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Packard contactor
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2-pole 40 amp contactor
With removable dust cover on top.
Select voltage needed to control coil.

Buy 2-Pole 40A resistive
120Volt coil At Amazon
240Volt coil At Amazon
24 volt coil at Amazon
Mars 2-pole and 3-pole contactors at Amazon
Rheem HVAC replacement contactors
Fasco info sheet
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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.

How to wire contactor for water heater
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 the contactor points
Each contactor has coil voltage rating: this is the voltage needed to operate the switching coil
Approx 1-3/4" wide  x 3-1/2" long x 3" tall
Coil burden or coil VA is 7.3 Watts, inrush is 27 Watts.
Life expectancy <> 0.5 - 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 at Amazon
30 amp, 2-pole, open frame power relay with enclosure
SPDT.... different from DPST shown above.
Both perform same job. Both have 2 sets contacts. SPDT has extra set contacts so a second load can be turned on-off exactly opposite from off-on other load.

Buy from my affiliate links
Magnecraft box and cover
Magnecraft w199 relays at Amazon
Siemens power relays at Amazon

Difference between relay and contactor
DC relays for solar panels
3 phase contactor 3-pole contactor for loads up to 90 amp
For loads up to 90 amp
For coil voltages: 24, 120, 208-240, 277, 480 volt
Control 3-phase with 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 contactor 3-pole contactor wired for DC loads
DC direct current is different than AC alternating current.

AC current is a wave that crosses zero volts each time generator rotates 50-60 times per second,. US 60 cycles. Europe Asia 50 cycles.
DC current is a straight line. The voltage does not oscillate or vary like AC. Electrons flow through circuit at same voltage at all times.
When high voltage AC is turned off, the voltage drops to zero frequently.
When AC voltage hits zero, then the arc or spark or heat is easy to extinguish.
Result: AC switchgear like contactors last million repetitions without melting the points
High voltage DC is different. When high voltage DC is turned off, the electrons keep pushing. Voltage never reaches zero.
Result: DC voltage causes arc or spark or heat that is difficult to stop. Basically the electrons keep piling into 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.
With a 4-pole contactor, 3 poles can be used to turn off Positive, and 1 pole to turn off Negative
Add resistor in parallel with inductive winding* helps eliminate arcs. *Inductive winding is motor load

3-pole contactors at Amazon

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
CA3750 can be set to operate as one switch or two switches
30 amp, Z-wave contactor with enclosure
Selectable voltage: 120, 208, 240, 277 volt
Operate DPST or 2 x SPST contactor with z-wave
Two sets of contacts can be operated at same time, or separately.
So you can control different voltages at same time.

Intermatic CA3750 at Amazon
Smarthings Hub at Amazon
Contactor controlled by remote Z wave

How to wire and set up CA3750
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 At Amazon
240Volt coil At Amazon
Mars 2-pole and 3-pole contactors at Amazon

Furnas cross reference
Siemens cross reference
3-pole contactors
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
PB 300 connected to water heater
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Connect modular timer to contactor
PB series and other timer modules
24 volt programmable timers
Sprinkler timer connects to contactor
Convert 24 volt sprinkler timer to 120 volt Resource:
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 40 amp box timers
Compare all box timers
Override T104 timer Override T104 timer
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 At Amazon

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

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 at Amazon / Choose 120Volt coil
30 Amp relay at Amazon

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

Motion sensor

Motion sensor at Amazon

How to wire motion sensor

Heavy-duty relay
Optional box and cover for Magnecraft
Recommend this relay for motors exceeding 120 volt 1 HP/ 240 volt 2 HP
Magnecraft relay with NO NC terminals 120 volt coil or 24 volt coil
Buy from my affiliate links
Magnecraft box and cover
Magnecraft w199 relays at Amazon
Siemens power relays at Amazon

How to reverse motor with switch
Difference between contactor and relay
Relays for DC motors and solar panels
Control motor with 2 switches
Start two motors at different times
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
AC to AC output 24V to 480V input  80 to 250V
Solid state with heat sink
Solid State relays at Amazon
Solid state relay at Amazon
100-240Volt AC input / 20 amp/ at Amazon
80-250Volt AC input/ AC output/ 40 amp/ at Amazon

Electromechanical relay vrs solid state relay/ pdf

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

Read how to 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
120Volt SPST miniature relay at Amazon
240 Volt at Amazon
Zettler relays at Amazon

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 relays for solar power
Omron DC-DC pdf
DC power relay spec sheet
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 at Amazon
3PST AC-DC at Amazon
Functional relays at Amazon

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 at Amazon
Suncourt relay 1.2- 40 amp at Amazon
NK technology .75 amp at Amazon
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 at Amazon

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

Gas and electric water heaters Support the economy:
Buy water heaters  from my associate links:

50 gallon Gas water heaters at Amazon
40 gallon gas water heaters at Amazon
50 gallon Electric water heaters at Amazon
40 gallon electric water heaters at Amazon
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Troubleshoot electric water heater
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Icon gas valve

How to replace water heater element Waste King disposal
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Install point of use water heater
Titan tankless
Anode rods anode rods
Recirculation system

Tankless recirculation
Point of use water heater
Type 1 and type 2 surge protection surge protection

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box timers Resource:
Compare box timers
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Intermatic control centers: and parts
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