallel shift for several different
heating systems and design temperatures are shown in
Table 2.
TABLE 2—RESET RATIO AND PARALLEL SHIFT SELECTION GUIDE
TYPE
RADIATION
HEATING
MEDIUM
TEMPER¬
ATURE
AT
DESIGN
TEMP. (°F)
DESIGN TEMPERATURE
-20 F
1
OF_1
+20 F
RESET
RATIO
PARALLEL
SHIFT
RESET
RATIO
PARALLEL
SHIFT
RESET
RATIO
PARALLEL
SHIFT
Direct
Standing
170-190
1:1
+10 F
1:1.5
+10 F
1:2
+15 F
Convector or
Baseboard
180-200
1:1.5
0
1:2.5
+10 F
1:2.5
+5 F
Fan Coil
Heating Only
165-180
1:1
+5 F
1:1.5
+10 F
1:2
0
Heating/Cooling
130-140
1:5.1
+10 F
1:1
0
1:1
+10
Indirect
Floor
Radiant
90
Not
Recom.
—
2.5:1
-25 F
2.5:1
-15 F
Ceiling
Radiant
110
2.5:1
-15 F
2.5:1
-5 F
2.5:1
0
NOTE ON SETBACK TEMPERATURE ADJUSTMENT
The Aquatrol panel is a water temperature controller—the scale of the setback adjustment being calibrated in degrees of
water temperature.
A change of ±4 F in water temperature is equivalent to a change of ±1 F in space temperature.
SETBACK TEMPERATURE
ADJUSTMENT
The Aquatrol maintains boiler discharge water at
control point temperature during occupied periods. The
control point is determined by the reset ratio adjustment,
parallel shift adjustment and by outdoor temperature.
Additional energy can be saved by setting back
(decreasing) the control point during unoccupied
periods. The time of each setback period is determined
by the placement of the blue (0) pins on the tim¬
er/programmer.
To obtain the desired amount of setback, turn the
discharge water temperature setback adjustment to the
10
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