LAARS NeoTherm NTV (Sizes 399-850 MBTU/h) - Service Manual - Manual (Page 42)

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Service Manual - NeoTherm 500
Each NT unit includes two switches which sense gas
pressure:
• The low gas pressure switch is located before
the gas valve. It will prevent the unit from firing if
there is not enough gas pressure to operate cor-
rectly.
• The high gas pressure switch is placed after the
gas valve. It will shut down the unit if excess gas
pressure gets past the gas valve.
Note that these two switches are similar, but not
identical.
• The low pressure switch (Honeywell p/n C6097A)
is wired N.O. (normally open), and has a manual
reset switch. (You will need to reset this switch
if you disconnect an old switch or install a new
switch.) The low pressure switch is set to trip
below 3” w.c. (water column).
• The high pressure switch (Honeywell p/n
C6097B) is wired N.C. (normally closed). The
high pressure switch is set to trip above 3” w.c.
(water column).
Removing and Replacing the High and Low
Gas Pressure Switches
Tools and equipment required:
• Small Phillips-head screwdriver (#1)
• Two medium-sized pipe wrenches or adjustable
wrenches
• Gas-resistant pipe dope or Teflon® tape
• Gas leak detection solution (“Hercules Mega-
bubble® or equivalent)
• Container for removed parts
Low gas
pressure
switch
High gas
pressure
switch
Gas valve
Fig. B15-1 - High and low gas pressure switches (typical)
B15