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How to wire EH10 water heater timer/ EH40/ WH40/ WH21

  
Terminals 1 and 2 send power to 120V clock.
Jumper hot wire from terminal 2 to terminal 3.
Neutral wires connect to terminal 1
Ground wires are kept away from other wiring.
Romex connectors used where wire enters metal box.
Tighten screws very tight against copper wire.

How to wire Intermatic EH 10 timer for 120Volt water heater

30Amp digital timer
DPDT
Uses AA battery for backup
Reset protocol for surge recovery
Use whold-house surge protector
1 year limited warranty
Minimum 1 minute set times
Up to 6 on-off per week

Buy:
EH10     120Volt 7-day digital timer at Amazon
12-2 wire at Amazon
Resources
EH10 manual
EH10 sell sheet
Figure volts amps watts for water heater
EH10 timer controls 240Volts
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EH10 timer controls 240Volt water heater


10 gauge wire, 30 amp breaker rated for 4500+ watt element
Timer rated 30 amp
     
 Select wire size                       Read about romex connector
10-2 wire at Amazon

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Fire safety/ only solid copper wire under screw plate

Use only solid copper wire
Do not put insulation under screw terminal

Take photo of wires before starting

Fire safety/ only solid copper wire under screw plate

Use only solid copper wire
Do not put insulation under screw terminal

Take photo of wires before starting
Insdulation under screw plate
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Fire safety/ maximum 2 solid copper wires under screw plate

Max 2 wires under screrw plate
Each wire must be same gauge
Attach multiple wires with wire connector, and run jumper to screw terminal
Resource:
Wire and breaker size charts

EH10 & EH40 are battery operated timers

Battery compartment located beneath buttons
Size A battery lasts 2-3 years

EH 40 timer

EH40
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EH40 water heater timer
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EH40 water heater timer

240Volt water heater timer
30Amp digital timer/ SPDT
10 gauge wire, 30 amp breaker rated for 4500+ watt element
AA battery for backup
Reset protocol for surge recovery
Use whole-house surge protector
1 year limited warranty
Minimum 1 minute set times
Up to 6 on-off per week
Override button located on face of timer

Buy:
EH40     240Volt 7-day digital timer at Amazon
10-2 wire at Amazon
Resources
Wiring diagrams: How to wire EH40
EH40 sell sheet
EH40 manual
Basic water heater circuit
How to wire off-peak water heater
How to wire water heater thermostats
Color code wire


Larger image off peak wiring

Jumper wire connects two terminals

10 gauge wire, 30 amp breaker rated for 4500+ watt element
Timer rated 30 amp
     
 Select wire size                       Read about cable connector
10-2 wire at Amazon

WH 40 timer

WH40
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WH40 water heater timer
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WH40 water heater timer

Timer rated 40 amp
10,000 watt capacity> can control one or two water heaters
WH40 timer can be wired many different ways: identical to T104
WH40 timer is same timer as T104 and T104-20, except WH40 has external override lever
Up to 12 on-off operations per day
Manual override reverses current program until next tripper returns timer to regular schedule
Buy:
WH40      208-240-277Volt 10000 watt 40 amp at Amazon
T104-20 (WH40)     208-240-277V (no external switch) at Amazon
156T1978 trippers at Amazon
Replacement trippers at Amazon
Clock motor WG1573 at Amazon
10-2 wire at Amazon
Resources
Wiring diagrams: How to wire WH40
WH40 manual
WH40 sell sheet
How to operate and set timer
List of replacement parts
Photographs of timer and timer parts
Troubleshoot Intermatic timer

WH40 timer
How to set WH40
WH21 timer

WH21 25amp 240Volt Water heater timer

Minimum 1/2 hour on-off times.
On trippers cannot be set closer than 2 hours
25 amp controls up to 5000watt water heater
SPST 240Volt
Red indicator light is ON when Load is ON
Buy:
WH21      240Volt 23 amp at Amazon
156EB1945a replacement trippers at Amazon
WH21 clock motor WG233-18 from Intermatic
10-2 wire at Amazon
Manuals/ Resource:
WH21 manual
Wiring and Troubleshoot WH21 timer
Intermatic trippers and parts
color-code household wire Color code wire
How to twist wire
Wire connectors
 
Intermatic control centers Intermatic control centers:
+ manuals and parts


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