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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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Building Ground (long-...sorry)
I've read a good deal about the above. Ideally, the grounds for various
(telephone, cable, power) electrical utilities should all be common; and the service entries for those sundry services should be located within 15' of each other. If I ever build a new house, I will take that into account. However, it's not practical at this time to realize the ideal. What I have currently is as follows: The phone drop (two lines) comes in on one side of the house and is grounded to the water supply line which comes in the front of the house (about of 20' of wire clamped to the pipe where it comes through the foundation into the unfinished basement). The power drop (100 amp 220v single-phase) enters at the back of the house, about 30' diagonally from the phone service. A ground wire snakes from the panel (inside a utility porch) around a couple of corners and through the floor to a ground post of unknown length/depth in the crawl space beneath the adjacent kitchen...approximately 20 feet of wire with at least two 90 degree bends. The cable drop is around 15' feet from the power service entrance, and grounded to an adjacent outside faucet a couple of feet away (all plumbing in the house is copper). Over the years, we've had a good deal of surge and lightning related damage to devices in the house...most recently a DSL modem. Would I derive any advantage by driving a new ground post outside, adjacent to the power drop and to run all the various service grounds to it (around 15' for cable, 25' or so for phone)? Alternatively, I could move the telephone ground wire to the existing power drop ground post (probably using the same 20' wire), and also extend cable ground to this point. That would give me a 'star' configuration with all utilities having around 20'-30' of wire from each drop to ground. Moving the phone service drop at this time (the ideal) is not practical. jak |
#2
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Building Ground (long-...sorry)
In article ,
jakdedert wrote: The phone drop (two lines) comes in on one side of the house and is grounded to the water supply line which comes in the front of the house (about of 20' of wire clamped to the pipe where it comes through the foundation into the unfinished basement). Could anyone explain why a US telephone cable needs a local ground? Aren't they balanced? The UK system only used a local ground for shared local lines which went out years ago. -- *Work like you don't need the money. Love like you've never been hurt. Dave Plowman London SW To e-mail, change noise into sound. |
#3
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Building Ground (long-...sorry)
System is balanced and isolated in US too. The ground is just for surge / lightning protection.
Eric Law "Dave Plowman (News)" wrote in message ... In article , jakdedert wrote: The phone drop (two lines) comes in on one side of the house and is grounded to the water supply line which comes in the front of the house (about of 20' of wire clamped to the pipe where it comes through the foundation into the unfinished basement). Could anyone explain why a US telephone cable needs a local ground? Aren't they balanced? The UK system only used a local ground for shared local lines which went out years ago. -- *Work like you don't need the money. Love like you've never been hurt. Dave Plowman London SW To e-mail, change noise into sound. |
#4
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Building Ground (long-...sorry)
In article ,
Eric Law wrote: System is balanced and isolated in US too. The ground is just for surge / lightning protection. Right. Few telephone cables in the UK are overground, so that explains it. The surge arrestor here is just wired between the incoming pair. -- *Time is fun when you're having flies... Kermit Dave Plowman London SW To e-mail, change noise into sound. |
#5
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Building Ground (long-...sorry)
hmm.. I can't say I know of many overground telephone wires in my area,
except in older houses that have overhead power service, they used to string the telephone wire under the power wire, but the main phone lines are all burried. I found out the hard way that burrying the wire doesn't help with lightning protection when I ran a cat5 ethernet wire from my house to a friends last year. That thing got zapped evey time we had a bad storm.. - Mike "Dave Plowman (News)" wrote in message ... In article , Eric Law wrote: System is balanced and isolated in US too. The ground is just for surge / lightning protection. Right. Few telephone cables in the UK are overground, so that explains it. The surge arrestor here is just wired between the incoming pair. -- *Time is fun when you're having flies... Kermit Dave Plowman London SW To e-mail, change noise into sound. |
#6
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Building Ground (long-...sorry)
Michael Kennedy wrote:
I found out the hard way that burrying the wire doesn't help with lightning protection when I ran a cat5 ethernet wire from my house to a friends last year. That thing got zapped evey time we had a bad storm.. The problem wasn't caused by the ethernet wiring; it was the difference in ground potential between the two homes. You should have optically isolated the two ends to avoid the problem. |
#7
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Building Ground (long-...sorry)
It is used for lightning protection.. Believe me you really need if you
happen to live in Florida. - Mike "Dave Plowman (News)" wrote in message ... In article , jakdedert wrote: The phone drop (two lines) comes in on one side of the house and is grounded to the water supply line which comes in the front of the house (about of 20' of wire clamped to the pipe where it comes through the foundation into the unfinished basement). Could anyone explain why a US telephone cable needs a local ground? Aren't they balanced? The UK system only used a local ground for shared local lines which went out years ago. -- *Work like you don't need the money. Love like you've never been hurt. Dave Plowman London SW To e-mail, change noise into sound. |
#8
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Building Ground (long-...sorry)
"Michael Kennedy" wrote in message . .. It is used for lightning protection.. Believe me you really need if you happen to live in Florida. - Mike OR Colorado WW "Dave Plowman (News)" wrote in message ... In article , jakdedert wrote: The phone drop (two lines) comes in on one side of the house and is grounded to the water supply line which comes in the front of the house (about of 20' of wire clamped to the pipe where it comes through the foundation into the unfinished basement). Could anyone explain why a US telephone cable needs a local ground? Aren't they balanced? The UK system only used a local ground for shared local lines which went out years ago. -- *Work like you don't need the money. Love like you've never been hurt. Dave Plowman London SW To e-mail, change noise into sound. |
#9
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Building Ground (long-...sorry)
"Michael Kennedy" wrote in message . .. It is used for lightning protection.. Believe me you really need if you happen to live in Florida. - Mike OR Colorado WW "Dave Plowman (News)" wrote in message ... In article , jakdedert wrote: The phone drop (two lines) comes in on one side of the house and is grounded to the water supply line which comes in the front of the house (about of 20' of wire clamped to the pipe where it comes through the foundation into the unfinished basement). Could anyone explain why a US telephone cable needs a local ground? Aren't they balanced? The UK system only used a local ground for shared local lines which went out years ago. -- *Work like you don't need the money. Love like you've never been hurt. Dave Plowman London SW To e-mail, change noise into sound. -- ---------------------------------------- I am using the free version of SPAMfighter for private users. It has removed 284 spam emails to date. Paying users do not have this message in their emails. Try www.SPAMfighter.com for free now! |
#10
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Building Ground (long-...sorry)
On Tue, 09 May 2006 10:41:48 -0500, jakdedert
wrote: I've read a good deal about the above. Ideally, the grounds for various (telephone, cable, power) electrical utilities should all be common; and the service entries for those sundry services should be located within 15' of each other. If I ever build a new house, I will take that into account. However, it's not practical at this time to realize the ideal. What I have currently is as follows: The phone drop (two lines) comes in on one side of the house and is grounded to the water supply line which comes in the front of the house (about of 20' of wire clamped to the pipe where it comes through the foundation into the unfinished basement). The power drop (100 amp 220v single-phase) enters at the back of the house, about 30' diagonally from the phone service. A ground wire snakes from the panel (inside a utility porch) around a couple of corners and through the floor to a ground post of unknown length/depth in the crawl space beneath the adjacent kitchen...approximately 20 feet of wire with at least two 90 degree bends. The cable drop is around 15' feet from the power service entrance, and grounded to an adjacent outside faucet a couple of feet away (all plumbing in the house is copper). Over the years, we've had a good deal of surge and lightning related damage to devices in the house...most recently a DSL modem. Would I derive any advantage by driving a new ground post outside, adjacent to the power drop and to run all the various service grounds to it (around 15' for cable, 25' or so for phone)? Alternatively, I could move the telephone ground wire to the existing power drop ground post (probably using the same 20' wire), and also extend cable ground to this point. That would give me a 'star' configuration with all utilities having around 20'-30' of wire from each drop to ground. Moving the phone service drop at this time (the ideal) is not practical. I'm assuming the DSL modem and computer are plugged into the same outlet . . . It sounds like you have two unknown grounds that are far from the ideal. You don't say what the failure mode of the equipment is and how severe - I'm guessing it is probably common-mode developing between the two ground systems. If you get something like bridge rectifiers in power supplies shorting - that could indicate a differential voltage spike. Or, better yet, start at the beginning . . .Check the power transformer. There should be a lightning arrestor for the transformer - a kind of insulator that sits off to the side of the can that is clamped to the can and has a small 1/2"-1" air gap between it and the HV terminal. (designs vary quite a bit but it should be there in some form - a collection of broken porcelain around the base of the pole and some carbon blocks means it is done its job once too often) The transformer pole and transformer must be grounded. There should be a thick soft copper wire running from the transformer down the length of the pole and into the ground. Usually the wire is wrapped in a spiral and nailed to the bottom of the pole. Without the transformer grounded - anything you do may be wasted effort. I had no problem getting a neighbor's lightening arrestor replaced with just a call to the power company and, in another instance, a pole ground wire replaced - they are subject to being stolen by people trying to salvage the copper. Two different power companies and no arguments - they just went out and fixed it. Your best option is probably to get the grounds on the same circuit. I'd sink a ground and wire to it, so I knew what its condition is like. (ten foot length of half inch dia copper water pipe washed into the soil is better than anything you're likely to drive into the ground) Braze or solder the heavy wire on. Put it at the power entrance as directly under the power meter as you can with no bends in the heavy wire. Five or six feet to ground if you can manage it with no bends. Use a large radius bend if you go around an obstacle. It may not be practical, but do the best that the conditions allow. What to do about the telephone line and power line separation? Sink a separate ground for the phone line and just use it for the lightening arrestor on the line and make sure it is bonded to the main power ground. There was some good stuff in an ARRL article some years ago that mentioned a similar problem. He solved it by adding a ground for the phone line directly under the phone's entrance box to the company supplied arrester then added a set of gas filled spark gaps in addition to the arrester. Cold water pipes are iffy - they can be excellent grounds or very poor grounds. Too many variables - you'd have to know the material and condition of the pipe, how straight the run to ground is, and what the joints are like electrically. Some old systems used cast iron pipe and the joints are not connected electrically. Some really old cities still pull up a wooden water main from time to time . . . Galvanized threaded joints are usually pretty good if the pipe was clean when the pipes where joined and someone didn't get carried away with Teflon tape. Beyond that you can still get fancy with isolation transformers or optical links. ----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
#11
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Building Ground (long-...sorry)
default wrote:
On Tue, 09 May 2006 10:41:48 -0500, jakdedert ... Or, better yet, start at the beginning . . .Check the power transformer. There should be a lightning arrestor for the transformer - a kind of insulator that sits off to the side of the can that is clamped to the can and has a small 1/2"-1" air gap between it and the HV terminal. (designs vary quite a bit but it should be there in some form - a collection of broken porcelain around the base of the pole and some carbon blocks means it is done its job once too often) The transformer pole and transformer must be grounded. There should be a thick soft copper wire running from the transformer down the length of the pole and into the ground. Usually the wire is wrapped in a spiral and nailed to the bottom of the pole. Without the transformer grounded - anything you do may be wasted effort. I had no problem getting a neighbor's lightening arrestor replaced with just a call to the power company and, in another instance, a pole ground wire replaced - they are subject to being stolen by people trying to salvage the copper. Two different power companies and no arguments - they just went out and fixed it. ... Default makes an important point. Defined for a house is a 'whole house' protection system - also called secondary protection. Primary protection is provided by the utility, as default has described. Pictures that demonstrate inspection of a Primary protection system: http://www.tvtower.com/fpl.html |
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