resideo Aquastat L7224U Manual Del Usuario página 7

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.
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.
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
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 Resideo 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.
Table 4. Thermal Purge Settings.
Minimum value
Not adjustable
120 °F (or OFF)
Not adjustable
1 minute
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.
7
Maximum Value
Not adjustable
160 °F 140 °F (L7248)
Not adjustable
10 minutes
®
CONTROLLER
Default
10 °F
5 °F/minute
2 minutes
69-1720EFS—13