10
NO
YES NO
Is the
Thermostat
(T-T) Calling
for Heat?
Is There
120 VAC
Between B1
and B2?
NO
Is the
External Zone
(ZC-ZR) Calling
for Heat?
NO
Is the
Low Limit Dial
Set to OFF?
YES
N
O
YES
I
s the
Red LED
(
LOW WATER)
On?
The Control is
S
ensing
L
ow Water.
CAUTION – ALWAYS ALLOW A BOILER TO COOL BEFORE ADDING WATER
The burner will not fire until the low water condition is satisfied.
Check that the system is filled with water.
Check that the sensor is inserted correctly into well.
NNoottee
: The use of heat-conductive grease may interfere with the
contact between the spring clip and the copper well tube.
Check that the control is tightly clamped to the well.
Is the
Yellow LED
(HI TEMP)
On?
The Control is
Sensing High
Temperature.
If both the red and yellow LEDs are off and
there is a call to fire the burner, there will be
120 VAC on terminals B1 and B2.
If 120 VAC is not present, the control should
be replaced.
HydroStat is supplying 120 VAC to the burner circuit.
Recheck wiring and operation of burner and other limit controls.
The Control
is Operating
Properly.
Replace
Control
The burner will not fire until the boiler water has dropped to the
high limit differential set-point (10° below high limit setting).
Check that the high temperature setting is correct.
Troubleshooting Flow Chart 1 – Burner Will Not Fire
Y
ES
Y
ES
N
O
Is the
Yellow LED
(TARGET)
On?
The Boiler has
Reached the
Target
Temperature.
When the ECONOMY function is active, the control monitors heating
demand and establishes Target boiler temperatures below the high
limit setting to conserve fuel (see “How Thermal Targeting Works”
on page 7). The burner will not fire until the boiler temperature
drops to the automatically calculated Target Temp Differential.
YES
NO
Is the
Green LED
(TEMP ACTIVE)
O
n?
The Control is
Not Powered.
T
he Temp Active LED will be on at all times when the control is
powered.
Check for 120 VAC on terminals L1 and L2.
YES
NO
When the low temperature
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 thermostat
(T-T) or an external zone
(ZC-ZR).
Set thermostat to call
for heat. Burner should
fire.
If the boiler has a tank-
less coil, set the Low
Temperature Limit to
maintain temperature.
YES
Does the
Display Read
?
The Control is
Purging Latent
Heat from the
Boiler.
The Thermal Pre-Purge feature holds off the burner until the
c
irculator has purged the boiler temperature down to 135°F.
N
O
Y
ES
(4 pages)
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