Lennox GCS16-413-100 User Manual

Page 18
4-Blower / Limit Control:
High Temperature Limit S10,
Blower Control K25
A combination blower/limit control with a bimetal sure
start heater (figure 13) is used to control blower operation
and protect unit from high temperature operation. It is lo
cated in the upper end of the heating vest panel. The blow
er control heater is a resistive type bemetal heat relay
(K25) used to reduce the time between blower demand
and blower startup. It is energized with the heating de
mand.
Internal contacts K25 are used to coordinate blower op
eration with burner operation. The N.O. contacts are actu
ated by a bimetal spring when temperature rise in the heat
ing compartment (in addition to heat added by the sure
start heater) is sufficient. The blower cycles on 20 to 90
seconds after the start of a heating demand and cycles off
120 to 240 seconds after heat demand is satisfied (when
bimetal swtich cools). Ontime will vary, depending on the
voltage applied to the bimetal heater and on the tempera
ture surrounding the K25 switch. The relay is SPST.
The blower control has a factory off setting of 90F. This
control can be field adjusted. In some cases, an unusual
duct design can cause the indoor blower to cycle on after
the heat demand is satisfied. If this situation occurs, the
Fan Off" setting on the blower/limit control should be set
below 90F. See figure 13.
NOTE - Blower OFF" settings above 90F will cause
the blower to recycle frequently (after a heating cycle)
due to residual heat in the heat exchange assembly.
Blower OFF" settings above 90F may also cause
nuisance trips of secondary limit S10.
Adjustment procedure is outlined in Heating System Ser
vice Checks" section.
Primary limit S10 contacts deenergize the ignition control
when excessive temperature is reached in the blower
compartment. The N.C. limit is a SPST autoreset switch.
It is fixed in position for a maximum discharge air tempera
ture. The limit is factory preset to trip on a temperature rise
and automatically reset on a temperature fall. On a tem
perature rise terminals 1-3 open to deenergize the igni
tion circuit. Table 2 shows factory settings. This is a safety
shutdown function of the unit.
TABLE 2
LIMIT CONTROL S10
Unit Input
Thousand
Btuh
High Limit
Cutout
+ 10F
50
75
100
510-125
160F
170F
150F
170F
650-125 160F
FIGURE 13
HONEYWELL BLOWER/LIMIT CONTROL
BLOWER SETTING
POINTERS
LIMIT SETTING
POINTER
FIXED STOP
5-Secondary Limit S21
100,000 Btuh Heat Exchangers Only
All GCS16-410-100 and GCS16R-411-100 units are
equipped with a secondary high temperature limit located
on the blower scroll (see figure 14). The limit is a SPST
autoreset temperature which opens (terminals 1-3) on a
temeprature rise. It is electrically connected in series with
the ignition control. The limit is used to deenergize the
ignition control and shut down the unit when temperature
in the blower scroll becomes too high. The limit is factory
preset to open at 170F+5F on a temperature rise and
close at 130F+10F on a temperature fall. It is not adjust
able. This is a safety shutdown function of the unit.

Lennox GCS16-413-100 Specifications

General

Brand	Lennox
Model	GCS16-413-100
Category	Industrial Equipment
Language	English