Hi, I was just answering a post for someone on another group regarding how to ground a CATV line and it got me thinking. Ademco panels all have a screw that they want tied to earth ground. I've never seen a residential install that had that wire attached. Why have it? why do it? why not do it? Just curious. Thanks
The protection on the board is minimal, I'd rather it was toast if it was hit. The ground is also a route IN and a long antenna. Maybe they are thinking more a safety issue with the ground stuff in the manuals.
If the system is inspected by an electrical official, they most likely will require it to be grounded if there is provisions for a ground on the panel. The NEC states that the metal box shall be grounded, at least. Some panels, DSC for instance, provides hardware and instructions to ground both, the box and the panel.
Because it is required by manufactures specifications and the testing labortory that approved the panel.
To protect the panel for surge damage
Some think that if you don't do it, it will protect the panel from surges, but the ground is only one avenue into the panel and is not the most likely one. If it is connected to a good ground, it helps much more than it hurts.
On DSC panels, it's best to leave them ungrounded. The panels that were grounded were damaged more often by lightning than panels that weren't. At least that was my experience in Edmonton (the lightning capital of the Prairies)...
The post in that other newsgroup was about grounding for human safety. OP was seriously (he implied) shocked when connecting coax cables. Every incoming utility wire must connect to a common ground at the service entrance - for human safety. Therefore that discussion kept telling the original poster to first verify or connect cable short to the same earth ground used by telephone and AC electric.
Furthermore, that service entrance ground serves a second function - transistor safety. Defined were other important conditions such as 'less than 10 feet', no splices, no sharp bends, and wire separated from other non-earthing wires.
The ground lug on Ademco is for human safety. Alarm system must connect to the same grounding system so that voltages don't float. Third prong on AC plug might also do this.
Meanwhile, if grounding that alarm panel causes lightning damage, then every utility does not connect *every* wire to that single point earth ground. Lightning damage directly traceable to a human mistake. Every wire connected either directly via hardwire (as suggested for cable in that other discussion) or via a surge protector.
Notice what a surge protector does. Make that 'less than 10 foot' connection to a common earth ground when wire cannot make that connection directly. A protector that does not connect from a wire short to earth is doing nothing effective
- a specific reference to plug-in protectors.
Original poster was also encouraged to verify each surge protector (such as one provided free by his telco) was also connected to earth ground. Single point earthing is THE surge protection. Wires or protector are nothing more than connection to protection.
I always use the ground in the panel and it has stopped many problems it also is essential when using the phone line monitor to prevent a false phone line loss alarm.
bottom line it is supppose to be used and if there is a system failure and the insurance carrir conducts an inestigation it will be cited in the report as not being installed. any one not using this ground is taking a huge liability if they have an alarm failure.
Thanks for the responses. I hope it doesn't sound like I'm beating a dead horse, I'm just curious. So it looks like we have two NO, two YES, and one YES/NO. So, if you are a YES and you come upon a panel that is not grounded, do you add it? If you are a NO and you come upon a panel that IS grounded, do you disconnect it? If so, why and if not, why not?
Regarding human safety and grounding the cans. The Ademco and Moose cans I am familiar with do not seem to have a good grounding location. Sure, I could tap in a sheet metal screw and that would cover it but it seems like if they didn't put it there in the first place and they don't mention it in the instructions, then it wasn't intended. The screw on the board, however, they do mention. You mention that DSC panels do provide hardware to ground the panel. I'm curious, do they have a good connection between the can and lid as well? If it's a human safety issue I would assume that they have a good non-painted contact between the two.
Many years ago, telephones were wired with 3 wires. The 3rd was a ground.
Well they stopped running that ground wire inside the house.
I think they figured out that if these is no ground inside the house associated with the phone system, then the lightning would stay outside?
Hard wired alarm systems have a different problem in that all the wires running all over the place can act as an antenna, and a nearby lightning strike can "induce" voltage in the wiring.
The question I have would be; is there "built into the alarm circuit board" surge protection for the wiring on each zone, surge protection for the phone line, and surge protection for the AC power lines?
And if there is surge protection in the form of zeiner diodes or MOV's, do these short to the ground connection on the panel in the case of a surge? (In which case I would think it would be better to provide a ground wire. However if the ground connection is just going to the common or negative wiring on the panel, then I would think it would be best not to connect a ground as this would just be "lightning bait" to attract lightning to travel
*through* all the circuits on the board [rather than bypassing them] and fry everything!)
NFPA 70 article 250 doesn't require systems operating at less than 50v to be grounded. Article 110.3(B), on the other hand, requires listed and labeled equipment to be installed in accordance with the manufacturer.
If the control panel enclosure has a green grounding screw and the manufacturer requires that it be connected to the grounding electrode system then the electrical inspector will require that they be connected.
To make a decision based only upon number of votes is a fool's errand. First question to ask was, "Were underlying reasons for that vote also provided." It is called "the devil is in the details". Too many just know without ever learning the reasons why. That is how junk science is created.
Should you only take what I have posted as one vote, then reverse my vote. I now vote for the most destructive alternative because you did not first do as even George Patten demanded: the good general knows what is happening three levels down. My post provided some underlying details - and more than others had provided to justify their 'votes'. Knowledge of underlying technical details always trumps a thousand votes to the contrary. Science types always demand 'why'. 'Yes or no' is not sufficient.
If you don't learn and appreciate the functions of grounding
- why the same wire can serve multiple functions - then you have no answer. IOW without the why's, then the real answer provided was "I don't know".
Basic electrical knowledge says everything in the building must connect to the common single point ground. This ground defined and essential for human safety. Which is completely different from another single point ground for transistor safety. Yes, both share common wires. But, for example, the AC receptacle ground is not an earth ground for very good reasons electrical. Yes, the AC receptacle ground is eventually connected to earth ground through a chain of wires. But it is not earth ground.
If AC receptacle ground is earth ground, then printed circuit motherboard ground is also a good place to earth a lightning rod. But since two ends of every wire is electrically different, then each ground is different.
The answer is not found in votes. Answer is found in science. The difference between resistance and impedance. The underlying reasons why. How many of those voters even know the difference between resistance and impedance? And how many can apply numbers to same? Therein lies a criteria to count only votes based in science - not speculation.
Immediately, you know this if only for human safety. Everything must have a sufficiently grounded (low resistance) connection to the building's single point safety ground. That unique safety ground is located inside main breaker box. That safety ground is different from the earth ground. Just another fact that responders must understand before your question could be properly answered. Just another benchmark to weed out votes from the technically naive.
The alarm panel is typically the s> Thanks for the responses. I hope it doesn't sound like I'm beating a
An interesting observation was made that the Ademco screw on the terminal board is mentioned, not the can. The circuit board attaching screw grounds it to the can approx 3/8 inch from the terminal. Ground the screw on the board and you ground the can.
Well for "personal safety" issues, whoever might be touching the alarm panel or associated wiring and devices (you, I, burglar), it is possible for a transformer to malfunction and send through house current, or perhaps an associated wire to come in contact with house current, or phone line to come in contact with high voltage.
And an air conditioning system can malfunction sending house current through all the metal vents and an alarm wire might be shorting to same.
I could have done this in the first place I guess but I wanted to know what some of the pros in the industry did and why. I pulled up my pdf for the Ademco V20se install manual and did a search for the word 'ground' and pertinent things that came up were....
The designated earth ground terminal (25) must be terminated in a good earth ground for the lightning transient protective devices in this product to be effective. The following are examples of good earth grounds available at most installations. metal cold water pipe AC Power Outlet Ground (to test the integrity of the ground terminal, use a three-wire circuit tester with neon lamp indicators)
If the panel is not connect to a proper earth ground you may get false line cut indications...
so it looks like it is more for the efficacy of the lightning transient protective devices that Ademco has on their boards and it is for the line current sense on the telco line, not really life safety, UL compliance, or for any code at all. At least I didn't see anything in the manual that indicated it was for life safety, UL, or code compliance.
The phone goes up to about 100 volts when it rings. A defective transformer may short the secondary to primary. Ever see 110 vac and the alarm zone on the same waterflow? Low voltage from the panel is used to trigger high voltage lighting circuits. etc., etc., etc. js
You are correct. Since the panel is low voltage, life safety isn't the primary reason for grounding it. However, code requires that you install the device in accordance with the manufacturer's instructions. Common sense agrees with the manufacturer in this case.
That said, while Honeywell (nee: Ademco) allows you to ground to an electrical outlet, that is not the best place to earth your panel. The best method is to connect it to the building's common earth ground -- usually a copper clad rod sunk in the ground near the electrical service entrance.
As others have already said and as I have also mentioned in earlier threads in this and other newsgroups, the best lightning protection for your electronic equipment is a bonded (aka "common") earth ground. It is very important that all services be grounded to the same point or, failing that, to a system of ground rods which are bonded together so as to provide a unified earth connection. This will help avoid one of the most common lightning damage situations where the current flows in one ground -- through your stuff -- and out another.