CHAPTER
7
Thermal relay units (overloads) are
of
the melt-
ing-alloy type and
when
tripped, the alloy must
be given time to resolidify
before the relay
can
be reset.
If
overloads trip
out
repeatedly
when
motor
current is normal, replace them with new
overloads.
If
this condition continues,
check
for
excessive current
draw
at the overloads.
The
power
supply to the boiler must be protected
with dual element
fuses
(fusetrons)
or
circuit"
breakers. Similar
fuses
should
be
used
in
branch
circuits. Standard
one-shot fuses are not recom-
mended. Information given in Fig. 7-2 is
in-
cluded for guidance to fuse requirements.
F.
FLAME
SAFEGUARD
CONTROL
This microprocessor based control requires
min-
imal maintenance because the safety and logic
timings are inaccessible. There also are
not any
any accessible contacts.
Check
to
see
that the ·
retaining
screw
is
securely holding the chassis to
the mounting base. Also
check
to
see
that the
amplifier and
the
program module are tightly
inserted.
The
relay's
self-diagnostic ability includes advis-
ing
when
it
or
its plug-in modules are at fault and
require replacement.
·
Your
spare control should be stored in a dry
atmosphere and wrapped
in plastic. During an
extended
shutdown
(e.g., seasonal), the active
control should be removed and stored. Moisture
can
cause problems with control operation.
It
is
recommended that service be rotated
be·
tween the active and spare control to assure a
working replacement is available.
CHAPTER7~
INSPECTION
AND
MAINTENANCE
!WARNING
When replacing a control, be sure
to
disconnect
the
main power
supply, since the control is
"hot"
even though the burner switch Is
off.
Failure
to
heed
this
warning
could result in serious personal
Injury or death.
Make
sure
the connecting contacts
on
the control
and its base are not bent
out
of
position.
The
flame detector lens should be cleaned as
often
as
operating conditions demand. Use a soft
cloth moistened with detergent to clean the lens.
A safety
check
procedure should be established
to
test the complete
flame
safeguard system at
least
once
a month
or
more
often. Tests should
verify safety
shutdown
and a safety lock-out
upon failure to ignite the pilot, upon failure to
ignite the main flame, and upon loss
of
flame.
Each
of
these conditions should be checked
on
a
scheduled basis.
The
following tests should
be
used to test the
complete safeguard system.
If the sequence
of
events is not as described, then a problem
may
exist.
Contact
your
Cleaver-Brooks
local
authorized representative for assistance.
Checking Pilot Flame Failure
Qose
the gas pilot
shutoff
cock (Fig. 1-3). Shut
off
the main fuel supply.
Tum
the burner switch
"on."
The
pilot ignition circuit will be energized at the
end
of
the pre-purge period. There should be an
ignition spark but no
flame.
Since
no flame is
detected, the program relay will signal this
con-
dition.
The
ignition circuit
wil~
be de-energized
and the control will lock
out
on a safety shut-
down.
The
flame failure light (and optional
alarm) will be activated.
The
blower motor will
run through the post-purge and stop.
750-150
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