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How to wire GE 15087 timer

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How to wire GE 15087 indoor-outdoor water heater timer

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GE 15207 water heater timer
See Close-up
GE 15087 Timer
See large image
Timer safe for 1 residential water heater.
15087 NEMA 3R indoor/outdoor
15207 & 56922 NEMA 1 indoor
GE 15135 24-hour/ 40 amp/ outdoor metal box at Amazon

Quick-start guide to wiring

Max 24 on-off periods per day

Step 1:
Remove screws on face to access wiring.
Set dip switch before connecting power.

Manual says that incorrect dip-switch setting will damage timer.
dip switch Step 2: Dip switches

GE 15087 timer can be used for 120V or 240V water heaters > simply change dip switches and select different voltage.

Water heater voltage is printed on side of water heater. Match dip switches to water heater voltage.

Figure Volts Amps Watts for your water heater

Review basic 240V water heater circuit


Use cable connector
1/2" & 3/4" knockouts

Terminals: TIMER  NO  NC  COM  NO2  NC2  COM2
Step 4: Wiring features

Four basic features inside 15087

1. Dip switches
2. Screw terminals for clock
3. Screw terminals to contactors
4. Contactors/relays that handle on-off switching to water heater


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More ways to wire for 240Volt
Step 5a: 

Wiring diagram for 240V water heater. Both white and black wires are hot.
Power connects to clock, and to COM terminals

Use 10 gauge wire for 240V water heater

GE 15087 timer is housed in plastic box
Ground wire is not connected to box
Ground wire travels continuously from breaker box to water heater.

Larger image
More ways to wire for 240Volt
Different way to do same wiring shown in first image above using NO and COM terminals in reverse.

Why show this variation when manual does not?
SPDT timer with dip switches, and dry NO NC contacts can be wired many different ways.
There is no ez way to show all options.
More ways to wire for 240Volt
Timer is open to experimentation by user.

Set dip switches BEFORE applying voltage to terminals.
Do not spark-test wires across terminals.
Wire GE timer for 120-240 voltsElement rated for 4500 watts @ 240Volt, will consume 25% or 1125 watts @ 120Volt

Timer toggles water heater between 120Volt and 240Volt

Use SPDT timer to change water heater between 120Volt and 240Volt

Use 120Volt at peak-electric price.
Water heater recovers slowly with 120Volt, and uses 1/4 power.

Use 240Volt when electric prices are lower, and faster recovery is needed.

How to change water heater to 120Volts

Off-peak water heater options

9 ways to save with water heater

Install electric meter on water heater
Timer toggle between applainces
Larger image
Dishwashers at Amazon


Use Timer to toggle between appliances

240Volt circuit can be cut off by turning off one hot wire.
Put water heater on NC normally open terminal, so water heater is ON all the time, except when timer turns ON, and then circuit to dryer is activated.

Same wiring applies to many timers including Intermatic GM40 & WHQ, Tork DTU40
Other timers can perform same operation such as Intermatic T1905 & T1975

How to wire 240Volt outlets
GE 15207 timer controls 2-speed pool pump
Always check pump voltage and wiring diagram located on nameplate


GE 15000 series timers control 2-speed pump

Low speed is connected to NC terminal, and then pump operates continuously in low speed until timer turns ON.
When timer turns ON, High speed turns ON.
Diagram applies for both 120V and 240V 2-speed pool pumps.
Other timers can be used for 2-speed pool pump:
Tork DTU40, GM40 timer, T106 timer, T1906 timer
Pump operates continuously. Install another timer on L2 Hot line to turn pump ON-OFF
Change water heater temperature using timer
Larger image
Change water heater temperature using GE 15207 timer
Same wiring applies to GE 15087- 15132 etc series timers
Applies to Tork DTU timer and Intermatic GM40 timer
and Intermatic WHQ series and Intermatic T106 timer


Use timer for two different temperatures on electric water heater.

Either upper thermostat and element have power or lower themostat and element have power. But not both at same time.

Install ECO-protected thermostat for lower thermostat.
Both upper and lower parts of tank are ECO-protected from overheating
Rewire tank so upper and lower parts are separate.
Use GM40 timer to switch power between lower and upper parts of tank.

Normal operation, the lower thermost and element receive power and keep tank at temperature set point. Upper thermostat and element have no power.
This is called 'redundant' water heater operation. This technique for heating tank more rapidly after cold water first enters tank.

When timer activates, power to lower part of tank turns OFF. Power to upper part of tank begins. Upper thermostat is set for higher temperature.
Since tank is at regular temperature, the higher setting means upper element will turn ON and begin heating tank to higher set point.

Use this technique to heat water very hot for laundry cycle.
Disadvantage: The lower part of tank will cool rapidly as new cold water enters tank, so this technique is good for making short-term batches of hot water.
Step 5b: 

Wiring diagram for 120V water heater. The black wire is hot, the white wire is neutral.

GE 15087 timer is housed in plastic box
Ground wire is not connected to box
Ground wire travels continuously from breaker box to water heater.
Wire GE15207 for under counter water heater Timer wired to control under-counter water heater
Avoids having to run additional wire to power 1500 watt under-counter water heater.
Circuit uses same wire that powers dishwasher.
Either dishwasher or water heater can be used, but not both at same time.
Set dip switches for 120Volt
How to install under-counter water heater
Step 6: How to set timer

See GE 15087 manual

Rotate dial to set time of day.
48 segments around dial divide 24-hour day into half-hour periods.
Photo shows all segments down.
> segments up = timer on
> segment down = timer off

Timer for water heater
See timer circuit

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