6 T-4000 Technical Bulletin
Switchover Point
Adjustment for T-4506,
T-4516, and T-4756
The above thermostats are
factory set to switch from one
element to the other at 17 psig
for a typical 15-20 psig supply
system. If a different supply
system is to be used, proceed
with the following instructions to
reset the switchover point to a
value between the two supply
pressures. The switch point is
adjustable from 15 to 20 psig
(105 to 140 kPa).
1.
Remove the controller from
the mounting bracket.
2.
Connect a variable pressure
source to the supply
connection and attach a
gage to the output
connection.
3.
Set the supply pressure to
15 psig and rotate the
lower dial to produce
approximately 5 psig
(35 kPa) on the output gage.
4.
Increase the supply pressure
to 20 psig and rotate the
upper dial to produce
approximately 15 psig on the
output gage.
5.
Set the supply pressure to
the desired switchover point.
6.
Slowly turn the switchover
adjusting screw (see Fig. 8)
clockwise to increase or
counterclockwise to
decrease the switch point
until the output changes.
Note: Do not turn the
switchover adjusting
screw more that 3-1/2
complete revolutions in
either direction.
7.
Recheck the switchover
point by increasing and
decreasing the supply
pressure over the switch
point to see that switchover
occurs at the desired value.
8.
Remove the gage and tubing
and replace the instrument
on the mounting bracket.
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