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Thread: Electric Service Rating vs Reality

  1. #31
    Join Date
    Feb 2008
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    Quote Originally Posted by Steve Demuth View Post
    Once, at the pole, when an idiot drove a steel post through the underground cable to the house.
    Ha, if we include the protection on the pole... My transformer at the house is fed by a 7200v line from the pole. On the top of the pole is a fuse. That fuse has tripped five times in 15 years.

    Three time it was tripped when a squirrel shorted the hot wire to ground. We found a cooked squirrel on the ground. Once it was tripped in the dead of winter when termites bridged the connection from warm transformer to the ground. Once it was tripped when the insulation failed on cable 4' underground causing a pinhole path from conductor to earth.

    Every time the fuse blew it sounded like a dynamite explosion..

    JKJ

  2. #32
    speaking of baked wildlife years back I was driving to the lumber company. On the other side of the road where big towers and many serious power lines. I looked over to see an alfred hitchcock number of birds all flying in formation together swoop around like all on the same flight program then come in and land on the high power lines. As they did they picked different lines and some were between. There was a huge bang and birds dive bombed to the ground only didnt pull up. Lights were out for miles and when I came back there were cops at every intersection. I told one of the cops what happened and he just looked at me like i was nuts.

    Fuses have blown a number of times here, a branch from a tree falls and ends up on the lines and bang. They finally come around and trim stuff regular now. People have had power out for a long time in the past and homes have flooded when sump pumps arent working and they didnt have generators. My own post had some sort of short on it, I told them a few times and they ignored me. A guy stopped one day at a neighbors and walked over and told me the post was wired wrong. I said Ive told them it sizzles when there is rain when its wet. He said stay away there is a charge in that post. I took a photo of burning and sent it to them and they finally woke up and next day a crew was there. Guy working on it said some days they dont pay him enough. Been fine ever since.

    P1270819A.jpg
    Last edited by Warren Lake; 02-15-2020 at 2:38 PM.

  3. #33
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    Lake Gaston, Henrico, NC
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    A squirrel shorted out the transformer for our house. It made a tremendous arc, like a welding arc, that I told everyone not to look at. The arc continued to burn until the wires parted. I called the power company. It caught the pole on fire, I called 911, and it was too hot to stop burning before the fire department got there. They needed to wait for the power company to come, and in the meantime, the pole burned all the way down to the ground. We were only out of power for a couple of hours, while they set a new pole, and transformer, and fixed the wires.

  4. #34
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    Feb 2003
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    Griswold Connecticut
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    Quote Originally Posted by Ole Anderson View Post
    I would think that the reason for 200 amp panels has more to do with the number of available circuits rather than the actual total load on the panel. Theoretical load, yes. When I built my house in 1975, my buddy's dad was an electrician and he convinced me to go with a 200 amp panel in a 1550 sf house. So glad he did as that panel is now full. Wired it under permit myself.
    Exactly!
    With all of the code requirements for dedicated circuits that have happened through the years in residential wiring, a 100 amp panel fills up pretty quick. The number of available/allowed poles in a 200 amp panel is typically greater. The ability to balance the neutral, based on expected daily loads is also more easily accomplished in a box with more poles/breakers.
    I know, I know, that folks will say that you can just use tandems to increase breaker availability, but they were not always as widely accepted in use as they are today.In some jurisdictions they were flat out not allowed! I would also venture to guess that a great majority of them are installed in violation of the panel manufacturers literature. We did a lot of panel remediation/ upgrades in the late 80's for this particular issue, for pending house sales, probably two or three a week in Connecticut during the late 80's housing boom.
    Last edited by Mike Cutler; 02-16-2020 at 8:42 AM.
    "The first thing you need to know, will likely be the last thing you learn." (Unknown)

  5. #35
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    Aug 2010
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    Quote Originally Posted by Tom Bender View Post
    At one time some houses had only 15 amp electric service This has been increased over the decades to the point where 200 amps is common. That's 240 volts x 200 amps which is in the neighborhood of 48kw. (someone will please inform us about the power factor an whatever other mistakes I have made to this point)

    When I estimated the loads that my generator would need to support it came to 11kw The 16 kw unit we installed has been fine

    I think the biggest load a normal house will put on a system is if it has electric resistance heating That might be around 20 kw (presumably A/C will not run at the same time)

    An ordinary one man workshop might draw up to 4 kw though it could go higher

    Motor starting loads may double some individual loads briefly but these would be a small percentage of the total

    Adding up my house plus electric resistance heat plus electric stove and water heater and a substantial shop load

    11 + 20 + 8 + 4 = 43 kw if it all runs at the same time, 200 amp service (48 kw) is more than adequate but 100 amp (24 kw) would be borderline

    or without the electric heat it would be 23 kw, 100 amp service (24 kw) would be good and 60 amps (12 kw) would be borderline

    So here's my question; Who has had main circuit trips and under what circumstances?
    Main breaker should NEVER trip!

  6. #36
    Quote Originally Posted by Mike Cutler View Post
    Exactly!
    With all of the code requirements for dedicated circuits that have happened through the years in residential wiring, a 100 amp panel fills up pretty quick. The number of available/allowed poles in a 200 amp panel is typically greater. The ability to balance the neutral, based on expected daily loads is also more easily accomplished in a box with more poles/breakers.
    I know, I know, that folks will say that you can just use tandems to increase breaker availability, but they were not always as widely accepted in use as they are today.In some jurisdictions they were flat out not allowed! I would also venture to guess that a great majority of them are installed in violation of the panel manufacturers literature. We did a lot of panel remediation/ upgrades in the late 80's for this particular issue, for pending house sales, probably two or three a week in Connecticut during the late 80's housing boom.
    And even if you could jam all them tandem breakers in without violating box fill requirements, they ain't cheap and you get to basically the same cost as doing it right with the right sized box and breakers

  7. #37
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    Andrew
    In Connecticut it was hit or miss back then if the town you were in would allow tandems. Some just did not allow them at all, while the town next door would allow them.
    Folks would go to sell their house, and fail the pre-inspection walk through due to the main service panel being overstuffed, and too many poles. It was an easy fail for the inspector. Look at the label on the panel and count. It was kind of a panic situation for the seller!
    I have no idea what will pass these days. I always ask my friends that stayed in the trade, and then check with the inspector before I start any work. I can't imagine that anyone is installing a 100 amp panel in new construction housing.
    "The first thing you need to know, will likely be the last thing you learn." (Unknown)

  8. #38
    Why do some places not allow tandem breakers? I expect there's some code problem but as long as you stay within the total box amperage it seems that it should be okay.

    Mike
    Go into the world and do well. But more importantly, go into the world and do good.

  9. #39
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    Sep 2016
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    Quote Originally Posted by Mike Henderson View Post
    Why do some places not allow tandem breakers? I expect there's some code problem but as long as you stay within the total box amperage it seems that it should be okay.

    Mike

    A tandem breaker is fed from one buss bar. A panel should have the breakers arranged so there is about equal load on each buss bar. A 240 breaker is equal on both bars. A 120 breaker is only drawing from one bar.
    A 200 amp panel is really rated for only 100 amps at a time on each bar.
    My Zinsco panel had aluminum buss bars which corroded and made a poor connection. It buzzed so loud I had an electrician replace the buss bars and about half the breakers under a home insurance policy. The corrosion caused overheating at the spring connections of the breakers which made it worse and caused arcing. Reducing spring pressure and cascading into a fire if not caught in time. He had copper buss bar stock on his truck of the correct size. He just had to cut it to length and maybe drill a mounting hole or two.
    Bill D.

  10. #40
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    Quote Originally Posted by Mike Henderson View Post
    Why do some places not allow tandem breakers? I expect there's some code problem but as long as you stay within the total box amperage it seems that it should be okay.

    Mike
    Mike

    This was in the mid to late 80's.
    The issue then was that panels, at least here in New England, were smaller 100 amp panels. The use of Tandems would quickly lead to over filling the box, and to many poles/breakers per the panel manufacturer. They were also installed in the wrong location per the manufacturers drawings and literature.
    For instance I have a 40 pole/breaker, 200 amp service panel, and the manufacturers details that a maximum of 10 tandems can be installed in the lower six position only. The 5th pole position up from the bottom cannot have tandems on either side. It would not have been uncommon back then to have more than 40 poles/breakers.
    I actually have 41 breakers installed, but three are not in use.
    If the tandems are not installed correctly, it's pretty easy to pull a lot of amps through one back plane stave. You could split one pole into two and end up with a microwave, slow cooker, and an electric skillet, on one pole/stave and potentially have a "hot spot" on the back plane.
    As I said though, this was many years ago.
    Last edited by Mike Cutler; 02-17-2020 at 4:50 AM.
    "The first thing you need to know, will likely be the last thing you learn." (Unknown)

  11. #41
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    SE PA - Central Bucks County
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    In addition to Bill's comments about balance, tandems bring the potential of "overstuffing" a box. While most folks might use one to solve a space problem for one or two circuits, there are other folks who would choose tandems to fill a box to avoid buying a correctly sized box for their application.

    Interestingly, our main 200A box has a few tandems in it, actually installed by a licensed electrician. (work done in 2005 to upgrade both the house and my shop) He did this because some of the existing wires were at that length where they could only get so far into the box (old box was much shorter) but were still usable and all of the available physical space for j-boxes to splice was already being taken up by other circuits that couldn't even come close to getting into the new panel. It's only a few circuits and was kosher with the inspector here.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  12. #42
    Thanks for your replies, Mike and Bill. I understand the problem.

    I have a few tandems in my subpanel but they are ones that replace a 240V breaker with a package that consists of two 120V circuits and the one 240V circuit. With that package the two 120V circuits pull from different buss bars.

    Mike
    Go into the world and do well. But more importantly, go into the world and do good.

  13. #43
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    Quote Originally Posted by Mike Henderson View Post
    Thanks for your replies, Mike and Bill. I understand the problem.

    I have a few tandems in my subpanel but they are ones that replace a 240V breaker with a package that consists of two 120V circuits and the one 240V circuit. With that package the two 120V circuits pull from different buss bars.

    Mike
    Mike
    We used to call that a "laundry" breaker,or an "appliance" breaker. It would give you the 240/30 for the dryer, a 120/20 for the washer, and the 120/20 convenience receptacle, that were required for a laundry. There is a 240/50, with the two 120/20's, for electric ranges.
    "The first thing you need to know, will likely be the last thing you learn." (Unknown)

  14. #44
    Quote Originally Posted by Mike Cutler View Post
    Mike
    We used to call that a "laundry" breaker,or an "appliance" breaker. It would give you the 240/30 for the dryer, a 120/20 for the washer, and the 120/20 convenience receptacle, that were required for a laundry. There is a 240/50, with the two 120/20's, for electric ranges.
    What happened to me is that I put in too small of a subpanel and then bought more 240 volt tools than I expected when I put in the subpanel. So I took two 120V breakers and replaced them with an "appliance" breaker. A magic way to add a 240 V bonded breaker to a box and still keep the two 120V individual breakers. I described it previously as replacing a 240V breaker to add 120V circuits but that was not what I really did - I went the other way, to add 240V circuits.

    Still waaay under the amp rating of the box.

    Mike
    Go into the world and do well. But more importantly, go into the world and do good.

  15. #45
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    Apr 2013
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    Quote Originally Posted by Warren Lake View Post
    speaking of baked wildlife years back I was driving to the lumber company. On the other side of the road where big towers and many serious power lines. I looked over to see an alfred hitchcock number of birds all flying in formation together swoop around like all on the same flight program then come in and land on the high power lines. As they did they picked different lines and some were between. There was a huge bang and birds dive bombed to the ground only didnt pull up. Lights were out for miles and when I came back there were cops at every intersection. I told one of the cops what happened and he just looked at me like i was nuts.

    Fuses have blown a number of times here, a branch from a tree falls and ends up on the lines and bang. They finally come around and trim stuff regular now. People have had power out for a long time in the past and homes have flooded when sump pumps arent working and they didnt have generators. My own post had some sort of short on it, I told them a few times and they ignored me. A guy stopped one day at a neighbors and walked over and told me the post was wired wrong. I said Ive told them it sizzles when there is rain when its wet. He said stay away there is a charge in that post. I took a photo of burning and sent it to them and they finally woke up and next day a crew was there. Guy working on it said some days they dont pay him enough. Been fine ever since.

    P1270819A.jpg
    Warren,
    Do you live in the NorthWest also?

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