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Message 985613 - Posted: 31 Mar 2010, 18:18:41 UTC

I was hoping that Al or hiamps might wander by and have the answer on the tip of their tongues....

Off to work now, mebbe they will check in whilst I am gone.
"Freedom is just Chaos, with better lighting." Alan Dean Foster

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Message 985614 - Posted: 31 Mar 2010, 18:18:50 UTC - in response to Message 985574.  

I seem to recall that there were certain situations where a in a subfeed box this was OK too....but sometimes it was not, and the correct thing was to have isolated neutral and ground buses. And I am not sure whether to bond the ground to the enclosure or not, although I think that was correct.

I'm sure this isn't the only case where it is important, but....

If the neutral and ground are connected in two different places, the two wire runs form a loop, and that loop has a resonant frequency.

Among other things, it can act as an antenna and cause all kinds of strange problems with wireless devices and radio reception and etc.

You can have (induced) current in the loop.

The same is true if you ground the main panel and put a ground rod on the sub-panel. The loop is completed through the dirt.

If you have a single point ground, you don't have a loop, and all of those issues, even if they're unlikely, become impossible.

This is outside electricity and more about higher power (radio) transmitters, but ground loops become inevitable when you have a transmitter, an antenna, and a shielded (shield is grounded) feedline between them.

The solutions are to change the length of the loop (change the resonant frequency) or to provide a second ground, AC-coupled (through capacitors) that is a different length -- one ground is part of a resonant loop.
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Message 985622 - Posted: 31 Mar 2010, 18:58:22 UTC - in response to Message 985574.  

OK guys and gurlz....

Got a start on the power rewire...
Bored the hole through the floor and strung 50' of the 6/3 through the basement. The length worked out just right. Will probably stub the cable into the main box and install the 50amp breaker tomorrow. Then I can start to assemble the branch cables and receptacle boxes.

One question...I have gotten a bit rusty on this.
At the mains, the neutral and ground are bonded together and also connected to the earth ground rods and the water mains ground. So really, neutral and ground are one and the same, and any of the lugs on the neutral/ground bus bars can be used for either connection. I believe the bus is bonded to the enclosure box as well.

I seem to recall that there were certain situations where a in a subfeed box this was OK too....but sometimes it was not, and the correct thing was to have isolated neutral and ground buses. And I am not sure whether to bond the ground to the enclosure or not, although I think that was correct.

If I need to keep neutral and ground isolated in the subfeed, I shall have to get an additional isolated ground bus kit, as the box only has 3 buses in it, L1, L2, and neutral.

Any advice from somebody who is current on this? (No pun intended, sparkys).

You are correct, in a sub panel the ground and neutral must be separate. Lowes or Home Depot will have a ground kit. Make sure it is for the brand of Sub panel you have as they will have a few.
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Message 985623 - Posted: 31 Mar 2010, 19:10:10 UTC

If in doubt refer to NEC 1996 edition at your local library.

Fixed appliances on three-wire circuits

In the USA, the cases of some ovens and clothes dryers were grounded through their neutral wires as a measure to conserve copper during the Second World War. This practice was removed from the NEC in the 1996 edition, but existing installations may still allow the case of such appliances to be connected to the neutral conductor for grounding. Note that the NEC may be amended by local regulations in each state and city. This practice arose from the three wire system used to supply both 120 volt and 240 volt loads. Because ovens and dryers have components that use both 120 and 240 volts there is often some current on the neutral wire. This differs from the protective grounding wire, which only carries current under fault conditions. Using the neutral conductor for grounding the equipment enclosure was considered safe since the devices were permanently wired to the supply and so the neutral was unlikely to be broken without also breaking both supply conductors. Also, the unbalanced current due to lamps and small motors in the appliance was small compared to the rating of the conductors and therefore unlikely to cause a large voltage drop in the neutral conductor.

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Message 985737 - Posted: 1 Apr 2010, 6:17:00 UTC - in response to Message 985622.  


You are correct, in a sub panel the ground and neutral must be separate. Lowes or Home Depot will have a ground kit. Make sure it is for the brand of Sub panel you have as they will have a few.

Thank you hiamps!
So my old memory does retain a few things...LOL.

Back to Meownards tomorrow to get an isolated ground bus bar kit.
"Freedom is just Chaos, with better lighting." Alan Dean Foster

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Message 985997 - Posted: 2 Apr 2010, 1:30:25 UTC - in response to Message 985737.  

mikeholt's forums confirms seperate ground from neutral on subpannel.
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Message 986009 - Posted: 2 Apr 2010, 3:50:42 UTC - in response to Message 985737.  


You are correct, in a sub panel the ground and neutral must be separate. Lowes or Home Depot will have a ground kit. Make sure it is for the brand of Sub panel you have as they will have a few.

Thank you hiamps!
So my old memory does retain a few things...LOL.

Back to Meownards tomorrow to get an isolated ground bus bar kit.
What he said, and you mentioned ground rodS, you have more than one? Good man, few understand the importance of a good earth, and often times they go into areas which have little soil moisture, so the ground potential isn't very good. How many rods do you have in your ground field?


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Message 986015 - Posted: 2 Apr 2010, 4:27:19 UTC - in response to Message 986009.  
Last modified: 2 Apr 2010, 4:31:48 UTC


You are correct, in a sub panel the ground and neutral must be separate. Lowes or Home Depot will have a ground kit. Make sure it is for the brand of Sub panel you have as they will have a few.

Thank you hiamps!
So my old memory does retain a few things...LOL.

Back to Meownards tomorrow to get an isolated ground bus bar kit.
What he said, and you mentioned ground rodS, you have more than one? Good man, few understand the importance of a good earth, and often times they go into areas which have little soil moisture, so the ground potential isn't very good. How many rods do you have in your ground field?

Oh, yeah.........

When I upgaded the service to the home, I almost killed myself driving those ground rods........

3 of them......all 8 foot down.

2 were close to the house,,,,,,,,,,
And one 10 feet back. just for insurance.
Meow.
"Freedom is just Chaos, with better lighting." Alan Dean Foster

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Message 986016 - Posted: 2 Apr 2010, 4:44:42 UTC



. . . JOE FACTOR SALES / Luky's Hardware and Surplus Company

3814 West Burbank Boulevard
Burbank, CA 91505-2115

FAX: (818) 569-0262


Military Surplus Hardware and Aerospace Salvage - buy anything by the lb . . .

Hydraulic Fittings and Hoses, Valves, Gauges,
Screws, Bolts and Nuts - surplus aircraft fittings

~ unusual size fasteners, made of exotic metals or with rare finishes ~

& basic electrical stuff too . . .




BOINC Wiki . . .

Science Status Page . . .
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Message 986018 - Posted: 2 Apr 2010, 4:57:02 UTC - in response to Message 986016.  
Last modified: 2 Apr 2010, 4:58:24 UTC



. . . JOE FACTOR SALES / Luky's Hardware and Surplus Company

3814 West Burbank Boulevard
Burbank, CA 91505-2115

FAX: (818) 569-0262


Military Surplus Hardware and Aerospace Salvage - buy anything by the lb . . .

Hydraulic Fittings and Hoses, Valves, Gauges,
Screws, Bolts and Nuts - surplus aircraft fittings

~ unusual size fasteners, made of exotic metals or with rare finishes ~

& basic electrical stuff too . . .



Tjanks Richard.........

I got all the hardware except the isolated ground bus, And I know where to get theat....Meownards...........

3 wires..240v........50 amps. one life. LOL.
"Freedom is just Chaos, with better lighting." Alan Dean Foster

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Message 986020 - Posted: 2 Apr 2010, 5:10:23 UTC - in response to Message 986018.  
Last modified: 2 Apr 2010, 5:19:20 UTC

3 wires..240v........50 amps. one life. LOL.


so you are going back to get a fourth wire along with that ground bus, right!

oh, surplus aircraft hardware, watch out for cadium plated fasteners as cadium causes cancer!!!

Matts catdemic inspired me to run two dedicated 20 amp sockets to the dog pound on 20 amp arc fault breakers...

remember, if you put sockets in bedrooms they should be on arc fault breakers.
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Message 986035 - Posted: 2 Apr 2010, 6:22:12 UTC - in response to Message 984974.  


Military spec parts? Biggest rip-off ever invented, by companies whose stuff was hard-pressed to be acceptable to large companies with high standards. In essence, all that 'miltary spec' means, is that it is tested a bit more. Where I used to work, we had 'military spec' materials, which were the same ones as used by Caterpillar, Solar Turbines, EMD, Garrett, Ruston Diesels, Alsthom, GEC, B&W and Wartsila...you get the picture. Sometimes, as my deceased younger brother pointed out, it meant, how each part was wrapped! Same material, same product, different wrapping paper, was about right. This is why a 'standard' stainless steel bolt for the military, costs several times (at least) more, than one you'll buy in a local hardware store!


wow, me thinks you have just dived into something you know little about. first off, there is material traceability. so if you find that a part broke in service because of a defect in the material you can trace all part made from that lot, you would probably go further then just that lot but you get what i mean. second, there are material specs. for instance, there is ams-4050 and lma-m7050 (7050-t7451) aluminum made to different specifications. the lma-m7050 spec controls the composition to tighter tolerance and has higher allowables, and the material is also fracture toughness tested out of each lot. now most 7050-t7451 that is made from US mill is to the lma-m7050 spec, but just hasn't been certified to the lma spec.
materials is a very sensitive area, you can't make statements like that. basically you can't buy material based off it's trade name to make parts, it needs to have a specification to go along with it, and perhaps tracibility.

now nas680x protruding head titanium shear bolt are cheap (less then a dollar), you start looking for high tensile tension bolt and they get very expensive fast. a one inch diameter bolt with a grip of two inches will cost a thousand bucks.
go price out arp head studs, they are not cheap either.

http://www.alcoa.com/aerospace/en/products/product.asp?market_cat_id=347&prod_id=606
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Message 986071 - Posted: 2 Apr 2010, 12:45:53 UTC

Enough of this.........

I sold industrial electronic parts for 17 years.........

I know the difference between 'mil spec' and industrial grade.

Often, there is none except the price.

Same bin, just somebody has a look see and puts it in a pretty little bag that says 'inspected by Joe Blow'.

Now don't get me wrong, there are some real specifications that come into play, most notably archae86's post about temperature ranges......
These are real specs, and not all parts will live up to them.

You want a processor that will run down to -50c? Not all will.

Takes a bit of sorting to ascertain which will and won't.

I know.

I sold them. And I run them, and archae86 knows what he is talking about.

He was a fab man.

Have had many discussions with him over the last few years, and he has knowledge that will knock your boots off.

And I don't patronize many.
"Freedom is just Chaos, with better lighting." Alan Dean Foster

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Message 986104 - Posted: 2 Apr 2010, 14:48:29 UTC - in response to Message 986035.  

Firstly, you know almost nothing of my career in Engineering - perhaps thats because I'm a woman and you've made some assumptions. Perhaps not. I've done M.O.D. work, for two different companies - one, involved hardening components for military aircraft landing gear and arrester hooks. We used Ipsen 'gas-atmosphere' furnaces and 'generators', with automated atmosphere control and process recording. It took six months of training before you were allowed to 'solo', in a training programme that was monitored by the HSE. I did not become that company's highest paid hourly-rated employee, for nothing - my standards were very high and I carried those forward to my next employer. Women, do, after all, have an eye for detail. Oddly enough, my late brother also had high standards and most of the work he did, was for Military equipment (multi-layer TTH plated PCBs, amongst other things) and some work only got as far as a comet and got smashed - the Giotto Probe.

Secondly, you assumed that QC procedures, including tracking of materials was different - wrong. The same procedures were in operation for all materials produced....a little something that I played a big part in. Bought-in materials were tested and checked, irrespective of any accompanying documentation - this also allowed us to change the processes involved, to take into account the different process chacteristics from a different raw material supplier (if not in-house or preferred) and mark it apprpriately. Frankly, you'd be surprised at just how much 'internal documentation' was held on materials - perhaps that is why many customers were more than happy to use our materials to make their components with; for prototypes, etc. Higher levels of QC become a second nature and should not mean massive increases in component cost. Indeed, it can bring about cost reductions, due to reductions in waste and scrap.

Thirdly, there are a number of Trade Name materials, used in Military Equipment, as these materials were produced for a specific purpose and the main, if not only use, was Military.

Finally, I'm pleased to see that the little wiring job, is going fairly well for Mark. Nice to see that you've got a fair margin of 'tolerance' in your build. Oh and just in case there are some keen Radio Amateurs, don't forget to water the rods, now and again! lol

PS. Apols for long post, but I was having difficulty finding 4500 mile long nail extensions on Google! lol



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Message 986111 - Posted: 2 Apr 2010, 15:52:57 UTC - in response to Message 986104.  

OMG.......you make a statement like that and assume I have a predisposition about you because you are female????????

You have always presented yourself as a very intelligent person.

You just trashed me with that statement, GURL.
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Message 986112 - Posted: 2 Apr 2010, 15:56:19 UTC - in response to Message 986111.  

OMG.......you make a statement like that and assume I have a predisposition about you because you are female????????

You have always presented yourself as a very intelligent person.

You just trashed me with that statement, GURL.



Please take a little time, Mark, to read the particulars of the message....it was in response to RottenMutt.



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Message 986118 - Posted: 2 Apr 2010, 16:24:27 UTC - in response to Message 986112.  

OMG.......you make a statement like that and assume I have a predisposition about you because you are female????????

You have always presented yourself as a very intelligent person.

You just trashed me with that statement, GURL.



Please take a little time, Mark, to read the particulars of the message....it was in response to RottenMutt.



OK.........I will reread.

But seriously........I think you a better person than that statement.
If taken out of context.

I have been misinterpreted and misquoted many times myself.

'S why I can call a gur; a b...... and still lover her.

Hmmm........I always considered that an affectionate term. Some aparently do not. It's like Carlin said..............
It't not words. It's what they mean.

I have always used the term B..........in an affectionate way to ost.

But, I can be a two edged sword. Or si that word......geez, what a simplsimple mistlu[e

I still do. If your are my only b....... you have to be really close to my heart.

I think some of u gurls still understand this..
"Freedom is just Chaos, with better lighting." Alan Dean Foster

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Message 986178 - Posted: 2 Apr 2010, 22:02:33 UTC - in response to Message 986104.  

Firstly, you know almost nothing of my career in Engineering - perhaps thats because I'm a woman and you've made some assumptions. Perhaps not

Wow, now i know a little about you; you like to throw down the women card if you get backed into a corner. didn't know you where an engineer, i will assume British, please correct me if i'm wrong.
sounds like you have worked on some fun projects. then you should understand that the processes called for added value and that two parts that look identical may not be.
Oddly enough, my late brother also had high standards and most of the work he did, was for Military equipment (multi-layer TTH plated PCBs, amongst other things) and some work only got as far as a comet and got smashed - the Giotto Probe.

sorry for your loss, sounds like you miss your brother.

I design aircraft, military and civil; and spacecraft, launch vehicles and space station components. I don't think we disagree. professionally designed products are built to rigorous standards with tight quality control, everything used has a specification. so that anyone can build the component and it will perform the same.
material used in an engineered product will have a specification which controls what it is and there maybe more then one specification for the same material and they may not be equal. most companies will write their own specifications for material or components so that they have revision control and know what they are getting and that it will always work.
sorry if i ruffled your feathers, you just made one of those generalization about military hardware which most laymen make.
for example the 400 dollar hammer. if a detailed specification for a tool, with lots of performance testing, is written, of coarse it will be expensive. if you write a specification that says it should look like a hammer and shall be yellow, careful what you ask for. what you get maybe made of wood and painted with yellow "lead" paint.

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Message 986189 - Posted: 2 Apr 2010, 22:44:59 UTC - in response to Message 986178.  


for example the 400 dollar hammer. if a detailed specification for a tool, with lots of performance testing, is written, of coarse it will be expensive. if you write a specification that says it should look like a hammer and shall be yellow, careful what you ask for. what you get maybe made of wood and painted with yellow "lead" paint.

I can't speak for the Brits and their military procurement process, but I worked for Rockwell and saw a lot of what happened.

Even if the spec. said "Hammer. Metal head, claw type, 12" wood handle" the problem was that you had to deliver one hammer as part of the evaluation process, had to deliver the same hammers when production started, and then deliver "spares" for 10 or 20 years.

... and every one had to be identical. No substitution.

(Actually, our spec. from the military said things like "van, communications, satellite, crypto" -- and went on to specify a complete set of tools to repair it, we got to spec. the hammer, if needed).
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Message 986234 - Posted: 3 Apr 2010, 1:57:28 UTC - in response to Message 986226.  


They simply couldn't see that it was pissing off all the engineers and causing dissatisfaction, which in the long term would be even more expensive. That's what happens when accountants who in turn listen to stockbrokers, run a company instead of management.

Not my example, so it's not much of an argument against.

The other side of the problem, at least on military gear in the U.S. is that the toolkit is actually tested as part of acceptance.

Tools are added or modified to make sure the equipment can be fixed with those toolkits, because the equipment and toolkit may be very far from a friendly hardware store (or maybe a friendly anything).

If you take a 9/16" wrench with a 6" handle and a 10 degree bend, it may fit in a particular space and easily be used. A shorter handle may not have enough torque, and a longer handle (or a different angle) might not fit in a tight space.

That's the problem.

So the rule is: supply at the end of the contract what you supplied at the beginning.

It's expensive, but the alternative can be even more expensive.

If I'm not mistaken, most BT central offices are outside war zones.

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