Coleman 7600 - Installation and Service

ANTICIPATION
The operation of
a
low voltage
thermostat
based solely
on
mechanical
means,
generally
results
in wide varia-
tions
in temperature
in the conditioned
area
whether
the
application
is for heating or
cooling.
To insure a
more
precise
control
of area
temperature,
low voltage
thermo-
stats
contain
heating
and cooling
anticipators.
In
addition
to
improved
room temperature
control,
heat
anticipation
contributes
to better
air circulation.
The
burner
may cycle
on and off
several
times
during
one
cycle
of the
fan. Since
heat
anticipators
are
powered
and
effective
only during
the
heating
cycle,
they are
placed in series with
the control
contacts.
When the
contacts
are
closed,
power
is supplied
to the
heat
anticipator
resistor.
MANUAL
SWITCHING
OPERATIONS
Generally,
a
sub-base used
to
control both
heating
and
cooling
equipment
will contain
two switches,
one
marked
"FAN"
and one
marked
"SYSTEM."
FAN
SWITCH
ON Constant
fan. The fan will
run continuously
re-
gardless
of
the thermostat
demand.
AUTO
The fan runs only as
required
by the system
operatlon.
SYSTEM
SWITCH
HEAT
-
Heating
system
only,
operates
in response
to
the
thermostat.
OFF
Heating system
and
cooling
system
both off.
COOL
-
Cooling
system
only,
operates
in
response
to
the thermostat.
CAL/TION:
Care
should
always
be taken
in the align-
ment of
the
thermostat
attaching
screws,
as they
may
also
serve
as
terminal
connectors.
If threads
are
stripped,
a
poor
electrical
connection
will result.
INSTALLATION
AND SERVICE
l. A low
voltage
thermostat
is a
precision instru-
ment and
should
be
treated as
one.
Care
must be
used
to
insure a
level
installation
with
thermostats
using
mercury bulbs.
2. Mount
on a solid
wall.
3.
Locate the
thermostat
on an
inside
wall
four to
five
feet above
the
floor in an
area
free
from
drafts
and direct
sunlight.
Do
not locate
where directly
affected
by
lamps, fireplaces,
appliances,
or on
walls
containing
hot or cold
pipes,
ducts,
chimneys.
4. Be
sure anticipator
matches
or is
adjusted
to
match current
(amp)
draw
of
equipment
being
controlled.
5.
Make
all
wiring
connections
clean
and
tight'
lf a
heating
system
has an
improperly
sized
anticipator
and
excessive
heat
is
generated in
the
thermostat,
the
result
is
a
short
"on"
cycle.
During
periods when
the
system
is
running
close
to its
full capacity,
more of
the
heat
sensed
by
the
bi-metal
is
from
the
anticipator
than
from
room
air;
and
the controlled
area
tempera-
ture
will
progressively
decrease.
THERMOSTATS
Insufficient
heat anticipation
in a
heating system
results
in the bi-metal
lagging behind
the
room temperature
change.
This will cause
longer
"on"
and
longer
"ofl'
periods
with
a
resultant
larger
room temperature
varlatlon.
A common
heating valve
current draw
is 0.4 amps,
and this
should be
matched on
any
adjustable antici-
pator.
If the adjustable
anticipator
is set appreciably
higher,
for example
rJ.1
amps,
it
will increase
the
room temperature
variations
by
3oF. or
4oF. and cause
longer running cycles.
For longer
"on"
periods,
set the
heat anticipation ad-
justment
pointer
at slightly
higher amp
value. For
shorter
"on"
periods,
set the
pointer
at
slightly
lower
amp
value. Move
only
t/q
to
/z
scale
division at a time.
(Never
set
the
pointer
at
more than
I
%
scale
divisions
below the amp
rating of the valve or
relay
current
rating.)
The
anticipation
function
in a cooling
thermostat
is the
reverse of
its heating application.
The cooling
antici-
pator
is
powered
during the
"ofl'
cycle.
As the
room
temperature
increases,
heat
is
applied
to the
bi-metal
decreasing the
time
necessary for
the bi-metal to
close
the contacts.
Excessive cool anticipator
temperature
results
in shorter
"offl'
periods,
consequently,
more
frequent cycling
of the cooling
equipment.
Insufficient
anticipation
in
a cooling
thermostat
causes
long
"ofl'
and
cycles
resulting
in
larger temperature
variations
in the room.
ANTICIPATION PROBLEMS
HEATING
SETTING
TOO LOW
l. Excess anticipation
"on"
cycles
too short.
2.
Rapid cycling.
3. Small temperature
swings
from the setting with
a tendency to drop.
SETTING TOO HIGH
l. Insufficient anticipation
cycles
too
long.
2. lnfrequent
cycling.
3.
Wide temperature swings
from the set
point
with
a tendencl
to lag.
COOI,ING
RESISTOR TOO SMALL
L Voltage too low.
2.
Short
"ofl'
time.
3. Short
"on"
time.
4. Rapid cycling.
5. Temperature
maintained closer
to
the set
point
with
a
tendency
to rise.
R'.S/.STOR
TOO
IARGE
l.
Voltage
roo
high.
2.
"Off'time too long.
3.
"On"
time too
long.
4. Fewer
"on"
cycles.
5. Wide
temperature
swings
from the
set
point
with
a
tendency
to lag.
l7