IEC receptacle grounds

[Ken Moon]

Looks great!

I would add a small hole on the top, centered over the IEC hole, for a safety earth ground post, but that's certainly not a big deal.

[EL34]

Not sure what a safety ground is

Most of the grounds all go to a bolt near the PT that is bolted to the chassis

[Willabe]

The green or green/yellow 3rd wire on the AC cord.


                Brad   

[EL34]

Well that goes to the same place as several other grounds

[Ken Moon]

UL/IEC standards require that the safety ground from the IEC socket to the chassis not be shared with any other connections.

If I get some time this afternoon I'll see if I can find that reference.

Merlin calls it the "Safety Earth", and I cut and pasted this from the Valve Wizard web site:

"15.1: Safety Earth

Where the mains cable enters the chassis –usually via an IEC inlet– a heavy-gauge wire should be soldered to the earth tab (do not use a push-fit
connector for this), and then connected to the chassis with a solder tag, as shown in fig. 15.2. The chassis area should be cleaned with emery
paper beforehand to ensure a good electrical connection. The wire should be short and should have the same colour scheme as the local mains
supply, which is green-and-yellow striped in Europe, or green in the US.

Where this wire is bolted to chassis is known as the safety-earth bond, and it should be a dedicated screw/bolt, not a screw which is used to fix some other piece of hardware which might become loose over time. A nyloc nut should be used, or else a shake-proof or star washer should be used, with two ordinary nuts, well tightened. This wire is the most important connection in the amplifier and is legally required, and it must be completely sound."

Here is an image from Ampmaker.com (wire would be green/yellow in Europe):

[EL34]

I don't do that

If you feel you must do that, just use one of the IEC screws or drill your own next to the IEC receptacle


Been doing the same thing with power cord grounds for many years
Not any difference between the IEC ground and a power cord ground to me

[Ken Moon]

No problem - as you say, it's easy to drill another small hole. Peace.

[sluckey]

If I get some time this afternoon I'll see if I can find that reference.

Please do. Thanks.

[Ed_Chambley]

It is according to class of appliance, or at least it is here at the ole printshop.  Class 1 can share earth and neutral ground whereas class o1 needs a separate earth to chassis ground.  Not sure about other places in the world.

Reference: IEC 61140

[Ritchie200]

How does the IEC define the two?


Jim

[Ed_Chambley]

How does the IEC define the two?


Jim

Jim,
2 things.  First I am way to  lazy to type the info.  Second, here is a link to a "general" description.
http://en.wikipedia.org/wiki/Appliance_classes

I do not know much about it, I just know I had to spend $22,000 dollars isolate a machine that does not need it.  I am still pissed and that was 8 years ago.  I normally use a separate earth and I use green always.  Often wondered if by doing this you can cause ground loops?  Don't know.

I have been busy lately so I will crawl back in my hole.   

[kagliostro]

Also here the connection of the IEG ground must be done separate and very near the IEC intake


Franco

[MakerDP]

How does the IEC define the two?


Jim

http://en.wikipedia.org/wiki/Appliance_classes

I'm with Ken... single very short thick green wire connecting to its own bolt/lug with star washers as close to the socket as possible. Nothing else connected to that wire. Why take a shortcut that saves you 30 seconds and $0.03 when if it comes loose it could turn into a widow-maker?

[tubeswell]

Here is an image from Ampmaker.com (wire would be green/yellow in Europe):

Ken, the mains earth ground in that image is not ideal. In this regard the wire should be braided type and the ring terminal should be crimped firmly onto unsoldered wire braid first. Whether or not it is soldered, the connection between the wire and the ring terminal should be immoveable. The ring terminal in the image is the wrong type of terminal for crimping. Also the proper (crimping) type of terminal lug should be used on the IEC socket terminal (instead of just poking the wire into the hole and soldering it.

[Ed_Chambley]

How does the IEC define the two?


Jim

http://en.wikipedia.org/wiki/Appliance_classes

I'm with Ken... single very short thick green wire connecting to its own bolt/lug with star washers as close to the socket as possible. Nothing else connected to that wire. Why take a shortcut that saves you 30 seconds and $0.03 when if it comes loose it could turn into a widow-maker?

If you solder an eyelet and connect the earth to the same transformer the chassis bolt as your neutral, why would that be any more dangerous than having them separate?

They are both chassis grounded, just at the same location.  What is the difference in an amplifier?

[tubenit]

If you feel you must do that, just use one of the IEC screws or drill your own next to the IEC receptacle

I typically just use one of the IEC screws for the ground and have had no issues from doing that.

With respect, Tubenit

[Ken Moon]

I think the problem with using a screw that holds the IEC connector is the possibility of the screw coming loose from inserting and removing the power cord lots of times.

Tubeswell has some great tips - thanks for those!

With the small Hoffman chassis, there's very little room between the PT and the edge of the chassis - so I may go with the closest transformer bolt for the earth ground, and put the star ground-to-chassis connection at the preamp end of the chassis, close to the input jack.

For those interested, here is a link to the IEEE 1100 standard:

http://www2.elo.utfsm.cl/~ipd411/archivos/apuntes/Std%201100-2005_Part1.pdf

[sluckey]

For those interested, here is a link to the IEEE 1100 standard:

That has nothing to do with the question at hand.

[Ken Moon]

Here is a reply from Merlin:

"It's covered by UL / BS / EN 60065
http://www.dianyuan.com/bbs/u/84/3393261261706823.pdf

The rules have been harmonised so you're allowed to use either green or green/yellow, i.e. both European and US colour codes are allowed (see section 15.2). No wires other than earth-connected wires may be green or green/yellow.

When live/neutral/earth wires are soldered to a tag or terminal they must be wrapped or ‘hooked’ into the hole to create a more reliable anchorage before soldering, or else the wires must be firmly anchored by other means close to the termination (section 15.3.4). If you use a crimp connector you must NOT tin the wire first.

In apparatus consuming <10A the earth bond must be >=3mm in diameter for a stud or pillar, or >=3.5mm for a screw (section 15.3.6). Apparently, “stud terminals shall be provided with washers”, although the exact meaning of this seems ambiguous, to me at least. I woudl normally use a star washer and Nyloc nut.

The earth bond is expected to be <0.1 ohms; (<0.2 ohms for a captive cable) and is UL tested with 10A for up to 4 seconds (N.1.3, see also 15.2)."

[MakerDP]

I think the problem with using a screw that holds the IEC connector is the possibility of the screw coming loose from inserting and removing the power cord lots of times.

Also, the IEC connector is just a piece of thin plastic where you insert the mounting screw. If anyone gets even a little crazy with the wrench and cracks that plastic, the whole screw/nut assembly can come loose creating a possibility for the safety ground to not make a good connection to the chassis.

VERY BAD IDEA imho.

[Willabe]

[If you solder an eyelet and connect the earth to the same transformer the chassis bolt as your neutral, why would that be any more dangerous than having them separate? They are both chassis grounded, just at the same location. What is the difference in an amplifier?

They, the regulatory board, who make up the rules, probably want a dedicated 3rd wire ground bonding point connection to the chassis. They'll say for safety.   

I use a separate 10/32 bolt with 3 internal star washers, a crimped/soldered eyelet with 2 hex nuts.   

We know MANY guys here and at other forums did and still do ground the 3rd AC cord wire to a PT bolt, with NO reports of any problems?

They talked about this at the old Power Scale forum and guys said that if you go in to get your amp certified(?) as a company product for sale to the public, they will not pass your amp unless it has a separate dedicated 3rd wire ground.

When I was rehabbing my house I had a new 100A 240acv mains cable (old 1 was 60A) brought in from the pole ~75' from the back of the house. So I asked the inspector what size mast could I use? He said they differ to the local electric company on that. So I set up an appointment for them to send a guy out and he says 3" mast!  It's only a 100A service at ~75' and I'm only going up ~5' with it. All the other houses I see in the neighborhood have an 1 1/2" mast      

But arguing would probably have only made trouble for myself, so I have a 3" mast. Lucky he didn't make me put in a 4" or 5" mast.


                     Brad   

[Willabe]

I think the problem with using a screw that holds the IEC connector is the possibility of the screw coming loose from inserting and removing the power cord lots of times.

Also, the IEC connector is just a piece of thin plastic where you insert the mounting screw. If anyone gets even a little crazy with the wrench and cracks that plastic, the whole screw/nut assembly can come loose creating a possibility for the safety ground to not make a good connection to the chassis.

I agree.

It may be convenient but I wouldn't trust the plastic.


                     Brad     

[tubenit]

the IEC connector is just a piece of thin plastic where you insert the mounting screw. If anyone gets even a little crazy with the wrench and cracks that plastic, the whole screw/nut assembly can come loose creating a possibility for the safety ground to not make a good connection to the chassis.

My opinion is that the IEC (on Doug's IEC socket and fuse) is NOT thin. And that it's very sturdy plastic & it's reasonably thick. Take another look at it in the picture I posted & in Doug's catalogue.

I would be very surprised if someone can tighten that enough to break that plastic.  The heads of the screws I use would probably strip well before the plastic was negatively impacted at all. And if you are using a lock washer, I would not envision that moving at all and coming
loose.

Think about what you are saying. Using that reasoning, then the IEC plastic could break and the IEC unit be loose on one of the sides and that could be dangerous  (whether there is an O-ring grounding there or not?).

You're saying the plastic is too fragile to be secured with a bolt? 



Do you know anyone who has ever actually had that problem with the IEC sockets?  Respectfully, Tubenit

[MakerDP]

As a matter of fact yes. I've personally tightened one  too tight and cracked the bracket.

I honestly can not comprehend all this resistance to comply with international safety regulations designed to prevent fatal electrocution. .. all to save a few cents and a few seconds.

[sluckey]

I also have a cracked IEC connector. Seen a couple more.

AFAIK, IEC, UL, etc. are not regulatory bodies. They provide guidelines, safety procedures, etc., and make an attempt to make international standards. And they do have requirements to be able to put their compliance sticker on stuff. All good, but they don't regulate anything.
Modify message

[tubenit]

I've personally tightened one  too tight and cracked the bracket.

I also have a cracked IEC connector. Seen a couple more.

OK, I stand corrected and would say you have a reasonable argument.

It does honestly surprise me to hear you guys have seen those cracked.  With the millions of computers out using IEC receptacles, I did not anticipate this would be a problem.

With respect, Tubenit

[Mike_J]

If you feel you must do that, just use one of the IEC screws or drill your own next to the IEC receptacle

I typically just use one of the IEC screws for the ground and have had no issues from doing that.

With respect, Tubenit

I too connect the ground to one of the IEC screws and have had no problems but can see the logic in moving away from that point.  Plastic can become brittle over time even if there are no problems during the initial build.

Considering the potential disaster to life and limb which could occur I can see the point in moving it an inch or so away from the IEC terminal.  It also makes sense two or three of the connectors stacked together would create a greater likelihood of it loosening versus having only one connector screwed to the chassis with a Keps nut.

I always use the #4 Keps nuts Doug sells and have never had a problem with them.  I am unsure why a nylon nut would be superior to the Keps nut.

Thanks
Mike

[steven]

Same way in Germany. It has to be a dedicated connection without anything else. Here's a document that shows what is expected:

http://hms.cobuilder.no/doc/Rittal/www.rittal.no/services_support/downloads/pdf/rittal_assem_ps_es_as_ak_ae_ap_grounding_0000_0000.pdf

The ground wire should be longer than the live or neutrals. This is so in case the power cord (or IEC or whatever) is accidentally ripped out of the box, the ground is the last connection to break.

"Contact washers" are recommended. They are special washers to bite in the metal. They look like this:

http://www.tube-town.net/ttstore/Screws/Machine-Srews-nuts-washer/Nuts-Washer/Contact-washers-for-cable-connections-M5::3925.html

It's easy enough to do it this way, so I always do it this way. "Right" according to code. Just like using double-pole switches on the mains. Of course, our plugs aren't polarized.

steven

[Willabe]

The ground wire should be longer than the live or neutrals. This is so in case the power cord (or IEC or whatever) is accidentally ripped out of the box, the ground is the last connection to break.

John Atwood, technical editor, Vacuum Tube Valley mag, brought that up in an article, issue 17, page 31, 'A Philosophy of Safety for the Home Constructor.'

It makes sense according to Murphy's law.


                  Brad       

[drgonzonm]

.........

Where the mains cable enters the chassis –usually via an IEC inlet– a heavy-gauge wire should be soldered to the earth tab (do not use a push-fit
connector for this), and then connected to the chassis with a solder tag, as shown in fig. 15.2. The chassis area should be cleaned with emery
paper beforehand to ensure a good electrical connection. The wire should be short and should have the same colour scheme as the local mains
supply, which is green-and-yellow striped in Europe, or green in the US.

Where this wire is bolted to chassis is known as the safety-earth bond, and it should be a dedicated screw/bolt, not a screw which is used to fix some other piece of hardware which might become loose over time. A nyloc nut should be used, or else a shake-proof or star washer should be used, with two ordinary nuts, well tightened. This wire is the most important connection in the amplifier and is legally required, and it must be completely sound."

......

Ken Moon, could I suggest you modify your post, and highlight, increase the font size, and bold it this portion,  That is how important I believe the information you provided. 

Thanks.