High Limit Operation; Low Limit Operation; Adjustable Differential - Burnham V8 Series Installation & Service Instructions Manual

•
Perform cad cell resistance check as
outlined in control feature. If
resistance is below 1600 OHMS and
burner runs beyond safety cut-out time,
cad cell is good.
• If safety switch shuts down burner and
resistance is above 1600 OHMS, open line
switch to boiler. Access cad cell under
ignitor, clean face of cad cell and see that
cell is securely in socket. Check gasket
around perimeter of ignitor lid for proper
seal. If gasket is missing or damaged,
replace gasket. Room light can effect cad
cell resistance. Reset safety switch.
•
Close line switch to boiler. If burner starts
and runs beyond safety switch cut-off
time, cell is good. If not, install new cell.
v. Power Failure Check: After Flame is
established, turn the power off to the control/
burner. The burner should shut down safely.
When power is restored a normal ignition
sequence should be started.
3. WARNING — Check High Limit Control
— Jumper Thermostat Terminals. Allow burner to
operate until shut-down by limit. Installation is not
considered complete until this check has been made.
W A
J u m p r e m u t s b e e r m
4. Check low water cut off control with water level at
normal water line (see Figure 1D). Raise thermostat
setting to allow burner to operate. Open boiler drain
to allow water level to drop to bottom of sight glass
until burner operation is shut-down by low water
cut-off.
Close boiler drain and refi ll to normal water line.
Burner should automatically restart during fi ll.
Lower thermostat setting.
5. Check operating control on boiler equipped with
tankless heaters. With burner off, draw hot water
until burner starts, then turn off hot water and check
burner shut-down.
J. IF CONTROLS DO NOT MEET
REQUIREMENTS outlined in Paragraph I.,
replace control and repeat checkout procedures.
AQUASTAT SWITCHING ACTION WITHIN L8124C
CONTROL
The switching action within the L8124C control has
three settings:
1. high limit
2. low limit
R N N I G
o v e d a t f r e h t s i c h e c

3. adjustable differential

HIGH LIMIT OPERATION —
The high limit opens and turns off the burner when
the water temperature reaches the set point. The high limit
automatically resets after the water temperature drops past
the set point and through the 10°F differential.
Set the indicator at desired shut-off temperature.
LOW LIMIT OPERATION —
On a temperature rise, with the adjustable differential at
the minimum setting of 10°F, the burner circuit (R-B) breaks
and the circulator circuit (R-W) makes at the low limit set
point. On a temperature drop of 10°F below the set point,
. k
the R-B circuit makes and the R-W circuit breaks.
ADJUSTABLE DIFFERENTIAL —
At any differential setting greater than 10°F, the R-B
make temperature and R-W break temperature will remain
the same-control setting minus 10°F. The R-B break and
R-W make temperature will be the set point temperature
plus the difference between the differential setting and 10°F.
EXAMPLE: Set point of 140°F; differential set at 25°F. On
a temperature rise, R-B will break and R-W will make at
155°F. On a temperature fall, R-B will make and R-W will
break at 130°F.
Set low limit indicator at the minimum temperature
recommended for domestic hot water supply. This setting
must be at least 20°F below high limit setting to prevent one
switch from locking out the other.
Set the differential the desired number of degrees. 25°F
differential gives longest burner cycles.
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