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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
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MII Series Commercial Electric Water Heaters 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
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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
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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 Upper Control Box Fuse Block(s) Surface Mounted Thermostats Lower With ECO Control Box Heating Elements Page 4 4
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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 5
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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. 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. Manual Surface Mount ECO (
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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. Surface Mounted Surface Mounted Thermostat ECO (High Limit) 59T Series Manual Reset Button Temperature control Dial Page 7 7
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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. Terminal connections of Termi
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GENERAL INFORMATION Commonly Used Formulas (balanced 3 phase) (Single phase) 2 Watts Watts Volts Amps = Amps = Watts = Amps x Volts Ohms = Volts x 1.732 Watts Volts Common Service Wire Configurations 240V 1Ph BLACK GREEN Ungrounded Grounding RED Ungrounded 240 120 120 208 3Ph 240 3Ph 480 3Ph/277 1Ph Neutral AB C Neutral AB C Neutral AB C 120 120 277 120 120 277 120 208 120 240 277 480 208 208 240 240 480 480 RED BLACK RED RED BLACK RED RED BLACK RED Full Load Current Amps 208 Volt 240 Volt 277 V
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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
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SEQUENCE OF OPERATION Line Voltage Sequence of Operation: 1 Surface Mounted Thermostats. OR Fuse Block Terminal Block Line voltage is applied across terminals of fuse block or a 1 terminal block. Line voltage continues down and connects to surface mounted thermostats at terminals L1 & L3. 2 ECO (high limit) in 2 thermostat is closed, so ECO Closed there is line voltage present at terminal L4 of thermostats and to one side of each element. Power to one side of element Surface Mounted Thermostat H
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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 1 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)
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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. Dry Firing. Elements may be partially submerged in water or most likely, completely exposed with no water in the tank at
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TROUBLESHOOTING Quick Step Plan to Hot Water WARNING High voltage exposure. Use caution when 1. STOP, DANGER! Turn power “OFF” to water heater. making voltage checks to avoid hazard to life or property. 2. Check all wire connections to insure they are snug and corrosion free. 3. Reset high limit (ECO) (page 18-20). 4. Check for inoperative heating element (page 15). 5. Check line voltage (pg 16), and internal fuses (page 17). 6. Refer to table below if items 1 through 5 above do not correct pro
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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 2. Remove access cover from lower control box. to water heater while performing this Remove insulation from inside of control box. procedure. 3. Disconnect wires from heating element. 4. Set multi-meter to “ohms” setting. 5. Touch probes of multi-meter to screw termin
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SERVICE PROCEDURE MCE-II Line Voltage Testing Line Voltage Testing DANGER 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 . located inside control panel. Determine heaters voltage and phase by referring to the rating plate located on the front of the heater. Apply the appropriate phase procedure below to determine if proper line voltage
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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. 3. Locate fuse block and remove fuses. 4. Set multi-meter to the “Ohms” setting. 5. Check continuity across fuse (see illustration 5). A) Continuity IS present, fuse is okay. B) Continuity NOT present, Replace
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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. 2. This procedure illustrates testing of just one ECO reset surface thermostat. Repeat this procedure for all button surface thermostats on the unit. 3. Turn power “OFF” to w
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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, ECO reset fuses, and thermostat are in working order. button 2. Turn power “OFF” to water heater. 3. Remove lower control box cover and remove insulation from inside of control box. 4. Check for continuity across
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SERVICE PROCEDURE MCE-VI High Limit (ECO) Testing High Limit Control (ECO) Testing for Contactor Models Switch Contacts: Observe heating cycle. N Is water temp Y Normally closed. Does switch open? over 196°F Open on rise @ 196°F ±4°F N Manual Reset. Y 1. Determine if Hi-Limit has actuated. This can be done by simply Is water temp Y depressing the reset buttons. If you hear and/or feel Switch OK over 196°F a small click, the switch has actuated. N 2. Use caution and turn power on to water heate
