Surge Protection on UPC cable

cullym

I had the AV board blown out on my TV during the thunderstorms two weeks ago. The UPC box is shot also. It looks like the surge came through the box and on to the TV through the HDMI cable.
I know you can buy surge protection modules for CATV but I'm wondering if the incoming UPC cable should be grounded. I know in the US it's part of the national code that cable be grounded. Anyone know if that's the case here?

coylemj

I think the shielding is grounded but I doubt the core is, otherwise it would defeat the purpose of having it shielded in the first place.

A lot of socket boards have in and out ports for TV cable and/or phone lines, I have one beside me that I bought in Lidl and there's co-ax sockets on it which are obviously for surge protection.

cullym

Thanks colyemj

I would hope the shielding is grounded, that really what I was getting at in my first post. The shield is there to protect the core and that's were lightning is most likely to travel as it seeks ground as I understand it. I've had a quick look outside and don't see anything resembling a grounding wire where the UPC cable enters my house. I've a tech calling tomorrow to check the box so I'll bring it up with him?
I've now got one of the surge protect blocks like you describe but I was thinking it would be best if a surge on the UPC cable had a way to ground as early as possible. I know it's no guarantee but it can only help.

coylemj

cullym wrote: »

I've had a quick look outside and don't see anything resembling a grounding wire where the UPC cable enters my house.

The local UPC network is probably grounded somewhere where you can't see it.

cullym wrote: »

I've a tech calling tomorrow to check the box so I'll bring it up with him?

What is he going to check for?

cullym wrote: »

I've now got one of the surge protect blocks like you describe but I was thinking it would be best if a surge on the UPC cable had a way to ground as early as possible. I know it's no guarantee but it can only help.

Surge protection and grounding are completely separate issues. Sorry if this offends you but I think you don't understand the basics of domestic electricity.

Grounding involves connecting a domestic electrical circuit to a metal rod embedded in the earth outside a house, it's done as a safety measure so that if your toaster becomes live because of faulty wiring, there will be an easier route to earth than through a human being. That's why most appliances in the house include an 'earth' wire which grounds them.

In modern houses, most of the major metal fittings such as the sink, hob, taps and most fitting in the bathroom are earthed so if there is loose wiring anywhere, they will not present a hazard to humans.

Surge protection means that the electrical circuit contains a protection against a sudden surge in the voltage which can in some cases damage delicate internal circuitry but it's only required for relatively modern sensitive equipment like broadband routers and computers.

westom

cullym wrote: »

I've now got one of the surge protect blocks like you describe but I was thinking it would be best if a surge on the UPC cable had a way to ground as early as possible. I know it's no guarantee but it can only help.

It must not only be earthed. The earthing connection must be to the same electrode used for AC electric and telephone. The concept is called 'single point earth ground'. And that connection must be low impedance. IOW the wire should be less than 3 meters, have no sharp bends, separated from other non-grounding wires, and other electrically significant requirements.

Generally, a properly earthed shield is best described by this industry professional:

Coax, inside, rejects common-mode propagation of lightning energy. Coax, outside, needs good grounding to make a good path around (bypass for) protected equipment.

If you still want a protector, well, remember that no protector does protection. Best protection is that wire to earth. A protector is only making a connection similar to that wire. So if that protector does not connect 'less than 3 meters', no sharp bends, etc, then the protector is not doing what you have asked for.

Nothing blocks or absorbs a surge. Protection is always about connecting that current to earth BEFORE it enters the building.

BTW, the most common source of surges is AC electric. Incoming on the power wire. Outgoing to earth via the cable. Often damaged is the outgoing path - ie the HDMI port. You only assumed damage was on the incoming port. If the outgoing current path does not exist, then a destructive surge does not exist.

cullym

coylemj wrote: »

The local UPC network is probably grounded somewhere where you can't see it.

I would expect that to be the case.

coylemj wrote: »

What is he going to check for?

Good question. The box is not producing a picture but is powering up so UPC insisted on sending out an engineer to replace the box. It's actually been replaced now.

coylemj wrote: »

Surge protection and grounding are completely separate issues. Sorry if this offends you but I think you don't understand the basics of domestic electricity.

I realise these are different issues but admit I don't have the correct terms to explain myself properly. No offence taken :-). I'm asking questions in order to better understand the issues.

As an aside when the engineer was here he was saying that the surge came from an ESB transformer that their equipment is connected to. This caused a load of amplifiers to blow out along the road. They had hundreds of call outs in this area. Lots of people with dead TV's and boxes.

white_westie

Am I missing something here - are you saying a surge from an ESB transformer blew UPC's line amps/routers which in turn blew your modem, your upc stb and your TV all through the coax from UPC?
Is there no protection on the UPC cable at all?
Are UPC not liable for the damage this has done?

westom

cullym wrote: »

As an aside when the engineer was here he was saying that the surge came from an ESB transformer that their equipment is connected to. This caused a load of amplifiers to blow out along the road. They had hundreds of call outs in this area. Lots of people with dead TV's and boxes.

Apparently many customers do not have that low impedance (ie 'less than 10 foot') connection to single point earth ground.

Locating earth ground is simple. The electrode must be within meters of where AC electric enters. AC must have a connection to that earthing electrode. Cable must also have a low impedance connection (ie 'less than 3 meter' long) that same electrode. If their modem box was damaged, then the required earth ground probably does not exist. Explains why you cannot find it.

If cable was properly earthed, then a surge would not have found earth destructively via that box. Instead, a surge would have found earth BEFORE entering. Box damage implies that earth ground - required to protect electronics - does not exist. Lots of people with dead TVs and boxes further suggests a low impedance (ie 'less than 3 meter') connection to earth is missing on numerous subscriber interfaces. IOW the company has plenty of defectively installed interfaces. Which would also explain their many damaged line amplifiers.

gerryo

cullym wrote: »

....As an aside when the engineer was here he was saying that the surge came from an ESB transformer that their equipment is connected to. This caused a load of amplifiers to blow out along the road. They had hundreds of call outs in this area. Lots of people with dead TV's and boxes.

I would assume the ESB will be paying for repairs to your TV.
AIUI, if they caused the surge that damaged your TV, they have to pay for repairs/replacement.

coylemj

Why do people need surge protectors if the domestic earth is able to protect them from surges?

white_westie

Still confused about what caused damage - spike/surge on esb supply coming into your house or something on upc cable?

SpaceTime

The device in the UPC (or predecessors') socket is a cable isolator. In older Cork Multichannel installations this was sometimes installed as a separate device where the cable entered your house.

But, basically unless you've removed the isolator somehow, it shouldn't have been possible for a surge to pass through the cable line.

Phone lines are probably more of a risk for surges than CATV lines as there's no surge protection on them.

The isolator protects you from the network (if there were any stray voltages) and also protects the network from your equipment too should your TV be faulty and apply a voltage to the network it won't be carried to your neighbors.

CATV networks had to be designed to protect against potentially very high voltages being sent down the cable line accidentally. Remember they were designed to be connected directly to CRT televisions, not to STBs or LCD TVs which are far less scary devices in terms of the voltages involved and the potential for a high voltage incident.

cullym

Lots of responses. The problem with a surge is how do you prove where it came from?

@SpaceTime - good to know (as I suspected) that the UPC network should have measures in place to prevent this kind of thing from happening. My cable etc is as installed by UPC engineers so I would hope it's to spec.

From the discussion with the engineer it looks as though the surge may have come in on ESB and back out through TV and box. As these were the only items damaged I initially suspected the fault to be with the UPC installation.

As for who's responsible and getting someone to pay, I think chasing that could be a fruitless exercise. I managed to get a second hand AV board for €50 from ebay and a friend who is an electronic engineer replaced it for me. So I got off light.

My original post was an attempt to figure if my UPC cabling etc was installed to spec ( how would I know? ) I now have the UPC cable going through a surge protect block with in & out ports for aerial. Hopefully this will provide an extra bit of protection.

white_westie

Just looked at the isolator at the end of the cable that comes from the tap.
Its a Trantec tris-226gen spec sheet here http://www.technetix.com/upload/products/connected-home/inline-isolators-wall-outlets/inline-isolators/471/tris/tris-226gen/TRIS-226GEN_020712_v13_final.pdf?dl=1

Looks like the 'Modem Safe' feature does the protection for us.

Is it because tv's, cable/satellite stb's, media players and av equipment do not have any earth and are generally interconnected, that a hit on one could easily be passed onto the other's?

cullym

white_westie wrote: »

Just looked at the isolator at the end of the cable that comes from the tap.
Its a Trantec tris-226gen spec sheet here http://www.technetix.com/upload/products/connected-home/inline-isolators-wall-outlets/inline-isolators/471/tris/tris-226gen/TRIS-226GEN_020712_v13_final.pdf?dl=1

Looks like the 'Modem Safe' feature does the protection for us.

Is it because tv's, cable/satellite stb's, media players and av equipment do not have any earth and are generally interconnected, that a hit on one could easily be passed onto the other's?

I had just looked at mine here too and exactly the same. Would the fact that this wasn't replaced when the engineer was here indicate that the surge came in on ESB?

westom

cullym wrote: »

Would the fact that this wasn't replaced when the engineer was here indicate that the surge came in on ESB?

Do not earth appliances. Earth the surge. Earthing an appliance simply creates a best (and destructive) path to earth via the appliance.

Appreciate how surges do damage. A surge is a current source. That means voltage will increase, as necessary, to blow through anything that might stop it. Any protector that tries to stop or block a surge current simply creates a higher voltage.

View numbers on a Trantec tris-226gen spec sheet. DC voltage is 2000. 50 Hertz isolation drops to something above 230 volts. As frequency goes higher, isolation quickly diminishes. Surges are radio waves. If that isolator stops a surge, then it also stops radio (internet or TV) reception. It does not claim to protect from surges.

You know the isolator was ineffective for two reasons. First nothing stops or blocks a destructive surge. And second, its spec numbers and purpose (conduct radio frequencies) also say it would be ineffective.

Is a surge block effective? Well, appreciate a fundamental concept of surge protection. If the surge block is earthed by a low impedance connection (ie 'less than 3 meters, no sharp wire bends, no splices, etc), then that wire has best possible protection. Because earth ground (not any protector) does the protection.

If a wire cannot be earthed directly, then we do the next best thing. We make the same low impedance connection with a protector. The protector only does what a wire does better.

So what defines protection? Single point earth ground. A ground that must both meet and exceed code requirements. Earth a surge before it gets anywhere near to an appliance. Earth the surge; not appliances.

Useful would be knowledge of how that surge entered. But summarized above is protection from all types of typically destructive surges. Bottom line - a destructive current (even from a failed neighborhood transformer) does damage by connecting to earth destructively via appliances. Superior protection inside appliances (or isolator) is not overwhelmed when that current connects to earth BEFORE entering a building.