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How to install water heater timer

 Page 1 of 2: Overview /and Gather materials
Skip to Page 2: Connect the wires
install water heater timer

Project overview: For timers and switches without neutral wire

Attic installation shown.
Same plan works for water heater in basement or garage or closet.
Also works for any heavy-amp load such as heater, motor, pump etc single-phase or 3-phase.

See inside box with contactor

Resources for timers without neutral wire
ST01 programmable timer
Spring wound timers
Leviton LLT countdown timer

See wiring for all switches and timers
Control 2 water heaters with 1 switch
Control water heater with 2 switches
Control 1 water heater with 30Amp switch
See box-type timers
See Intermatic 'box-type timer' installation
See GE 'box-type timer' installation
ST01C timer controls 240Volt water heater
Larger image/ ST01 timer no neutral wire needed
Larger image with timer that has neutral wire

Example using ST01C 7-day timer

Use this diagram if timer does not have Neutral wire

Includes ST01 timer, Ei600 timer, any ordinary switch

ST01C timer does not require neutral wire
Battery operated timer, so no neutral wire required
ST01 can control any voltage
Timer must be fuse-protected with inline fuse as shown in illustration
Illustration shows SPDT contactor with 240Volt coil.
All materials and wiring shown below:

Intermatic ST01 timer
See wiring for other switches and timer

Larger image

Use this diagram if timer has Neutral wire

This is CODE wiring for timers and Zwave and WiFi devices that require Neutral

Black Hot from fuseholder connects to Timer Black
White wire connecting to one side of contactor connects to Timer Red wire (or blue wire)
Green or bare ground wire connectes to ground wire
Neutral for timer and contactor control comes from an available independent 120V source  See illustration
programmable timer wiring
Larger image

NOT CODE but will work

Wiring illustration applies to any programmable or countdown timer with neutral wire

Using Ground as neutral is not code.

Use image above for correct wiring

Black Hot from fuseholder connects to Timer Black
White wire connecting to one side of contactor connects to Timer Red wire (or blue wire)
Timer White and Timer Green connect to bare ground wire
wifi contactor
Larger image
control water heater with WeMo

Control water heater with WeMo

WeMo programming resources are online
No subscription
WeMo plugs into ordinary 120volt outlet
Control WeMo using phone or tablet
WeMo at Amazon
Square box extension ring
Box cover
Box cover
More illustrations

Gather materials for project

materials for water heater timer
Intermatic EI500  Grasslin ET616   

Choose timer or switch

Intermatic ST01 in-wall programmable single-pole or 3-way timer
More Intermatic in-wall timers (suggest Ei500 or Ei600... do not use EJ500)
Intermatic Ei200 single-pole countdown timer
Woods In-wall programmable single-pole timers
GE in-wall programmable single-pole or 3-way timers

More in-wall programmable
Spring wound mechanical timers
More countdown timers
Ordinary 15-20 amp switches
Old work boxe

Buy old work box

Available home center or online
Thomas and Betts old work box at Amazon
Old work boxes at Amazon
See How to install old-work box

Buy contactor with 240V coil

Project calls for 2-pole contactor with 240Volt coil
Available local electric supply or HVAC supply
240Volt coil 2-pole contactor At Amazon
120Volt coil 2-pole contactor At Amazon

Read more about contactors
carlton 6x6x4 junction box
Plastic 6x6x4

6X6X4 Metal box w/ Contactor

Choose metal or plastic 6x6x4 junction box

Choose Plastic box?
no pre-drilled holes, but easy to drill... must drill holes for Wire connections, 1/2" hole for fuseholder, 3/16" holes for bolts to hold contactor, plastic box does not need ground screw connected to box
Buy Plastic 6x6x4:
Cantex 6x6x4 PVC plastic enclosure with cover at Amazon
Thomas and Betts 6x6x4 plastic with cover at Amazon
Bud industries 11x7x5 box without knockouts

Choose Metal box?
metal box has knock-outs for 1/2 and 3/4" ... must drill 1/2" hole for fuseholder, drill bolt holes to hold contactor,
threaded holes for 10-32 ground screw, metal box must be grounded.
Buy Metal 6x6x4
Bud industries 6x6x4 best value
Raco 6x6x4 metal pull box
Weigman 6x6x4 pull box
Hoffman 6x6x4 pull box
Outdoor 6x6x4 box

Indoor 6x6x4 metal pull box with cover and knock-outs/ Raco
Indoor/ hinged door 10x10 x 6 / Bud Industries

Indoor / hinged door/ 6x8x4 box / Bud Industries

Bud industries boxes at Amazon
Arlington boxes at Amazon
See more about boxes
tapered drill bit

Optional: Tapered drill bit for plastic or metal box

Buy tapered drill/ step drill bit for any size hole
Step drill bits at Amazon
Neiko tapered drill bit 1/4"-1-3/8 holes

Buy electric wiring Book
Black and Decker Complete guide to wiring
More resources;
See inside main breaker box
household wire
120Volt 14-2 wire will have Black-white wires
240Volt, 10-2 wire can have red-black or white-black wires... alsways add piece of black tape to white wire when used for 240Volt power. Adding black tape will signal that wire carries power


See wire color code and amp ratings

buy Lengths of wire

I prefer 14 gauge wire for timer connection for this project because it is easier to connect to fuseholder if fuseholder requires solder connection.
Also 14 gauge is easier to bend, and to easier to attach to small wires on timer

White/ #14 gauge wire for 15 amp
25 foot 14-2 NMB indoor wire with ground
50 foot 14-2 indoor wire with ground
100 foot 14-2 indoor wire with ground
100 foot 14-2 UF outdoor burial with ground
Yellow/ #12 gauge wire for 20 amp
25 foot 12-2 NMB indoor with ground
50 foot 12-2 indoor with ground
100 foor 12-2 UF outdoor burial with ground
#10 wire required for water heater
Orange/ #10 gauge for for 30 amp circuits including water heater
25 foot 10-2 NMB indoor with ground
100 foot 10-2 NMB indoor with ground
50 foot 10-3 indoor with ground
See wire color code and amp ratings
fuseholderBusman fuse holder

Buy fuseholder and 15 amp fuse

Panel mount fuse holders at Amazon
Buy fuseholder at Amazon
Buy fuseholders at Amazon

30 amp fuseholder at Amazon

Ceramic fuses at Amazon

Read about fuseholders
wire nuts     

Wire connectors

Wire connectors at Amazon
Push-in wire connector up to 14-12 gauge

How to install wire connector

Optional Indicator light

240Volt Pilot light at Amazon
120Volt pilot light at Amazon
Indicator lights at Amazon
See illustration of 120Volt & 240v pilot light
cable staples Cable staples plastic at Amazon
Cable staples metal at Amazon
romex connector Wire connectors at local hardware or home store


Terminal kit at Amazon with crimp tool
Electrical terminals at Amazon
Blue 14-16 gauge female terminals 20 pcs at Amazon
Yellow 12-10 gauge female terminal 16 pcs
360 pc assortment at Amazon
520 pc assortment at Amazon
More about #10 & 14 female terminals

notes 14-16 B002UZXTYC   B002UZUIYQ   B000FPAJXS
12 ga  B00G9VVL0M   B00176877E
12-10   B0071NBGMA   B0071NC78C  B00176877E
8-32 bolts

8-32 x 3/4" bolt w lock nut

Ground screws at local home store or hardware

ground screws

Ground screws at local home store or hardware

Needed when using metal box so ground wire can connect to box
Use 10-32 tap to thread hole
Use regular 10-32 bolt with small washer
100 pack ground screws amazon

You have the materials.

hand Go to Page 2: connect the wires.
Insteon 30 amp z-wave load controller
Insteon load controller manual

main breaker box
Larger image 
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Including Z-wave
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