Honeywell Boiler C User Manual

L7224A,C; L7248A,C,L  
Oil and Electric Boiler  
®
Electronic Aquastat Controllers  
INSTALLATION INSTRUCTIONS  
IMPORTANT  
APPLICATION  
Use of Outdoor Temperature Reset on a tank-  
less coil application requiring a Low Limit setting  
will result in reduced system effectiveness and  
efficiency.  
The L7224A,C and L7248A,C,L 2012 Compliant  
®
Electronic Aquastat Controllers provide electronic  
temperature sensing in a UL limit-rated control with a  
single sensing probe. The L7224A,C and L7248A,C,L  
control the circulator, oil or electric burner or contactor,  
and boiler temperature. The L7224/L7248 is “Outdoor  
Temperature Reset” ready which is enabled when  
connected to the W8735Y1000 wireless or W8735S1000  
wired Outdoor Reset Kit. Outdoor Reset with the L7224/  
L7248 is intended for all applications except for tankless  
coil systems for domestic hot water. Compliance to 2012  
DOE regulation ensures efficiency is maximized without  
interfering with domestic hot water demand.  
SPECIFICATIONS  
Electrical Ratings:  
Voltage: 120 Vac, 60 Hz.  
Power: 7 VA maximum at 120 Vac plus external loads.  
Thermostat current: 100 mA nominal at 24 Vac.  
Burner Relay:  
7.4 A at 120 Vac Full Load Amperage (FLA);  
44.4 A inrush Locked Rotor Amperage (LRA);  
Less Ignition Load: 360 VA.  
The L7224A,C and L7248A,C,L replace the L8124A,  
L8124C, L7124A,C, L7148A and L8148A Controllers.  
The L7224A,C and L7248A,C,L series controls provide  
status and diagnostic information through an LED display  
combined with LED lights as well as EnviraCOM™  
communications enabled thermostats and diagnostic  
tools to enhance the diagnostic process.  
Circulator Relay:  
7.4 A at 120 Vac FLA; 44.4 A inrush LRA.  
Zone Controller (ZC): 7.4 A at 120 Vac FLA;  
44.4 A inrush LRA.  
NOTE: All loads combined cannot exceed 2000 VA.  
Environmental Ratings:  
Temperature: -30 °F to +150 °F (-34 °C to +66 °C).  
Humidity: 0 to 95% relative humidity, noncondensing.  
L7224/L7248 Aquastat Controllers are intended for use  
in residential-type applications.  
Approvals:  
Underwriters Laboratories Inc. Component Recognized.  
Canadian Underwriters Laboratories Inc. Component  
Recognized.  
2012 DOE Compliance and Operation  
Operation of this control may delay the burner operation while the residual heat is  
circulated out of the boiler.  
®
NOTE: This operation may be different than earlier electronic Aquastat  
revisions which did not implement thermal purge.  
68-0281-16  
 
®
L7224A,C; L7248A,C,L OIL AND ELECTRIC BOILER ELECTRONIC AQUASTAT CONTROLLERS  
New Installation  
SENSOR WIRES  
CONTROLLER CASE  
Order well assemblies separately; see Table 1 and form  
no. 68-0040, Immersion Wells and Compression Fittings  
for Temperature Controllers. Boilers usually have tappings  
that allow the well to be mounted horizontally so boiler  
water of average temperature can circulate freely over the  
well.  
BOILER  
IMMERSION  
WELL  
SENSOR  
1. Turn off all power and drain the boiler, if applicable.  
2. If no tapping is provided, prepare properly sized and  
threaded tapping near the top of the boiler.  
3. Sparingly coat the well threads with pipe dope.  
HEAT-CONDUCTIVE COMPOUND  
(OPTIONAL)  
NOTE: Do not attempt to tighten by using the case  
as a handle.  
IMMERSION  
WELL CLAMP  
M16120  
4. Install the well in the boiler tapping and tighten  
securely.  
IMMERSION WELL  
CLAMP SCREW  
5. Refill boiler and check for water leakage.  
6. Loosen but do not remove the well clamp screw.  
7. Fit the case into the well so the clamp on the case  
slides over the flange on the well.  
Fig. 2. Position of sensor in immersion well.  
8. Securely tighten the clamp screw.  
9. Insert the sensor element into the well until it bot-  
toms. See Replacement Sensor Installation section  
for details. (If necessary, slightly bend the wire  
inside the case to hold the sensor against the bot-  
tom of the well.)  
Flush-Mounted Aquastat  
Replacement  
Turn off all power and remove the old control. Refer to the  
cover insert of the old control to identify and tag each  
external lead as it is disconnected. If the old well is  
unsuitable for the new installation, remove it and replace it  
with a suitable new well. If the old well is suitable, use it.  
10. Turn power ON.  
11. Set High Limit, Low Limit and Low Limit Differential  
to the settings recommended by the boiler OEM.  
(See OPERATION section.) (See INSTALLATION  
steps 6 and 7.)  
Well-Mounted Aquastat  
Replacement  
12. On L7248L models, adjust ELL option to match your  
configuration (see OPERATION section, and Fig. 11  
and 13).  
Turn off all power and remove the old control. Refer to the  
cover insert of the old control to identify and tag each  
external lead as it is disconnected. If the old well is  
unsuitable for the new installation, remove it and proceed  
with instructions for new installation. If the old well is  
suitable, use it.  
IMPORTANT  
Best thermal response is obtained with a well  
that snugly fits the sensor. Insert the sensor until  
it rests against the bottom of the well. Use a well  
of correct length and bend the wiring, if neces-  
sary, to hold the bulb against the bottom of the  
well.  
1. Loosen, but do not remove, the well clamp screw on  
the side of the control case.  
2. Position immersion well clamp snugly over the  
flange of the adapter and tighten the clamp screw.  
3. Insert the sensor into the well as shown in Fig. 2 or  
3. (See Replacement Sensor Installation section for  
details.)  
If the well is not a snug fit on the sensor, use the  
heat-conductive compound (furnished with  
TRADELINE models) as follows: Fold the  
®
plastic bag of compound lengthwise and twist it  
gently. Then snip off end of bag and work the  
open end of the bag all the way into the well.  
Slowly pull out the bag while squeezing it firmly  
to distribute compound evenly in the well. Bend  
the wiring, if necessary, to hold the sensor  
against the bottom of the well and to hold outer  
end of the sensor in firm contact with the side of  
the well. See Fig. 2. Wipe excess compound  
from the outer end of the well.  
THERMOSTAT  
TERMINALS  
DISPLAY  
FUSE  
L I N E  
ENVIRACOMTM  
TERMINALS  
SENSOR  
SENSOR HOLES  
CONNECTOR  
M32186  
Fig. 3. Circuit board, showing sensor connection and  
well holes for horizontal mount models.  
3
68-0281—16  
 
®
L7224A,C; L7248A,C,L OIL AND ELECTRIC BOILER ELECTRONIC AQUASTAT CONTROLLERS  
WIRING  
SENSOR WIRES  
BOILER  
WARNING  
Electrical Shock Hazard.  
Can cause serious injury or death.  
Disconnect power supply before making wiring  
connections to prevent electrical shock or  
equipment damage.  
IMMERSION  
WELL  
SENSOR  
HEAT-CONDUCTIVE COMPOUND  
(OPTIONAL)  
All wiring must comply with local electrical codes and  
ordinances. Do not exceed the specifications in the  
Application section when wiring this control. Use wire  
rated for 194 °F (90 °C) or higher.  
M22026  
Fig. 4. Replacement sensor installation.  
IMPORTANT  
The terminals on these Aquastat Controllers are  
approved for use with copper wire only.  
Replacement Sensor Installation  
Follow the appropriate wiring diagrams shown on the  
inside of the front cover of the L7224A,C; L7248A,C,L or  
in Fig. 8–13.  
Turn off all power and:  
1. Carefully disconnect sensor from circuit board by  
pulling gently on the connector.  
2. Gently pull sensor from thermo well and through cir-  
cuit board by pulling on leadwires.  
3. Carefully align replacement sensor with hole in cir-  
cuit board and guide through Aquastat case and  
into well. (See Fig. 5).  
Refer to Fig. 6 for Connections for the optional Outdoor  
Reset Module and the Domestic Hot Water (DHW)  
module. In subsequent wiring diagrams these modules  
will be displayed with a dotted line signifying that they are  
optional.  
4. Make sure sensor is fully seated to bottom of well  
(See Fig. 4). Use a small pencil to measure depth of  
sensor in well, if necessary.  
5. Connect sensor to circuit board by pressing con-  
nector on sensor unit into mating connector on cir-  
cuit board (See Fig. 5).  
6. For remote sensors (flush-mounted Aquastat Con-  
trollers) be sure to use 121571AA Clamp (see  
Accessories) to securely hold sensor in place.  
W8735Y1000 OR W8735S1000  
OUTDOOR RESET MODULE  
(W8735S1000 SHOWN)  
1
2
3 OT OT  
T
T
3
2
1
C7089U1006  
OUTDOOR  
SENSOR  
ENVIRACOMTM  
THERMOSTAT  
TERMINALS  
TERMINALS  
ZR  
L1  
W8735S1008  
DOMESTIC HOT  
WATER MODULE  
T
L2  
T
3
2
1
C2  
B2  
C1  
B1  
ZC  
1
2
3 TS TS  
DISPLAY  
32003971-003  
TEMPERATURE  
SENSOR  
ZR  
L1  
M34961  
SENSOR  
L2  
CONNECTOR  
Fig. 6. Wiring the Outdoor Reset Module and the  
Domestic Hot Water Module.  
RELAYS  
C2  
B2  
C1  
B1  
ZC  
OPERATION  
SENSOR HOLES  
FUSE  
General  
M32187  
The L7224A,C and L7248A,C,L Oil Electronic Aquastat  
Controllers are primary safety limit-rated devices  
designed for use with oil fired boilers with line voltage  
burners and circulators. Many boilers do not include  
wiring or control compartments as part of the design, but  
are provided with an integral, replaceable, immersion well  
that is the mounting hardware for the Aquastat  
Controllers. Wiring to the other controls is done through  
flexible metal conduit.  
Fig. 5. Circuit board, showing sensor connection and  
well holes for vertical mount models.  
Fuse  
The 1 Amp fuse located near the transformer is intended  
to protect the EnviraCOM circuit from incorrect wiring. The  
Aquastat will continue to function should the fuse blow or  
be removed though no EnviraCOM communication will be  
possible on the bus and Err 6 will be displayed. See  
Table 10.  
For boilers that do include a remotely (flush) mounted  
control, the wiring may be completed with conduit or  
routed behind the boiler sheet metal.  
68-0281—16  
4
 
®
L7224A,C; L7248A,C,L OIL AND ELECTRIC BOILER ELECTRONIC AQUASTAT CONTROLLERS  
A separate electromechanical high-limit is not required in  
a system that uses this control to meet Underwriters  
Laboratories Inc. requirements for oil-fired boiler  
assemblies, UL 726.  
Table 3. Adjustable Features.  
Definition  
Display  
HL_  
Hdf  
High Limit.  
On the L7224 models, the High Limit, Low Limit, Low Limit  
Differential, and Anti Short-Cycle time can be adjusted to  
the setting recommended by the boiler OEM. On the  
L7248 models, the High Limit, and Anti Short-Cycle time  
are also adjustable, see “Adjusting Settings”.  
High Limit Differential.  
LL_  
Low Limit. (L7224A, C)  
Ldf  
Low Limit Differential (L7224A, C)  
External Low Limit (L7248L only)  
ELL  
duu  
The overall range of the High Limit is from 130 °F to  
240 °F (54 °C to 116 °C). Select devices may have  
different ranges. Some models have limited ranges on the  
High Limit setpoint; this limited range is listed on the  
device label.  
ZR input configured as external Domestic Hot  
Water (DHW) request (ON/OFF) (L7224A,C/  
L7248L)  
ASC  
otL*  
otH*  
btL*  
bP*  
Anti Short-Cycle Timeout (seconds); “OFF” is  
disabled.  
Some models also have a Low Limit and Low Limit  
Differential adjustment. The range of the Low Limit is from  
110 °F to 220 °F (43 °C to 104 °C). Select devices may  
have different ranges.  
Outdoor Temperature Low (minimum)  
parameter for the outdoor reset curve (°F or °C)  
Outdoor Temperature High (maximum)  
parameter for outdoor reset curve (°F or °C)  
The Zr setting can be set to DHW, Zoning, or for tankless  
coil applications depending on the L7224/L7248.  
Boiler Temperature Low (minimum) parameter  
for outdoor reset curve  
If an Outdoor Reset Module is installed, the reset curve  
can be set by entering the minimum outdoor temperature,  
minimum (boiler) temperature, and maximum outdoor  
temperature on the 3-digit display. The range of the  
minimum outdoor temperature is from -40 °F to 40 °F (-  
40 °C to 4.4 °C) and has a default setting of 0 °F (-18 °C).  
The range of the maximum outdoor temperature is from  
30 °F to 70 °F  
(-1.1 °C to 21.1 °C) and has a default setting of 40 °F. The  
range of the minimum (water or boiler) temperature is  
from 80 °F to 180 °F (26.7 °C to 82.2 °C) and has a  
default setting of 130 °F. See the “Outdoor Reset Module”  
Installation Instructions (form number 69-2335) for more  
information on setting the boiler reset curve and all related  
parameters.  
Boost Period (minutes). “OFF” is displayed if  
Boost is inactive  
bS*  
Boost step (°F or °C) shown only if Boost is  
active (bP=ON)  
UUS*  
tPL**  
tPt**  
Warm Weather Shutdown Temperature  
(°F or °C)  
Thermal Purging Limit Temperature (°F or °C),  
“OFF” if disabled  
Termal Purging Time Delay (minutes), shown  
only if tPL is enabled  
PC  
Pump Cycling (ON / OFF)  
Temperature units (°F or °C)  
F-C  
* Settings available for adjustment on the 3-digit display  
only if a W8735Y1000 or W8735S1000 Outdoor Reset  
Kit is installed.  
**Settings available for adjustment only when the  
W8735Y1000 or W8735S1000 Outdoor Reset Kit is  
NOT installed.  
The L7224A,C and L7248A,C,L are designed for use with  
24 Vac electronic and electromechanical thermostats or  
EnviraCOM™ enabled thermostats, and have screw-type  
terminals for easy field connection.  
Adjusting Settings  
Then press the UP and/or DOWN buttons to move the set  
point to the desired value, to change between °F and °C,  
or to enable (On) or disable (Off) the External Low Limit.  
After 60 seconds without any button inputs, the control will  
automatically return to the RUN mode.  
To discourage unauthorized changing of Aquastat  
settings, a procedure to enter the ADJUSTMENT mode is  
required. To enter the ADJUSTMENT mode, press the  
UP, DOWN, and I buttons (Refer to Fig. 5) simultaneously  
for three seconds. Press the I button until the feature  
requiring adjustment is displayed:  
Display  
In the RUN mode, the Aquastat will flash “bt” (boiler temp)  
followed by the temperature (i.e., 220), followed by °F or  
°C.  
To read boiler settings, press the I key to read the  
parameter of interest. For example, press I and High Limit  
(HL) is displayed, followed by a three-digit number, i.e.,  
220, followed by °F or °C. Pressing the I button again (on  
L7224 models) will display the Low Limit (LL) followed by  
a three-digit number and the corresponding degree  
designator. See Display Readout, Table 4.  
After approximately 60 seconds without any key presses,  
the display will enter a dim display mode. To return to the  
bright display mode, simply press any key.  
5
68-0281—16  
 
 
®
L7224A,C; L7248A,C,L OIL AND ELECTRIC BOILER ELECTRONIC AQUASTAT CONTROLLERS  
has not gone below the Low Limit setting (minus the  
Differential); or, ZR input is not powered with 120  
Vac (only L7248L with ELL set On).  
Table 4. Display readout definitions.  
2. High Limit: Boiler temperature went above the High  
Limit setting and has not dropped below the High  
Limit setting (minus the Differential).  
3. Low Limit: Boiler temperature went below the Low  
Limit setting (minus the Low Limit Differential) and  
has not gone above the Low Limit setting; or, ZR  
input is powered with 120 Vac (only L7248L with  
ELL set On).  
4. Error: The controller has detected an error condition  
(e.g., open sensor) and has shut down the burner  
output. The ZC output is energized. The controller  
continues to monitor the system and automatically  
restarts if the error condition clears. Refer toTable 4.  
Text  
Err  
Description  
Display  
  
  
Error Code (if one is present)  
bT  
Boiler Temperature  
1
HL  
HdF  
LL  
High Limit  
  
  
  
  
  
  
  
  
  
High Limit Differential  
Low Limit (L7224 only)  
Ldf  
tt  
Low Limit Differential (L7224 only)  
Local Thermostat Status  
The operating sequence for the L7224/L7248 is shown in  
Table 6–9.  
ttE  
brn  
Cir  
ZC  
Zr  
EnviraCOM Thermostat Status  
B1 (Burner) output (ON or OFF)  
C1 (Circulator) output (ON or OFF)  
ZC (Zone Control) output (ON or OFF)  
High Limit Controller  
The High Limit opens and turns off the burner when the  
water temperature reaches the setpoint. The High Limit  
automatically resets after the water temperature drops  
past the setpoint and through the Differential. The L7248  
models have High Limit Differential presets of 15 °F  
(8 °C). The L7224 models have High Limit Differential  
presets of 10 °F (6 °C).  
ZR (Zone Request) Call for HEAT (ON or OFF)   
External Low Limit Enabled (L7248L only)  
ELL  
duu  
  
  
ZR Configured as Domestic Hot Water  
Request (L7224, L7248L only)  
Low Limit and Circulator  
Controller  
On a temperature rise, with the adjustable Differential at  
the default setting of 10 °F (6 °C), the burner circuit  
breaks and the circulator circuit makes (assuming no call  
for heat is present) at the Low Limit setpoint. On a  
temperature drop of 10 °F (6 °C) below the Low Limit  
setpoint, the burner circuit makes and the circulator circuit  
breaks. See Fig. 7.  
ASC  
bSP  
dhc  
ot  
Anti Short-Cycle Timeout  
  
  
  
  
  
  
  
  
2
Boiler Set-Point  
3
DHW Module Connected (YES or NO)  
2
Outdoor Temperature  
2
otL  
otH  
btL  
bP  
Outdoor Temperature Low  
2
Outdoor Temperature High  
2
SWITCH BREAKS ON  
TEMPERATURE RISE.  
BURNER TURNS OFF.  
Boiler Temperature Low  
2
HIGH LIMIT  
SETTING  
CIRCULATOR OPERATES  
ON A CALL FOR HEAT.  
Boost Period  
L7224: 10°F (6°C)  
DIFFERENCE  
2
SWITCH MAKES ON  
TEMPERATURE FALL.  
BURNER OPERATES ON A  
CALL FOR HEAT.  
bS  
Boost Step  
L7248: 15°F (8°C)  
DIFFERENCE  
  
  
2
UUS  
1
Warm Weather Shutdown Temperature  
LOW LIMIT  
SETTING  
WITH NO HEATING  
Display shows local setting; not the setting as modified by an  
external enviracom control.  
Settings are viewable only if the outdoor reset module and out-  
door temperature sensor are installed and functioning properly.  
Settings are viewable only if the domestic hot water module  
and sensor are installed and functioning properly.  
DEMAND, SWITCH BREAKS  
10ºF (6ºC)  
DIFFERENCE  
ON TEMPERATURE RISE.  
1
2
SWITCH MAKES ON  
TEMPERATURE FALL,  
BURNER IS ON TO  
MAINTAIN MINIMUM  
WATER TEMPERATURE.  
CIRCULATOR IS OFF.  
3
WHEN WATER REACHES LOW LIMIT SETTING, THE BURNER SHUTS  
OFF OR THE CIRCULATOR PUMP STARTS (WHEN CALLING FOR HEAT).  
1
Operation  
M23364  
The L7224 and L7248 models can be in any of four  
operational states: Normal, High Limit, Low Limit and  
Error. The controller moves back and forth from  
High Limit to Normal to Low Limit state as part of normal  
operation. Only devices having High Limit settings are  
restricted to the High Limit and Normal states. However,  
the controller will enter the Error state when there is an  
abnormal condition. The operating states are:  
Fig. 7. Setpoints and differentials.  
Anti Short-Cycle Feature  
The Anti Short-Cycle feature allows for field selection of a  
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. The range of the Anti Short-  
Cycle time is from OFF to five minutes.  
1. Normal: Boiler temperature went below the High  
Limit setting (minus the Differential) and has not  
exceeded the High Limit setting; or, the boiler  
temperature went above the Low Limit setting and  
68-0281—16  
6
 
®
L7224A,C; L7248A,C,L OIL AND ELECTRIC BOILER ELECTRONIC AQUASTAT CONTROLLERS  
NOTE: This feature is blocked if a Domestic Hot  
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.  
Water demand occurs. Domestic Hot Water  
demands are serviced immediately, without  
any delay.  
NOTE: When the Aquastat is connected to the oil  
primary 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.  
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 to cold start Aquastat models (L7248) and  
will not interfere with domestic hot water call for heat or  
boilers equipped with Honeywell outdoor reset  
ZR-Domestic Hot Water (DHW)  
Request  
The ZR terminal can be selected to service an indirect  
water heater heat request. This parameter is set via the 3  
digit display (see Adjusting Settings section of this  
document). A heat request via the ZR 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 #69-2335 for more information).  
accessories. For warm start models 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:  
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.  
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.  
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.  
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".  
Table 5. Thermal Purge Settings.  
Parameter name  
Boiler temperature drop  
Minimum value  
Not adjustable  
120 °F (or OFF)  
1 minute  
Maximum Value  
Not adjustable  
160 °F  
Default  
10 °F  
Thermal purge temperature limit  
Thermal purge temperature rate of drop  
Thermal purge time delay  
140 °F (L7248)  
5 °F/minute  
2 minutes  
Not adjustable  
10 minutes  
Thermal Purge and Domestic Hot  
Water  
The thermal purge feature is automatically disabled  
whenever there is a call for domestic hot water either from  
the Zr terminal or from the DHW Module to insure hot  
water is available in a timely manner. See “ZR-Domestic  
Hot Water (DHW) Request” on page 7.  
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.  
TROUBLESHOOTING  
When attempting to diagnose system performance,  
reference to the LED display can help to identify specific  
areas not working properly. The LED display will scroll  
Err, followed by a digit (1-8). Refer to Table 10 and 11 for  
a description of each error and suggested actions.  
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.  
7
68-0281—16  
 
 
®
L7224A,C; L7248A,C,L OIL AND ELECTRIC BOILER ELECTRONIC AQUASTAT CONTROLLERS  
LINE VOLTAGE INDIRECT  
TANK AQUASTAT  
L1  
(HOT)  
W8735Y1000 OR  
W8735S1000  
INDIRECT  
TANK  
CIRCULATOR  
L1  
(HOT)  
L2  
1
2
3 OT OT  
1
L2  
C7089U  
OUTDOOR  
SENSOR  
2
T
T
3
2
1
SENSOR  
ZR  
L1  
LINE  
L2  
VOLTAGE  
CIRCULATOR  
C2  
B2  
C1  
B1  
ZC  
LINE  
VOLTAGE  
OIL BURNER  
RELAY  
1
2
OUTDOOR RESET MODULE IS OPTIONAL. W8735S1000 WIRED OUTDOOR  
RESET MODULE SHOWN.  
FOR BEST PERFORMANCE SET DUU=”ON”.  
M32023A  
Fig. 8. L7224A,C; L7248L single heat zone with indirect water tank and circulators. Optional Outdoor Reset  
Module.  
68-0281—16  
8
 
®
L7224A,C; L7248A,C,L OIL AND ELECTRIC BOILER ELECTRONIC AQUASTAT CONTROLLERS  
Table 6. L7224/L7248 Controller Operating Sequence.  
Action  
System Response  
Thermostat calls for heat.  
Circulator starts when water temperature is above Low Limit setting (if  
applicable) or above the Thermal Purge Temperature Limit (tPL) if  
Thermal Purge is enabled. Boiler temperature is checked. Burner  
starts when water temperature is below High Limit setting minus the  
differential or at or below the Thermal Purge Temperature Limit (tPL)  
for cold start boilers if the Thermal Purge Temperature Limit is  
enabled. If tPL is enabled, the burner may also start if the boiler  
temperature is cooling at 10 ºF or greater per minute or the Thermal  
Purge Time Delay (tPt) has expired.  
If Anti Short-Cycle Time is enabled, the burner does not start until the  
set Anti Short-Cycle Time between cycles expires after the previous  
call for heat was satisfied.  
Boiler temperature exceeds the High Limit.  
Thermostat is satisfied.  
Burner is turned off. Burner restarts when the water temperature  
drops below the High Limit setting minus the Differential. If Thermal  
Purge is enabled, the burner is turned on when either the Thermal  
Purge Temperature Limit is reached, the Thermal Purge Time Delay  
has expired or the boiler temperature cooling rate exceeds 10 ºF/  
minute.  
Circulator and burner turn off.  
Boiler temperature drops below the Low Limit Burner is turned on, Circulator is turned off. Burner stops when the  
setting minus the differential (if applicable).  
water temperature exceeds the Low Limit setting. Power to Zc is  
removed.  
Error condition  
1-5.  
If an error condition is detected, all outputs except ZC are shut down.  
Burner is off. Control continues to function and restarts when error is  
corrected.  
During the error check sequence, the system checks for drift in the  
sensor and corrosion in the connections.  
Error condition 6.  
Error condition 7.  
EnviraCOM communication is not available.  
The control has reset the High Limit, Low Limit and Differential setting to  
a default setting and will continue to run at those settings.  
Performance of the system will be degraded.  
Error condition 8.  
If the error condition is detected, all outputs except ZC are shut down.  
Burner is off. Control continues to function and restarts when all three  
user keys have been pressed longer than 60 seconds.  
Error condition 9*.  
Error condition 10*.  
System continues to run with no outdoor reset functionality  
System continues to run with outdoor reset parameters enabled as  
programmed. Error cleared automatically.  
Error condition 11*.  
System continues to run with boiler temp set to High Limit.  
* Error condition only available when the Outdoor Reset Module is installed.  
Table 7. L7224/L7248 Controller Operating Sequence with multiple zones connected through the ZR terminal.  
Action  
System Response  
Zone Request (ZR) terminal is connected to Boiler temperature is checked. Burner starts when water temperature  
L1 (Zone calls for heat).  
is below High Limit setting or at or below the Thermal Purge  
Temperature Limit (tPL) for cold start boilers if the Thermal Purge  
Temperature Limit is enabled. If tPL is enabled, the burner may also  
start if the boiler temperature is cooling at 10 ºF or greater per minute  
or the Thermal Purge Time Delay (tPt) has expired. Anti Short-Cycle  
Time is applied, see Table 6.  
Boiler temperature exceeds the High Limit.  
Burner is turned off. Burner restarts when the water temperature  
drops below the High Limit setting minus the Differential. If Thermal  
Purge is enabled, the burner is turned on when either the Thermal  
Purge Temperature Limit is reached, the Thermal Purge Time Delay  
has expired or the boiler temperature cooling rate exceeds 10 ºF/  
minute.  
Zone Request input is de-energized (Zones  
are satisfied).  
Burner turns off.  
Boiler temperature drops below the Low Limit Burner turns on and Zone Control is de-energized. Burner turns off  
setting minus the differential (if applicable).  
and Zone Control is re-energized when the water temperature  
exceeds the Low Limit setting.  
9
68-0281—16  
 
®
L7224A,C; L7248A,C,L OIL AND ELECTRIC BOILER ELECTRONIC AQUASTAT CONTROLLERS  
.
Table 8. Controller Operating Sequence with External Low Limit device connected trough the ZR terminal.  
Action  
System Response  
Zone Request (ZR) terminal is connected to Boiler temperature is checked. Burner starts when water temperature  
L1 (External Low Limit call for heat).  
is below High Limit setting. Circulator turns off.  
Boiler temperature exceeds the High Limit.  
Burner is turned off. Burner restarts when the water temperature  
drops below the High Limit setting minus the Differential.  
Zone Request input is de-energized (External Burner is turned off.  
Low Limit is satisfied).  
Table 9. L7224 Controller Operating Sequence with Domestic Hot Water connected trough the ZR terminal.  
Action  
System Response  
Zone Request (ZR) terminal is connected to Boiler temperature is checked. Burner starts when water temperature  
L1 (Domestic Hot Water calls for heat).  
Boiler temperature exceeds the High Limit.  
is below High Limit setting.  
Burner is turned off. Burner restarts when the water temperature  
drops below the High Limit setting minus the Differential.  
Zone Request input is de-energized  
(Domestic Hot Water is satisfied).  
Burner is turned off.  
Table 10. LED Error Codes.  
Aquastat  
EnviraCOM  
Alarm  
Error Code  
Cause/Action  
Aquastat sensor fault; check water sensor.  
ECOM fault; check EnviraCOM™ wiring.  
Err1  
Err2  
Err3  
Err4  
Err5  
18  
18  
Excessive electrical noise or frequency out of range. Hardware fault; replace controller.  
B1 fault; check B1 wiring/voltage.  
18, 58  
64  
Low Line; check L1-L2, 110 Vac.  
59  
a
Warning: Fuse; check ECOM wires, replace fuse.  
92  
Err6  
Err7  
Warning: EEPROM, HL, LL, Hdf, Ldf; reset to default values.  
N/A  
b
Repeated B1 fault (voltage present at B1 when output is turned off); check B1 wiring/voltage. 25  
Err 8  
a
Warning: Outdoor Reset System failure; communication to Outdoor Reset Module lost,  
Outdoor Reset Module failure, multiple outdoor temperature sensors detected on the bus, or  
outdoor temperature sensor failure. Check EnviraCOM wiring (1, 2, 3), check sensor wiring.  
50, 53, 149  
Err9  
a
a
Warning: Boost Failure; Boost Mode active at least once per cycle for the last 60 consecutive 150  
cycles. Check Outdoor Reset curve settings.  
Err 10  
DHW Module/Sensor failure; communication to DHW Module lost, DHW Module failure, or 146, 147,  
Err 11  
a
temperature sensor failure. Check EnviraCOM wiring (1, 2, 3), check sensor wiring.  
148  
Warnings are generated to enunciate the system is not operating optimally, but the Aquastat is still operating and  
maintaining boiler temperature. In the instance where an Outdoor Reset Module is used, the warnings may indicate a  
reset curve setting error one or more features is not running optimally, and the Aquastat is reverting to default settings  
or has stopped running the Outdoor Reset algorithms. The warnings are cleared when the issue(s) is resolved.  
To clear Err 8 condition, depress and hold all three user keys simultaneously for 60 seconds. Err 8 condition clears  
and display returns to normal. Err 8 condition is designed to catch welded relays on the Aquastat and will normally  
only occur near end of life for the control. If Err 8 condition has occurred early in the controls life, be sure to check for  
voltage feedback to B1 when B1 should be off and check current draw on b terminal to be sure oil burner is not draw-  
ing excessive current. Err 8 condition will keep repeating if B1 fault is not cleared.  
b
Table 11. Troubleshooting Guide  
System  
Diagnostic  
Condition  
Condition  
Check  
Action  
Turn system power on.  
Boiler is cold, Display is OFF. 120 Vac System power.  
house is cold.  
Display is ON.  
24 Vac T-T  
No 24 V; replace control.  
24 V present; disconnect  
thermostat, short T-T.  
Boiler starts, check wiring and thermostat.  
120 Vac at B1-B2  
Refer to Err on display.  
10  
If no, replace control.  
If yes, check burner and wiring.  
68-0281—16  
 
®
L7224A,C; L7248A,C,L OIL AND ELECTRIC BOILER ELECTRONIC AQUASTAT CONTROLLERS  
Table 11. Troubleshooting Guide  
Diagnostic  
System  
Condition  
Condition  
Check  
Action  
Boiler is hot,  
house is cold.  
Display is ON.  
120 Vac at C1-C2  
120 Vac at C1-C2, check wiring to pump.  
Wiring OK, is pump running?  
If not, replace the pump.  
If pump is running, check for trapped air or  
closed zone valves.  
Boiler below the Low Limit  
temperature, wait for boiler to go  
above Low Limit temperature.  
Boiler above LL? If yes, check for  
120 Vac between ZC and L2.  
If no 120 Vac, replace control.  
If yes, check zone relays, circulators and  
wiring.  
ELL setting (L7248L only)  
Set ELL to Off for multizone system (see Fig.  
11).  
Set ELL to On for External Low Limit (see  
Fig. 13).  
Boiler above LL? If yes, check 120  
Vac at ZR-L2 (only L7248L with  
ELL set On)  
If no 120 Vac, check C1-C2 (see above).  
If yes, check the External Low Limit control.  
Boiler is hot,  
no hot potable  
water.  
Display is ON.  
Boiler Demand signal from the  
water heater (either 120 Vac at  
ZR-L2, or 0 Vac on T-T; depends  
on installation and “duu” setting)  
24 Vac on T-T (or 0 Vac on ZR-L2), check  
wiring to water heater  
Wiring OK, check the water heater  
“duu” setting  
Set duu to ON if 120 Vac water heater  
demand is connected to ZR  
Set duu to OFF if open/closed water heater  
demand is connected to T-T  
Check DHW Module and DHW  
Sensor  
DHW Module not properly connected and/or  
DHW Sensor improperly positioned  
TO ADDITIONAL R845A  
RELAYS FOR OTHER ZONES  
ZONE 2  
CIRCULATOR  
LOW  
VOLTAGE  
THERMOSTAT  
1
2
L1  
L7224  
L2 (HOT)  
R845A RELAY ZONE 2  
T
T
6
5
3
2
1
3
SENSOR  
4
1
ZR  
L1  
LINE  
2
VOLTAGE  
L2  
CIRCULATOR  
C2  
B2  
C1  
B1  
ZC  
ZONE 2  
LOW VOLTAGE  
THERMOSTAT  
LINE  
VOLTAGE  
OIL BURNER  
RELAY  
1
2
POWER SUPPLY. PROVIDE DISCONNECT  
MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
CONTROL CASE MUST BE CONNECTED  
TO EARTH GROUND. USE GROUNDING  
SCREW PROVIDED.  
M27115  
Fig. 9. L7224A,C multizone system with circulator connections.  
11  
68-0281—16  
 
®
L7224A,C; L7248A,C,L OIL AND ELECTRIC BOILER ELECTRONIC AQUASTAT CONTROLLERS  
LINE VOLTAGE  
W8735Y1000 OR  
W8735S1000  
INDIRECT  
TANK AQUASTAT  
3
2
1
1
2
3 OT OT  
C7089U1006  
OUTDOOR  
SENSOR  
6
TH9421C  
INDIRECT  
TANK  
CIRCULATOR  
R7184/R7284  
L1  
(HOT) L2  
L2  
T
2
1
3
1
T
T
LIMIT  
L1  
L7224  
3
L2  
2
1
T
3
2
1
5
3
BURNER  
MOTOR  
ENVIRACOM™  
TERMINAL  
BURNER  
MOTOR  
SENSOR  
7
3
3
IGNITER  
VALVE  
IGNITER  
VALVE  
ZR  
L1  
LINE  
VOLTAGE  
CIRCULATOR  
L2  
C2  
B2  
C1  
B1  
ZC  
4
TO REMOTE  
ALARM  
CIRCUIT  
CAD  
CELL  
CAD  
CELL  
2
JUNCTION  
BOX  
LEGEND  
SCREW TERMINAL  
1/4 IN. (6 MM) QUICK CONNECT TERMINAL  
SOLDERLESS WIRE CONNECTION  
5
6
ENVIRACOM™ TERMINAL 3 IS ALSO THE FIRST THERMOSTAT TERMINAL.  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
OPTIONAL OUTDOOR RESET MODULE AND OUTDOOR SENSOR.  
W8735S1000 WIRED OUTDOOR RESET MODULE SHOWN.  
OPTIONAL FEATURE ON SELECT MODELS.  
REFER TO DEVICE LABEL FOR WIRE COLOR CODE.  
VALVE IS OPTIONAL ON SPECIFIED MODELS.  
2
3
4
7
DUU MUST BE SET TO “ON” ON THE AQUASTAT.  
M32025B  
Fig. 10. L7224A,C single zone system with circulator and indirect water tank with EnviraCOM™ thermostat.  
68-0281—16  
12  
 
®
L7224A,C; L7248A,C,L OIL AND ELECTRIC BOILER ELECTRONIC AQUASTAT CONTROLLERS  
ELL=OFF  
TO ADDITIONAL R845A  
RELAYS FOR OTHER ZONES  
CIRCULATOR  
ZONE 2  
1
L1  
(HOT) L2  
R845A RELAY ZONE 2  
6
5
3
4
1
2
ZONE 2  
LOW VOLTAGE  
ENVIRACOM  
TERMINALS  
THERMOSTAT  
4
LOW VOLTAGE  
THERMOSTAT  
W8735Y1000 OR  
W8735S1000  
2
L7248L  
T
T
1
2
3 OT OT  
3
2
1
3
C7089U1006  
OUTDOOR  
SENSOR  
SENSOR  
ZR  
W8735S1008  
5
DOMESTIC HOT  
WATER MODULE  
L1  
L2  
C2  
B2  
C1  
B1  
ZC  
LINE  
VOLTAGE  
CIRCULATOR  
1
2
3 TS TS  
LINE  
VOLTAGE  
OIL BURNER  
RELAY  
32003971-003  
TEMPERATURE  
SENSOR  
1
2
3
4
5
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
CONTROL CASE MUST BE CONNECTED TO EARTH GROUND. USE GROUNDING SCREW PROVIDED.  
OPTIONAL OUTDOOR RESET MODULE AND OUTDOOR SENSOR. W8735S1000 WIRED OUTDOOR RESET MODULE SHOWN.  
ENVIRACOM TERMINALS.  
OPTIONAL DOMESTIC HOT WATER MODULE AND TEMPERATURE SENSOR.  
M29655A  
Fig. 11. L7248L multizone system with circulator connections.  
13  
68-0281—16  
 
®
L7224A,C; L7248A,C,L OIL AND ELECTRIC BOILER ELECTRONIC AQUASTAT CONTROLLERS  
W8735Y1000 OR  
W8735S1000  
W8735S1008  
MULTI-ZONE  
RELAY PANEL  
1
2
3 TS TS  
1
2
3 OT OT  
C7089U  
OUTDOOR  
SENSOR  
7
6
32003971-003  
TEMPERATURE  
SENSOR  
T
T
9
8
R7184/R7284  
L1  
1
(HOT) L2  
T
T
LIMIT  
L1  
L7224  
3
L2  
2
1
T
T
3
2
1
5
3
BURNER  
MOTOR  
ENVIRACOM™  
TERMINAL  
BURNER  
MOTOR  
SENSOR  
3
3
IGNITER  
VALVE  
IGNITER  
VALVE  
ZR  
L1  
L2  
C2  
B2  
C1  
B1  
ZC  
LINE  
VOLTAGE  
CIRCULATOR  
4
TO REMOTE  
CAD  
CELL  
CAD  
CELL  
ALARM  
CIRCUIT  
2
JUNCTION  
BOX  
LEGEND  
SCREW TERMINAL  
1/4 IN. (6 MM) QUICK CONNECT TERMINAL  
SOLDERLESS WIRE CONNECTION  
6
OPTIONAL OUTDOOR RESET MODULE AND OUTDOOR SENSOR.  
W8735S1000 WIRED OUTDOOR RESET MODULE SHOWN.  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
7
8
OPTIONAL DOMESTIC HOT WATER MODULE.  
OPTIONAL FEATURE ON SELECT MODELS.  
2
3
4
5
WIRE ONLY THE ENVIRACOM TERMINALS (1, 2, 3) ON OIL PRIMARY  
IF CONNECTING TO REMOTE DIAGNOSTICS, OTHERWISE CONNECT  
A JUMPER BETWEEN THE TT TERMINALS.  
REFER TO DEVICE LABEL FOR WIRE COLOR CODE.  
VALVE IS OPTIONAL ON SPECIFIED MODELS.  
9
ZONE PANEL TERMINALS MAY HAVE DIFFERENT LABEL. CHECK  
PANEL MANUFACTURER SPECIFICATIONS FOR WIRING INSTRUCTIONS.  
M32024A  
ENVIRACOM™ TERMINAL 3 IS ALSO THE FIRST THERMOSTAT TERMINAL.  
Fig. 12. L7224/L7248 multizone system with Outdoor Reset and Domestic Hot Water Modules (indirect tank  
applications).  
68-0281—16  
14  
 
®
L7224A,C; L7248A,C,L OIL AND ELECTRIC BOILER ELECTRONIC AQUASTAT CONTROLLERS  
ELL=ON  
1
L2 L1 (HOT)  
L6006  
R
LOW LIMIT  
CONTROLLER  
W
B
LOW  
VOLTAGE  
THERMOSTAT  
2
L7248L  
T
T
3
2
1
SENSOR  
ZR  
L1  
L2  
LINE  
VOLTAGE  
CIRCULATOR  
C2  
B2  
C1  
B1  
ZC  
LINE  
VOLTAGE  
OIL BURNER  
RELAY  
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
CONTROL CASE MUST BE CONNECTED TO EARTH GROUND.  
USE GROUNDING SCREW PROVIDED.  
M27113  
Fig. 13. L7248L External Low Limit connections.  
15  
68-0281—16  
 
®
L7224A,C; L7248A,C,L OIL AND ELECTRIC BOILER ELECTRONIC AQUASTAT CONTROLLERS  
Automation and Control Solutions  
Honeywell International Inc.  
1985 Douglas Drive North  
® U.S. Registered Trademark  
© 2013 Honeywell International Inc.  
68-0281—16 M.S. Rev. 09-13  
Golden Valley, MN 55422  
Printed in United States  
customer.honeywell.com  
 

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