39
110839-01 -8/20
AP-U
Installation & Service Manual
CA
UT
ION–ALWAYSALLOWABOILER
T
OCOOLBE
F
OREADDINGWA
T
ER
The burner
will not fire until
the
low water
condition
is satisfie
d.
�
Check that the
system is
filled with
water.
�
Check that the
sensor is
inserted
fully into
the
well
and
contact
between its
spring clip and the copper
well tube is ma
d
e.
�
Check that the
control is
tightly clamped
to
the
well.
The Control
is
Sensi
ng
Low Water.
The Boiler h
as
Reached the
T
ar
g
et
T
em
p
erature.
Whe
n
th
e ECONOMY function is active,
th
e control monitors
h
eatin
g
demand
an
d establishe
s
Targe
t boiler
temperature
s below
th
e
high
limit settin
g
to conserve fuel (see “How
Therma
l
Targeting
W
orks
” .
Th
e burner will not fire until
th
e boiler tem
p
erature
drop
s to
th
e automatically calculate
d Targe
t
T
em
p
Differential.
Troubleshooting Flow Chart 1 – Burner Will Not Fire
Does
the
Display
Rea
d
?
YES
The Control
is
Purging
Latent
Heat from
the
Boiler.
The Thermal
Pre
-Purge
feature
holds
off
the
burner until
the
control
determines
if
the
latent
heat
in
the
boiler can satisfy
the h
eat call.
NO
Is
the
Green LED
(TEMP ACTIVE)
NO
On?
The Control
is
Not Powere
d.
The Temp
Active LED will be on at all times
when the
control is
po
were
d.
�
Check
for
120 V
AC on terminals
L1 and L2.
YES
Is
the
Red
LED (LOW
WA
TER)
On?
YES
NO
Is
the
Yellow LED
(HI
T
EMP
)
On?
YES
The Control
is
Sensing High
T
em
p
erature.
The burner
will not fire until
the
boiler water
has dropped
to
the
high
limit
differential
set
-point (10°
below
high
limit setti
ng)
.
�
Check that the high temperature setting
is correct.
NO
Is
the
Yellow LED
(
T
ARGE
T)
On?
YES
NO
Is
the
Th
ermostat
(
T-T) Calling
NO
for Heat?
Is
the
External Zone
(ZC
-ZR) Calling
NO
for Heat?
Is t
he
Low Limit Dial
Set to O
FF
?
YES
When the
low tem
p
erature
setting
is set to
OFF
,
the
HydroStat
will act as a
cold
start control.
The
burner
will not fire unless
there
is
a call from
the
t
h
ermostat
(
T-T)
or an external
z
one
(ZC
-
ZR
)
.
�
Set
thermostat
to call
YES
YES
NO
for
heat.
Burner s
hou
l
d
fire.
�
If
the
boiler
has
a tan
k-
less coil, set
the
Low
Temperature
Limit to
maintain tem
p
erature.
Is
Th
ere
120 V
AC
Between B
1
and
B
2?
YES
The
Control
is O
p
erati
ng
Pr
op
erly.
HydroStat
is
supplying 120 V
AC to
the
burner circuit.
�
Recheck wiring and operation
of burner
and other
limit controls.
NO
Re
p
lace
Control
If
both the red and
yellow LEDs are off a
nd
there
is a call to fire
the
burner,
there
will be
120 V
AC on terminals
B1 and
B
2.
�
If
120 V
AC is not
present, the
control s
hou
l
d
be re
p
lace
d.
Troubleshooting Flow Chart 1 - Burner Will Not Fire
11
Troubleshooting
(continued)
Summary of Contents for AP-U AP-110U-N
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