Firebrick Damage - Gilson HM-378 Operating Manual

Gilson Company, Inc.
i. Remove four screws holding the front plate above
the door to the furnace and remove the front plate.
Be careful not to damage the gasket.
j. The top slab of fire brick is now free to be removed.
Start at the front of the furnace and insert a flat
putty knife or screw driver to lift the slab just
enough to insert your fingers. Gently lift and pull
the slab toward you as you slide your hand under
the slab. Lift the firebrick slab clear of the furnace.
k. The after burner element is now exposed in grooves
on the floor of the after burner chamber. Using
long-nose pliers, remove any staples that hold the
elements in place. Save the staples and mark the
locations of the holes for later installation.
l. Remove the old element carefully to prevent
breaking of the firebrick. If the old element burned
out due to contact with foreign materials, there will
probably be a melted, glazed spot in the element
groove. Glazed spots left in the grooves may ruin
the new elements, so dig out any of these spots.
The small hole left in the groove will not affect the
new element. Pieces of firebrick in the grooves
should be removed with a dry paint type brush
or vacuum cleaner.
m. Reach inside the after burner chamber and push
one end of the new element into one of the ele-
ment holes. The element end will appear at the
other side of the hole outside the case. Begin
threading the element into the groove.
n. The element must fit all the way into the groove and
follow the serpentine pattern to the other end.
o. To hold elements in grooves, reinstall staples at
marked locations by pressing them in using a
pair of long nose pliers.
If the element is slightly too long when you reach
the second firebrick hole, insert element end into
the firebrick hole and let the curved groove take up
the extra length. You can compress the element
with long nose pliers if necessary. If the element
is several inches too long, it was not pushed all
the way to the back of each corner and should be
re-threaded. If the element is too short to reach
the second firebrick hole, unthread some of it.
Gently stretch it in your hands. Avoid stretching
only a short portion of the element. It is better to
distribute the stretch over a longer section.
Press the element down into the lower part
of the groove with a plastic comb or wooden
tongue depressor. Reinstall the porcelain insula-
tors. Push them flush against the furnace case.
They protect the element from contact with the
case, so they must not work their way out after
the element connector is tightened into place.
Sandpaper the eyelet of the element lead wires
if insulation on old ones is brittle. Use the brass
screw to connect lead wire eyelets to the new
element connectors.
Before tightening the screw, adjust eyelet to
where it will be tilted away from furnace case
when connector is attached to element. Then
hold the connector with pliers and tighten brass
screw securely with nut driver. Pull the end of the
element tight and install new element connec-
tors even against porcelain insulators to prevent
insulator from slopping away from brick wall. Use
stainless screw in the element connector to hold
the element. The brass screw holds the lead wire
eyelet.
Hold connector with pliers as you tighten the
screw. Tighten the screw until it squeaks, and
then tighten some more. Cut off twisted end of
element even with side of element connectors.
NOTE: Leaving the excess element sticking out past
element connector could ruin your new element!
The element can short against something in the
switch box.
p. Replace the top slab of firebrick and reassemble
the furnace by reversing the above steps.
q. As you move the switch box back into place, check
to see that no wire touches an element connec-
tor. Wires and wire nuts must also not touch the
furnace case inside the switch box. Wires and
wire nuts will burn if they touch the case or ele-
ment connectors. Replace screws in switch box
and tighten into place.

10.3 Firebrick Damage

If large chips occur in the firebrick, DO NOT fill them
completely with repair cement because expansion of the
cement differs from expansion of the brick. The cement
will break out when fired. Instead, seal large chips with a
very thin coat of repair cement and leave the chips unfilled.
Suitable cement is available from Gilson in dry form in
one-pound bags as Model RPHM-378-17.
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Gilson Binder Ignition System: HM-378