Bradford White MII Series User manual

Save this manual for future reference
Manual 238-47174-00B
SERVICE
MANUAL
Troubleshooting Guide
and Instructions for Service
(To be performed ONLY by
qualified service providers)
Models Covered
by This Manual:
MII50(A)-*-**-(SF,CF,SCF)-***
MII80(A)-*-**-(SF,CF,SCF)-***
MII120(A)-*-**-(SF,CF,SCF)-***
*Denotes kW Rating
**Denotes Warranty Years
***Denotes Wiring Code
IMMERSION AND SURFACE MOUNTED
THERMOSTAT MODELS
COMMERCIAL ELECTRIC ENERGY SAVER
WATER HEATER
MII SERIES
®

Table of Contents Page Service Procedure
Introduction ………………………………………………………………………. 2 - - -
Tools……………………………………………………………………………… 2 - - -
General Information ……………………………………………………………… 3 - - -
Sequence of Operation …………………………………………………………… 10 - - -
Troubleshooting …………………………………………………………………. 13 - - -
Heating Element Testing …………….................................................................... 15 MCE-I
Line Voltage Testing………………...…………………………………………… 16 MCE-II
Fuse Testing…........................................................................................................ 17 MCE-III
High Limit (ECO) Testing (Surface Mounted Thermostats)……………………. 18 MCE-IV
High Limit (ECO) Testing (Surface Mounted Thermostats at 600V)……………. 19 MCE-V
High Limit (ECO) Testing (Contactor Models)…………………………………. 20 MCE-VI
Thermostat Operation Testing (Surface Mounted Thermostats).............................. 21 MCE-VII
Thermostat Operation Testing (Surface Mounted Thermostats at 600V)………… 22 MCE-VIII
Thermostat Operation Testing (Contactor Models)..................................................23 MCE-IX
Contactor Operation Testing……………………………………………………… 24 MCE-X
Thermostat Removal and Replacement (Surface Mounted Thermostats)………… 26 MCE-XI
Thermostat Removal and Replacement (Contactor Models)………………………27 MCE-XII
ECO Removal and Replacement (Contactor Models)……………………………..28 MCE-XIII
ECO Removal and Replacement (Surface Mounted Thermostats at 600V)……….29 MCE-XIV
Heating Element Removal and Replacement …………………………………….. 30 MCE-XV
Anode Inspection and Replacement ……………………………………………… 31 MCE-XVI
Generic Parts List ………………………………………………………………… 32 - - -
Glossary of Terms……………………………………………………………….... 33 - - -
Page 2
This service manual is designed to aid service and maintenance professionals on the function, proper diagnosis and repair of
Bradford White Commercial Electric Water Heaters.
The text and illustrations in this manual provide step by step instructions to facilitate proper operation and troubleshooting
procedures. Contact the Bradford White Technical Support Group immediately if diagnosis can not be made using the
methods described in this service manual.
Introduction
MII Series Commercial Electric
Water Heaters
Tools
- Multi Meter. - Phillips Head Screw Driver.
- 1-½” Deep Well Socket. - Common Screw driver.
- 1-1/16" Deep Well Socket. - Thermometer.
- ¼" Nut Driver. - Drain Hose.
- Other Hand Tools: Pipe Wrench, Channel Locks, Pliers (common & needle nose), Wire cutters, Wire Strippers,
Allen Wrench Set, Flash Light.
2

GENERAL INFORMATION
Bradford White MII Series Commercial Electric water heaters can be manufactured with a choice between two
different types of thermostat control options as follows:
Surface Mounted Thermostats.
Immersion Thermostat (contactor models).
The model number is coded to identify the specific thermostat control system used for a particular unit. Below is
typical model number and coded definitions:
MII50 12 3 SF 018
Wiring Code
C-Contactor (Immersion Thermostat)
CF-Contactor w/Fuse (Immersion Thermostat)
S-Surface Thermostat
SF-Surface Thermostat w/Fuse
SC-Surface Thermostat (w/Contactors)
SCF-Surface Thermostat w/Fuse (w/Contactors)
Warranty
kW Rating
Tank
The wiring code at the end of the model number is used at the factory to facilitate proper construction based on the
electrical characteristics such as voltage, phase, kW rating and amp draw. In the field this information is determined
from the heaters rating plate located on the front of the water heater.
BRADFORD WHITE CORPORATION
200 LAFAYETTE ST. MIDDLEVILLE MI 49333
Model No: MII50123SF018
Serial No: ZB2564812
Cap. 50(gal.)/189.3(liters)
Press: Test 300(psi), Working 150(psi)
Volts 240 Max Temp 180°
Phase Three Amps 29
kW Each 4 Total kW 12 3 Elements
Wattage Rating Based Upon 60 Hz
Page 3
Typical Rating Plate
Located On Front Of Water Heater
Model Number
Electrical Characteristics
3

Page 4
GENERAL INFORMATION
Upper
Control Box
Lower
Control Box
Ground Lug
Terminal Block
Fuse Block(s)
Contactor(s)
High Limit (ECO) Control
Immersion Thermostat
Control
High Limit (ECO)
Direct Immersion Bulb
Thermostat
Direct Immersion Bulb
Heating Elements
Contactor Models
General Controls Layout
Surface Mounted Thermostat Models
General Controls Layout
Upper
Control Box
Lower
Control Box
Ground Lug
Terminal Block
Fuse Block(s)
Heating Elements
Surface Mounted Thermostats
With ECO
4

Page 5
GENERAL INFORMATION
Upper
Control Box
Lower
Control Box
Ground Lug
Terminal Block
Contactor(s)
Surface Thermostats
Heating Elements
High Limit (ECO) Control
600V Surface Thermostat (w/Contactors) Models
General Controls Layout
5

GENERAL INFORMATION
Page 6
Surface Mounted Thermostats
Manual
ECO (high limit)
Reset button
Temperature
control Dial
Surface Mount
Combination Thermostat/
ECO (high limit)
89T Series
Surface mounted thermostats are mounted into a bracket above each heating element. The bracket holds the
thermostat against the side of the tank responding to tank surface temperatures to sense a call for heat, set point
temperature and high limit (ECO) activation. As each element has a dedicated thermostat (for all models excluding
600V), it is possible to sequence the elements by varying the settings on the thermostats.
The thermostat will complete control circuit
voltage upon a call for heat. Likewise, the control
will interrupt control circuit voltage when the water
temperature is sufficient to satisfy the adjustable
temperature limit of control.
Immersion Style Thermostat Control for
Contactor Models
Direct
Immersion
bulb
The high limit (ECO) control will interrupt control circuit voltage
causing the heater to shut down when the high temperature limit of
the control is reached (196°F±4°F). Once the cause for over
heated water has been determined, The control must be manually
reset to restore normal operation.
Immersion Style High Limit (ECO) Control for
Contactor Models
Direct
Immersion
bulb
Manual Reset
Buttons
6

GENERAL INFORMATION
Page 7
Surface Mounted Thermostats (w/Contactors) for
600V Models
600V models use contactors to deliver line voltage to the heating elements. However, rather than the immersion type
high limit and thermostat devices, surface mounted thermostats are used to operate the control circuit of the water
heater.
Temperature
control Dial
Surface Mounted
Thermostat
59T Series
Manual Reset
Button
Surface Mounted
ECO (High Limit)
7

GENERAL INFORMATION
Contactor
1-½” Hex
Screw-in Flange
Terminal Block
Screw
Terminal Block
Zinc Plated Copper or
Incoloy Sheath
Element Rating Ink Stamped
on side of Terminal Block.
Direct Immersion “Screw-in” Type Heating Element
0642
4500W 240V
RC02404524
Page 8
Contactoroperation is achieved by energizing an operating coil in response toa call forheat fromthe immersion
thermostat.Upon a call forheat,one or morecontactorswill energizeall heating elementssimultaneously.The
operating coilsare voltage specific,When contactorreplacementis required be suretoorder the proper operating coil
baseon the voltage rating found on the rating plate located on thefront of thewater heater.
Terminalconnectionsto the
fuseblock and/or terminalblock
Terminal connections to the
heating elements
Terminal connections of
contactor operating coil.
8

GENERAL INFORMATION
Watts
Volts x 1.732 Watts = Amps x Volts Volts
Watts
2
Commonly Used Formulas
240V 1Ph
Ungrounded
Ungrounded
Grounding
BLACK
RED
GREEN
240
120
Common Service Wire
Configurations
Page 9
120
(balanced 3 phase)
Amps =
Watts
Volts
(Single phase)
Amps = Ohms =
120
ABCNeutral
RED BLACK RED
120
120 208
208 208
208 3Ph
120
ABCNeutral
RED BLACK RED
120
120 240
240 240
240 3Ph
277
ABCNeutral
RED BLACK RED
277
277 480
480 480
480 3Ph/277 1Ph
Full Load Current Amps
208 Volt
1 Ph 3 Ph
6
kW
9
12
13.5
15
18
24
27
30
36
45
54
28.8 16.6
43.2 25.0
57.6 33.3
64.9 37.5
72.1 41.6
86.5 50.0
115.4 66.7
129.8 75.0
144.2 83.3
173.0 100.0
216.3 125.0
259.6 150.0
240 Volt 277 Volt 380 Volt 415 Volt 480 Volt 600 Volt
25.0 14.4
37.2 21.6
50.0 28.9
56.2 32.5
62.5 36.1
75.0 43.4
100.0 57.8
112.5 65.0
125.0 72.2
150.0 86.7
187.5 108.3
225.0 130.0
12.5 7.2
18.7 10.8
25.0 14.4
28.1 16.2
31.2 18.0
37.5 21.6
50.0 28.9
56.2 32.5
62.5 36.1
75.0 43.3
93.7 54.1
112.5 65.0
1 Ph
21.6
32.4
43.3
48.7
54.1
64.0
86.6
97.4
108.3
129.9
162.4
194.9
3 Ph
8.3
12.5
16.7
18.8
20.9
25.0
33.4
37.5
41.7
50.1
62.6
75.1
3 Ph
9.1
13.6
18.2
20.5
22.7
27.3
36.4
41.0
45.6
54.7
68.4
82.0
3 Ph
5.8
8.7
11.5
13.0
14.4
17.3
23.1
26.0
28.9
34.6
43.3
52.0
1 Ph 3 Ph 1 Ph 3 Ph
9

SEQUENCE OF OPERATION
MII Series Commercial Electric Water Heaters can use either immersion thermostat (contactor models) or
surface mounted thermostats. Sequence of operation for each configuration is explained below. It would be impractical
to show all wire diagrams applicable to both configurations. A “typical wiring diagram” is illustrated to aid in
understanding the principles of the operating sequence.
Immersion Thermostat (Contactor Models): Configured to use a single immersion thermostat to control one or more
contactors to energize or de-energize all elements simultaneously. In addition, a separate high limit (ECO) control with
manual reset is wired in series with the thermostat. Both controls use a direct immersion bulb inserted into the tank to
sense water temperature. Immersion thermostat and high limit control are mounted to provide temperature adjustment
and manual reset access from the exterior of the unit.
Surface Mounted Thermostats: Surface mounted thermostats are mounted inside the lower control box, in a bracket
above each heating element. The bracket holds the thermostat against the side of the tank responding to tank surface
temperatures to sense a call for heat, set point temperature and high limit (ECO) activation. As each element is controlled
by a dedicated thermostat, it is possible to sequence the elements by varying the settings on the thermostat. However,
600V models w/ surface mounted thermostats operate contactors in the same manner as an immersion thermostat
model, only using surface thermostats to sense the call for heat.
Sequence of operation for each system is explained below.
Sequence of Operation:
Immersion Thermostat (Contactor Models).
Line voltage is applied across terminals of fuse block
or a terminal block. Line voltage continues down and
connects to terminals L1, L2 & L3 of one or more
contactors.
A) Contactor is open (no call for heat), so there is no
voltage across terminal T1, T2 & T3
of contactor.
B) The contactor is controlled by the control circuit
consisting of the immersion thermostat,
ECO (hi limit) and contactor coil.
Page 10
1
2
OR Terminal Block
Fuse Block
Line Voltage
Contactor
Contactor
Coil ECO
(High Limit)
T’stat
When the thermostat calls for heat, contacts close
inside the thermostat completing the circuit through
the ECO and energizing the contactor coil.
The system has two distinct circuits.
1. Power circuit (shown solid line).
2. Control Circuit (shown dotted line).
The energized contactor coil causes the contactor to
close energizing the elements from terminals T1, T2
& T3 of the contactor.
3
When the temperature setting of the thermostat is
reached, the contacts in the thermostat open. This
interrupts current flow through the control circuit de-
energizing the contactor coil.
4
The de-energized contactor coil causes the contactor
to open, interrupting current flow through the
elements. The heater is now in stand-by waiting for
the next call for heat.
5
Heating Elements
10