# Any electricians on here?



## charly (Jul 18, 2013)

1840 Farmhouse, 200 amp service.. What they did do is leave a knife switch ahead of the main panel with two 100 amp fuses, plus the breaker box has it's own 200 main breaker.. Since we bought the place , I always noticed if you run a saw, or the vacuum, you can see the lights do a slight but noticeable quick dim.. Well for the heck of it I plugged a digital volt meter into an outlet in the kitchen.. Now I watched,, had 119 volts, had the wife turn the vacuum on , it dropped and stayed at 116 volts while it's running... She was plugged in upstairs on a different circuit.. If I open our refrigerator door I can watch the meter drop a half of volt as the light comes on... Do I have corrosion on a meter leg or a bad neutral or main ground issue some wheres? How about those old fuses? I checked every wire except the mains in my box, all tight.. Couldn't wiggle the mains.. Shouldn't the voltage stay the same as things are powered up?    I'm wondering if this is causing us to use more power then needed, thus giving us a higher bill then we should be seeing.. Try to figure where to start.. Another person said we could be at the end of a primary run, thus needing transformer on the pole...I'm all open for what might be the issue here. Be nice to find out we have an issue and can get our power usage down...I always thought our KWH usage was higher then it should be for what's running here..


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## begreen (Jul 18, 2013)

Not sure why the knife switch was left, particularly with lower amperage fuses. I'd eliminate it for starters. Many things can influence voltage drop. As you have noted, corroded meter jaws, and oxidizing connection (esp. if aluminum), bus corrosion, undersized wire, etc.. In our house we had a serious voltage drop that turned out to be the neutral leg from the pole was failing. It was rubbing up against maple tree and slowly failing.


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## Jack Straw (Jul 18, 2013)

They probably left the knife switch so they could cut the power to install the breaker box. The 2-100 amp breakers equal the 200 amp breaker box. The old famers were very cheap!


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## begreen (Jul 18, 2013)

It's easy to just to pull the meter if you want to cut the power. The knife switch add 4 connection points and the knife contacts which are all potential loss points and the switch presents a potentially lethal shock hazard.


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## seige101 (Jul 18, 2013)

Can  you post a few pics for us? One of the outside wire going into the meter and then the wires going in and out of the knife switch.

Sounds like they only upgraded half your service


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## Highbeam (Jul 18, 2013)

Jack Straw said:


> They probably left the knife switch so they could cut the power to install the breaker box. The 2-100 amp breakers equal the 200 amp breaker box. The old famers were very cheap!


 
Not true, the 100 amp breakers are one per leg so you are only breakered at 100 amps to feed a 200 amp panel. Remember this is 240 so each hot line must have have a 200 amp CB.

Another thing to consider is that the entire service between the panel and the transformer may be sized for 100 amps. Removing that 100 amp knife switch means you are doubling the potential current in the line. Time to get the whole thing checked out, you may be limited to 100 amps.


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## Jack Straw (Jul 18, 2013)

Oh your right! I never realized that.


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## charly (Jul 18, 2013)

I'll get some pics together.


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## charly (Jul 18, 2013)

says 240 vac on the tag






	

		
			
		

		
	
 I notice the braided ground go no wheres on the lower left in the box... Maybe an issue coming from the neutral.


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## begreen (Jul 18, 2013)

Hare to tell but it looks like they kept the original 100 amp feed from the strike and meter. What is the gauge of the neutral going to the breaker panel?


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## ewdudley (Jul 18, 2013)

Highbeam said:


> Not true, the 100 amp breakers are one per leg so you are only breakered at 100 amps to feed a 200 amp panel. Remember this is 240 so each hot line must have have a 200 amp CB.
> 
> Another thing to consider is that the entire service between the panel and the transformer may be sized for 100 amps. Removing that 100 amp knife switch means you are doubling the potential current in the line. Time to get the whole thing checked out, you may be limited to 100 amps.



What HB said.  If the service wiring is only good for 100 amperes then need to leave well enough alone.  The fuses and knife switch look just fine from the pictures.

You can investigate the voltage drop further by connecting your meter to the mains or other unrelated circuits to see if the whole house leg is dropping as opposed to just the circuit that the vacuum is connected to.


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## charly (Jul 18, 2013)

begreen said:


> Hare to tell but it looks like they kept the original 100 amp feed from the strike and meter. What is the gauge of the neutral going to the breaker panel?


2/0   I'm thinking my triplex from the pole might be undersized? Maybe for 100 amp.. Was all done before we bought the place... I was shocked to see a 200 amp box filled for the 1900 sq ft.. They must have really broke the circuits down, which I guess is a good thing.. Just don't like seeing that voltage drop thing going on and staying there.. I think that's odd.. Have to look inside the meter box,,, maybe major corrosion on one leg or a neutral. Something is pulling current because of the lights dimming when a load comes on..


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## ewdudley (Jul 18, 2013)

Also:  " had 119 volts, had the wife turn the vacuum on , it dropped and stayed at 116 volts while it's running.."

If circuit is 150 ft round trip 12 gauge copper, and vacuum draws 15 amperes, then 15 amperes times 150 ft times 1.588 ohm per 1000 ft equals 3.573 volts.  Dropping from 119 to 116 VAC would be a small surprise.


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## charly (Jul 18, 2013)

ewdudley said:


> Also: " had 119 volts, had the wife turn the vacuum on , it dropped and stayed at 116 volts while it's running.."
> 
> If circuit is 150 ft round trip 12 gauge copper, and vacuum draws 15 amperes, then 15 amperes times 150 ft times 1.588 ohm per 1000 ft equals 3.573 volts. Dropping from 119 to 116 VAC would be a small surprise.


So that is a normal voltage drop?  Thing is the vacuum was on another circuit.  Even when running a circular saw plugged into an outdoor receptacle , the kitchen lights still do that quick dim thing... That's what I'm trying to figure out..


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## ewdudley (Jul 18, 2013)

charly said:


> So that is a normal voltage drop?  Thing is the vacuum was on another circuit.  Even when running a circular saw plugged into an outdoor receptacle , the kitchen lights still do that quick dim thing... That's what I'm trying to figure out..



Inrush amperage on the circular saw maybe 4X rated amperage, call it 60 amperes, with long extension cord  even worse.  Certainly enough draw to cause a voltage dip for the whole house that you could see in all the light bulbs.


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## jharkin (Jul 18, 2013)

[Not an electrician]

First off I concur with everybody else - You have a 200 amp panel but they left the 100 amp service.  Looking at the photos the wires looked a bit small. You say that the wires from the disconnect to the panel are 2/0  - looks like copper 2/0. Its hard to see but the service entrance wires on the other side of hte fuse look like similar sized aluminum? If you do indeed have 2/0 Aluminum service entrance than you definitely still have e old 100amp service entrance setup - When I had 200amp service put in they wired me with* 4/0* Aluminum to the weatherhead.

So my guess? Somebody ran out of panel space for more circuits and decided to cheap out on an all new service and just put in the 200 box for the breaker space.  In this case the 200amp main is only acting as a box disconnect and not providing main overcurrent protection.


Now, all of this doesn't explain your voltage drop around the whole house. Ewdudley's calculations sound right (other than I dont think I've ever seen a vacuum over 12A) but you would only see that behavior at the far end of the circuit with the load on it. You seem to see it on all circuits when any one circuit is loaded and that tells me the problem is upstream.  First I would confirm that by randomly trying loads on a few different circuits and testing other circuits - ideally test an outlet as close to the panel as possible.

Once confirmed that this is really effecting the entire house its time to check everything upstream - look at the blade fuse disconnect. Check that they properly connected those aluminum wires (aluminum rated connectors, clean wire, coated connections with anti-oxidant grease). You might want to hire a pro to look at this and to check the connections up at the weatherhead.  If all that checks out (and it might well) it could be a problem on the utility side - maybe a transformer going bad or something (this is beyond me).


[/Not an Electrician]


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## charly (Jul 18, 2013)

jharkin said:


> [Not an electrician]
> 
> First off I concur with everybody else - You have a 200 amp panel but they left the 100 amp service. Looking at the photos the wires looked a bit small. You say that the wires from the disconnect to the panel are 2/0 - looks like copper 2/0. Its hard to see but the service entrance wires on the other side of hte fuse look like similar sized aluminum? If you do indeed have 2/0 Aluminum service entrance than you definitely still have e old 100amp service entrance setup - When I had 200amp service put in they wired me with* 4/0* Aluminum to the weatherhead.
> 
> ...


Definitely going to have it looked at... I want to see what the home inspection guy missed!


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## charly (Jul 18, 2013)

jharkin said:


> [Not an electrician]
> 
> First off I concur with everybody else - You have a 200 amp panel but they left the 100 amp service. Looking at the photos the wires looked a bit small. You say that the wires from the disconnect to the panel are 2/0 - looks like copper 2/0. Its hard to see but the service entrance wires on the other side of hte fuse look like similar sized aluminum? If you do indeed have 2/0 Aluminum service entrance than you definitely still have e old 100amp service entrance setup - When I had 200amp service put in they wired me with* 4/0* Aluminum to the weatherhead.
> 
> ...


The hots from the fuse box are copper that go to the main breaker panel.. They are of the proper size, twice as big as the 2/0 aluminum neutral . Can't see any wire gauge size on the copper..The fuse box is labeled 200 amps, so 100 amps on each leg coming in.. It's aluminum wire coming into the fuse box from the meter.. I'm betting there is an issue in the meter box.. Think I will ditch the aluminum from the pecker head in and by pass the fuse box,  going directly to the 200 amp service panel..  I'll also confirm the wire size coming in from the pole... That's a good 100 ft plus run as well... Maybe that service entrance wire should be sized bigger for the run as well.. I know a few local electricians who will check things out for me...


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## jharkin (Jul 18, 2013)

Highbeam was right up thread... 200 amp service means a 200 amp breaker on each leg. Since you have a 100 amp fuse on each leg you effectively have 100 amp service regardless of what the panel sticker says.


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## charly (Jul 18, 2013)

jharkin said:


> Highbeam was right up thread... 200 amp service means a 200 amp breaker on each leg. Since you have a 100 amp fuse on each leg you effectively have 100 amp service regardless of what the panel sticker says.


I thought 100 amps on each side gave you 200 total  Plus the breaker box has a 200 amp main breaker.  I really have to get this looked at and find out what's what...  I know I want to get rid of those fuses...


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## jharkin (Jul 18, 2013)

The 200 breaker in the main box is a double pole breaker - I.e. 200 on each leg.

A 200 amp residential service gives you 200A at 240v ( hot to hot) for 48kW of available power. Wire up enough 120 volt loads and in theory you could draw 400A at 120v (hot to neutral) if you max both hot legs.

Needless to say most of us don't come anywhere close to maxing one out, even all electric households.


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## charly (Jul 18, 2013)

Just took a closer look, each fuse does say 200 amps, my mistake... I'm thinking in the meter can there are some issues with the aluminum service wire...corrosion or loose connection..  Plus the wires coming out of the weather head look pretty sun beat...insulation is showing wear..


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## oldspark (Jul 18, 2013)

Doesn't sound like much of a voltage drop to me, electricity is not magic.


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## fbelec (Jul 19, 2013)

from what i see you have a 200 amp service. the wires coming in 2/0 copper is 200 amp. the wire coming from the meter to the fuse disconnect look like aluminum but are copper. when those wires were put in they didn't use aluminum wire i don't think that aluminum was on the market at that point. those wires are what is called copper clad. which is copper with a small coat of i think lead to keep the copper from corroding. water could get into those old wires so they did not want in to turn green. you need to do the same test with your vac or saw but take the volt reading at the line side of your meter. also check the other phase to see if there is a voltage drop or rise if you get a voltage rise you could be having issues with the neutral and are using the ground as neutral which would be a #4 copper. if you have 116 volts under load the power company prob won't listen. but if you turn on a few heavy draws in the house and you are dropping to 110 or lower they come out to see. those old crimp connectors that are outside up at the weatherhead are always a problem. and or at the pole. i run into that old wiring all the time here in mass. lots of old houses up here. btw up here the only time i see the power company up size their wire is when the old stuff failed due to the current load. i have had the power company a number of times hook up my 500 mcm copper (400 amp) wire to their 1/0 aluminum service drop and when questioned they told me it was fine and would replace it if it failed. single phase like houses and commercial power 3 phase.NICE.

frank


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## charly (Jul 19, 2013)

fbelec said:


> from what i see you have a 200 amp service. the wires coming in 2/0 copper is 200 amp. the wire coming from the meter to the fuse disconnect look like aluminum but are copper. when those wires were put in they didn't use aluminum wire i don't think that aluminum was on the market at that point. those wires are what is called copper clad. which is copper with a small coat of i think lead to keep the copper from corroding. water could get into those old wires so they did not want in to turn green. you need to do the same test with your vac or saw but take the volt reading at the line side of your meter. also check the other phase to see if there is a voltage drop or rise if you get a voltage rise you could be having issues with the neutral and are using the ground as neutral which would be a #4 copper. if you have 116 volts under load the power company prob won't listen. but if you turn on a few heavy draws in the house and you are dropping to 110 or lower they come out to see. those old crimp connectors that are outside up at the weatherhead are always a problem. and or at the pole. i run into that old wiring all the time here in mass. lots of old houses up here. btw up here the only time i see the power company up size their wire is when the old stuff failed due to the current load. i have had the power company a number of times hook up my 500 mcm copper (400 amp) wire to their 1/0 aluminum service drop and when questioned they told me it was fine and would replace it if it failed. single phase like houses and commercial power 3 phase.NICE.
> 
> frank


Thanks for the info Frank... I'm going to get a hold of someone to check those weather head connections... Wire up there is getting pretty beat looking so maybe run a new wire into the meter can and see what the connections look like in there as well.. I have a friend that works for the local power company,, she was a lineman at one point... I'm sure she can get someone out here if it comes down to that...Just don't want to leave things they way they are, with the lights dimming.. I think there's a solution for that...and maybe be better for my power bill as well.
Charlie


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## oldspark (Jul 19, 2013)

Your lights will dim if you have one leg loaded up more then the other causing an unbalanced load.


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## charly (Jul 19, 2013)

oldspark said:


> Your lights will dim if you have one leg loaded up more then the other causing an unbalanced load.


  Have to look and see how many big draws are on the one leg... I'm thinking more a bad connection some wheres or corrosion.. That would be an easy fix...


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## Highbeam (Jul 19, 2013)

Now that you have 200 amp fuses in the knife switch you are double protected. If you end up replacing the wires between the panel and the peckerhead or even the pole, get rid of that old knife switch. It does nothing for you and can only add resistance and trouble.

For now, turn someone loose on that vacuum and use your voltmeter to verify the voltage drop at the knife switch. If the voltage is low at the knife then you know the problem is between the knife and the transformer. I would not expect a 15 amp load to drop you 4 volts at the knife. Check volts before the vacuum load and then after. Line voltage in the street can vary throughout the day.

I had a bad connection at the peckerhead (weatherhead) once. I would totally lose one leg on occasion and the hot tub GFCI would chatter loudly. It took a couple visits before the leg would stay dead long enough for the power company to see it. They just replaced the connectors the the WH.


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## oldspark (Jul 19, 2013)

You can read the voltage accross the knife switch and it might tell you exactly where the problem is if you have one. Try it while starting up the device.


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## begreen (Jul 19, 2013)

Check the tightness of the wire connections going to all of the breakers and on the neutral bus. They should be tight. When I first checked our panel you could actually pull some of the wires out! Now it is completely rewired, neatly and snugly.

Also, do all lights dim or just the kitchen lights? If just the kitchen lights, do they have a dimmer switch on them? These can be more sensitive to voltage drop.


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## charly (Jul 19, 2013)

begreen said:


> Check the tightness of the wire connections going to all of the breakers and on the neutral bus. They should be tight. When I first checked our panel you could actually pull some of the wires out! Now it is completely rewired, neatly and snugly.
> 
> Also, do all lights dim or just the kitchen lights? If just the kitchen lights, do they have a dimmer switch on them? These can be more sensitive to voltage drop.


No dimmer on the kitchen lights...they're the 15w fluorescent. Yes I believe other lights dim as well.. Kind points towards the main feed..


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## begreen (Jul 19, 2013)

If the feed is old, it may need replacing. The wiring from the strike down to the switch is also worth  investigating, especially if it was originally for a 100 amp service and never replaced. Or did the house always have a 200amp feed? That's unusual for an older place. The meter jaws and connections should also be checked.


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## oldspark (Jul 19, 2013)

I never balanced the load on my house and my lights have dimmed when the well motor started since the house was new, I should do it, just saying it might be something simple.


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## oldspark (Jul 19, 2013)

If you have an infared tester you can test the connections for heat.


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## Ashful (Jul 19, 2013)

This has already been suggested, piecemeal, thru about a half dozen posts. But in case you somehow missed it, what you need to do is go thru the system in order, and find where your drop is occuring. You said that a load on one circuit causes a drop on another circuit, if I read you correctly, and if that is the case you know your drop is not occuring in a branch line... it's upstream somewhere.

Your electric company guarantees your mains voltage will remain 228 -252V at service entrance, up to the capacity of your 200A service. Nominally, this translates to 114 - 126V to ground, although I do not recall what restriction they place on load balancing with that regard. In any case, if you see your service dropping below 228V with loading up to 200A (or scale accordingly at 0.06 V/A), then you have a service problem. If you see either leg dropping below 114V to ground, you have one of three possible problems (unbalanced loading in your box, center tap service problem, ground rod problem).

Start at the meter side of that knife switch, and check your mains voltage under various loading. Check between the legs, as well as each leg to ground. If all looks good there, move down stream to the load side of the knife switch. Repeat at the panel main breaker, and so on, until you find the source of the problem.

FWIW, oldspark's idea of a thermal camera (FLIR) is a good one, as any connection provided resistance (thus power loss) will be warm. Unfortunately, FLIR's are not cheap, unless you happen to have access to one thru your job. IR guns, like those we use for measuring stove top temps, will be difficult to use in this search.


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## jharkin (Jul 19, 2013)

Wow I have no idea what NStars guarantee is, but Id be absolutely thrilled if they could deliver me a consistent 114/228.   Its not at all unusual to see ours drop to 110-112 in the evenings and even lower on hot days like today. If I pull out the kill-a-watt I'd bet I see something line 109 right now.

back on topic.....


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## charly (Jul 19, 2013)

I checked both sides of the knife switch,, 236 volts,,, nothing really moved when the wife flipped the vacuum on so maybe it's a simple unbalanced load in the panel box... Still going to have the service checked,, looks very weather beaten at the weather head..


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## begreen (Jul 19, 2013)

Check the tightness of the connections in the panel starting with the kitchen lighting circuit.


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## charly (Jul 19, 2013)

begreen said:


> Check the tightness of the connections in the panel starting with the kitchen lighting circuit.


Checked all the connections about a year ago,, tightened every screw except the mains,,,didn't have an Allen with me...Nothing was really loose as far as the hots, grounds or neutrals.. I'll have to go through the box sometime and look at each load and see if the box is unbalanced..


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## Ashful (Jul 19, 2013)

jharkin said:


> Wow I have no idea what NStars guarantee is, but Id be absolutely thrilled if they could deliver me a consistent 114/228. Its not at all unusual to see ours drop to 110-112 in the evenings and even lower on hot days like today. If I pull out the kill-a-watt I'd bet I see something line 109 right now.


 
+/- 5% is the North American standard.  That is measured at point of service.


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## jharkin (Jul 19, 2013)

Ok, this thread helped me out.  Jofuls comment got me to thinking so I just checked a few things. The kill-a-watt says Im getting 106.7v on one leg and 117.1v on the other right now.  The whole house monitor shows that the current instantaneous draw is 2.8kW.

hmmm. Significant loads on right at the moment are 4 5000btu ACs and the basement dehumidifier.

Looking at the panel it looks like 3 ACs and the dehumidifier are all on the same leg.  Looks like I need to rebalance my circuits a bit!


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## oldspark (Jul 19, 2013)

All three of your AC's 120 volt?


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## jharkin (Jul 19, 2013)

Yes they are all 120v window units, and its the lower voltage leg that has 4 of the 5 big loads on it.


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## begreen (Jul 19, 2013)

How hot are those breakers getting? Check you connections and make sure the breaker screws are tight. also check the outlets that the ACs are plugged in to. Make sure they are not getting hot.


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## fbelec (Jul 20, 2013)

let us know how you make out. next time you get a chance take a look at where your power lines go and see how far and how many houses are on the same transformer.


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## oldspark (Jul 20, 2013)

jharkin said:


> Yes they are all 120v window units, and its the lower voltage leg that has 4 of the 5 big loads on it.


 I would move that stuff around then, should make a difference.


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## oldspark (Jul 20, 2013)

http://electrical.about.com/od/appliances/qt/Balancing-Electrical-Loads.htm
Some of the info in this article may not apply, seems to be a difference in some of the meters being used in the field, but most now should measure both legs so as far as saving money by balanced the load may not apply.


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## jharkin (Jul 20, 2013)

I don't think I have a breaker or outlet issue, nothing seems warm and I've rewired all the outlets in the house since we moved in. Panel was done 4 years ago. Its the entire leg that's low, I'm measuring a utility outlet in the basement on an unloaded circuit but the ac's are on other circuits on that leg. I turned off 2 ac and the imbalance dropped to 1v.

I need to pull the cover and put the meter right on the incoming legs to verify but am pretty sure. It surprised me that a 10 amp or so imbalance could throw off a 200amp service so much.

That about article doesn't seem right. If I have 2 10 amp loads on one leg I know I have 20 amps hot to neutral. If you put the loads on different legs the neutral load cancels out but you are still drawing 10a on each hot leg, not 1a. The power company still bills me for the same amount of kWh used. The meter measures each leg.


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## oldspark (Jul 20, 2013)

I think there is a 0 missing, I edited my post to talk about the meters, some meters used to only measure one leg I guess, I doubt if there are any like that left in the field.


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## oldspark (Jul 20, 2013)

This is a good read with all sorts of guesses to the problem, notice how a few say a flicker can be normal but a prolonged dimming may indicate a problem.
http://www.mikeholt.com/mojonewsarc...hts-Flicker-(Dim)-When-AC-Starts~19991007.php


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## Ashful (Jul 20, 2013)

I'm getting confused now... can't keep track if you're responding to charly or Jeremy.

Jharkin's problem is load balance, combined with a bit of under voltage (224V) at the mains.  Charly's problem, at least the way he described one circuit dragging down a separate circuit, is also at the mains.

In both cases, when checking mains voltage, try to get the probes right on the little bit of exposed main wire, right above the main breaker/knife switch lugs.  Measuring on the lugs themselves will be affected by possibly loose or corroded lugs.

A loose breaker or receptacle lug can be frustrating, as they may not get hot enough to trip the thermal mechanism in the breaker, particularly if its a cyclical load at the end of a long branch circuit.  We had a window AC in a bedroom in the house where I grew up, and it would run about 12 hours before tripping the breaker.  It took a while to figure out the problem was a too-loose receptacle, which took about 12 hours to transfer sufficient heat down the copper wiring to eventually trip the breaker.  Potentially dangerous situation, but has nothing to do with either of the problems I read here.


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## oldspark (Jul 20, 2013)

Joful, sorta responding to both of them but in the one case he has several high amp. items on one leg, I can check my voltage but I doubt if it is is supposed to be as out in the country. I have seen loose connections get the wire hot enough to melt the insulation and never trip a thing, loose connections can burn houses down.


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## jharkin (Jul 20, 2013)

I thread jacked    Spark was helping me... I know what I need to do now.


Back to Charlies issue.....


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## oldspark (Jul 20, 2013)

jharkin said:


> I thread jacked  Spark was helping me... I know what I need to do now.
> 
> 
> Back to Charlies issue.....


 I thinks it's ok, close enough to the OP's problem I am sure he got some good out of it.


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## jharkin (Jul 20, 2013)

Speaking of which, my problem is fixed it think. I mapped out my big loads (easy since I had mapped every outlet in the house when we had the new service installed 4 years ago) and figured which ones are on simultaneously typically. I.e half the ac's on each leg, fridge and basement freezer on different legs, etc.


Turns out I was able to do 2 circuit pair swaps and get it all relatively balanced. Now with everything on my service reads 111.5 and 112.8 measured directly at the main lugs.

Thanks Joful, oldspark.


Update.

I watched it through the day. Biggest variation was about 3v, until around 7pm when suddenly the readings were 118 and 110 with no significant change in usage, meter reading 3.7kw. Then I put the dryer on and the readings dropped to 110 and 104  at 8kw total draw.

Correct me if I'm wrong, but i think a few houses share the same secondary winding on the tranformer right? could load from other homes be unbalancing the feed?

Something is up. Might have to call NStar after all.


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## fbelec (Jul 21, 2013)

one other thing. if you had a bad connection with the copper and it was making heat you would be able to see it in the color of the copper. if at the connection the copper wire looks like it has a rainbow of color or purpleish blue then it has been getting hot and could be you problem. if you call the power company they will measure your voltage at the top terminals of your meter and if it is within there specs they will tell you have a nice day and you should call a electrician. so the next time you have a low reading go out to the meter and take it there also,


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## oldspark (Jul 21, 2013)

"Correct me if I'm wrong, but i think a few houses share the same secondary winding on the tranformer right? could load from other homes be unbalancing the feed?"

Something is up. Might have to call NStar after all."
I think they do in some places, so yes you might have to call them.


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## Ashful (Jul 21, 2013)

Shut off your main breaker, and check the voltages.  That'll tell you if that's the case.


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## jharkin (Jul 22, 2013)

Joful said:


> Shut off your main breaker, and check the voltages. That'll tell you if that's the case.


 
Yea, I thought of that as well.  Going to try and find a chance to due that during a high load period.

I wouldn't be surprised if the utility has issues. Its an old neighborhood, with correspondingly old infrastructure.  I know this house was first wired for K&T, probably in the 20s and updated many times since, other houses around are of similar vintage. Certainly for many years most of these houses on my street where on 60amp or lower services and I have no idea if NStar has done much to update the lines and transformers as the loads have increased.


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## Ashful (Jul 22, 2013)

It's probably been updated more than you anticipate. Most of those old transformers had pretty short service life, something like 15 years, before they required replacement.

The funny thing is that I have all the same troubles with my under-sized 200A service and too-long run to the transformer, and I'm an electrical engineer! The cobbler's children have no shoes...


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## raybonz (Aug 28, 2013)

Joful said:


> It took a while to figure out the problem was a too-loose receptacle, which took about 12 hours to transfer sufficient heat down the copper wiring to eventually trip the breaker.


That makes no sense at all.. I suspect a loose outlet caused a low voltage situation (brownout) which would make for a hard start of the AC compressor leading to a trip. Bad connections are the weakest link in any electrical system and can lead to fires.. Heat doesn't travel over a 12 hour period down to the breaker..

Ray


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## raybonz (Aug 28, 2013)

jharkin said:


> Speaking of which, my problem is fixed it think. I mapped out my big loads (easy since I had mapped every outlet in the house when we had the new service installed 4 years ago) and figured which ones are on simultaneously typically. I.e half the ac's on each leg, fridge and basement freezer on different legs, etc.
> 
> 
> Turns out I was able to do 2 circuit pair swaps and get it all relatively balanced. Now with everything on my service reads 111.5 and 112.8 measured directly at the main lugs.
> ...


Ran into a similar issue years ago as my power would drop a lot with just about anything turning on. The problem was out at the transformer caused by a bad connection at the power company's Insulug. I verified the connections were good at the main breaker and meter socket before N-star found the problem at the pole..

Ray


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## charly (Aug 28, 2013)

I'm finding my dimming lights are most likely going to be because of the wire run at the poles.. My drop service comes from down the street from the one transformer pole to another pole by my house, probably 4-5 hundred feet of drop service run, then from the pole to my house, another 100 plus feet.. Electrician is coming shortly and going to talk to someone he knows about the service run from the poles.. Seems awful long and my neighbors service entrance wires are twice as big and only a 50 ft run... Be interesting to see what caused the dimming of my lights.. Breaker box checked out fine.. Installing a new meter and entrance cable and getting rid of my two 200 amp fuses and knife switch box before my main panel... Basically going to clean up any faults..


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## Ashful (Aug 28, 2013)

raybonz said:


> Bad connections are the weakest link in any electrical system and can lead to fires.. Heat doesn't travel over a 12 hour period down to the breaker..


 
A residential circuit breaker has two trip mechanisms, magnetic and thermal. The thermal trip mechanism is driven by a bimetalic element, thru which the load current is drawn, causing heating of the element. A given load at or over rating will trip the breaker in a given time, and there can be trouble with these elements, as they are somewhat sensitive to heat.

Now, as you've already indicated a loose connection can drive temperatures easily exceeding the ignition temperature of wood. This would mean at least 300C, under most conditions, and typically much, much hotter... as there will be significant temperature drop between the actual heat source (loose connection) and any wood outside of the receptacle box.

Copper is a very good thermal conductor, roughly 400 W/m°K, and AWG 12 has a diameter of 2.053 mm. Completely ignoring the heat generated by drawing current thru the wire (which can be significant, but is an intended component of the system), and just focusing on the heat transfer from a hot loose screw in a receptacle to a "cold" breaker, 20 meters of this wire would have a thermal transfer of 23 milliwatts, from receptacle into wire.

Now, consider that little bimetallic element in the breaker, which is designed to heat as current is drawn thru the breaker, and trip when it generates sufficient heat. These elements are designed to dissipate minimal power, so as to not cause a voltage drop in the system, so they are typically designed to operate on microwatts of power themselves. Now, you're pumping an addition 23 milliwatts of unintended heat into the wire, some portion of which will directly reach the breaker, after loosing some heat out thru the insulation (1000x poorer conductivity than the copper wire).  What do you think is going to happen, after a period of time?


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## fbelec (Aug 29, 2013)

joful so what your saying is heat can now travel down not only up. i change out receptacles all the time. thats my job. under normal use, volts and amps a breaker can get warm to the touch and run that way for ever. now you say that the heat that is generated at a receptacle that usually goes bad way before anything gets back to the breaker or fuse can trip the breaker or fuse before it melts the insulation on the wire and either shorts hot to neutral or hot to ground or shorts to the metal of a box, which is ground. and so what if it's a plastic box it would still short the wires. when i get to the house that i get a call for a outlet that is not working the insulation is all burnt off and the copper wire got so hot that when i move it it broke or was already broken. way before it even gets to a wood stud. i must have missed something not only in school but in the real world experience i get daily. what ray said a few up is what happens. the more hot and cool cycles and arcing is made the more carbon on the wire and screw to the receptacle and it snow balls until that receptacle and the ones down stream shut down. the breaker is still on. what charly is seeing, the length of the service drop and a long distance from transformer to his house across a wire that is aluminum and size 1/0 is his problem. all those houses along the wire is to much for the wire and is draging down the voltage. if there were a problem with a main breaker or fuse holder you would be able to smell it long before something happen.


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## jharkin (Aug 29, 2013)

fbelec said:


> joful so what your saying is heat can now travel down not only up.


 
It always has. and sideways too.  Heat will travel in any direction moving from hot to cold until temperature equilibrium is reached in a material.  Its only "hot air" which naturally wants to rise above regions of cold air, due to hot air being less dense.




Joful said:


> Now, consider that little bimetallic element in the breaker, which is designed to heat as current is drawn thru the breaker, and trip when it generates sufficient heat. These elements are designed to dissipate minimal power, so as to not cause a voltage drop in the system, so they are typically designed to operate on microwatts of power themselves. Now, you're pumping an addition 23 milliwatts of unintended heat into the wire, some portion of which will directly reach the breaker, after loosing some heat out thru the insulation (1000x poorer conductivity than the copper wire). What do you think is going to happen, after a period of time?


 
Not to say that this is not all theoretically possible, but without doing the math itself it sounds like a bit of a stretch?? Did you actually find the wire hot near the load center? Are sure that the loose connection in  that receptacle for your AC wasn't just causing enough resistance to push the steady state circuit draw over the limit by a tiny fraction (say to 15.00000001 A or something) which took a long time to trip the coil....


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## Ashful (Aug 29, 2013)

jharkin said:


> Did you actually find the wire hot near the load center?


 
yes. This is how the problem was discovered. Realized this wire was getting warmer than the rest, feeling around in the panel, so I checked the connection at the breaker, which was fine. Swapped breaker, and new one did the same. Then thought to pull the receptacle, and found the problem.

Now, I have an MSEE (actually 75% complete on my Ph.D.), and do thermal simulations and calculations as a part of my job. Back when this happened, I was 14 or 16 years old, and just trying to keep mom's house running.


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## raybonz (Aug 29, 2013)

Joful said:


> A residential circuit breaker has two trip mechanisms, magnetic and thermal. The thermal trip mechanism is driven by a bimetalic element, thru which the load current is drawn, causing heating of the element. A given load at or over rating will trip the breaker in a given time, and there can be trouble with these elements, as they are somewhat sensitive to heat.
> 
> Now, as you've already indicated a loose connection can drive temperatures easily exceeding the ignition temperature of wood. This would mean at least 300C, under most conditions, and typically much, much hotter... as there will be significant temperature drop between the actual heat source (loose connection) and any wood outside of the receptacle box.
> 
> ...


No what I am saying is your breaker will never see this heat however your wire at the bad connection will and your house will be on fire long before your breaker ever trips.. I have been a licensed electrician for 25 years and have worked industrial for 35 years plus and I do have an education as well. FBelec is just like me and we have been there and done that. The OP like FB said is experiencing voltage drop which gets worse with loading to the point that his service cables essentially become heaters.. It's a vicious circle that will not end until his service wires are upsized. BTW I fully understand how breakers work along with many other things..

Ray


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## fbelec (Aug 29, 2013)

hot air rises but also with heat on metal like a heat sink pulling heat away from the heat maker and it's usually at the top


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## fbelec (Aug 29, 2013)

sorry charly didn't mean to hijack the thread.


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