Honeywell L7224U Manual Del Usaurio página 7

Anti Short-Cycle Feature
The Anti Short-Cycle feature allows for field selection
of a minimum delay time between burner cycles.
Should a call for heat occur following the end of the
previous heat cycle and before the Anti-Short Cycle
delay time is expired, the circulator will be allowed to
run, but the burner will be held off until the time has
elapsed.
NOTE: The Anti Short-Cycle feature is blocked if
DHW demand occurs. DHW demands are ser-
viced immediately, without any delay.
NOTE: When the Aquastat is connected to the oil pri-
mary and/or thermostat via the EnviraCOM
bus, the Anti Short-Cycle time does not apply
to recycle events such as loss of airflow or
flame. It applies only to loss of demand.
ZR-Domestic Hot Water (DHW)
Request
The ZR terminal on the L7224U can be selected to
service an indirect water heater heat request. This
parameter is set via the 3 digit display (see "Adjusting
Settings" on page 5). A heat request via the ZC
terminal will have priority over all other features such
as the Anti-Short Cycle feature or those enabled by the
Outdoor Reset Module (See form 69-2235 for more
information).
Frost Protection
The Frost Protection function protects the boiler and
potentially the boiler plumbing from possible damage
which may occur should the water in the system begin
to freeze. The Frost Protection feature is enabled only
in the L7248 (cold start models). The feature default
setting is enabled (ON), but can be disabled using the
3-digit display. See "Adjusting Settings" on page 5.
When the Boiler temperature drops to the Frost
Protection Limit temperature (fixed 40 °F), the burner
is forced on. The Circulator and ZC outputs remain in
the same state as before the Frost Protection function
was enabled. They can be either ON or OFF during the
Frost Protection cycle.
Parameter name
Boiler temperature drop
Thermal purge temperature limit
Thermal purge temperature rate of drop
Thermal purge time delay
Pump Cycling
The Pump Cycling feature exercises the system pump
for 15 seconds after a non-adjustable five day period
of no boiler activity. The Pump Cycling feature default
setting is enabled (ON) but can be disabled (OFF)
using the 3-digit display. See "Adjusting Settings" on
page 5.
L7224U OIL AND ELECTRIC BOILER ELECTRONIC AQUASTAT
Table 4. Thermal Purge Settings.
Minimum value
Not adjustable
120 °F (or OFF)
Not adjustable
1 minute
7
When the Boiler temperature reaches the Frost
Protection Limit temperature plus a fixed 10 ° F
differential, the burner is turned off unless requested
to stay on due to a different demand.
Thermal Purge Operation
The intent of thermal purge is to insure usable
residual heat in the boiler is circulated until it is
sufficiently depleted from the system before the
burner is allowed to fire. To that end, on a call for heat,
the burner is held off while the circulator runs until the
boiler temperature drops to the thermal purge
temperature or a time delay is exceeded. Both of these
parameters are adjustable. When the boiler
temperature reaches the thermal purge temperature,
the burner is allowed to fire. Thermal purge is only
applied when the low limit is set to OFF and will not
interfere with a domestic hot water call for heat or
boilers equipped with Honeywell outdoor reset
accessories. For applications where a Low Limit must
be set, thermal purge is not applied.
In addition to the thermal purge temperature and
thermal purge time delay parameters, two other
conditions release the Aquastat from thermal purge in
order to maintain comfort in the space:
• The boiler temperature has dropped 10 °F from the
beginning of the thermal purge.
• Boiler temperature is cooling at a rate greater than
5 °F/minute while the circulator is running.
The thermal purge feature applies to single zone as
well as multi-zone applications.
Thermal Purge Settings
Some thermal purge parameters are configurable
using the 3 digit display. See "Adjusting Settings" on
page 5. Thermal purge may be disabled by setting the
thermal purge temperature limit to "OFF".
Thermal Purge and Domestic Hot
Water
The thermal purge feature is automatically disabled
whenever there is a call for domestic hot water from
the Zr terminal to ensure hot water is available in a
timely manner. See "ZR-Domestic Hot Water (DHW)
Request" on page 7.
Maximum Value
Not adjustable
160 °F
Not adjustable
10 minutes
CHECKOUT
Put the system into operation and observe at least one
complete cycle to make sure that the controller
operates properly. See TROUBLESHOOTING section
to use LED to assist in determining system operation.
®
CONTROLLER
Default
10 °F
140 °F (L7248)
5 °F/minute
2 minutes
69-1720EFS—11