Stupid Question #29 - Grounding Plastic Enclosures

[jimswinder]

I have four controllers per Enclosure.

I know on my LOR units, the Power-In Ground just goes to the metal Enclosure.

But mine are Plastic Enclosures...

So...should I:

1) Just cut off the ground
2) Run it to an open Neutral spot on a Board (or to all 4 boards)
3) Something Else

My concern was still having the GFCI's to work properly.

PS: I just have one Power-In dongle for all four boards...

[-klb-]

Do not run it to a neutral. The only place ground and neutral are to be connected in a residence is one connection in the main service entry panel. Connecting them on the controller would also create a ground fault.

Are you using ungrounded dongles? In the standard LOR PC enclosure, the ground is tied only to the strain relief bracket, and the grounds of the dongles. It does not even go to the card or heatsinks..

If you do not have grounded dongles, and feel the need to connect it to something in a plastic case, the heatsinks are probably the best bet.

Actually, if you are using metal fasteners, and they go through the plastic case, you probably should ground the heat sinks.

[jimswinder]

-klb- wrote:

Are you using ungrounded dongles?

*Nope..have grounded dongles**

In the standard LOR PC enclosure, the ground is tied only to the strain relief bracket, and the grounds of the dongles. It does not even go to the card or heatsinks..

**What is a "standard LOR PC Enclosure"? I have seen both Metal (LOR) and plastic (WOW LIGHTS) enclosures.**

If you do not have grounded dongles, and feel the need to connect it to something in a plastic case, the heatsinks are probably the best bet.

**I'm confused..if I DON'T have grounded dongles, how/what would I connect to the heatsinks?**

Actually, if you are using metal fasteners, and they go through the plastic case, you probably should ground the heat sinks.

**I have metal cable connectors that the dongles pass thru.**

[-klb-]

Some people use grounded inlet cords, but ungrounded outlet dongles.

If you are using grounded outlet dongles, they must have their grounds connected to the inlet cord grounds, and fastened in a way that they do not have any risk of coming in contact with the controller card itself.

The PC series controllers is what WOW lights sells, with the same enclosures and all, if you get a case from LOR with them.

The metal cable clamps might be nice to have grounded against the extremely unlikely chance that the clamps somehow cut through the insulation, and became hot, but I think that is far less likely than the chances of a triac blowing in a way that would conduct to the heat sink.

Some people have used through bolts between the heatsink and the outside of the case. In that case, there is value in having the heatsink grounded, so that in the case of a triac failure, you blow the breaker, or GFCI, rather than risk having live voltage exposed outside the case.

[jimswinder]

-klb- wrote:

Some people use grounded inlet cords, but ungrounded outlet dongles.

Sorry..YES, to grounded inlet and ungrounded Outlet (SPT2 Dongles).

So (still a bit confused) are you saying to ground my Power-In ground to the heatsinks? And if so I guess I need to tie the ground to both sides of the board and to ALL the boards in the enclosure, right?

[-klb-]

I would probably just connect the inlet ground to one of the heat sinks, and call it good... Unless your fasteners mounting the cards electrically connect the heatsinks to any point on the outside, then I would take the extra steps to ensure that all heatsinks are grounded.

[jimswinder]

-klb- wrote:

I would probably just connect the inlet ground to one of the heat sinks, and call it good... Unless your fasteners mounting the cards electrically connect the heatsinks to any point on the outside, then I would take the extra steps to ensure that all heatsinks are grounded.

Nope...fasteners just connect boards to the enclosure...but the fasteners do go THRU the enclosure to the outside...

[Max-Paul]

jimswinder wrote:

-klb- wrote:

I would probably just connect the inlet ground to one of the heat sinks, and call it good... Unless your fasteners mounting the cards electrically connect the heatsinks to any point on the outside, then I would take the extra steps to ensure that all heatsinks are grounded.

Nope...fasteners just connect boards to the enclosure...but the fasteners do go THRU the enclosure to the outside...

Oh good grief Jim, you might be having one of those days. You and KLB sure are doing the tangle today.

Ok, are you using metal screws that go through the case and are going to the heat sinks? If so, klb is saying that you need to put the inlet ground on one heat sink and then have jumpers tying the other heat sinks to the first heat sink.

Here is what I believe he is saying. If a short was to make the heat sink hot (think electrical here not temperature). And you where to touch the enclosure and the metal screw head and another part of your body was grounded. You could get a good zap or electrocution.

[-klb-]

I might easily not be making sense today. I've been spray paining some wire frames, so I might not be in my usual messed up state of mind...

[jimswinder]

Max-Paul wrote:

Oh good grief Jim, you might be having one of those days. You and KLB sure are doing the tangle today.

**Is it the Argentine Tangle?? I like that dance on Dancing With The Stars!!!

Ok, are you using metal screws that go through the case and are going to the heat sinks?

**No...just through the board**

Thought...

If I just cut my Power-In ground and don't use it, will the GFCI still trip if there is a problem?

[-klb-]

Yes, the ground wire has nothing to do with GFCI, except as one more possible source of places for current to leak, and cause trips...

Technically, there is nothing wrong with cutting the ground wire out, but personally, if anyone ever looked over my system, I would rather have it fastened to something metal, rather than explain away that it was cut off. Or use an ungrounded inlet cord to start with.

[boborino]

I guess I don't fully understand the issue here. The LOR plastic box has a long stud for you to connect all the grounds of the dongles to. Then you tie the ground wire from your two incoming AC lines to the same stud. That brings the house ground out to the dongles. If you don't use grounded exentions then the ground stops at the box. Since the box is plastic, there is nothing to ground. The ground is simply for your protection in the case of a short. In a metal enclosure, you want the short taking the least resitive path to ground, so if the case is grounded it will go there and not through you when you touch it. Plastic boxes don't conduct (very well) so no need to connect it to the ground.

I don't think I'd tie the heat sink's to ground either. There's always a potential for miswired AC coming to the box and it could fry the controller. But that's just my opinion. I'm sure others here have more experience if they are wiring the controllers outside of the standard enclosure.

[-klb-]

This discussion comes up from time to time, usually by people who have cards, and have never seen the standard case and strain relief bracket. Some fraction of them never think about bolting through the plastic case, to the high power heat sinks, and that those bolts breach the insulation of the plastic case.

A correctly operating controller has the heat sinks completely isolated from anything on the card. The Showtime series does have the heatsinks grounded by virtue of the heatsinks being bolted to the grounded metal case.

The one time that the heatsinks are likely to be connected to the card in any way is if a triac blows, it may short hot to the triac tab, and in turn the heatsink. As long as the controller is in a plastic case, and nothing connected to the heatsink protrudes through the case, it isn't a big deal.

But in the discussions here, we have had a few people who are using the high power heatsinks and bolts through the plastic case to attach the card to the case via the holes in the heatsink, and not think about it.. If they are using metal through hardware, fastened to the heatsink, your own argument about grounding metal cases comes into play for grounding the heatsink...