Bradford-White Corp CF, MII120A, MII80A, MII50A User Manual

COMMERCIAL ELECTRIC ENERGY SAVER

WATER HEATER

MII SERIES

IMMERSION AND SURFACE MOUNTED

THERMOSTAT MODELS

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

Manual 238-47174-00B

Save this manual for future reference

Table of Contents

Page Service Procedure

I

ntroduction ………………………………………………………………………. 2 - - -

Tools……………………………………………………………………………… 2 - - -

G

eneral 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

G

ENERAL 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.
I

mmersion 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. MIDDLE VILLE 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

G

ENERAL INFORMATION

Upper

Control Box

L

ower

Control Box

Ground Lug

Terminal Block

F

use Block(s)

C

ontactor(s)

High Limit (ECO) Control

Immersion Thermos tat
Control

High Limit (ECO)
Direct Immersion Bulb

Thermostat

Direct Immersion Bulb

Heating Elements

C

ontactor 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

G

round Lug

Terminal Block

C

ontactor(s)

S

urface Thermostats

Heating Elements

H

igh Limit (ECO) Control

600V Surface Thermostat (w/Contactors) Models

General Controls Layout

5

G

ENERAL INFORMATION

Page 6

Surface Mounted Thermostats

M

anual

ECO (high limit)

Reset button

Temperature

c

ontrol Dial

S

urface Mount

C

ombinat ion Thermostat/

ECO (high limit)

89T Seri es

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

G

ENERAL 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

Contactor

operationis ac

hievedby

energizing an operating coil in res

pons

e toa callforh

eat from the immersion

thermostat. Upon a call for

heat,o

neor

moreconta

ctorswil

l ener

giz

e

allhea

tin

g elem

entssimult

a

ne

ous

l

y.

The

operating coils ar

e volt

age specific, Whencontactorreplacement is requiredbe sure to or

der the properoperatin

g coil

bas

e

on t

he v

o

lt

age rating found on t

h

e r

ati

n

g plat

e loc

a

t

ed on thefr

o

nt

ofth

e

wat

erheater

.

T

e

rminalconnections to

th

e

fus

e

bl

o

c

k an

d

/

or

t

erminal

bl

ock

Terminal connections to the

h

eating elements

T

erminal connections of

contactor operating coil.

8

G

ENERAL INFORMATION

Watts

V

olts x 1.732

W

atts = 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)

A

mps =

Watts

Volts

(Single phase)

Amps =

O

hms =

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

S

EQUENCE 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

F

use Block

L

ine 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 de­energizing 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

S

EQUENCE OF OPERATION

Sequence of Operation:
Surface Mounted Thermostats.

OR

Terminal Block

F

use Block

L

ine Voltage

Heating Element

Surface Mounted
Thermostat

Line voltage is applied across terminals of fuse block or a
terminal block. Line voltage continues down and connects
to surface mounted thermostats at terminals L1 & L3.

1

1

ECO (high limit) in
thermostat is closed, so
there is line voltage present
at terminal L4 of thermostats
and to one side of each
element.

2

E

CO Closed

P

ower to one

side of element

2

3

Water in tank is cold, so
all thermostats are
closed at terminal T2
(calling For heat). This
completes the circuit and
allows current to flow
through heating elements.

3

Thermostat closed
at terminal T2

4

As each thermostat is
satisfied, it opens at
terminal T2 interrupting
current flow through the
respective element. The
system is now in stand-by
mode, waiting for the next
call for heat.

4

Thermostat open
at terminal T2

Page 11

11