26
Check Operation and Safety Controls
Figure 14C - Manifold to Furnace Pressure Drop vs Rate CG50*
0
1000
2000
3000
4000
5000
6000
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

Pressure Drop, In. WC

Rate, MBH

CG50.5S

CG50.4S

CG50.3S

CG50.2S

CG50.1S

* Charts represent both natural and propane gas.
Testing by Qualifi ed Technician Required.Failure to properly test and verify the correct function of operation and safety controls could lead to equipment malfunction and result in asphyxiation, explosion or fi re.
The testing of operation and safety controls requires
technical training and experience with commercial
gas burning systems.
Carefully follow the manufacturer’s instructions
supplied with the controls.
Verify the correct function of all operation and safety
controls used in the installation.
If instructions are not available, use the following
recommended procedures and record all results in a
start-up log.
Refer to Figure 7 for typical test points and
component locations.
y
y
y
y
y
Section: Start the Burner
Operating control – Run the burner until the
operating control shuts it off. If necessary, make
adjustments to ensure the control cycles the burner
in the desired temperature or pressure range.
Operating controls should be
set to minimize the number of
fi ring cycles that the burner runs. High cycling rates
increase the possibility of light-off lock outs.
Low water cutoff (LWCO) – With the burner fi ring,
open the blow down valve on the low water cutoff,
if applicable. As the water level drops, the LWCO
switch contacts open and shut the burner off. When
the water level rises, the LWCO contacts close
and restart the burner. Monitor the LWCO switch
operation in relation to the water level in the sight-
glass for synchronization.
Airfl ow proving switch – With the burner fi ring at
its lowest rate, loosen the tubing connection to the
airfl ow proving switch. A loss in air pressure at the
tubing should immediately cause the diaphragm
in the switch to open and recycle or lockout the
safeguard control.
Low gas pressure switch – With the burner fi ring
and a manometer attached to a test port near
the low pressure switch, gradually close the main
leak test cock to shut off the gas supply. Note the
pressure at which the low gas pressure switch
opens and shuts the burner off. Manually reset the
switch. The low gas pressure switch should be set
at half of the normal supply pressure in the line.
2.
3.
4.
5.
High limit – To check the High Limit, raise the
temperature or pressure of the operating control to
a higher level and lower the limit to a setting less
than the operating control. Run the burner until the
high limit opens and shuts the burner off. Adjust the
controls back to the desired settings.
1.