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How to repair EH40 timer
30 amp breaker use 10 gauge /

10-2 gauge/ 30 amp
10-3/ 30 amp
Southwire electric tools
Yellow 12 gauge 20 amp

Yellow/ #12 gauge wire for 20 amp
with ground
12-2 gauge/ 20 amp
12-3/ 20 amp

NMB is house wiring
UF is underground
Rolls of stranded wire
White 14 gauge 15 amp

White/ #14 gauge wire for 15 amp
with ground
14-2 gauge/ 15 amp
14-3/ 15 amp

NMB is house wiring
UF is underground
armored cable
Armored cable
Southwire armored cable cutter
Southwire armored cable cutter
Rolls of stranded wire

Stranded wire
stranded wire
Rolls of stranded wire
50-60 amp breaker use 6 gauge /
6-2 wire
6-2 wire
Southwire electric tools
NMB is house wiring
UF is underground
40-50 amp breaker use 8 gauge /
6-2 wire
8-2 wire
Southwire electric tools
NMB is house wiring
UF is underground
Copper ground wire
Use same size as other wire in circuit

12 gauge copper ground wire
Ground wire
Green ground wire
Ground pigtails
Ground rods/ ground clamps at Amazon

End cutting nippers at Amazon

Buy tools:
Wire strippers at Amazon
Linesman pliers
Utility knife at Amazon
Electrical testers
EH40 timer Basic troubleshoot steps
-Flip circuit breaker fully off and then fully on to make sure timer has power
-Test for 240 volts across terminals 1 and 2
-Check AA battery located below the buttons, replace with new, clean terminals
-Reset timer and reprogram
Intermatic EH40 timer at Amazon
Intermatic EH40 240-Volt Electronic Water Heater Timer
Electrical testers
240V EH40 manual
Figure volts amps watts of water heater
How to wire EH40 water heater timer
Compare all box timers

EH40 is battery operated timer

Battery compartment located beneath buttons
Size AA battery lasts 2-3 years
Clean battery terminals, If terminals are corroded, the timer may be not functional. Clean with white vinegar using q-tip to remove corrosion.
Install new battery, reset timer using reset button, reprogram and see if function is restored.
Check load rating:
EH40 is rated for 240 volt AC alternating current at 60Hz
(Hz is number of rotations per second of power plant generator: US and Americas 60Hz. Europe, Asia, Africa etc 50 Hz)

30A resistive at 240V AC.
30A inductive (motor, LED) 2.0 hp at 240V AC.
5.0A at 240V AC Tungsten (incandescent light bulb)

EH40 is rated for 4500-5500 watt 240 volt water heater
Is the Load working?
Load is the water heater, motor, light bult etc.
Check if load is functioning: by-pass relay terminals and hardwire directly to terminals 1-2
Don't assume override is functioning

Do not expose timer to freezing temperatures: battery will fail

EH40 timer wiring
Is one relay working?
EH40 has 2 relays, terminals 3-4 and terminals 5-6...
240 volt circuit has 2 hot wires... and EH40 has 1 relay for each hot wire
But 240V load can also be switched on-off using 1 relay
If one relay stops working, you can use the other relay and control circuit
Test EH40 to see if one relay is still good:
First, test terminals 1-2 to makes to sure you have 240V
Next, Turn timer ON using the override button
Test across terminals 2 and 4 for 240 volt
Test across terminals 1 and 6 for 240 volt

EH40 wiring By-pass one relay and timer still controls 240 volt
If one test reveals 240V and other test reveals 0 volts, then 1 relay is good and other relay is bad.
By-pass the bad relay by moving wire from terminal 4 to terminal 3 -or move wire from terminal 6 to terminal 5

T100 series timers and manuals
How to wire T100 series
How to set box timers
Troubleshoot box timers
Trippers and parts
Model numbers, and manuals
Match wire size and breaker and load
Timer caught fire

Are there any loose or burned wires?

Loose wire will spark and cause carbon deposits, melt end of wire, melt insulation or screw plate or start fire.
Prevent major issue by keeping enclosure door closed all all times.... this will reduce damage, starve fire from oxygen and extinguish flames.

Cut back melted part of wire, clean up screw plate if possible, reattach wire, use only solid copper wire, never stranded wire, reset timer, change battery and check timer functionality.

10 gauge wire and 30 amp breaker is rated for 4500+ watt water heater
Timer is rated 30 amp
EH40 does not have a connection terminal for Neutral.
Neutral is not needed for 240 volt circuits.

Keep wires straight
Use solid copper wire
If wiring terminal  or end of wire are covered with green, use emery board to clean terminal and sandpaper to clean wire.
Insdulation under screw plate
Larger image
Both wires MUST be same gauge
Straighten each wire
If wire is corroded or overheated, clean the end with sandpaper and wipe with cloth.
If wire has been melted, cut back and reattach, or replace wire.
Tighten screw very tight against copper wire

Use wire connector  
Push on wire connectors
Use push-on wire connectors
3 wires/ or different gauge wires
Join wires with wire connector or push-on connector
Run jumper to screw terminal.
Push on wire connectors at Amazon
Red 3P connector (shown) for 10-14 gauge wire
Connector assortment
How to select and install wire connector
Fire safety/ Do not put stranded wire under screw plate
Do not install stranded wire under screw.
Problem1: picture shows 2 different gauge wires under screw plate
Problem2: Stranded wire will expand and contract and come loose under screw plate, even if it is the only wire under the screw plate
Attach stranded wire and solid wire with wire connector, and run solid copper jumper wire to screw terminal
Take photo of wires before starting.

Timer caught fire
Load ratings for Intermatic timers/ pdf

Larger image
10-3-wire  12 Ga
10 gauge or 12 gauge?
Compare your wire with short pieces of 10 and 12 gauge wire from local box store

10 gauge for 30 amp breaker.
10 gauge wire can have black-white and sometimes black-red

12 gauge for 20 amp breaker
12 gauge will have black and white wires
Match color code and amp rating for wire
Basic house wiring
Add black tape when White wire carries voltage (applies to 208 and 240V circuits)
With 120 and 277 Volt circuits, White wire is Neutral, and Black is Hot
With 208 and 240 circuits, both wires are Hot, and both wires carry voltage
Black tape on White wire identifies wire is Hot and not Neutral


Test for breaks in wire/ Test for voltage
Most appliance require 80% rated voltage to function correctly
Multimeters at Amazon
Electric testers at Amazon
How to test and replace element
How to test thermocouple
Element tests for 120 volts
How to test wire
Safety when testing wires:
Never touch wet or previously flooded appliance.
Never stand on wet surface when working on electric.
Never stand on bare soil, put down dry boards.
Tape tester leads to wood sticks to keep hands away from power.
Use non-contact voltage tester before touching wires.
Never touch or lean into any made of metal.
Remove metal objects from pockets.
Do not use oxygen or fuel accelerants in same room as electrical repairs

Basic house wiring

Non-contact voltage tester

Test for power without touching connectors
NEVER assume power is OFF
Non-contact voltage tester Amazon
Electric testers at Amazon
How to test electric power is off
wire connector assortment

Twist-on wire connector assortments

Do not reuse old connectors
Connector assortment at Amazon
Connector assortment at Amazon
How to select and install twist-on wire connectors
Weatherproof wire connector

Weatherproof wire connector

Connector cavity is full of silicone
Built-in cover keeps silicone in place
Protect from water, dust etc
Buy from my affiliate links
Weatherproof size 14 to 6 Amazon
Weatherproof size 22 to 8 Amazon

How to select and install connectors
Wire connector wrench
Wrench to apply wire connectors
Tighten connector

Wire connector blaster
Twist connector wrenches at Amazon

How to twist wire
How to select and install twist-on wire connectors

Blue for 16-14 wire
Yellow for 12-10 wire

How to install terminals


Terminal kit
Blue for 16-14 wire
Yellow for 12-10 wire
Push on wire connectors

Push-on wire connectors in place of twist-on connectors

Push on wire connectors Amazon
Red 3P connector for 10-14 gauge wire
Lever connectors for stranded wire at Amazon
remove cable staple
End cutting nippers at Amazon

linesman pliers
Buy tools:
Wire strippers at Amazon
Linesman pliers
Utility knife at Amazon
End cutting nippers at Amazon

Use solid copper wire
Fire inside timer caused by stranded wire
Keep enclosure door closed at all times
soldering guns

Timer caught fire

How to wire contactors/ relays
Busman HKP-HH fuse holder
How to wire inline fuseholder
AH3 off delay timer
How to wire delay timers
How to wire twin timers
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Icon gas valve

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box timers Resource:
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Control water heater w/ Z-wave
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Intermatic control centers: and parts
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