Bock Water heaters CE050 Service manual

Page 1
To the Consumer:
Please read these and all component
instructions and keep for future reference.
To the Installer:
Please attach these instructions
next to the water heater.
WARNING
Improper installation, adjustment, alteration,
service or maintenance can cause serious
injury or property damage. Refer to this
manual. For assistance or additional
information, consult a qualified installer or
service agency.
CAUTION
The recommended water temperature for
normal residential use is 120°F/49°F. Outlet
water temperatures may exceed the thermostat
setting. Measure water temperature at the tap
nearest to the water heater.
WARNING
Hotter water increases the risk of scald injury.
Before adjusting the water temperature setting,
read this instruction manual. Temperatures at
which injury occurs vary with the person’s age
and the length of exposure.
The slower reaction time of children, elderly,
and physically or mentally challenged persons
increases the scalding hazard to them. It is
recommended that lower water temperatures
be used where these exposure hazards exist.
Such households may require a temperature
setting less than 120°F to prevent accidental
contact with hot water.
To lower water temperature use point-of-use
temperature limiting devices.
WARNING
Water heater blankets are not recommended
and will void the warranty.
CAUTION
This water heater is not intended for space
heating applications.
THIS MANUAL HAS BEEN PREPARED
TO ACQUAINT YOU WITH THE INSTALLATION,
OPERATION, AND MAINTENANCE OF
YOUR WATER HEATER AND TO PROVIDE
IMPORTANT SAFETY INFORMATION.
INSTALLER RESPONSIBILITIES
Please read all instructions thoroughly before
installing or placing the heater into service.
This unit must be installed by licensed or
authorized installers, or technical personnel
that service water heating equipment. The
heater must be installed in accordance with all
local codes and ordinances.
FAILURE TO FOLLOW THESE INSTRUCTIONS
OR ALL APPLICABLE BUILDING CODES AND
REGULATIONS VOIDS THE WARRANTY
ON THIS WATER HEATER.
Local plumbing and electrical codes must
be followed in the installation of this water
heater. In the absence of a local code use the
UNIFORM PLUMBING CODE and the National
Electric Code, NFPA 70, or the Canadian
Electrical Code CSA C22.1. Local codes may
supersede instructions in this installation
manual.
These instructions are a guide for the
correct installation of the water heater.
The manufacturer will not be liable for
damages caused by failure to comply with
the installation and operating instructions
outlined on the following pages.
HANDLING
Before uncrating, check for shipping damage.
Report any damage to your carrier. Note damage
on bill of lading or delivery receipt and file a
claim.
Installation and Operation Instructions Manual
Commercial Electric Water Heater
Models: CE050, CE080, CE119
Warranty, Registration Card and Parts List are included.
Owner: Please remember to return the Registration Card!
#23582 Rev 1 10/18

Page 2
IMPORTANT SAFETY INSTRUCTIONS
The proper installation, use and servicing of this water heater is very
important to your safety and the safety of others.
This is the safety alert symbol. Statements following this symbol contain
important safety information. Obey all safety messages that follow this
symbol to avoid possible injury or death.
Important safety information will be preceded by the safety alert symbol
and the words DANGER, WARNING, CAUTION, OR NOTICE.
DANGER indicates an imminently hazardous situation which, if not
avoided, will result in serious injury or death.
WARNING indicates a potentially hazardous situation which, if not
avoided, could result in serious injury or death.
CAUTION indicates a hazardous situation which, if not avoided, could
result in minor or moderate injury.
NOTICE calls attention to observe a specified procedure.
SAVE THESE INSTRUCTIONS
DANGER
Water heaters utilizing Liquefied Petroleum gas (LP) are different from
natural gas models. A natural gas heater will not function safely on LP gas
and vice versa. To avoid possible equipment damage, personal injury or
fire: DO NOT connect this water heater to a fuel type not in accordance
with the rating label. These units are only certified for a single fuel type.
DANGER
Failure to properly install the vent and combustion air intake system as
outlined in this manual can result in unsafe operation of the water heater.
To avoid the risk of fire, explosion, or asphyxiation from carbon monoxide,
never operate this water heater unless it is properly vented and has
adequate air supply for combustion and dilution of flue gas. Be sure to
inspect the system for proper installation at initial start-up; and at least
annually thereafter. See the Maintenance section for more information.
IMPORTANT SAFETY INSTRUCTIONS
The proper installation, use and servicing of this water heater is very
important to your safety and the safety of others.
This is the safety alert symbol. Statements following this symbol contain
important safety information. Obey all safety messages that follow this
symbol to avoid possible injury or death.
Important safety information will be preceded by the safety alert symbol
and the words DANGER, WARNING, CAUTION, OR NOTICE.
DANGER indicates an imminently hazardous situation which, if not
avoided, will result in serious injury or death.
WARNING indicates a potentially hazardous situation which, if not
avoided, could result in serious injury or death.
CAUTION indicates a hazardous situation which, if not avoided, could
result in minor or moderate injury.
NOTICE calls attention to observe a specified procedure.
SAVE THESE INSTRUCTIONS
DANGER
Water heaters utilizing Liquefied Petroleum gas (LP) are different from
natural gas models. A natural gas heater will not function safely on LP gas
and vice versa. To avoid possible equipment damage, personal injury or
fire: DO NOT connect this water heater to a fuel type not in accordance
with the rating label. These units are only certified for a single fuel type.
DANGER
Failure to properly install the vent and combustion air intake system as
outlined in this manual can result in unsafe operation of the water heater.
To avoid the risk of fire, explosion, or asphyxiation from carbon monoxide,
never operate this water heater unless it is properly vented and has
adequate air supply for combustion and dilution of flue gas. Be sure to
inspect the system for proper installation at initial start-up; and at least
annually thereafter. See the Maintenance section for more information.

Page 3
TABLE OF CONTENTS
Section I: Specifications .............................................4
Section II: General Information ....................................... 6
Section III: Pre-Installation ...........................................8
Section IV: Installation ..............................................9
Section V: Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Section VI: Maintenance ........................................... 22
Section VII: Troubleshooting......................................... 24
Section VIII: Parts List .............................................. 27
Section IX: Warranty ............................................... 29

Page 4
Figure 1: All Models
Table 1: Dimensions
Model
Number of
Elements
G
degrees
H
degrees
I
degrees
Shipping
Weight
lbs (kg)
CE050-*# 58 57 92 273 (124)
CE080-*# 54 53 72 395 (179)
CE119-*# 50 41 57 521 (236)
* - denotes input (kW) with a number (1-9), see Input Designations table
# - denotes voltage (V) with a letter (A-D), see Voltage Designations table
Input Designations Voltage Designations
13.5 15.0 18.0 24.0 27.0 30.0 36.0 45.0 54.0 208 240 277 480
Number 1 2 3 4 5 6 7 8 9 Letter A B C D
36.80 (93)
Voltage (V)
based on
input - see
Table 3
80 (303)
119 (450)
17.84 (45)
17.84
(45)
32.00 (81)3.81 (10)
3.79 (10)
41.91
(106)
55.91
(142)
30.00 (76)
55.94
(142)
F
inches
(cm)
50 (189) 17.84 (45) 29.89 (76)3.54 (9)
A
inches
(cm)
B
inches
(cm)
C
inches
(cm)
D
inches
(cm)
Actual
Storage
Capacity
gallons
(liters)
46 (174) 24.00 (61) 49.70
(126)
E
inches
(cm)
76 (288)
108 (409)
Input (kW)
64.82
(165)
Nominal
Storage
Capacity
gallons
(liters)
26.00 (66) 64.50
(164)
Table 2: Approved Elements
SECTION I: SPECIFICATIONS
Table 2: Approved Elements
208 240 277 480
4.0 x x x x
4.5 x x x x
5.0 x x x x
6.0 x x x x
Input Rating
(kW)
Voltage Rating (V)
Approved Element Ratings
Heating elements with input and voltage rating
combinations that are not listed in Table 2 shall
not be used with this water heater. All heating
elements in this water heater must contain the
same ratings.
Table 1: Dimensions
CAUTION

Page 5
Table 1: Dimensions
Model
Number of
Elements
G
degrees
H
degrees
I
degrees
Shipping
Weight
lbs (kg)
CE050-*# 58 57 92 273 (124)
CE080-*# 54 53 72 395 (179)
CE119-*# 50 41 57 521 (236)
* - denotes input (kW) with a number (1-9), see Input Designations table
# - denotes voltage (V) with a letter (A-D), see Voltage Designations table
Input Designations Voltage Designations
13.5 15.0 18.0 24.0 27.0 30.0 36.0 45.0 54.0 208 240 277 480
Number 1 2 3 4 5 6 7 8 9 Letter A B C D
36.80 (93)
Voltage (V)
based on
input - see
Table 3
80 (303)
119 (450)
17.84 (45)
17.84
(45)
32.00 (81)3.81 (10)
3.79 (10)
41.91
(106)
55.91
(142)
30.00 (76)
55.94
(142)
F
inches
(cm)
50 (189) 17.84 (45) 29.89 (76)3.54 (9)
A
inches
(cm)
B
inches
(cm)
C
inches
(cm)
D
inches
(cm)
Actual
Storage
Capacity
gallons
(liters)
46 (174) 24.00 (61) 49.70
(126)
E
inches
(cm)
76 (288)
108 (409)
Input (kW)
64.82
(165)
Nominal
Storage
Capacity
gallons
(liters)
26.00 (66) 64.50
(164)
SECTION I: SPECIFICATIONS (cont.)
Table 3: Recovery Capacities
°F 40 50 60 70 80 90 100 110 120 130 140
°C 22.2 27.8 33.3 38.9 44.4 50.0 55.6 61.1 66.7 72.2 77.8
GPH 135 108 90 77 68 60 54 49 45 42 39
LPH 513 410 342 293 256 228 205 186 171 158 147
GPH 151 120 100 86 75 67 60 55 50 46 43
LPH 570 456 380 326 285 253 228 207 190 175 163
GPH 181 145 120 103 90 80 72 66 60 56 52
LPH 684 547 456 391 342 304 274 249 228 210 195
GPH 241 193 161 138 120 107 96 88 80 74 69
LPH 912 729 608 521 456 405 365 332 304 281 260
GPH 271 217 181 155 135 120 108 99 90 83 77
LPH 1026 821 684 586 513 456 410 373 342 316 293
GPH 301 241 201 172 151 134 120 109 100 93 86
LPH 1140 912 760 651 570 507 456 414 380 351 326
GPH 361 289 241 206 181 161 145 131 120 111 103
LPH 1368 1094 912 781 684 608 547 497 456 421 391
GPH 452 361 301 258 226 201 181 164 151 139 129
LPH 1709 1368 1140 977 855 760 684 622 570 526 488
GPH 542 434 361 310 271 241 217 197 181 167 155
LPH 2051 1641 1368 1172 1026 912 821 746 684 631 586
Recovery (GPH & LPH) at Temperature Rise (°F & °C)
4.036.0 5.045.0 4.024.0 4.527.0 5.030.0
6 6 6
6.018.0 6.054.0
9 9 9
Element
Wattage
(kW)
Input
(kW)
13.5 4.5
5.015.0
Number of
Elements
3 3 3
Input
(BTU/hr)
184,248 153,540 122,832 102,360
92,124 81,888 61,416 51,180 46,062

Page 6
SECTION II: GENERAL INFORMATION
OVERVIEW
This manual covers three, six, and nine element commercial electric water heaters. All
models are wired for connection to a three phase delta branch circuit and contain factory
supplied internal fusing. Please reference the installation section of this manual for single
phase applications. All models are UL listed to UL 143 and CAN/CSA C22 No. 11094.
WATER TREATMENT & FILTRATION
In areas where poor water conditions are suspected (i.e. lime, iron, and other minerals), it
is essential that the water be tested and appropriate action taken to prevent damage to the
water heater and ensure the quality of the water.
TEMPERATURE CONTROL
All models are equipped with a digital temperature control that is programmed with a
setpoint range from 100˚F - 182˚F and a fixed, manual reset high limit set at 200˚F. Operating
differentials (subtractive) are 8˚F for the setpoint and 10˚F for the high limit. The temperature
control monitors tank temperature by means of two thermistors located in a single
immersion well, which is located slightly above the highest heating element. Each thermistor
is connected to the back of the temperature control board. The setpoint is factory set to 120˚F
to reduce the risk of scald injury.
CAUTION: Hot water in excess of 120°F can cause scalding!
Bock recommends a thermostatic mixing valve be installed and used according to the
manufacturer’s directions to prevent scalding. Many state and local codes now require
installation of these devices. Point of use temperature may be hotter than the setting on the
water heater thermostat. The mixing valve will ensure potable water temperatures at the
desired set point with a higher degree of accuracy.
APPROXIMATE
TEMPERATURE/TIME
RELATIONSHIPS TO
SCALDING
120°F More than 5 minutes
125°F 1
1⁄2 to 2 minutes
130°F About 30 seconds
135°F About 10 seconds
140°F Less than 5 seconds
145°F Less than 3 seconds
150°F About 1 1⁄2 seconds
155°F About 1 second
Table 4: Scald Temperature/Time Relationships

Page 7
SECTION II: GENERAL INFORMATION (cont.)
ANODE RODS
The anode rods are used as sacrificial elements within the volume of the storage tank. The
purpose of the rods is to protect the inside of the tank against corrosion. Anode rods should
be inspected twice in the first year and at least yearly once a time interval for inspection has
been developed. Water conditions will influence the consumption rate of the anode rods.
Please see the Maintenance section of this manual for instructions on how to change the
anode rods in your water heater.
CAUTION
Hydrogen gas is produced in a hot water system served by the heater that has not
been used for a long period of time (2 weeks or more). Hydrogen gas is extremely
flammable. To reduce the risk of injury under these conditions, it is recommended
that the hot water faucet be opened for several minutes at the kitchen sink before
using any electrical appliance connected to the hot water system. When hydrogen
is present, there will probably be an unusual sound such as air escaping through the
pipe as the water begins to flow. There should be no smoking or open flame near the
faucet at the time it is open.
TEMPERATURE AND PRESSURE RELIEF VALVE (T&P)
CAUTION
To reduce the risk of excessive pressures and temperatures in this water heater, install
temperature and pressure protective equipment required by local codes and no less
than a combination temperature and pressure relief valve certified by a nationally
recognized testing laboratory that maintains periodic inspection of production of listed
equipment or materials, as meeting the requirements for Relief Valves and Automatic
Gas Shutoff Devices for Hot Water Supply Systems, ANSI Z21.22. This valve must be
marked with a maximum set pressure not to exceed the marked maximum working
pressure of the water heater. Install the valve in an opening provided and marked for
this purpose in the water heater, and orient it or provide tubing so that any discharge
from the valve exits only within 6 inches above, or at any distance below, the
structural floor, and does not contact any live electrical part. The discharge opening
must not be blocked or reduced in size under any circumstances.
The T&P valve is factory installed. A discharge drain tube must be installed (responsibility
of the installer) and shall terminate plain, not threaded, 6 inches above the floor drain.
The drain tube material must be approved for temperatures of 120°F or greater and a
pressure of 150 PSI or greater.
BACKFLOW PREVENTER (CLOSED LOOP SYSTEM)
Some local municipal codes and ordinances require the use of these devices on potable
(domestic) water lines. Where backflow preventers are required, it will be necessary to install
a thermal expansion tank (designed for used with potable water) in order to prevent
pressure build up in the water heater and associated piping, which could cause the T&P valve
to discharge. Follow the expansion tank manufacturer’s recommendations when selecting a
tank for your hot water system.
Note: Working pressure of the water heater is 150 PSI. Do not exceed 150 PSI.

Page 8
SECTION III: PRE-INSTALLATION
LOCATION
CAUTION
This water heater must be located in an area where leakage of the tank, water line
connections, or the temperature and pressure relief valve will not result in damage to
the area adjacent to the water heater or to lower floors of the structure. When such
location cannot be avoided, a suitable drain pan must be installed under the water
heater. The drain pan depth must be suitable for draining and collecting water. The
drain pan can be purchased from your plumbing professional. The drain pan must
be piped to an adequate drain and all drain piping must be at least 0.75” in diameter
and pitched for proper drainage.
CAUTION
DO NOT store or use gasoline or other flammable, combustible, or corrosive vapors
and/or liquids in the vicinity of the water heater or any other appliance.
IF YOU SMELL GAS:
• DO NOT try to light any appliance.
• DO NOT touch any electric switch; do not use any telephone in your building.
• Immediately call your gas supplier from a telephone in another building. Follow your
gas supplier’s instructions.
• If you cannot reach your gas supplier, call the fire department.
DO NOT OPERATE THE APPLIANCE UNTIL THE LEAKAGE IS CORRECTED!
CAUTION
Do not drop water heater or lay heater down on its side. Move the water heater into
position by sliding or using an appropriately sized hand truck.
The water heater must be installed indoors. Locate the water heater as close as practical
to the water piping system and leave sufficient clearances for servicing the heater. This
water heater may be installed on combustible flooring. DO NOT install this water heater
on carpeting.
See Tables 5 and 6 for combustible and service clearances.
Top Sides Front Rear
0" 0" 0" 0"
Top Sides
(non-piping)
Side
(T&P Relief Valve) Front Rear
36" 4" 8" 24" 0"
Table 5: Clearance from Combustible Materials
Table 6: Recommended Service Clearances

Page 9
SECTION IV: INSTALLATION
WATER CONNECTIONS
CAUTION
This water heater incorporates fittings that contain a nonmetallic lining. DO NOT apply
heat to these fittings when making sweat connections to the heater. Sweat tubing to
an adapter before securing adapter to any fittings on water heaters.
ALL PIPING SHOULD CONFORM TO LOCAL CODES AND ORDINANCES. It is highly
recommended that unions and shut-off valves are installed at the potable water connections
to allow for isolation and/or movement during service. In addition, all piping should be
adequately insulated with an approved material to minimize heat loss.
CAUTION
THE WATER HEATER MUST BE FILLED WITH WATER BEFORE CONNECTING
ELECTRIC POWER.
1) Close the main water supply valve before continuing with the installation. After the
main water supply is shut-off, relieve the water line pressure by opening a faucet. Once the
pressure has been relieved, close the faucet. The “Cold” and “Hot” potable water connections
are labeled on the water heater.
2) Install a union and shut-off valve on both the cold and hot water sides of the water heater.
3) If a backflow preventer is required in the cold water supply, a properly sized expansion
tank must be installed to control thermal expansion. Do not operate the water heater in
a closed system without installing a thermal expansion tank. Follow the expansion tank
manufacturer’s recommendations when selecting a tank for your system.
4) Following installation of the water lines, open the main water supply valve and fill the
water heater. Open several hot water faucets to relieve air from the system. After water is
flowing through the faucets and the system is void of air, close the faucets and check for
water leaks in the system.
5) Finally, before connecting electric power, remove the element access cover and check for
leaks around all heating elements and plugs (as applicable). Remove the insulation in order
to view the heating elements. All insulation must be repositioned to its original location
upon completion.

Page 10
SECTION IV: INSTALLATION (cont.)
Piping connections for all models are shown in Figures 2.
Figure 2: Piping Connections
PIPING DIAGRAMS

Page 11
PIPING DIAGRAMS
SECTION IV: INSTALLATION (cont.)
Figure 3: One Unit
Figure 4: One Unit with 4-port Storage Tank

Page 12
SECTION IV: INSTALLATION (cont.)
PIPING DIAGRAMS
Figure 5: One Unit with 3-port Storage Tank
Figure 6: Two Units

Page 13
PIPING DIAGRAMS
SECTION IV: INSTALLATION (cont.)
Figure 7: Two Units with 3-port Storage Tank
Figure 8: Three Units

Page 14
SECTION IV: INSTALLATION (cont.)
PIPING DIAGRAMS
Figure 9: Three Units with 3-port Storage Tank
Figure 10: Four Units

Page 15
PIPING DIAGRAMS
SECTION IV: INSTALLATION (cont.)
Figure 11: Four Units with 3-port Storage Tank

Page 16
ELECTRICAL CONNECTIONS
DANGER
Confirm that all electrical connections are unpowered before installing or servicing
electrical components/connections within the water heater.
WARNING
The water heater must be electrically grounded in accordance with local codes or, in
the absence of local codes, with the National Electric Code, NFPA 70, or the Canadian
Electrical Code, CSA C22.1.
Failure to properly wire electrical connections may result in serious physical harm.
THE WATER HEATER MUST BE FILLED WITH WATER BEFORE CONNECTING
ELECTRIC POWER.
All electrical connections on the water heater must be made with copper conductors only.
A separate branch circuit with copper conductors, overcurrent protection, and means for
disconnection must be provided by qualified service personnel. The total wattage load and
voltage requirements for the water heater are specified on the rating label located on the
front of the heater.
The terminal block, internal fusing, contactors, heating elements, and control circuit are pre-
wired at the factory. The electrical enclosure accommodates 1/2” - 2” trade size electrical
conduit connectors. Factory wiring connections may loosen during shipment. Inspect for
loose wires prior to turning on the power supply.
See Figure 12-14 for factory wiring diagrams. Converting from three to single phase may be
done in the field by a qualified service agency. Element conversion (i.e. changing voltage
and wattage) must be done with a UL listed, factory supplied, conversion kit. Contact Bock
Water Heaters for ordering information.
GROUNDING INSTRUCTIONS
A grounding lug is located adjacent to the power supply terminal block. Please refer to Figure
12-14 for wiring diagrams.
BRANCH CIRCUIT SIZING AND WIRE SIZE
The branch circuit must conform to local code requirements. In the absence of local codes,
compliance to the current editions of the National Electric Code (NFPA 70) or the Canadian
Electrical Code (CSA C22.1) is required. Table 7 provides full load current and recommended
overcurrent protection for every voltage, wattage, and phase combination.
CONVERTING TO SINGLE PHASE
Models are factory wired for operation on a three phase circuit. If operation on a single
phase circuit is required, the conversion shall be performed by a qualified installer or service
agency. Prior to connecting electric power, open the enclosure door and locate the power
supply terminal block. Move the blue wires from L3 to L1 (red wires) and the yellow wires
from L3 to L2 (black wires). Refer to the wiring diagrams on the following pages or on the
inside of the enclosure door. 208V/54kW models shall not be converted to single phase.
SECTION IV: INSTALLATION (cont.)
NOTICE: If the unit was converted for operation on a single phase circuit, it must be
noted on the lower right corner of the rating label.

Page 17
SECTION IV: INSTALLATION (cont.)
Table 7
: Full Load Current and Overcurrent Protection
13.5 15.0 18.0 24.0 27.0 30.0 36.0 45.0 54.0
333666999
4.5 5.0 6.0 4.0 4.5 5.0 4.0 5.0 6.0
Full Load Current
(Amps)
64.9 72.1 86.5 115.4 129.8 144.2 173.0 216.3 n/a
Recommended
Overcurrent
Protection Rating
(Amps)
90 100 110 150 175 200 225 300 n/a
Full Load Current
(Amps)
37.5 41.6 50.0 66.7 75.0 83.3 100.0 125.0 150.0
Recommended
Overcurrent
Protection Rating
(Amps)
50 60 70 90 100 110 125 175 200
Full Load Current
(Amps)
56.2 62.5 75.0 100.0 112.5 125.0 150.0 187.5 225.0
Recommended
Overcurrent
Protection Rating
(Amps)
80 80 100 125 150 175 200 250 300
Full Load Current
(Amps)
32.5 36.1 43.4 57.8 65.0 72.2 86.7 108.3 130.0
Recommended
Overcurrent
Protection Rating
(Amps)
45 50 60 80 90 100 110 150 175
Full Load Current
(Amps)
48.7 54.1 64.0 86.6 97.4 108.3 129.9 162.4 194.9
Recommended
Overcurrent
Protection Rating
(Amps)
70 70 80 110 125 150 175 225 250
Full Load Current
(Amps)
28.1 31.2 37.5 50.0 56.2 62.5 75.0 93.7 112.5
Recommended
Overcurrent
Protection Rating
(Amps)
40 40 50 70 80 80 100 125 150
Full Load Current
(Amps)
16.2 18.0 21.6 28.9 32.5 36.1 43.3 54.1 65.0
Recommended
Overcurrent
Protection Rating
(Amps)
25 25 30 40 45 50 60 70 90
208 V
Element Wattage
# of elements
kW
240 V
1 ɸ
3 ɸ
3 ɸ
1 ɸ
277 V 1 ɸ
1 ɸ
480 V
3 ɸ

Page 18
SECTION IV: INSTALLATION (cont.)
Figure 12: Wiring Diagram for 3 Element Model

Page 19
Figure 13: Wiring Diagram for 6 Element Model
SECTION IV: INSTALLATION (cont.)

Page 20
SECTION IV: INSTALLATION (cont.)
Figure 14: Wiring Diagram for 9 Element Model