What's the safest way to improve upon an existing network cable running next to AC power in underground PVC conduit?

Question

Yes, I know! You shouldn't do that...

Here's the thing: it's already done. This is an existing underground PVC conduit that provides both AC power (two phase 120V) and network (via unshielded (!) cat 5e) from the house to a barn and other buildings adjacent to the barn (in US/Pennsylvania). It was installed quite a while ago, hasn't burned down the house, and works ok-ish (@100Mbps).

Also: this is an old house and a (probably) even older barn. There's knob and tube wiring in some places that's still in use! It's not my house, but it's family.

Right now they would like faster networking (there's cameras, online machinery, and an office). There's gigabit switches on both ends of the ~ 150' cat5e run, and sometimes they negotiate gigabit speeds initially, but then they throttle down to 100Mbit eventually. Not exactly a surprise, as the network cable is unshielded and running right next to AC power.

Installing an additional conduit is not really an option. The yard has been paved over since the conduit was installed. Getting rid of the network connection isn't going to happen either. They need it, and it works ok. So, either I help them upgrade the network and hopefully improve safety somewhat, or the existing solution remains in place.

We have a large spool of good quality cat6 network cable available. Individually shielded pairs + overall shield around all pairs + spline, rated for 550Mhz.

My options are:

• use the cat6 cable available, make sure to ground it (on one end?). Lowest cost, should hopefully enable gigabit speeds, and should be somewhat safer / closer to code-ish.
• use higher rated cable? Cat7/8? We'd just need to buy the cable, so not a huge cost. Would it enable higher bandwidth and/or be closer to code-ish?
• run fiber instead? Probably safest / most code-ish solution? We don't have fiber cable though, nor do we have fiber capable switches. I've also never terminated a fiber cable, but we could get someone to do that part. Still an option, though more expensive.

Thoughts?

Answer 1

Fiber is the only code compliant solution. You are not allowed to put SELV wires (like network cables) in a power conduit, but because fiber is electrically non-conductive it is allowed.

Alternatives are wireless networking and powerline networking. But if you need gigabit it may be tricky to get sufficient performance with these options.

Answer 2

Before you start planning a pull through that old conduit you will need to check if it can still be pulled through, root intrusion might have clogged it.

There's a few more options you might not have considered yet:

A fourth option is to make a wireless bridge, take a paired set of directional wifi antennas and point them at each other.

The fifth option is to cut into the pavement and bury a second conduit and then patch the pavement again.

A sixth option is to suspend the network run above ground. Take a steel wire and some tall poles and create a run that way.

For a fiber run you can get a pre-terminated cable and you would only need a converter at each end not a full switch. That should bring the cost down to a few $100.

Answer 3

Fiber is the obvious answer, both from future-proof perspective and the voltage isolation. It also protects the equipment from induced voltages from lightning strikes, which can be an issue in long wire runs.

Media converters between Ethernet RJ45 and fiber are readily available.

Pre-terminated fiber cable is available with a pull loop on one end, ordered to the length you need:

_{(Image source: Discount Low Voltage)}

You would need enough space in the conduit to fit it through. This manufacturer recommends 1" diameter, so with the another cable already there, you'd probably want at least 1.5".

There is also a risk that the original conduit has collapsed under weight or tree roots have grown into it, in which case pulling any type of new cable is likely to fail. As you probably need to remove the old Cat5 cable to make space and to get a drawstring in, you run the risk of being left without any connection.

Answer 4

Split the current Cat5e connection

100 Mbit Ethernet only uses 2 pairs out of the 4 available in the Cat5e cable.

You can get two independent 100 Mbit connections through the currently installed cable. It would need separate switches at the far end, and you would connect some devices (such as the cameras) to one switch and the rest to the other switch.

This solution gives you twice the speed with minimal effort.

The code compliance issues will remain as they are. Having the switches at either end grounded will provide some protection, as Ethernet itself has isolation transformers at both ends.

Answer 5

Option 7, is powerline, or ethernet-over-power.

Personally I hate them and have a low success rate, though other people tell me my results are a-typical.

To improve the chance of success given you have one power backhaul, there would ideally be a power socket/outlet in the house and in the barn, on the same power circuit.

Then you have these modules plugged in, one in each building.

This provides you with effectively a replacement for your existing wire, with the signal "hetrodyned" or modulated on top of the 50/60hz AC wave form.

Large spikes in the power load could cause dropouts, so welders, large motors and other such huge startup current demands can affect throughput.

Best part, they're reasonably cheap and can be on-sold if they don't suit your requirements, to help fund the fibre that should have gone in originally.

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STP or Shielded Twisted Pair might help too, but there's a cost and no guarantee it will help. If you do go this way, remember to get shielded jacks for each end, and ground one end.

Cat 7/8 is a waste of money - the cat6 would be fine. Even cat5 can carry gigabit.

Another consideration - if you're going to the effort to run one cable, run two or more for future proofing/channel bonding.

Also pull through some nylon string as a draw-cable for the next guy, which may be you.