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#190841 - 12/08/09 09:21 AM Loose connections  
derater  Offline
Joined: Mar 2002
Posts: 179
Do loose connections use excess energy ? Do they waste electricity ?

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#190842 - 12/08/09 10:44 AM Re: Loose connections [Re: derater]  
ghost307  Offline
Joined: May 2005
Posts: 917
Chicago Illinois USA
Only if they result in heat. If the wire is loose but there is no heating, there is no waste.


#190843 - 12/08/09 10:57 AM Re: Loose connections [Re: derater]  
testguy  Offline
New Member
Joined: Jun 2007
Posts: 7
My thinking is that a "loose connection" equals either an open circuit or a higher resitance joint. With no current flow, no real power is "wasted". With current flow, you have higher I^2*R (watts) losses, so technically it's "wasted". But obviously, the real issue is that this energy can be enough to cause heating (and arcing), which leads to bad outcomes.

#190846 - 12/08/09 02:19 PM Re: Loose connections [Re: testguy]  
mikesh  Offline
Joined: Jun 2006
Posts: 613
Victoria, BC, Canada
Since loose connections usually get hot they waste power. Many electrical caused fires start with a loose connection. The longest time from connection to fire I have seen was a house wired circa 1910 had a connection related fire around 2000 or 2001. It took 90 years to ignite the structure and still left enough evidence to reveal the cause. That was a cold solder joint in Knob and tube.

#190851 - 12/08/09 09:17 PM Re: Loose connections [Re: mikesh]  
wa2ise  Offline
Joined: Nov 2002
Posts: 784
Oradell NJ USA
The amount of energy in a hot bad connection may be similar to that used by a 30W soldering iron. It won't run up the electric bill much, but that energy is happening where you don't want it.

#190853 - 12/08/09 09:44 PM Re: Loose connections [Re: wa2ise]  
HotLine1  Offline

Joined: Apr 2002
Posts: 6,874
Brick, NJ USA
OK, now it's math time, based on Wa2ise's input.

30 watts at 24 hrs equals 720 watts. Seven days a week = 5040 watts, carry on to a 52 week year, and we have 262 KWHr. Using approx. $ 0.15/KWHr. = $ 39.31 cost

Now....that's only one 'loose connection.

Further, using Mikesh's comment of approx. 90 years...$ 3538.00 wasted, excluding the replacement cost for the fire damage. I'll need one of those actuary type bean counters to factor in the cost of electrical energy for that 90 year span, thou.


#190857 - 12/08/09 10:44 PM Re: Loose connections [Re: HotLine1]  
gfretwell  Offline

Joined: Jul 2004
Posts: 9,135
This becomes a lot more complicated when you put the voltage drop in there. The entire circuit will have higher resistance so the equipment plus the bad splice uses less power than it would if the splice was OK but voltage drop may make motors less efficient and you lose that saving. If it was only lights and you were happy with the light output it is better than a wash. You save money on power and your bulbs last longer. The extra heat costs money in the summer when the A/C is on, again probably a wash when the heat is on.

All of that is true until the fire starts wink

Greg Fretwell

#190883 - 12/09/09 09:49 PM Re: Loose connections [Re: gfretwell]  
HotLine1  Offline

Joined: Apr 2002
Posts: 6,874
Brick, NJ USA

I didn't factor in anything except the hypothetical soldering iron 30 watt figure.

I give my students a typical 'line-loss' calc with the Vd calcs. Boy, you want to see some $$$ costs from the math challenged!


#190889 - 12/09/09 10:08 PM Re: Loose connections [Re: HotLine1]  
gfretwell  Offline

Joined: Jul 2004
Posts: 9,135
Just bear in mind utilities "brown us out" when they want to reduce consumption. All of the I2R calculations I see assume the load will still be drawing the same current with the dropped voltage.
Pretty soon we will be revisiting the light bulb saver thread.

Greg Fretwell

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Brick, NJ USA
Posts: 6,874
Joined: April 2002
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