Tip & How-To about Heating & Cooling

How it works: Central AC Contactor

Magnetic relays commonly known as definite purpose contactors are used in a variety of different applications throughout the HVAC and Appliance world. They can have anywhere from 1 pole or up to 4 poles or more. The coils on them can be 24 volt 120 volt 240 volt or even 440volt and better. Their main job is to power compressors and fan motors on various equipment. On a home unit the contactor is almost always a 24 volt, 2 pole, 30 amp one. Some smaller units have what is known as a pole and a half. or 1.5 poles. The coil pulls down only one side of the contactor, while the common leg has a straight bar across it. On home units smaller thermostat wires connect to the 24 volt coil powered by a transformer.When the temp rises the thermostat calls for the contactor to yank down and power up the compressor and fan outside. If those small wires are chewed up by an animal or a weed eater then power to the coil cannot do its job. Very often the 24 volt coil on the base of the contactor just dies. A couple videos I found on line will give an idea of various types used in home units. A guy had a unit which would not shut down because of fried welded together contacts. He did an autopsy of the old part. I thought it was cool.

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Electrical sub panel


yes, as long as you don't have anything that runs off 240vac, if you do and it runs at a lower voltage, the device will run at a ampere rating. good rule of thumb to remember, lower the voltage, higher the amps. with every ampere you add, you add units of heat. but as long as you are running single phase devices you should be fine. Now, if you are feeding a transformer with two phases, check the load side voltage. you might need to adjust your taps on the transformer accordingly. it will affect any type of sensitive electronics such as; control voltage for frequency drive, rectifiers, the coils on magnetic contactors and auxiliary contactors as well, due to a problem known in lament terms as relay bounce.

Jan 18, 2014 | Electrical Supplies

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I need to put a 24 volt coil relay in my furanace for an EAC and I'm not sure how to hook it up. I'm guessing the low voltage wires from the thermostat (w & b wire) will go to coil side and then there are three prongs that are stick out on top side of relay are those for the hot wires?


Electricians don't guess, they test.
Usually 'relays' used for HVAC are called contactors, for some reason.

1) 24Volt wires connect to coil. Make sure contactor coil is rated 24Volts or 24vac
Coil terminals are typically located on side of contactor.
Usually you can see small copper wires from coil that are soldered to these terminals.
Test across terminals with multimeter set to read ohms, and you will get ohm reading of coil.

2) The 120V or 240V wires connect to terminals located on ends -or- on top of contactor.
If there are three terminals, then check these terminals with multimeter.
Push down contactor to simulate the contactor turning on and off.
Hold contactor down and test terminals again.
And compare test results with same test from old contactor being replaced.

3) Open following link to see typical 24V coil contactor with DPST with 2 NO contacts
The contactor shown in diagram is similar to your contactor, except the contactor shown has 4 terminals for 120V or 240V. This is why testing contactor and comparing with old contactor is necessary.
http://waterheatertimer.org/images/ON-delay-timer-diagram2-300.jpg

Sep 20, 2011 | Honeywell International Honeywell...

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significant applications of anaerobic respiration in winemaking?


Vinegar is s the natural result of air exposure of beer and wine, as acetic acid-producing bacteria are present throughout the world.For most of human history, acetic acid, in the form of vinegar, has been made by acetic acid bacteria of the genus Acetobacter. Given sufficient oxygen, these bacteria can produce vinegar from a variety of alcoholic foodstuffs. Commonly used feeds include apple cider, wine, and fermented grain, malt, rice, or potato mashes.Vinegar is s the natural result of air exposure of beer and wine, as acetic acid-producing bacteria are present throughout the world.For most of human history, acetic acid, in the form of vinegar, has been made by acetic acid bacteria of the genus Acetobacter. Given sufficient oxygen, these bacteria can produce vinegar from a variety of alcoholic foodstuffs. Commonly used feeds include apple cider, wine, and fermented grain, malt, rice, or potato mashes.

Aug 24, 2011 | Computers & Internet

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fan grill light warmer all working but main oven wont heat up


Late models rely on a circuit board with a small black relay to power the oven and broiler elements. These relays often fail shortly after the warranty period. If you're handy with electronics and a soldering gun you can replace the relay components with parts from Radio Shack. Otherwise buy the circuit board. Get the part number from the board and shop on-line for best prices. I have repaired once using optical semiconductor relays to pass low voltage to new definite purpose contactors rated 40Amps and normally used for HVAC systems. This required addition of a 24vac control voltage transformer. Isolation of the circuit by the optical semiconductor relays makes clear where the add-on circuit starts for future repairmen who examine the unit.

Dec 12, 2009 | Whirlpool Ovens

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Dayton Motor and capacitors for Carrier AC Unit (model # 38ck030300)


The 2 brown wires to the cap in first legend is how they are wired electrically,inside that motor the run winding is common to that brown one they cappped off in the 2nd option, but the powers still going to Run.ommon and run get the juice either way, its just another way to do it, but electrically as to sides of power and where they go is no different, just different way to do it.you can run power in on the Run terminal on the run cap, the run winding and run cap and start cap if equipped are Run to Run to Run.So the hot leg for the run winding also goes to run on the caps, run to run to run.,run winding to run cap to run on start cap.

Apr 07, 2008 | Carrier 38CKC036 Air Conditioner

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