If you are going to disconnect, disconnect everything. Remember that
1000 volts per meter of wire from a lightening strike a mile away and
there are how many meters of wire in the house?
In my case I had the stations disconnected from the computers, but I
failed to disconnect the computer network and it sure made an expensive
and time consuming mess in the network and computers. The CAT-5 went
through protection at each computer's UPS, but it welded the contacts
together in one and melted the plastic RG-45 plug and socket together.
It also took out 3 of 4 NICs. and one motherboard. The only things left
were the 850 W PS, the video card and the hard drives. It also wiped out
the 8 port smart switch and a 4 port router which also had dual channel
wireless. Fortunately my wife's computer is wireless as is the printer.
The UPSs are under warranty, but weigh around 40# each. So there's the
cost of shipping both ways, plus the down time. I'll probably just
purchase the stock parts and DIY.
Had this computer and the one in the shop been hooked into the rigs
using HRD it could have been much more expensive. I now have two
servers in the den so I can leave the two computers in the shop, off
line "most of the time" although I'm working toward remote control of
both stations.
I have a 30 A 120 VAC line conditioner that I have to hurry and run a
new circuit for. then the computers and rigs in the den will be on a
regulate 120 VAC that is a clean sine wave. That does not include the
amps that run on 240 VAC. In the early days computers ran on line
conditioners, but the expense brought about simple UPSs. Like many
things we become accustomed to, UPSs are now thought of as normal and
line conditioners a gimmick, but in many areas with wide variations in
line voltage, the line conditioners with a clean, regulated 120 VAC is
good protection and a good investment even if a bit pricey compared to a
UPS. If you can find one.
73
Roger (K8RI)
On 5/17/2015 9:03 AM, Bry Carling AF4K wrote:
I guess the moral of this story is don't connect your phone line to your
amplifier?
On 16 May 2015 at 17:26, Chuck Dietz wrote:
I used to pull all plugs and disconnect all antennas but had a problem because
I left the
equipment grounded and strike came over phone line through an amplifier to
ground. Now I have
an equipment ground disconnect too.
Chuck W5PR
On Saturday, May 16, 2015, Bry Carling <bcarling@cfl.rr.com> wrote:
My solution is to pull all AC plugs from the wall and disconnect all
antennas whenever a
storm is coming. That pretty much takes care of most problems.
My ground system is going to be improved from the current setup but I'm not going to the
kinds of extremes that some people have, and assuming that will be a
perfect system of
protection.
Best regards - Brian Carling
AF4K Crystals Co.
117 Sterling Pine St.
Sanford, FL 32773
Tel: +USA 321-262-5471
> On May 15, 2015, at 9:11 PM, Roger (K8RI) on TT <K8RI-on-TowerTalk@tm.net> wrote:
>
> Having worked with literally thousands of MOV,s from little ones up to
50,000 Joul ratings,
They will typically fail shorted, BUT I have seen many fail open. It
depends on the power
contained in the "final spike" that causes them to fail. From power line
spikes and nearby
lightening strikes the ODDS ARE it/they will fail shorted. If enough
power/energy is
contained in that final spike at failure time, it becomes likely they will
fail open and that
anything on that line will fail as well.
>
> Based on experience, you can expect the MOV to fail shorted and it will
PROBABLY
protect any electronic device connected to it. That being the case, the
prop pitch motor will
PROBABLY need some sort of "fail safe" to prevent over rotation.
>
> That's a lot of probables, but it's unfortunately a fact of life,
leaving you playing the odds
which favor the MOV failing shorted, but with no guarantee it will do so.
If the MOV works
as we all hope, then you will need some sort of "fail safe"
>
> Since the big ground system was installed my tower has been hit at least
7 times that can
be verified with nothing disconnected and NO MOVs in the rotator lines.
No damage was
seen.
>
> I can not say the same for my computers and network. A nearby strike
did nothing to
either station, but it sure cost me a lot in network and computer damage.
The CAT-5 lines
go through protection at the UPS for each computer. The connectors were
melted and the
wire contacts welded together at one UPS. The router, 8 port switch and
most NICs were
shot!
>
> So, lightening and MOVs are a crap shoot. They will protect you from
the smaller stuff,
but cause other problems. They are unlikely to protect you from the larger
stuff.
>
> In the end, I'd use them, plan on the MOVs failed as a short, and hope
for the best There
is no guarantee, but you have tilted the odds in your favor..
>
> 73
>
> Roger (K8RI)
>
> .
>> On 5/15/2015 10:38 AM, Paul Christensen wrote:
>> N4CC and I have finally completed our remote Internet station in
Hilliard, FL. Probably
half our time spent before and during construction was studying and
implementing lightning
abatement. Ground rings were created around each tower, and the
communications
shelter. All grounds, including the adjacent electrical service ground
are brought together at
an external ground bus (EGB). In total, 55+ ground rods are used with
four rods each 24 ft.
Lines are bonded at the top and bottom of the towers. We do not
disconnect anything.
Everything stays up and running 24/7 regardless of the WX.
>>
>> Poyphaser rotator MOV protection devices are installed at the base of
each tower. At
the EGB, we're using an Array Solutions model. In looking at all the
failure modes, I missed
one: If the MOV on the rotator return lead was to short to ground, it
creates a disastrous
situation where the prop pitch will turn freely beyond the electrical stop
point. The MOSFET
is controlled by a PWM circuit and the duty-cycle is what varies motor
speed. A shorted
MOV will cause the lines to break apart up the tower at the coax loop.
The prop pitch would
stop at nothing and keep turning. Do the MOVs in these units generally
fail open or closed?
>>
>> We're using a pair of M2 PCX2800 controllers. To help protect the
MOSFET device
from a similar "short-to-ground failure" during a lightning event, I
designed a circuit that
engages a vacuum relay such that the MOSFET is only exposed to the outside
world during
rotation. It's not a 100% guarantee against MOSFET failure, but should
help to mitigate
damage. This is an add-on that's similar to what K7NV did with the Green
Heron prop pitch
controller model.
>>
>> Here's my thought for a potential fix: While another vacuum relay
could be added on the
+48V supply side to the prop pitches, I could isolate circuit ground from
chassis ground on
the secondary side of the controller's power transformer. The primary
would still be safety
protected and meet UL. Isolating circuit ground from chassis ground would
inhibit rotator
turning in the event of a MOV failure on the return line.
>>
>> Anyone been through this? I welcome comments on any better ways to
manage this.
>>
>> Paul, W9AC
>> _______________________________________________
>>
>>
>>
>> _______________________________________________
>> TowerTalk mailing list
>> TowerTalk@contesting.com
>> http://lists.contesting.com/mailman/listinfo/towertalk
>
>
> --
>
> 73
>
> Roger (K8RI)
>
>
> ---
> This email has been checked for viruses by Avast antivirus software.
> http://www.avast.com
>
>
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
--
73
Roger (K8RI)
---
This email has been checked for viruses by Avast antivirus software.
http://www.avast.com
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|