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Water heater contactors
Also read: 3 phase water heater
Packard contactor
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2-pole 40 amp contactor
With removable dust cover on top.
Select correct voltage needed to control coil.
Water heaters typically use 240 volt coil, HVAC replacement is 24 volt coil. Typical 2-pole contactors are rated with 24, 120, 208-240 volt coils. Three pole contactors for 3-phase are available in more coil voltages not found in residential applications such as 277, 480 etc. Using the wrong coil voltage will cause problems. Selecting a contactor rated for more amps is better, so using 240 volt 40 amp contactor for 240 volt 30 amp water heater is fine.

Buy 2-Pole 40A resistive
120Volt coil
40 amp 240Volt coil
24 volt coil
Packard contactor
Mars 2-pole and 3-pole contactors
Rheem HVAC replacement contactors
50 amp contactor
60 amp contactor
Fasco info sheet
3-pole contactors
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What is a contactor?
Contactor is a switch. It is rated for high amp loads.
High amp causes heat. Heat will damage regular electrical parts.
Timers and wall switches can be damaged by high amperage.
Each switch and timer has amp rating.
Contactors are rated for more amps than ordinary wall switch or timer.

The electrical circuit lasts longer when a contactor is used because contact points on a contactor are designed to switch high amp loads without melting or being damaged by heat.
The electromagnetic coil can be switched on-off using ordinary wall switch or timer.
When voltage is applied to coil, then contact points close, and heavy amp circuit turns on.
This lets you control heavy amp loads using ordinary wall switch or timer.
45EG20AF in box
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Contactor safety
All wire connections must be inside enclosure with cover.

2-pole 40 amp contactor in 6x6x4 enclosure

Using #8-32 x 3/4" bolts
Install contactor at angle leaves room for wire

This is DPST contactor
Double pole, single throw.
So the contactor is double pole, or 2-pole. It can turn off 2 wires.
And single-throw because both poles are on-off at same time.
So you can switch both wires in 240 volt circuit.

6x6x4 pull box
6x6 enclosures


How to wire contactor for water heater
Types of enclosures
Compare types of enclosures
Specifications for 2 pole contactor
Each contactor has amp rating: this is the number of amps that can be safely handled by the contactor points
Each contactor has coil voltage rating: this is the voltage needed to operate the switching coil. Incorrect voltage will cause contactor to chatter or cause coil to burn up.
30-40 amp contactors are approx 1-3/4" wide  x 3-1/2" long x 3" tall
Coil burden or coil VA is 7.3 Watts. Inrush when contactor is activated is 27 Watts.
Life expectancy = .5 - 2.0 million operations
Life expectancy of Siemens definite purpose controllers
Contactor dimensions
single-pole contactor
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1-pole contactor
Only leg is turned on-off, while other leg is continuously connected

Single pole contactors
3 phase contactor 3-pole contactor for loads up to 90 amp
Same as 2-pole contactor except with extra pole.
Normally used for 3-phase commercial applications with 30-90 amp loads, but can be used to control 3 separate loads, or be used as a ordinary 2-pole contactor.
Coil voltages include 24, 120, 208-240, 277, 480 volt
Control 3-phase with contactor

3-pole contactor

3-pole contactors
What is 3-phase
How to wire 3-phase timers and contactors
How to convert 3-phase water heater to single phase
DC contactor3-pole contactor wired for DC loads
DC direct current is different than AC alternating current.

AC current oscillates back and forth on the wire each time generator rotates 50-60 times per second. US and Americas the standard is 60 cycles. Europe Asia Africa etc 50 cycles. With AC electricity, the electrons actually change direction. At the midpoint in each oscillation, the voltage crosses zero volts, making it easier to extinguish the arc caused by disconnection of a switch.
DC current does not oscillate. Instead, the electrons flow through circuit at same direction and voltage at all times.
When AC voltage hits zero volts, then the arc or spark or heat is easy to extinguish.
Result: AC switchgear, like contactors, last million of repetitions without melting the points.
High voltage DC is different. When high voltage DC is turned off, the electrons keep pushing because the voltage never reaches zero.
Result: DC voltage causes arc or spark or heat that is difficult to stop. Basically the electrons keep piling up and pushing the arc across the points of the contactor.
DC switchgear must be rated for DC voltages, and be capable of extinguishing DC arc.
Illustration shows one method of extinguishing DC arc using 3-pole contactor. The circuit has 3 parallel switches on the positive wire, thus helping to stop the arc better than 1 switch
With a 4-pole contactor, 3 poles can be used to turn off Positive, and 1 pole to turn off Negative.
To help eliminate arcs, add a resistor in parallel with inductive winding. Example of inductive winding is motor load

3-pole contactors

Solar contactor/ pdf
DC relays for solar
DC contactor wiring diagrams/ pdf
What is 3-phase electricity
Can AC circuit breaker be used for DC
Smarthings Hub Zwave Contactor controlled remotely
30 amp, Z-wave contactor with enclosure
Selectable voltage: 120, 208, 240, 277 volt 

GE z-wave contactor
Zwave from GE
Smarthings Hub

How to wire and set up ZW4004
Wires connect to contactor using female terminals
Hot and neutral can connect to either side.

Solid wire vs stranded
Terminals are best with stranded wire, but solid copper is most reliable connection for 120-240 volt high-amp loads.
With solid copper wires (instead of stranded wire), I recommend putting the heavy amp load wires under screw plate instead of using terminal.
When using terminal with solid copper wire, it is best to add a bit of solder so the connection is not loose... it is very difficult to get reliable connection using terminal on solid wire. Never use aluminum wire.

120Volt coil
240Volt coil
Mars 2-pole and 3-pole contactors

Furnas cross reference
Siemens cross reference
3-pole contactors
Terminal kit with crimp tool
Electrical terminals
Blue 14-16 gauge female terminals 20 pcs
Yellow 12-10 gauge female terminal 16 pcs
360 pc assortment
520 pc assortment
More about #10 & 14 female terminals
PB 300 connected to water heater
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Connect modular timer to contactor
PB series Battery-operated/ pool spa timer
7 programs
7-day 0r 24 hour
120V or 240V
Buy 240 volt:
240Volt 24 hour
240Volt 24-hour

PB series and other timer modules
24 volt programmable timers
Sprinkler timer connects to contactor
Convert 24 volt sprinkler timer to 120 volt

Sprinkler timers
Intermatic sprinkler timers


How to wire Intermatic sprinkler timers
3-pole contactor
Control 3-phase using contactor

3-phase contactors

How to wire 3-phase timer
How to wire 3-phase
What is 3-phase
Compare DPDT 40 amp box timers
Compare all box timers
voltage monitorLine phase- voltage monitor
The problem of low voltage does not affect resistance loads like, light bubs or electric water heater, except to make them burn at dimmer capacity... low voltage does affect inductive loads like contactors, relays, motors, pumps, HVAC causing problems such as lower rotation speed on motor, causing higher temperatures, and burning out the motor.
Voltage monitor  Protect motors and equipment from low voltage
Adjustable voltage range
Caution: select incoming voltage to match Line voltage
Select amp rating of contactor to match amp rating of Load
Select matching contactor voltage and coil voltage range
Undervoltage on contactor coil will cause chattering, Overvoltage on coil will melt coil. Single and 3-phase
Single phase 95-270 volt range
3-phase 80-300 volt range
120Volt 24 hour
ICM phase monitor
Siemens monitoring relay
Difference between single phase and 3-phase
How to wire voltage monitor
Override T104 timer Override T104 timer

T104 series timers
Contactor with 240Volt coil
40 amp contactor, 208-240 volt coil

T104 timer wiring
T100 series timers
Compare all box timers
Pool control centers
Freeze controls
Control motor with 2 switches
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Control motor with 2 switches
Same wiring diagram applies to single-pole switch

Buy Contactor with 240Volt coil

240Volt coil

Start winding pulls more amps than switch can safely handle.
Over time, the switch will fail.
Contactors are rated for heavy amp loads, with expected life of millions of operations

Delay timer for motor or pump
Control motor with 2 switches or timer
Motor troubleshoot and resources
30 amp, 2-pole, open frame power relay with enclosure
SPDT relay.... different from DPST contactor.
Both perform same job. Both have 2 sets contacts. Open frame relay SPDT has extra set contacts so a second load can be turned on-off exactly opposite from off-on other load.

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Magnecraft box and cover
Magnecraft w199 relays
Siemens power relays

Difference between relay and contactor
DC relays for solar panels
Reverse motor using DPDT relay
Control motor with 2 switches
Start two motors at different times
How to reverse motor with switch
Relays for DC motors and solar panels

Omron LY23 AC Model terminals/ back to front:
7-8 magnet terminals (turned opposite direction from other pins)
5-6 common terminals
3-4 NO normally open terminals (power is off when relay off)
1-2 NC normally closed terminals (power is On when relay is off)
Load rating 7.5 amps AC
900 watts incandescent @ 120V
1800 watts incandescent @ 240V
1/4 Hp motor @ 120V; 1/2 Hp @ 240V
To reverse operation of photo-eye
So Load comes on during daylight hours
photo eye connected to DPDT relay

30 Amp relay x 80% = 24 amp max up to 2880 watt @ 120V or 5600 watt @ 240V
30 amp 10 gauge wire up to 2 Hp @ 50' or 1.5 Hp @ 100' @ 120V See load charts
Use Omron 120volt LY2-AC 8-pin relay for 7.5 amp.
    NO NC Relay
    7.5Amp Omron         30Amp DPDT
Omron LY2 / Choose 120Volt coil
30 Amp relay

Omron relay/Page 450 / pdf
Reverse Motion detector Reverse motion sensor so Load turns OFF

Motion sensor

Motion sensor

How to wire motion sensor
Solid state relay Solid state relay/ SPST
Check for AC-AC input-output
DC input to AC output is most common

AC to AC input 80-280V AC input 24-380V AC
Uxcell solid state relays
Solid State relays

Electromechanical relay vrs solid state relay/ pdf

DC to DC solid state relays
Buy from my associate links
200 volt 25 amp DC relay
Relay safety cover
Heat sink

Convert AC water heater to DC/ high voltage
Convert AC water heater to DC/ low voltage
Electromechanical relay vrs solid state relay/ pdf
SPDT model C shown/ 30 amp NO terminal/ 20 amp NC @ 277 V
Also available SPST model A/ 30 amp NO terminal @ 277 V
Base 1.08" x 1.98" / 1.09" high
Zettler 30 amp miniature power relay
Coil voltage 120-240 VAC / also DC ratings
Contact ratings 277 volt AC/ 28 VDC
Use quick connect terminals


Atwood miniature relay
Zettlet 240-120Volt SPST miniature relay

Zettler relay wiring
Override thermostat with programmable timer
Manual/ spec sheet
DC power relay
250VDC    25 amp                                                                     400VDC  200 amp     
DC to DC relay/ mechanical type
DC power relays
Full on-off contacts/ 12 or 24 volt DC coil
250 volt / 25 amp DC load
250V x 25 amp = 6250 watt
Connect 12 or 24 volt DC to terminals 3-4;
Connect load to terminals 1-2

Electromechanical DC-DC G9EB-1 relay
24 VDC coil and 400 VDC/ 200 amp contacts
Omron relay at online

DC power relay spec sheet
DC relays for solar power
Omron DC-DC pdf
12 Volt DC relay
Coil 12-24 VDC
Load contacts 26 VDC  40-50 Amp
12 VDC 40-50 amp DC power relay
W199AX-3 relay
W199PX-13/ 50 amp at 26 VDC = 1400 watt
X199 Magnecraft relay
Magnecraft W199 DC relay

Magnecraft relay / pdf
enclosed relay Enclosed relays/ Functional devices
Enclosed relays
Functional relays
Aprilaire relay Amp relay
When amp exceeds amp set point, the relay activates 120 volt circuit.
Recirculation pump is 1/25 Hp or 30 watts divided by 120 volts = .25 amp\
1 Hp motor is 750 watts divided by 120 volts = 6.25 amp
Use relay to control contactor when load exceeds 50 watts
Use to activate duct booster fan
Take off bracket and install bracket around a control wire that carries amperage
When amperage flows across line, the Aprilaire relay activates... and closes circuit going to 120 Volt load... such as indicator light... or another relay etc... the indicator light turns ON.
Wrap the wire multiple times to increase measurable current
Use a current transformer to reduce current
Aprilaire relay 4 amp
Suncourt relay 1.2- 40 amp
Current relays
NK technology sensing switch
Louensy 0-200 amp
Johnson current sensing
Low amp current indicator
Current sensing relays
Current sensing switch
Current Transformer
Current sensor module
Aprilaire manual .pdf
Johnson control amp sensing switch/ pdf
NK technology AC current sensing switch/ pdf
Contactor maintenance
Life expectancy <> 0.5 - 2.0 million operations

Contact points stick sometimes

Solution: use nail file or emery board or folded sandpaper to clean off points.

Handy trick
Add indicator light so you can see when water heater is on. If points stick, indicator light remains on.

Electrical formulas
Indicator light
240Volt Pilot light

How to wire water heater pilot light

Add to water heater indicator light page:
Low amp current indicator
Additional links
Electricity leaves power plant Electricity:
The grid is defined by three parts: transmission, distribution and end user. The following links show how it works
Power plant to end user power pole
Power pole to residential breaker box
Power pole to commercial breaker box

How to wire residential electric
How to wire commercial 3-phase
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Icon gas valve

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Control water heater w/ Z-wave
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