Low Draft Voltage Adjustment - Harman XXV Installation & Operating Manual

Fig.29

low draft Voltage adjustment

These units are pre-tested at the factory with exactly
10 Volts A.C., 60 Hz. They are checked and adjusted
for firebox tightness, gasket leakage, motor operation
and igniter operation. The XXV is then factory set at a
mid-point adjustment and in most cases will not need any
adjustments. nOte: the factory low draft setting may
not be correct for the unit's permanent installation
conditions.
The control board on the XXV is equipped with a low
draft adjustment port. Located on the control face just
to the left of the igniter light. This voltage adjustment
is provided to allow the unit to be adjusted for the
household voltage where the unit is going to be in
permanent operation. nOte: the line voltage varies
from area to area and often home to home.
The low draft voltage should be adjusted to achieve
the most efficient burn on low burn or "maintenance".
This voltage adjustment allows the installer to change
the low voltage set point approximately 10 volts. This
adjustment should be done by the installer during set
up because a draft meter reading is required to insure
proper set up.
If the unit is not adjusted properly, it does not cause
a safety concern. If the unit is adjusted too high, only
effiency is lost. If the unit is adjusted too low, the low
draft pressure switch will not allow the feed motor or the
igniter to operate.
A simple draft test should be performed after
completing the flue pipe installation. To record the results
for future reference:
low draft Voltage adjustment
Combustion
Motor Speed
Control
Low draft
only set
point.
The small
straight
screwdriver
slot is plastic;
therefore, the
unit can be
adjusted while
in operation.
Draft Meter
Fig.30
1. Plug unit into a 10VAC, 60 HZ outlet.
. Close the hopper lid, front view door, and the ash pan.
Neither pellets or a fire are required for this test.
. With the mode selector in the "OFF" position, turn
the feed adjuster to "TEST".
4. Record the high draft_____in W.C. (Normal is -.50
to -.60) The control will be on the High Draft for a total
of  minutes.
5. After  minutes, the combustion motor will go down to
low draft and the distribution blower will go on high. Allow
approximately 15 seconds to pass for the combustion
motor to slow before checking the low draft.
6. If the low draft is between -.5 and -.45, record the
reading _____ in W.C. If the reading is higher, slowly
turn the set screw counter-clockwise until the draft
lowers. If the reading is lower, very slowly turn the set
screw clockwise until the draft increases.
nOte: the test mode alternates from high to low
draft every 60 seconds. if more time is needed
for draft adjustment, wait until the next low draft
cycle.
nOte: in some cases, the draft may not go as low
as -.35 to -.45 even with the set screw completely
counter-clockwise, ideally, you should just set it as
low as possible.
Draft Meter bolt hole location
is just behind the left front
leg, near the top of the ash
pan area.
XXV Pellet Stove 15