83
X. Operation
C. Boiler Protection Features (continued)
C.
Boiler Protection Features
1.
Supply Water Temperature High Limit
The boiler is equipped with independent automatic reset
and a manual reset High Limit devices. The automatic
reset high limit is provided by a supply manifold mounted
Limit Device. The automatic high limit is set to 200°F.
The Control monitors a supply water temperature sensor
that is also mounted in the supply water manifold and
supplies an internal, manual reset high limit. If supply
water temperature exceeds 190°F, the control begins
to reduce the blower maximum speed setting. If the
temperature exceeds 200°F, a forced recycle results.
If the temperature exceeds 210°F, a manual reset hard
lockout results. Additionally, if the supply temperature
rises faster than the degrees Fahrenheit per second limit
a soft lockout is activated.
2.
High Differential Temperature Limit
The Control monitors the temperature difference between
the return and supply sensors. If this difference exceeds
43°F the control begins to reduce the maximum blower
speed. If temperature difference exceeds 53°F a forced
boiler recycle results. If the temperature difference
exceeds 63°F the control will shut the unit down. The
unit will restart automatically once the temperature
difference has decreased and the minimum off time has
expired.
3.
Low Water Cut Off
(
LWCO)
The Control shuts down the boiler when either the
supply water temperature is too high or supply to return
temperature differential temperature is too high. This
ensures the boiler is shutdown in the event of a low water
level or low water flow condition.
Some codes and jurisdiction may accept these integral
features instead of requiring a low water cutoff. ADHERE
TO ALL LOCAL CODE REQUIREMENTS. Contact
your local code inspector prior to installation. If required, a
LWCO four-position wire harness connection is provided
for an external LWCO kit (p/n 102097-01) to be added.
If the LWCO opens, the boiler will shut down and an
open limit indication and error code is provided. If the
limit installed is a manual reset type, it will need to be
reset before the boiler will operate.
4.
Return Temperature Higher Than Supply Temperature
(Inversion Limit)
The Control monitors the supply and return temperature
sensors. If the return water temperature exceeds the
supply water temperature for longer than a limit time
delay the Control shuts down the boiler and delays
restart. If the inverted temperature is detected more than
five times the boiler manual reset Hard Lockout is set.
This condition is the result of incorrectly attaching the
supply and return piping.
5.
External Limit
An external limit control can be installed between
terminals 11 and 12 on the low voltage terminal strip.
Be sure to remove the jumper when adding an external
limit control to the system. If the external limit opens, the
boiler will shut down and an open limit indication and
error code is provided. If the limit installed is a manual
reset type, it will need to be reset before the boiler will
operate.
6.
Boiler Mounted Limit Devices
The Control monitors individual limit devices: pressure
switch, high limit device, condensate level switch,
Thermal Link, Burner Door Thermostat with manual
reset, low water cutoff (optional), fuel gas pressure
switches (optional) and external limit (optional). If any
of these limits opens, the boiler will shut down and an
individual open limit indication is provided.
7.
Stack High Limit
The Control monitors the flue gas temperature sensor
located in the vent connector. If the flue temperature
exceeds 184°F, the control begins to reduce the maximum
blower speed. If the flue temperature exceeds 194°F, a
forced boiler recycle results. If the flue temperature
exceeds 204°F, the control activates a manual reset Hard
Lockout.
8.
Ignition Failure
The Control monitors ignition using a burner mounted
flame sensor. In the event of an ignition failure:
• APX399 - the control retries five (5) times and
then goes into soft lockout for one hour.
• APX500 and APX800 - the control retries one (1)
time and then goes into hard lockout. Manual reset
is required to resume boiler operation.
9.
Central Heating System Frost Protection
When enabled, Frost Protection starts the boiler and
system pump and fires the boiler when low outside air
and low supply water temperatures are sensed. The
Control provides the following control action when frost
protection is enabled:
Device
Started
Start
Temperatures
Stop
Temperatures
Boiler & System
Pump
Outside Air < 0°F
Supply Water < 45°F
Outside Air > 4°F
Supply Water > 50°F
Boiler
Supply Water < 38°F
Supply Water > 50°F
Table 28: Frost Protection
FROST PROTECTION NOTE
The Control helps provide freeze protection for the boiler water.
Boiler flue gas condensate drain is not protected from freezing.
Since the Control only controls the system and boiler circulators
individual zones are not protected. It is recommended that the
boiler be installed in a location that is not exposed to freezing
temperatures.
Summary of Contents for Apex APX399
Page 65: ...65 VIII Electrical continued Figure 43 Ladder Diagram ...
Page 66: ...66 VIII Electrical continued ...
Page 67: ...67 Figure 44 Wiring Connections Diagram VIII Electrical continued ...
Page 110: ...110 1P 3 1P 2 1P 1 XIII Repair Parts continued 1C 1D 1E ...
Page 116: ...116 XIII Repair Parts continued ...
Page 118: ...118 XIII Repair Parts continued ...
Page 129: ...129 SERVICE RECORD DATE SERVICE PERFORMED ...
Page 130: ...130 SERVICE RECORD DATE SERVICE PERFORMED ...
