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4
DIAL SETTINGS
When using this control as an exact replacement, use same dial settings as for old control.
A. SETTING THE ROUND DIAL:
Set the round dial for “N” initially. This will enable minor
additional adjustments to be made later if the specific instal-
lation should require it (refer to “C”.)
B. SETTING THE SQUARE DIAL:
Select the proper square dial setting from table 1 or 2 below.
For the majority of installations, the dial setting selected
should provide satisfactory boiler operation without requiring
any further dial adjustments. When required, additional
adjustments may be made as explained in “C”.
ROUND DIAL
Adjusts comfort
level required
SQUARE DIAL
Adjusts for
heat-loss of
specific
installation
OUTDOOR
DESIGN SUGGESTED SQUARE DIAL SETTING
TEMPERATURE
20°F (-7°C) 3 4.5 -- -- -- --
10°F (-12°C) 2.5 3.5 5 -- -- --
0°F (-17°C) 2 3 4 5 -- --
-10°F (-23°C) 1.5 2.5 3.5 4.5 5 --
-20°F (-29°C) 1 2 3 4 4.5 5
140 160 180 200 220 240
(60) (71) (82) (93) (104) (116)
BOILER DESIGN TEMPERATURE °F (°C)
Adjustment screw
for changing setting
of square dial
Table 2 shows suggested square dial settings for various reset
ratios. The first number of the reset ratio refers to the outdoor
bulb, the second number refers to the inside bulb. For 1-1/2 to
1 ratio, for example, each 1-1/2°F drop in outdoor temperature
will cause a 1°F increase in boiler water.
Reset Ratio Suggested Square
Dial Setting
1.5 to 1 1
1 to 1 2.5
1 to 1.5 4.5
C. ADDITIONAL ADJUSTMENTS:
If, due to system variables such as heat loss of building,
boiler size, etc., the square dial setting selected in “B” does
not give desired boiler temperatures, additional adjustments
may be made as follows:
Round Dial – One division change in the round dial setting
changes boiler water temperature about 5° at all
outdoor temperatures.
Square Dial – Changing the square dial setting 1/2 division (3
full revolutions of adjusting screw) changes boiler
water temperature about 10° at low outdoor
temperatures (0° to -20°)
CONDITION SUGGESTED ADJUSTMENT
Area too cool at low Raise square dial setting.
outdoor temperatures.
Area too warm at low Lower square dial setting.
outdoor temperatures.
Area too cool at all Raise round dial setting. (Also
outdoor temperatures raise square dial setting if round
dial has been set to “warmest”
setting.)
Area too warm at all Lower round dial setting. (Also
outdoor temperatures lower square dial setting if
necessary.)