Very warm solenoid

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jbeletti

Member - Posts: 36

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Joined: February 06, 2006

Location: United States

Posted: December 30, 2006 at 10:19 PM / IP Logged

I am using a White-Rodgers 12 VDC / 80 amp, normally-open, continuous-duty solenoid (image below) to switch the output of my auxiliary battery into my fuse block for some CarPC gear.

This solenoid takes the positive output of the battery and passes it to the fuse block. I "will" have one side of the coil grounded to the battery negative and the other side connected to the battery positive with an inline switch.

My switch wiring is not yet complete so for testing purposes, one side of the coil connected to the ground buss of the fuse block (which is connected to the battery negative). I have temporarily jumpered the other side of the coil to battery positive (battery input terminal of the solenoid). The coil clicks firmly when energized and again when de-energized.

My issue is that without any load (other than the coil), the metal case of this solenoid gets very warm. I have searched this forum for warm and hot relays. I read all matching threads and it seems normal for some relays to be somewhat warm when their coils are engergized, depending on the load being pulled through the relay. I found no warm or hot solenoid threads here.

So I am wondering if my solenoid case under a no-load scenario should be warm to very warm?

Under standard operation, my system will be on (i.e. an energized coil) up to 10 hours per day. And when I rework my system in my truck, that system could be on for several days at a time. This is why I chose continuous-duty units.

Thanks for any input.

Jim

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sk8er666

Member - Posts: 9

Joined: December 26, 2006

Location: Canada

Posted: December 31, 2006 at 10:25 PM / IP Logged

2 reasons it will get hot

1: overvoltage of the coil ===more heat

2: undervoltage of the coil=== more current= more heat

100% of coils designed can handle 110% of the voltage its rated for, but you dont want to go over that, at all., so a 12 volt coil should be able to handle 13.2volts no problem, so you dont want to go any higher then that.. if the voltage is lets say 14volts or something you might want to hook a resistor to it in series with coil to lower the voltage to coil. To figure out the right size you will need to do some ohms law.

and on the other hand the heat might be normal, or it could be a poorly designed solenoid. The cont duty rating has nothing to do with the heat, its just the rating at which the contacts can handle, so lets say a intermit duty solenoid will be rated for 80amps the contacts would be smaller then normal, and a cont duty will have atleast 125% larger size contacts rated for 80 amps, so lets say it will handle 100amps for intermit duty.

hope that helps

Master Electrician

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jbeletti

Member - Posts: 36

Joined: February 06, 2006

Location: United States

Posted: December 31, 2006 at 11:12 PM / IP Logged

sk8er666,

Thanks for the reply. Jope to put some time in on the system tomorrow and I'll measure the voltage with the car running and car off. After my last test, I closed the breakers at the battery input and the battery isolator output to the battery could start taking a charge from the alternator. Perhaps my charge state was low.

Jim

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electrostatic

Copper - Posts: 154

Joined: January 06, 2006

Location: United States

Posted: December 31, 2006 at 11:18 PM / IP Logged

yes overvoltage can cause problems. undervoltage, no. the coil has a fixed resistance and ohm's law says that current is directly proportional to voltage. less voltage=less current=less heat.

Prove your connections, use a meter!

I promise, I'll behave!

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Very warm solenoid

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