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Posted by bud-- on July 28, 2007, 10:31 am
Terry wrote:
> wrote:
>
>> Terry wrote:
>>> The thing I am pondering now it that I have a dead modem, dead router,
>>> and 2 dead motherboards.
>>>
>>> I would like to be able to pin it on the CATV guys as it almost had to
>>> come in on the CATV as I have a UPS and both computer power supplies
>>> are good. The only thing that was not connected to the surge
>>> suppressor were the Cat 5s going to the network cards. That was an
>>> over site on my part as the UPS does have network jacks.
>>>
>>> I agree with you that the piping "should" be grounded. I want to know
>>> if it "has" to be grounded.
>>>
>> Originally your water pipe was required to be used as a grounding
>> electrode and connected to the power system ground. That connection now
>> has to be within 5' of the entrance of the water pipe to the house. Your
>> house is old enough the connection could have been anywhere.
>>
>
> Originally my house was supplied by a well. The house has a partial
> basement and a crawl space. The well is located in the crawl space.
> The first drop from the well is to the clothes washer. (This could
> actually be the grounded part if the pipes are indeed grounded. The
> panel is located on an inside wall in the washer/dryer room. That
> part has a poured slab floor) My health is not good, so crawling
> under the house is a big deal. I did take a flashlight and look. None
> of the copper pipe is even in contact with the earth although I would
> not have been able to see a ground clamp if there was one.
>
>> With the PVC water service you now have, the interior metal water pipe
>> has to be bonded to the electrical system ground with similar rules, but
>> the connection no longer has to be within 5' of the entrance. Bonding
>> requirements are in 250.104-A.
>>
>> If the water pipe is not connected to the power system ground it is not
>> the CATV guy’s problem.
>
> Would it not be the CATV guy's problem if the pipes were PVC? Everyone
> now a days uses PCV for repairs. I pay $100 a month for
> Internet/Cable. I think I would be justified in asking them to come
> back out and ground their system to the service mast. I am still
> considering asking them to pay for my computer repairs.
>
If I were the cable company, and if you had interior metal water pipes,
I would argue that the NEC (if it is enforced in your area) requires the
water pipe to be either bonded (pvc water service) or connected as a
grounding electrode (10' underground metal water service). In either
case I (the cable company) would argue that I connected the cable to a
permissible electrode (assuming they did) and that it was not my
responsibility to verify that all water pipes are connected to the
electric service properly. Of course you could try asking them to pay.
If the CATV drop is near the power service, I suspect they would move
the grounding point to the metal service mast.
>> ---------
>> The requirements for grounding electrode for CATV are in 820.100-B.
>> (They are about the same for phone.)
>>
>> The only point on water pipe that can be used for the CATV ground is the
>> first 5 feet inside the house. (This may have been different in the past.)
>>
>> Your metal electric service mast is another permissible grounding point.
>>
>> (In recent versions of the code, there has to be an accessible point
>> provided to connect the CATV, phone, ... ground to.)
>>
>> The grounding conductor from the CATV entry block has to be 20' or less,
>> (or a ground rod has to be added and the CATV block still has to connect
>> to the power grounding system). But the connection from the CATV entry
>> block to the earthing wire at the power service should be as short as
>> possible as I said under single point ground in your previous thread.
>>
>> ---------
>> You don’t describe your computer setup. If you have widely separated
>> computers, each connected to its own suppressor, and interconnected by
>> ethernet, a surge can shift the ground potential at one end resulting in
>> a high voltage between computer and ethernet cable at both ends.
>>
> The two computers that were damaged were setting within 3 ft of each
> other. There were actually 3 all plugged into the same place. The
> cheapest one that I had built from spare parts didn't get damaged.
>
> All 3 computers were plugged into the same UPS (1500va). The router,
> modem, speakers and monitor were also plugged into the UPS. One of
> the computers that took a hit was plugged into the surge suppressor
> only jack (No battery backup) The other one that took a hit was on
> battery. (I only have one monitor. I use a KVM switch)
>
> The thing that is most puzzling to me is what was damaged. Changing
> the modem fixed my Internet connectively problem. I also have a
> wireless laptop. The laptop could still talk to the good computer,
> but neither computer could access the Internet. Changing router
> allowed them to talk to the Internet.
>
> This causes a question. Why would the LAN card still be good in one
> computer and take out two others plugged into the same router? For
> this to happen, the hit would have to enter in the cable modem. It
> then would have had to continue on the CAT 5 cable. Then through the
> router to fry 2 out of 3 motherboards.
Sounds like a good possibility. I don't remember you wrote the CATV lead
went through the UPS/suppressor.
Particularly if there is *no* bonding between CATV entry and power
service to shunt some of the surge, that could result in a surge too
large for the suppressor (which may now be damaged).
For damage you need a difference in the voltage between power and CATV.
Particularly with no interbonding that could also result from a surge on
the power lines. And if the electric service is not earthed at the house
the possibilities grow.
And low suppressor ratings could be a problem.
>
> The power supplies in all 3 computers are good.
>
>> As I said in your previous thread, when using a plug-in suppressor all
>> interconnected equipment needs to be connected to the same plug-in
>> suppressor, or interconnecting wires need to go through the suppressor.
>> And external connections, like ethernet, phone, CATV also need to go
>> through the suppressor . Connecting all wiring through the suppressor
>> prevents damaging voltages between power and signal wires. A UPS can act
>> as a plug-in suppressor.
>>
>> If *all* equipment was connected to the same suppressor, the ethernet
>> cables wouldn’t have to go through the UPS.
>
> All the equipment was connected to the same suppressor.
>> Another question is what are the surge protection ratings of the
>> suppressor/UPS.
>
--
bud--
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