Suggestions for connecting 2 buildings > 300 feet apart

Resistance to surges. Remember phones was invented before fiber sp phone equipment had to be quite tolerant.

But by all means, run your RJ-45 between buildings. It won't cost me a cent :-)

Surge protectors are required. These surge protectors would interfer with proper ethernet.

-Chris

I am aware of surge protectors as used on the phone networks. However, some people have a phobia about running cables between two building, talking about differences in ground potential etc. Given that ethernets are capable of withstanding a few hundred volts and there's no connection to the NICs, other than the coupling transformers, there's no way that's likely to be a problem. If there is enough voltage difference to be a problem, then a very unsafe situation exists, even without ethernet. What may be a problem, is nearby lightning strikes, but if there's one close enough to be a problem for ethernet cables, it's also likely to cause problems via phone and power lines. Also, I seem to recall surge protectors for ethernet were availble, but I don't recall where.

Yes, this is the main concern. A strike elevates ground potentials ringwise (kV/m), and the two buildings groundstakes could be momentarily pushed beyond the 500V transformer isolation.

Yep, them too. That's why they have surge protectors. Phones normally have surge protection on the NID (grey box on the outside of the house). A friend would lose a couple of modems every year because his wasn't grounded.

Power systems are similar, but the PSU systems give some protection to the more vulnerable electronics.

-- Robert

Surge protectors that would not interfere with ethernet may not be acceptable on phone lines. Phone lines with surge protectors even must carry ISDN and xDSL on those wires without problem. Phone line protectors are more than sufficient for ethernet because they must not interfere with xDSL.

In the meantime, any connection between two buildings requires a connection to single point earth ground. Some wires make that earthing connection via a protector. Others earth by a hard wire connection. But it is not the protector that provides protection. Wires must be earthed before entering the building. Earthing is the protection. Any wire between two buildings is earthed at both ends - where the wire enters each building. That is how phone companies did it 70 years ago. That is how copper wire ethernet is safely run between buildings.

Effective protector are sold both for ethernet and phones:

snipped-for-privacy@nospam.com wrote:

Telephone lines are not grounded, except at the CO, where the positive side of the 48V batteries are grounded. At the subscribers end, there is a protection block, which is grounded, but the wires are not. A brief high voltage surge, will be shunted to ground, by the protection block. If you were to ground the phone line, you'd unbalance the circuit and likely get a lot of noise on the phone.

Phone lines are NOT connected to ground at the subscribers premise. Only the protection block is grounded, so that it can shunt voltage surges to ground. Ethernet cable is electrically isolated from the equipment, by the transformers that pass the desired signal between the NIC and cable, but cannot pass DC or low frequency AC.

Why is this a guarantee? xDSL was specifically designed to pass through carbon blocks and other telco antisurge protection. It also operates at much lower frequency (3-5 MHz) than ethernet (5-50MHz sorta).

Agreed, with the refinement that interbuilding wiring isn't directly earthed (that would kill signal) but an earth path is available through an antisurge device.

-- Robert

I've got no personal experiance with this, but here is a product that seems to contridict you. Am I misunderstanding what this thing does?

First I said earthed - not grounded. The word earth defines a specific type of ground. Second, even the NEC requires that the earthing connection to incoming phone line be less than 20 feet to the same earth ground used by AC electric breaker box. As posted previously - some incoming services are earthed by a hardwire (CATV). Others must be earthed through a surge protector (phone). But every incoming utility wire must connect to single point earth ground before entering the building.

In North America, properly installed phone line entering the building has an earthing connection for the phone line 'whole house' protector. It is even required by National Electrical Code Article 800.30A:

James Knott wrote:

Others may have assumed surge protectors sit between the appliance and a surge. Effective protectors don't work that way as you have noted. Shunt mode protectors connect to the uility wires just as another light bulb connects to AC mains. The surge protector makes no connection to earth - does not conduct telephone signals - until voltage is exceeded. Numbers for that threshold are provided in another post that specifically quotes the National Electrical Code requirements for that protector.

xDSL signals do not pass through carbon blocks (obsolete technology) or the newer semiconductor based protectors. xDSL is short wave frequencies - at and above the frequencies used in 10Base-T ethernet. Conventional MOVs are not used on phone lines (except in many cheap plug-in protectors) due to too much capactiance. Telephone 'whole house' protectors (provided free by the telco) must have so little capactiance as to not even interfere with xDSL. These would also be more than sufficient for ethernet.

Others also make protectors for ethernet. In each case, the protector would only be as effective as its earth ground (earthing - not the protector - is the protection):

?productID=153#spec Again for the benefit of others, an effective protector does not sit between the CO and premise telephone. That connection from CO to household phone is straight through wire. The surge protector connects from each phone wire to earth ground. xDSL signals don't pass through a surge protector.

In the meantime, every incoming service including phone is earthed at the premise interface. Specific paragraph from National Electrical Code that requires this earthing is provided in another post.

Bottom l> w_tom wrote:

Don't let that product deceive you. Protection is not in the protector. See that green ground wire? Some pictures type to hide that wire. Wire must make a less than ten foot connection to single point earth ground. A very specific earth ground. Many APC products don't have such necessary earthing wires. Therefore APC forgets to mention that earthing - not the protector - is protection. If they mentioned earthing, then many would learn which grossly profitable APC products are ineffective.

How to identify an ineffective protector - 1) no dedicated connection to earth ground AND 2) manufacturer avoid all discussion about earthing. The PNET1 does have necessary earthing. I don't remember if it meets other necessary parameters. But the PNET1 appears to be an effective protection - even though most APC products are not.

It is not that surge protectors are required. Some c> snipped-for-privacy@nospam.com wrote:

Carbon blocks were obsoleted sometime after the seventies. The carbons were a special design MOV structured to have lower capacitance than conventional MOVs. Pictures of the carbons:

Carbons also were a junction block between incoming telco wire and interior building wire. Notice the carbons do not sit between incoming and interior wires. Center in the assembly is the earth ground bolt. Each carbon remains open circuit most of the time. When excessive voltage appears on a wire, then the carbon connects that phone wire to the earth ground bolt (which connects to earth ground using a 12 AWG green or gray wire).

Newer construction replaces the carbons with an NID:

typically use a semiconductor protector (that also doubles as the junction bolts for telco wire). Unlike carbons, the semiconductor protector becomes a dead short circuit when failed. Unlike the carbons, the semiconductor protector therefore announces its failure by keeping phone line connected to earth.

This semiconductor protector acts like conventional avalanch diodes (Transzorb or Transil) but was specially constructed to have low capacitance. It was sufficient for xDSL (in most cases) before xDSL even was implemented. (I heard of but cannot confirm a notification for some NID surge protectors that had too much capacitance for xDSL and had to be replaced.) The concepts are described in:

I am posting these from memory and did not check the URLs. Hope they still work and are informative.

Robert Redelmeier wrote:

Do you have some reference? I find this hard to believe because carbon blocks were used through the late 1970s, and I haven't heard of many people needing their NID replaced to get xDSL. Sometimes a whole-house splitter is installed.

I don't see carbon blocks or MOVs as having capacitance that would cause problems.

Useful references. I think I'd prefer an NID-type device that I could tie to the building groundstake nearby. Some of these are just dongles, longwired to ground. But I suppose it depends on ground impedence versus rise rates.

-- Robert