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Page 3 of 3: Wiring details
Return to Page 1: Overview and buy materials for timer project
Return to page 2: Assembly and wiring for timer project

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Electric box knock out Use hammer and screwdriver to remove knock outs
Hit with sharp strike of hammer, and then twist out blank using pliers
Use linesman pliers to bend and then remove extra metal for larger hole
Fill unused holes with snap-in plug from electric dept
. Use tapered drill bit to make hole anywhere

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
45EG20AF contactor
Contactor shown is safe for 1 residential water heater.
Use 1 contactor per each water heater
Bolt contactor into 6x6x4 enclosure using #8-32 bolts
6x6x4 boxes
drop wire from attic Install old work box/   inside hollow wall
old work box
Drop one end of 14-2 wire into old-work box
I prefer 14 gauge wire 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

See How to install old-work box
Twisted wire Connect solid wire to stranded wire
1) Strip stranded wire longer
2) Wrap stranded around solid wire
3) Twist wire connector over both wires
4) Twist wire connector very tight
5) Pull stranded wire and make sure it will not come loose
Wire connector must cover all exposed wire
Solid copper wires do not need to be twisted to make good connection.
Stranded-to-stranded and solid-to-stranded need to be twisted.
Do not use aluminum wire.
Twist connector very tight so it will not fall off.
Use only wire connectors with metal coil inside so it will bite into copper wire.
Do not re-use old wire connectors. Always use new wire connectors.

Busman fuse holder
Install busman fuseholder
Drill 1/2" hole
Install Busman fuse holder with 15A fuse
Push fuseholder cap inward and twist to open fuseholder
Cartridge fuse installs either end first
Fit fuse into fuseholder cap snugly, and then insert into fuseholder
Push in and rotate cap to make connection
BuyBuy fuseholder at Amazon
Buy fuseholders at Amazon
Best electric practice:
Solder wires before installing fuse
Hot wire from contactor will connect to top fuseholder connection.
Wire going to timer will connect to side of fuseholder
Electrically separate these connections by bending away from each other and/or adding tape as insulator
15 Amp ceramic fuse

Why fuse is required
To avoid fire hazard.
To protect 15 amp timer and 14 gauge wire from too many Amps, and overheating.
This water heater timer project draws 120 Volts off 'one leg' of the 240 Volt 30Amp water heater circuit.
It is against code to connect 15 amp wires and timers to 30 amp circuit without fuse protection.
15 Amp fuse will protect wire between contactor and fuseholder, protect wire going to and from timer, and protect timer.
Busman fuseholder Solder 14 ga solid copper wire directly to fuseholder
Unless fuseholder accepts terminals

Some fuseholders are solder-only connection
Instructions how to solder:
Shape end of wire into U-shape... insert wire onto fuseholder... bend wire down tightly
This is why 14 gauge wire is better choice over 12 or 10 gauge
Put solder iron or gun tip where wire terminates.
Wait until hot. Keep tip in place on wire until hot.
Touch solder to copper wire where it meets fuseholder.
Solder melts. Withdraw solder. Withdraw solder point.
Use terminals for solid wire or stranded wire
Yellow female for #10-12 wire
Blue female for #14-16 wire
Crimp terminal onto wire/ also suggest soldering
Read more about terminals
Always add solder to terminal when using solid 14 gauge wire
Instructions how to solder:
after crimping terminal onto wire
Put solder iron or gun tip where wire terminates.
Wait until hot. Keep tip in place on wire until hot.
Touch solder to copper wire where it meets terminal.
Solder melts. Withdraw solder. Withdraw solder point.
Contactor Terminal connections required for contactor

See additional image:
Read more about contactors
Each water heater must have a separate contactor See illustration for controlling 2 water heaters to same timer
tighten screws Wires connected to contactor
There is notched groove on either side of screw
Wire must fit into groove
Straighten copper end of wire
No insulation can be under screw
Tighten screws VERY tight
Intermatic terminal wires Do NOT use stranded wire or install solid wire and stranded wire under same screw
Do NOT install #10 and #14 wire under same screw

With the contactor on this project:, install only #10 wire under screw on contactor
Install #14 wire to contactor using female terminal: illustrations show above

Stranded wire can be connected to solid wire using wire connector, and then put stranded under screw plate. Stranded wire can gradually loosen under screw plates as wire is heated and cooled by current (amperage = heat). Eventally the lose wire starts to arc and then
ground screws
Illustration shows #14 ground wire from timer connected to metal box using green ground screw
Metal box requires grounding/ plastic box does not require grounded box
green ground screw
2 ground screws/ drill hole in box and thread with 10-32 tap
hand tighten Ground wires that are connected with wire connector must be down and away from all other wires
Straighten ends of wire
Keep ends of wire aligned
Apply wire connector very tightly
ground wires Push ground wires down and away from all other wires
If any wire comes loose from wire connector, the connection must be re-done using new wire connector

ResourceHow to select right wire connector
romex connector All wires entering box MUST be held firmly in place with clamp
Read about wire clamps:
water heater timer circuit Here is where we are so far
All open wires are stapled to solid structure.
Wire inside wall cannot be stapled to structure, but is secured inside wall by old work box
Work inside 6x6x4 enclosure
>Note: Wire connector used in each hole where wire enters enclosure
>Mount contactor at angle using 8-32 bolts with lock nut
>Attach 10-2 wire from breaker to one side of contactor
>Attach 10-2 wire going to water heater to other side of contactor
>Put 2 green ground screws in bottom of 6x6x4 metal box (when using 6x6x4 plastic enclosure: connect all grounds with wire connector)
>Connect all ground screws
indicator light to water heater
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How to install 240Volt indicator light
Drill 1/2" hole in enclosure

Indicator will light up when power is turned ON going to water heater
Does not tell you if water heater is actually working.

As long as wires remain inside enclosure, fuse protection on pilot light wires is not required.
If you are installing the pilot light in remote location, and run wires outside of box, then wires must be fuse-protected or must be 10 gauge wires.

240Volt Pilot light at Amazon
120Volt pilot light at Amazon
Indicator lights at Amazon

Panel mount fuse holders at Amazon
Buy fuseholder at Amazon
Buy fuseholders at Amazon
Water heater pilot light
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240 Volt pilot light/ Pilot light turns ON when water heater is sending power to element
Element and thermostat wiring must be identical to wiring shown
If upper element is burned out, then tank will have no hot water.
If lower element is burned out, then tank will have less hot water.
If ECO reset button, located on upper thermostat, is tripped, then power is not available to elements.

Required in-line fuseholder and 120Volt 15 amp ceramic fuse located on black wire, and another fuseholder on red wire, going to pilot light.
This is to protect pilot light and wire-to-pilot-light from 30 amp overheat danger
Insulation must be put back over thermostats, and metal cover re-installed on front of water heater for heater to operate correctly and safely.
if thermostats exposed to room-temperature air, they will not read temperature correctly.

Buy contactor and indicator/pilot light
Panel mount fuse holders at Amazon
Buy fuseholder at Amazon
Buy fuseholders at Amazon

240Volt Pilot light at Amazon
Indicator lights at Amazon

How to wire water heater pilot light for 120V or 240V
How non-simultaneous household water heaters work
How to wire water heater thermostats
Inline fuseholders
See inside main breaker box
Troubleshoot electric water heater
6x6x4 box Install cover over 6x6x4 enclosure
All boxes and switches and panels must have cover.

All boxes and switches and panels must have cover
Cover ensures containment of spark and possible fire hazard

Troubleshoot household electricity
do it yourself
Each water heater must have a separate contactor see
Project is done
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