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COMMERCIAL ELECTRIC ENERGY SAVER
IMMERSION AND SURFACE MOUNTED
Manual 238-47174-00B
WATER HEATER
MII SERIES
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
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Summary of Contents for Bradford White MII50A-SF
- Page 1 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...
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Page 2: Table Of Contents
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. -
Page 3: General Information
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... - Page 4 GENERAL INFORMATION Contactor Models General Controls Layout Ground Lug Terminal Block Upper Control Box Fuse Block(s) Contactor(s) High Limit (ECO) Thermostat Direct Immersion Bulb Direct Immersion Bulb High Limit (ECO) Control Immersion Thermostat Control Lower Control Box Heating Elements Surface Mounted Thermostat Models General Controls Layout Ground Lug Terminal Block...
- Page 5 GENERAL INFORMATION 600V Surface Thermostat (w/Contactors) Models General Controls Layout Terminal Block Ground Lug Upper Control Box Contactor(s) High Limit (ECO) Control Surface Thermostats Lower Control Box Heating Elements Page 5...
- Page 6 GENERAL INFORMATION Surface Mounted Thermostats 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.
- Page 7 GENERAL INFORMATION 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.
- Page 8 GENERAL INFORMATION Contactor Contactor operation is achieved by energizing an operating coil in response to a call for heat from the immersion thermostat. Upon a call for heat, one or more contactors will energize all heating elements simultaneously. The operating coils are voltage specific, When contactor replacement is required be sure to order the proper operating coil base on the voltage rating found on the rating plate located on the front of the water heater.
- Page 9 GENERAL INFORMATION Commonly Used Formulas (balanced 3 phase) (Single phase) Watts Watts Volts Amps = Watts = Amps x Volts Ohms = Amps = Watts Volts x 1.732 Volts Common Service Wire 240V 1Ph Configurations BLACK GREEN Ungrounded Grounding Ungrounded 208 3Ph 240 3Ph 480 3Ph/277 1Ph...
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Page 10: Sequence Of Operation
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. - Page 11 SEQUENCE OF OPERATION Sequence of Operation: Line Voltage Surface Mounted Thermostats. Fuse Block Terminal Block 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. ECO (high limit) in thermostat is closed, so ECO Closed...
- Page 12 SEQUENCE OF OPERATION Sequence of Operation: 600V Surface Mounted Thermostats (w/Contactors). Line Voltage 6 Element Configuration Shown The system has two distinct circuits. (9 Elements Possible) 1. Power circuit - Line Voltage (600V) Fuse Block 2. Control Circuit - 120V Transformer 60VA Line voltage is applied across terminals of fuse block...
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Page 13: Troubleshooting
TROUBLESHOOTING Most common cause for improper electric water heater operation can be linked to heating element failure. When troubleshooting an electric water heater with the incidence of “No Hot Water” or “Insufficient Amount of Hot Water” It is always a good idea to check the heating elements first following the procedure on page 15. Common Heating Element Failures Are: 1. - Page 14 TROUBLESHOOTING Quick Step Plan to Hot Water WARNING High voltage exposure. Use caution when making voltage checks to avoid hazard to 1. STOP, DANGER! Turn power “OFF” to water heater. life or property. 2. Check all wire connections to insure they are snug and corrosion free.
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Page 15: Heating Element Testing
SERVICE PROCEDURE MCE-I Heating Element Testing Test for Open or Burned Out Element. DANGER High voltage exposure. To avoid hazard to 1. STOP, DANGER! Turn power “OFF” to water heater. Life or property, be sure power is turned OFF to water heater while performing this 2. -
Page 16: Line Voltage Testing........................................................................ 16 Mce-Ii
SERVICE PROCEDURE MCE-II Line Voltage Testing DANGER Line Voltage Testing High voltage exposure. To avoid hazard to Line voltage (single phase or three phase) will life or property use extreme caution when connect to a terminal block or directly to a fuse block making voltage checks . -
Page 17: Fuse Testing
SERVICE PROCEDURE MCE-III Fuse Testing Fuse Testing DANGER High voltage exposure. To avoid hazard to Life or property, be sure power is turned OFF to water heater while performing this procedure. 1. Turn “OFF” power to water heater. 2. Open upper control box to allow access to fuse block. -
Page 18: High Limit (Eco) Testing (Surface Mounted Thermostats)
SERVICE PROCEDURE MCE-IV High Limit (ECO) Testing DANGER High Limit Control (ECO) Testing for High voltage exposure. To avoid hazard to Surface Thermostat models (not including 600V) life or property use extreme caution when making voltage checks . 1. This procedure assumes line voltage and fuses are in working order. -
Page 19: High Limit (Eco) Testing (Surface Mounted Thermostats At 600V)
SERVICE PROCEDURE MCE-V High Limit (ECO) Testing DANGER High Limit Control (ECO) Testing for High voltage exposure. To avoid hazard to 600V Surface Thermostat Models life or property use extreme caution when making voltage checks . 1. This procedure assumes line voltage, transformer, fuses, and thermostat are in working order. -
Page 20: High Limit (Eco) Testing (Contactor Models)
SERVICE PROCEDURE MCE-VI High Limit (ECO) Testing High Limit Control (ECO) Testing for Contactor Models Switch Contacts: Observe heating cycle. Is water temp Normally closed. Does switch open? over 196°F Open on rise @ 196°F ±4°F Manual Reset. 1. Determine if Hi-Limit has actuated. This can be done by simply Is water temp depressing the reset buttons. -
Page 21: Thermostat Operation Testing (Surface Mounted Thermostats)
SERVICE PROCEDURE MCE-VII Thermostat Testing Surface Mounted Thermostat. DANGER Operation Testing (not including 600V models) High voltage exposure. To avoid hazard to life or property, use extreme caution when making voltage checks . Water In Tank Is Cold With Power ON. 1. -
Page 22: Thermostat Operation Testing (Surface Mounted Thermostats At 600V)
SERVICE PROCEDURE MCE-VIII Thermostat Testing 600V Surface Mounted Thermostat Models. DANGER Operation Testing High voltage exposure. To avoid hazard to life or property, use extreme caution when making voltage checks . Water In Tank Is Cold With Power ON. 1. This procedure assumes line voltage, ECO, transformer thermostat, and elements are in working order. -
Page 23: Thermostat Operation Testing (Contactor Models)
SERVICE PROCEDURE MCE-IX Thermostat Testing Immersion Thermostat Operation Testing DANGER High voltage exposure. To avoid hazard to Thermostat Specification: life or property use extreme caution when Calibration: 184°F/176°F Max Differential: 6°F making voltage checks . Operating Range 80 to 180°F Providing the water temperature in tank is within the operating range of the thermostat, checking thermostat operation can be as simple as rotating the thermostat dial and listening to the contactor(s) to see if they respond to a call... -
Page 24: Contactor Operation Testing............................................................... 24 Mce-X
SERVICE PROCEDURE MCE-X Contactor Testing DANGER Contactor Operation Testing High voltage exposure. To avoid hazard to life or property, use extreme caution when making voltage checks . Noisy Contactor Noisy or chattering contactor operation in most cases is due to voltage variations being supplied to the water heater. Extended periods of voltage variations will cause damage to the operating coil of the contactor causing noisy operation. - Page 25 SERVICE PROCEDURE MCE-X Contactor Testing Contactor Operation Testing (continued) DANGER High voltage exposure. To avoid hazard to This procedure assumes control circuit is operating correctly. life or property, use extreme caution when Providing the water temperature in tank is within the operating making voltage checks .
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Page 26: Thermostat Removal And Replacement (Surface Mounted Thermostats)
SERVICE PROCEDURE MCE-XI Thermostat Removal and Replacement DANGER High voltage exposure. To avoid hazard to Surface Mounted Thermostat Removal Life or property, be sure power is turned OFF 1. STOP, DANGER! Turn power “OFF” to water heater. to water heater while performing this 2. -
Page 27: Thermostat Removal And Replacement (Contactor Models)
SERVICE PROCEDURE MCE-XII Thermostat Removal and Replacement DANGER Immersion Thermostat Removal & Replacement High voltage exposure. To avoid hazard to 1. STOP, DANGER! Turn power “OFF” to water heater. Life or property, be sure power is turned OFF to water heater while performing this 2. -
Page 28: Eco Removal And Replacement (Contactor Models)
SERVICE PROCEDURE MCE-XIII Contactor Model High Limit (ECO) Control Removal and Replacement DANGER Contactor Model High Limit (ECO) Control High voltage exposure. To avoid hazard to Removal and Replacement Life or property, be sure power is turned OFF to water heater while performing this 1. -
Page 29: Eco Removal And Replacement (Surface Mounted Thermostats At 600V)
SERVICE PROCEDURE MCE-XIV 600V Model High Limit (ECO) Control Removal and Replacement DANGER 600V Surface Thermostat Model High voltage exposure. To avoid hazard to High Limit (ECO) Control Life or property, be sure power is turned Removal and Replacement OFF to water heater while performing this 1. -
Page 30: Heating Element Removal And Replacement
SERVICE PROCEDURE MCE-XV Heating Element Removal and Replacement DANGER High voltage exposure. To avoid hazard to Heating Element Removal Life or property, be sure power is turned OFF 1. STOP, DANGER! Turn power “OFF” to water heater. to water heater while performing this 2. -
Page 31: Anode Inspection And Replacement
SERVICE PROCEDURE MCE-XVI Anode Inspection and Replacement Anode Inspection and Replacement DANGER High voltage exposure. To avoid hazard to Life or property, be sure power is turned OFF to water heater while performing this procedure. WARNING Heater components and stored water may be HOT when performing the following steps in this procedure. -
Page 32: Generic Parts List
Generic Parts List Page 32... -
Page 33: Glossary Of Terms
Generic Parts List Item Description Item Description Anode. Heating Element Gasket. Hot Water Outlet Nipple. Cold Water Inlet Nipple. T&P Nipple. Plastic Snap Bushing. T&P Coupling. Lower Control Box. T&P Relief Valve. Upper Control Box. High Limit Switch. Terminal Block (Block A) Surface High Limit Switch. - Page 34 NOTES Page 34...
- Page 35 NOTES Page 34...
- Page 36 Email parts@bradfordwhite.com techserv@bradfordwhite.com www.bradfordwhite.com...