sky dish

deafroadrunner

sorry if this sounds like a reali stupid question but i have my HD sky box on a surge protecter but can lightning damage the dish????????????

swoofer

well if lightning hits the dish I'd be more worried about rest of house!! in other words yes, its rare, the surge protector is a good idea, it does not need a direct hit for a surge to happen so relax.

and its a very valid question.

gbc

deafroadrunner

GBCULLEN wrote: »

well if lightning hits the dish I'd be more worried about rest of house!! in other words yes, its rare, the surge protector is a good idea, it does not need a direct hit for a surge to happen so relax.

and its a very valid question.

gbc

Thanks for that i actually have on two surge protecterd lol. So for arguments sake if the dish was hit. Could the surge carry through the coaxial cable an hit the sky box

zg3409

deafroadrunner wrote: »

Thanks for that i actually have on two surge protecterd lol. So for arguments sake if the dish was hit. Could the surge carry through the coaxial cable an hit the sky box

Yes. Surge protectors inside extension leads etc. are only the size of a smarty, If lightning strikes directly on your house the roof could come off, nearby everything electrical could blow, including light bulbs.

Surge protectors are only designed to help protect from a lightning strike more than a few hundreds of meters away.

Either way nearly all modern electronics have the same lightning protection inside them, so no need to pay above the odds for a special "surge protection" lead. 99% of the protection they give is physiological.

You can buy special Satellite cable lightning protectors, which need an earth connection, but again I wouldn't bother.

westom

deafroadrunner wrote: »

i actually have on two surge protecterd lol. So for arguments sake if the dish was hit. Could the surge carry through the coaxial cable an hit the sky box

You have assumed a box called surge protector is also surge protection. Those are two completely different items.

Read numbers on your protector. Will it stop or absorb a typically destructive surges - hundreds of thousands of joules? Will it stop or block what three kilometers of sky could not? What do its spec numbers say?

Protection is never about a protector. An application note demonstrates how all surge protection is implemented:
http://www.erico.com/public/library/fep/technotes/tncr002.pdf

Two structures. Each must have its own single point earth ground. Any wire that enters either structure must first connect to that structure's earth ground.

Treat your building and dish as two structures. Best protection for a dish is no protector. It must have its own earth ground. A coax wire that interconnects a dish and receiver must connect short to the dish earth ground and building earth ground. Again, no protector required.

To make protection better, the app note also shows both single point grounds interconnected by a buried ground wire.

What does a protector do? Make that earthing connection only when a wire cannot connect directly. Coax can connect without a protector. If that protector is not connected to single point earth ground (ie is only connected to receptacle safety ground), then that protector does not even claim protection.

Dish or receiver is damaged because a surge found a best connection from a cloud to earth via that electronics. Nothing will stop or block that current. The only solution - even implemented by Ben Franklin in 1752 - is to give that electric current a shorter (ie 'less than 3 meter') connection to earth that remains outside a building. As the application note also demonstrates. And that always exists in every facility that can never have damage.

A dish must have its own earth ground. Its coax wire must enter at a service entrance to also connect to the one and only building earth ground. No protector does protection. Either the protector connects a surge to protection. Or the protector claims only to protect from surge that typically cause no damage.

bud_

The best information on surges and surge protection I have seen is at:
http://www.lightningsafety.com/nlsi_lhm/IEEE_Guide.pdf
- "How to protect your house and its contents from lightning: IEEE guide for surge protection of equipment connected to AC power and communication circuits" published by the IEEE in 2005 (the IEEE is a major organization of electrical and electronic engineers).
And also:
http://www.nist.gov/public_affairs/practiceguides/surgesfnl.pdf
- "NIST recommended practice guide: Surges Happen!: how to protect the appliances in your home" published by the US National Institute of Standards and Technology in 2001

The IEEE surge guide is aimed at people with some technical background.

westom wrote: »

Read numbers on your protector. Will it stop or absorb a typically destructive surges - hundreds of thousands of joules? Will it stop or block what three kilometers of sky could not? What do its spec numbers say?

Neither service panel protectors or plug-in protectors ''stop", "absorb" or "block" surges.

The author of the NIST surge guide investigated how much energy can reach the MOVs in a plug-in protector. Branch circuits were 10m and longer, and surges coming in on power wires were up to 10,000A (which is the maximum probable surge). The maximum energy was a surprisingly small 35 joules. In 13 of 15 cases it was 1 joule or less. For a couple reasons, the current that can reach a plug-in protector is quite limited, so the energy that is absorbed in a plug-in protector is very limited. Plug-in protectors with much higher ratings are readily available. High ratings mean long life.

Both the IEEE and NIST surge guides say plug-in protectors are effective.

When using a plug-in protector all interconnected equipment needs to be connected to the same protector. External connections, like cable, also must go through the protector. Connecting all wiring through the protector prevents damaging voltages between power and signal wires.

westom wrote: »

Treat your building and dish as two structures. Best protection for a dish is no protector. It must have its own earth ground.

It is seldom, if ever, a good idea to have a separate ground rod at a dish. Assume the house uses a ground rod as the earthing electrode and you put a ground rod at the dish as an earthing electrode. If there is a very near strike, like to a tree, the separated ground rods can have thousands of volts between them.

The protection for a dish is not intended for a direct lightning strike to the dish. Protection from a direct lightning strike requires much more elaborate protection.

westom wrote: »

A coax wire that interconnects a dish and receiver must connect short to the dish earth ground and building earth ground. Again, no protector required.

Doesn't need a protector? The IEEE guide says "there is no requirement to limit the voltage developed between the core and the sheath. .... The only voltage limit is the breakdown of the F connectors, typically ~2-4 kV." And "there is obviously the possibility of damage to TV tuners and cable modems from the very high voltages that can be developed, especially from nearby lightning."

This is much more likely with cable than a dish, unless you put a ground rod at the dish.

At least a ground block is required where the dish coax enters the building, with the ground block connected to the building earthing system.