200 amp, single phase, one to the house and one to the garage, think of
a farm type set up. Sorry I don't have a big freaking knife switch like
in Frankenstein but that would be cool! Open air switch with no safety
nutn'. Don't lean there.
On most of the CT metered service entrances I've installed, there is a
big fused safety switch to kill the main power going into the building.
This is so the fire department can knock the lock off and kill the
power. At a home, the fireman will knock the power meter out of the can
to kill the power. In your case, I suppose the power company didn't want
multiple meters. :-)
I didn't want separate meters because the 2nd one would be billed at
commercial rates along with a service charge each month. Some time ago
I posted here that I have no disconnect to the garage and I got replies
saying code doesn't call for a disconnect. Going to the house is the
old meter base with jumpers, so I'd say that could be considered a
There have been occasions when I had to kook up a service entrance to a
drop and I use a special insulation piercing connector that takes a
wrench to install. I would cut the drop loose, swap the meter can for
a fused safety switch or big breaker in the range that matches the amp
rating of the wire then reconnect the drop with the Blackburn taps.
I've worked 15kv underground service cable taps and splices to hook up
transformers. Little old 240 volt service doesn't scare me but I treat
power cables like like they are energized at all times. It's good
practice to always treat electrical power with respect. ^_^
At my old house I saw them working on the underground cables at a big
box thing with a lid down by the road. The cables were lying in water!
I think it was high voltage because the cable ran 250 feet to my
propety line to an above ground transformer and then to my house. (Had
it marked for digging purposes.) They were moving the cables around
with a long fiberglass? pole. Turned out they couldn't find the short
and backtracked and replaced the insulator on the pole a few hundred
feet up the road were the fuse blew. It always seemed odd that there
were above ground lines except for me and 4 other houses. There was a
high tension line above the area and I wondered if that had something to
do with our services being underground?
MOVs are voltage limiters. They are like parallel reverse connected
MOVs have an energy (joule) rating. They can absorb as much energy as
the joule rating (and at that point are still functional). This is a
rating for a single surge. MOVs (and both service panel and plug-in
suppressors) with very high joule ratings are readily available. If the
energy hits a MOV takes are a small fraction of the single hit rating,
the cumulative energy the MOV can absorb will be far larger than the
stated rating. From another post, the energy dissipated in a plug-in
suppressor is surprisingly small. If a plug-in suppressor has a very
high rating it is likely to never fail. That is one reason why some of
them have protected equipment warranties.
As detailed in another post(and at length in the IEEE surge guide
below), some plug-in suppressors will disconnect the protected load if
the MOVs fail and are disconnected. Another reason why some suppressors
have protected equipment warranties.
The best information on surges and surge protection I have seen is at:
- "How to protect your house and its contents from lightning: IEEE guide
for surge protection of equipment connected to AC power and
communication circuits" published by the IEEE in 2005
The IEEE surge guide says "the vast majority (>90%) of both hard-wired
and plug-in protectors use MOVs to perform the voltage-limiting
function. In most AC protectors, they are the only significant voltage
I agree with trader.
If a device is not using a MOV it is probably marked as a feature.
Surges produced in the house are not likely to damage to equipment,
which typically has an immunity level of 600-800V.
Service panel suppressors are good protection., The main hole left by a
service panel suppressor is that it does not limit the voltage between
power and phone and cable wires, which is likely to cause most damage.
If phone and cable (and dish) entry protectors are connected to the
power earthing system (as in gfretwell's post) and the wires are short,
much of that hole is filled. It is still possible to get about 4kV
between the coax shield and the center conductor, and a very near
lightning strike can induce damaging voltages with the wiring inside the
house acting as a loop or long-wire antenna.
UPSs seldom have ratings as high as are readily available in plug-in
suppressors. And UPSs with a surge rating often are not listed under UL1449.
The best protection is a service panel suppressor, short wires from
cable/phone/dish entry protectors to the power earthing system, and
plug-in suppressors for expensive equipment (particularly if it has
And as stated elsewhere, if using a plug-in suppressor all
interconnected equipment needs to be connected to the same suppressor
and external wires (power/phone/cable/...) needs to go through the
Meter base suppressors (supplied by the utility) provide protection. The
IEEE surge guide talks about the length of wire used to connect a
service panel suppressor - as the wires get longer the let-through
voltage goes way up. In a meter base suppressor the earthing system is
usually connected to the service panel neutral. That means the neutral
wire from the meter to the service panel will raise the let-through
voltage of the suppressor.
The meter base suppressor works best if the ground electrode conductor
lands in the meter base.
You really want your grounding paths to be as short and straight as
possible. You also want your cable and phone suppressors grounded
The plug in, point of use protection is just supposed to be
supplemental to that. A good plug in protector will also have smaller
capacitors and maybe an inductive element, meant to shunt off high
frequency transients (noise).
I live in a place with a thunderstorm just about every day for 6-7
months of the year and I never unplug anything ... but I have several
layers of protection for everything.
On 3/13/2011 12:25 PM, firstname.lastname@example.org wrote:
We had a bad storm system come through The Southeast last week and I was
sitting at my computer when I heard my UPS click and my electric heater
reset/shut off (electronic control) then a few seconds later a very loud
BOOM almost knocked my out of my chair. Computers and network equipment
never skipped a beat but my heart did. :-)
I agree. I would not want a meter base suppressor that did not have the
earthing electrode system connected at the meter. I don't think I have
ever seen one though.
I don't think this is as widely appreciated as it should be. You want
the minimum distance to the common connection point.
In some cases, the phone or cable entry point is too far distant from
the power service to make a short enough connection.
A surge suppressor at the service is a good idea.
But I don't see why a plug-in suppressor wouldn't be effective if there
is no service suppressor. As noted in another post, with no service
suppressor the energy that makes it to a plug-in suppressor is
surprisingly small because of arc-over at the service and impedance of
branch circuit wires. The paper that this comes from is probably still
on-line if you want to read it. I would want high joule ratings on the
suppressors. And particularly I would want high ratings if the branch
circuit to the service under 30 feet. Plug-in suppressors with high
ratings are readily available.
Seems to be a real common feature. I never figured out if it does
something that is actually useful.
I agree that layers of protection are the best, and where you are you
want the best.
You can protect against about anything (including a direct building
strike - with lightning rods). (But I don't think I would want to run a
ham station with a high antenna in a thunderstorm.)
I liked your pseudolightning rod from another thread.
Landing the GEC in the meter base is pretty common here in Florida.
The thinking is to stop a lightning hit before it gets into the house.
Typically it will travel down the outside of the mast, over the meter
can and down the GEC raceway. Lightning is seen to actually travel on
the outside skin of the conductors. That is why they use finely
stranded conductors on lightning rods.
In the case of your GEC the metal raceway probably carries more
current than the 4 ga solid copper wire,
The big problem is time, on the nano second scale. The faster you sink
the shot, the less chance you have that some leaks through to your
equipment. We had some luck simply using ferrite beads to slow down
the shot and a shorter grounding path going the other way.
Our operation was protecting about 1000 customers who were not going
to turn off their computers every afternoon and unplug them.
We were on the leading edge of a lot of lightning protection schemes
but we did get pretty good at it.
The sooner you can bond all of your utilities the better off you are.
I understand nobody is going to be installing a new phone line and
most cable TV is already in place but I would not tolerate any new
installation that did not come in right next to my electrical entrance
... even if they had to run the cables all the way around the house
before it came in.
In fact the NEC has added a requirement for a multi system bonding
point right at the service, just for this reason.
I don't know of anything you get at a service panel or plug-in
suppressor that has a rise time that is too fast for MOVs on power
lines. If there is a very fast rise time the inductance of the wiring
will lower the rise time (and spread out the pulse). Gas discharge
tubes, which may be used on signal lines, may be slow
I don't remember the basic requirement has changed, but the making the
connection is getting easier. You had a link to an "intersystem bonding
terminator" recently which I didn't look at right away. Looks slick.
I don't disagree with you, but for 50 to 75, you get an MOV kind that
you calleed almost worthless. The ones I've seen do have a LED that
stops being lit when the protector has been zapped.
Actually, I got one of those for about 26 or 36 dollars and the next
one up was an Intermatic for 130 or 160. The picture and the
description said it had 3 LED's iirc, green ones for each leg and a
red one that glowed when one of the legs had been zapped. Sounded
great, but a comment said that when the guy received it, it only had
one LED, and a few days later, I saw ads for that one. I tried to buy
it in person at an electrical supply house, but they didn't have it so
I just bought the cheap one. I don't know that I ever have such
surges and if I ever do, I'll decide what to replace it with if it
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