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Posted By charly,
Jul 18, 2013 at 2:49 PM
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...
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.
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.
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..
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.
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.
If you have an infared tester you can test the connections for heat.
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.
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.....
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..
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..
+/- 5% is the North American standard. That is measured at point of service.
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!
All three of your AC's 120 volt?
Yes they are all 120v window units, and its the lower voltage leg that has 4 of the 5 big loads on it.
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.
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.
I would move that stuff around then, should make a difference.
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.
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.
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.
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.