How to wire GM40 timer

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2012

How to wire Intermatic GM40 timer

Intermatic timers and manuals

Overview of timer: Set dip switches BEFORE applying voltage:

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GM40 instruction manual
Sell sheet with model numbers

Set dip switches before applying voltage to timer

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Rating: SPDT; DPDT
Nema 3 indoor/outdoor enclosure
Up to 8ga AWG solid copper wire
Manual override on timer dial

120 volt; 208-240; 277Volt
NO contacts 40 amp resistive
NC contacts 30 amp resistive
1Hp 120V
2 Hp 208-240V

24-hour 15 minute timer
7-day 2-hour timer w/ skip-a-day
Backup battery option

Wire GM40 timer to control DC motor:
Use same diagram to control any single-phase voltage.

Do not mix different gauge wires under same screws. Smaller wire comes loose, causing sparking and high heat and fire.
Do not mix solid wire and stranded wire under same screw.
Intermatic terminal wires

240 Volt

Wire GM40 for 240Volt water heater

Basic 240Volt wiring
Turns OFF both hot wires going to load

Figure volts amps watts for water heater
Wire size charts

240 volt

GM40 controls two 4500 watt 240Volt water heaters
Turns off 1 hot wire to each water heater

Use 50 amp breaker and 6 gauge wire to timer.
10 gauge ire to each water heater
Timer not rated for controlling two 5500 watt water heaters

How water heaters work
How to wire water heaters
Figure volts amps watts for water heater
Two water heaters
Wire sizes

240 volt

GM40 controls two 4500 watt 240Volt water heaters using dry terminals
Set dip switches for 240Volt
Timer can control two different voltages, and two separate circuits.
Both circuits turn ON-OFF at same time.
Control any voltage with dry terminals that are separate from clock terminals
Two separate wires from breaker box.
Turns off 1 hot wire to each water heater

Use two 30 amp breakers and 10 gauge wires when wiring two 240Volt water heaters with element wattage over 3800 watts.

240 volt

GM40 controls two 240Volt water heaters

One or other water heater is ON.
Both heaters not ON at same time
Use 10 gauge wire

Two water heaters

120 volt

Wire GM 40 for 120Volt water heater

Set dip switches for 120Volt.
Dip switches must be set before power is applied to timer

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120 volt

Use GM40 to control 3-phase circuit

Most buildings with 3-phase also have 120Volt outlets.
Use 120volt to power timer. Wire timer as shown in illustration directly above.
Timer opens-closes circuit to 3-pole contactor with 120Volt coil.

See more 3-phase

120 volt or 240 Volt

Wire GM40 timer to toggle water heater between 120Volt and 240Volt.

Use this technique for peak electric prices.
When prices are peak, set water heater to opeate at 120 volts for slower heating. Tank stays hot, but hot water does not recover quickly.
When peak price ends, resume 240Volt operation for faster heat recovery inside tank.

Wiring inside water heater is not changed
Elements and thermostas will work wirh 120 or 240
This will not work for Whirlpool energy smart water heater
Off-peak water heater options

Turn Load ON once every 10 minutes for 8 hours per day.

Set 120Volt cycle timer for chosen time duration. For example once per each 10 minutes. Or once each 5 seconds. The cycle timer dial rotates continually, and turns load ON-OFF for each cycle.

To operate the cycle timer at different hours, install 2nd timer.
The second timer can be installed on the Hot line before or after the cycle timer.
Read more
CT2000 cycle timer

Whole house surge
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Surge
Whole house surge protector

Digital timers should be protected from surge.
Same with any water heater that is plugged into outlet.
All new appliances and water heaters with digital controls are vulnerable to surge

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Control 2 water heaters

Each water heater can have different 7-day schedule

10 gauge wire and 30 amp breaker run cooler.
30 amp circuit breaker and 10 gauge wire for water heater runs cooler with less energy loss. Breaker box lasts longer.

Different wiring:
For two 4500 watt water heaters, you can use one 40 amp breaker and 8 gauge wire to bring power from breaker box to the first timer.

For two 5500 watt water heaters, you can use 50 amp breaker and 6 gauge wire
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Set the FM1 clock
Rotate dial until current time shows on clock face Larger image	How to set timers
Timer dial has switch located on right side of face, below the arrowhead. This is the manual switch. With the manual switch in middle position, the GM40 is in automatic mode and will switch at the programmed times. In the upper position "I", the load is permanently ON. In the lower position, "O", the load is permanently OFF	Move pins out for times you want DC motor to operate. All consecutive pins must be out for hours you want motor to operate. Manually rotate clock dial to watch when motor turns on. After pins are set, manually rotate dial until current time lines up with arrowhead located on inner dial.
Link for replacement timer modules Buy GM40 at 1000 Bulbs

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