Cleaning The Heat Exchanger; Refractory Firepot; Burner; Drawer Assembly - Dettson OLR105A12D Mode D'emploi

4.2.1

Cleaning the heat exchanger

Remove the 4-bolt flange from the front of the furnace to
expose the clean-out port and check for soot deposits. If
there is very little soot in the radiator section visible from the
clean-out port, you will not need to clean it. However, if you
notice scaling in the radiator, you should remove it.
The wrap-around radiator can now be cleaned entirely from
the front inspection port. The furnace also has external
clean-out ports so the soot does not fall into the fan
compartment during the cleaning operation.
IMPORTANT
DO NOT VACUUM THE CERAMIC CHAMBERS—they are
easily damaged.
Soot will have collected in the first sections of the heat
exchangers only if the burner was started after the
combustion chamber was flooded with fuel oil, or if the
burner has been operating in a severely contaminated
condition.
4.2.2

Refractory firepot

Remove the burner and check the firepot.
IMPORTANT
This furnace has a fibre type refractory combustion
chamber. Normal servicing of this unit does not require
cleaning of the combustion chamber. If cleaning of the pot
should be required, use extreme care. After firing, the pot
becomes very fragile. Do not use any commercially
available soot removers.
If the pot is damaged, it must be replaced. A damaged pot
could lead to premature heat exchanger failure. Cracking of
the firepot is normal, however, replace the pot only if the
cracks have propagated more than 2/3 the way through the
wall thickness. The average wall thickness of the firepot is
19 mm (3/4").
CAUTION
If you observe the red warning light on the burner, push
ONLY once to try and restart. If the burner does not
start, call a qualified service technician. Do NOT press
the button again.
Flooding of the firepot
Flooding can occur when the oil primary control has been
reset a number of times in a no-heat situation. Each time oil
is fired into the pot and does not ignite, it is absorbed into
the pot. Even if the burner is removed and the pot is felt for
wetness, it is difficult to assess the degree of oil absorption
by the pot.
There is only one way to properly service a flooded firepot,
and that is to replace it.
Self-aligning firepot
The primary heat exchanger of the furnace is comprised of
an upper and lower half. The lower half is essentially a "can"
that contains a self-aligning firepot. The firepot fits into the
bottom half in one direction only.
Removing the firepot
The firepot is seldom replaced, but when it must be replaced
one must simply:
1. Remove the burner;
2. Remove the burner Limit Control;
3. Remove the breech plate;
4. Remove the front panel;
5. Remove the brass nuts on the stainless steel heat
exchanger studs;
6. Pry the bottom half of the heat exchanger apart by
using the designated prying tabs;
7. Remove the bottom half of the heat exchanger through
the front of the furnace;
8. Pull the firepot up and out of the bottom half of the heat
exchanger;
9. Remove the old sealing gasket from the flange of the
upper half of the heat exchanger;
10. Scrape any residual gasket material off the matching
flanges of the heat exchanger.
Replacing the firepot
1. Align the slot at the front part of the firepot with the
burner tube sleeve and gently lower the firepot into the
bottom half of the heat exchanger;
2. Holding the firepot near the perimeter, gently push the
firepot all the way into the bottom half of the heat
exchanger until it is properly seated;
3. Thoroughly wet the gasket with water using a spray
pump bottle, position the tabs over the studs, and push
the gasket upward against the sealing flange of the
upper half of the heat exchanger;
4. Install the brass nuts on the studs by engaging only 2 or
3 threads;
5. Position the bottom half of the heat exchanger under
the upper half and align the bottom half so that the slots
in the bolting tabs engage the stainless steel studs.
There is no further need to hold onto the bottom half as
it will now be suspended on the stud nuts;
6. Push upward on the housing and thread the nuts finger-
tight as far as possible;
7. Intermittently tighten the brass nuts with a wrench in a
sequence that will pull the heat exchanger halves
together evenly. Tighten all nuts to 90 inch-lbs torque
once and then alternately re-tighten all nuts again to
100 inch-lb. THE RE-TIGHTENING SEQUENCE IS
ABSOLUTELY NECESSARY TO ENSURE A TIGHT
JOINT;
8. Re-assemble the front panel, breech plate, Limit Control
and burner in reverse sequence to their removal;
9. Follow the instructions for starting the burner for the first
time to cure the firepot and perform combustion checks.
4.3

BURNER

4.3.1

Drawer assembly

Remove the drawer assembly. Clean all foreign matter from
the retention head and electrodes. If a Beckett AFG burner
has been installed, the burner will have to be removed to
check the retention head.
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