8
W884B,E
SETTINGS AND ADJUSTMENTS
The recommended maximum settings for mildew pre-
vention are 60 percent RH and 85
°
F [29
°
C].
HUMIDITY ADJUSTMENT (All Models)
In some cases, it may be desirable to deviate from
recommended setting. The setting knob has a movable
pointer, which can be adjusted to produce an upward or
downward shift in the setpoint of as much as six percent
relative humidity. Adjust as follows:
1. Remove the cover of the W884.
2. While holding the knob still, push the movable
pointer on the humidity setting dial toward MORE or
LESS. See Fig. 10.
For W884B only, set the pointer according to the type
of building construction (Table 1).
Fig. 10—An adjustment of
±
six percent RH in
the humidity control point is possible by
moving the pointer of the knob.
HUMIDITY INDICATOR RECALIBRATION
(All Models)
The humidity indicator in the W884 Comfort Control
Center has been carefully calibrated at the factory and
should require no further adjustment.
If, after several hours of operation, it appears that
recalibration is necessary, proceed as follows:
1. Obtain a proven test hygrometer (humidity gauge).
Do not attempt to use the humidity from the weather
report or an ordinary hygrometer. This will result in an
inaccurate setting.
2. Place it near the humidity indicator and allow
several hours for its reading to stabilize.
3. Rotate the bracket holding the spiral sensing ele-
ment in the W884 until the humidity indicator agrees
with the test hygrometer.
THERMOSTAT HEAT ANTICIPATOR
ADJUSTMENT
Adjust the heat anticipator to match the current rating
of the primary control; this rating is usually stamped on
the control nameplate. Move the indicator on the scale to
correspond with this rating and the heat anticipator will
be properly adjusted. Move the indicator with your fin-
gers, a pin, a pencil point, or a wire inserted in the small
hole. See Fig. 11. If the current rating is not given,
proceed as follows before mounting the thermostat:
1. Connect an ac ammeter of appropriate range (0 to
2.0A, for example) between the terminals R and W on
the subbase. The subbase system switch must be in the
HEAT position.
2. Let the heating system operate for one minute
before reading the ammeter.
3. Use this current reading to set the heat anticipator.
A slightly higher setting will produce longer burner-
on times (and thus fewer cycles per hour). This may be
desirable on some systems such as a one-pipe steam
system.
Fig. 11—T87F Heat Anticipator is adjusted to
match the current draw of the primary control.
EXAMPLE: If burner-on time is too short with a set-
ting of 0.4, adjust it to 0.45 and check system opera-
tion. Make further adjustments as necessary until the
desired burner-on time is obtained.
THERMOSTAT CALIBRATION
The thermostat was accurately calibrated at the fac-
tory and should not need recalibration. If the thermo-
stat seems out of adjustment, first check for accurate
leveling. Also check the location to be sure the thermo-
stat is exposed to average room temperature only. Heat
due to nearby appliances, hot water pipes, fireplaces,
solar heat, radiators, and registers or cold due to drafts
or cold water pipes may affect operation.
If the thermostat is still out of calibration, order Part
No. 104994A Calibration Wrench. Instructions for
recalibration are furnished with the wrench.