[millhouse_]

Hi,

at the moment I'm building the control panel and could need a little help with the size of the ground wires.


The source wire is 1,5mm^2. All consumers are internal connected to a star point. Would it be a problem if the consumers ground wires to the star point are thicker (2,5mm^2) than the input source ground wire or is it necessary that the wires to the star point are smaller than the source wire?


Here are some pictures: (In the future all ground wires will go to ground temrinal blocks on a rail..)

[nwrepair1]

Never smaller .Larger ok.

[millhouse_]

Ok. Thanks. Another question:

As you can see on the picture the panel has three line-in wires. Each one with hot/neutral/ground.


I would like to crimp their grounds together and use them like one large ground wire. Is this a problem?

[mactec54]

Ok. Thanks. Another question:

As you can see on the picture the panel has three line-in wires. Each one with hot/neutral/ground.


I would like to crimp their grounds together and use them like one large ground wire. Is this a problem?

That is not a good Idea, how can you have 3 Main Power Supplies from 3 different power outlets, you should only have ( 1 ) for your whole cabinet

[Al_The_Man]

Ok. Thanks. Another question:

As you can see on the picture the panel has three line-in wires. Each one with hot/neutral/ground.


I would like to crimp their grounds together and use them like one large ground wire. Is this a problem?

One example is DIN rail mount terminals, you can get them with automatic ground to the enclosure, they are half green, half yellow, and are intended for such cables that also include a ground conductor.
The ground in this instance is through enclosure bonding, but also pays to take a single correctly sized one to the star point also.
This is the method I have used for over 50yrs.
Al.

[maxspongebob]

Ok. Thanks. Another question:

As you can see on the picture the panel has three line-in wires. Each one with hot/neutral/ground.


I would like to crimp their grounds together and use them like one large ground wire. Is this a problem?

What you want to do is try not to create a ground loop. If you connect all the grounds together from the three sources you have created 3 loops. Most likely the 3 ground wires from the power panel are all connected together in the panel. So, only a single wire is needed for your ground. It should be a large enough gauge to carry the load of the 3 lines combined.

The purpose of the ground wire is to provide any stray energy in your device the path of least resistance to ground. If there was no ground connection then a short of a main wire could cause the cabinet to be at a high potential. When you touch the cabinet, then you become the shortest path to ground (this is bad).

[Al_The_Man]

The Ground wire should be the same gauge as the supply conductor or same as the combined size, if supply is from difference sources.
All ground wires should terminate at the star point or be joined and continued with a single conductor equal to the combined gauges.
The service ground should also terminate at the Star Point GND.
There was a copy of NFPA79 out there if needing guidance on regs for enclosure wiring.
Al.

[mactec54]

Hi,

at the moment I'm building the control panel and could need a little help with the size of the ground wires.


The source wire is 1,5mm^2. All consumers are internal connected to a star point. Would it be a problem if the consumers ground wires to the star point are thicker (2,5mm^2) than the input source ground wire or is it necessary that the wires to the star point are smaller than the source wire?


Here are some pictures: (In the future all ground wires will go to ground temrinal blocks on a rail..)

This is a good question, so if other devices require or have a larger Ground wire, this could indicate that your main supply is to small 1.5mm is only 15 Gauge ( close enough to 16 Gauge ) most cabinet's need at least a 30A supply which would be 10 Gauge, so I would say you input supply is a little on the light side

What size is the VFD Drive ??? this will need a Power Filter on it input supply

The Mains Power Supply Ground Connects at the Star Point

[millhouse_]

Thanks for the feedback.


The first power input is for the 5v and 12v power supplies and maybe for other stuff in the future like a vacuum cleaner etc. And it is connected to a contactor that switches on the other two inputs ( one for the steppers and one for the spindle ). Normally I would have used 3-phase current for this but I don't have the possibilities for this.

@mactec54

The consumers don't need 2,5mm^2. I just used it for them.

[mactec54]

Thanks for the feedback.


The first power input is for the 5v and 12v power supplies and maybe for other stuff in the future like a vacuum cleaner etc. And it is connected to a contactor that switches on the other two inputs ( one for the steppers and one for the spindle ). Normally I would have used 3-phase current for this but I don't have the possibilities for this.

@mactec54

The consumers don't need 2,5mm^2. I just used it for them.

Ok what size is the Spindle Motor and VFD Drive how many Kw and Amps

[wmgeorge]

We routinely build control panels for production lines with multiple power sources and grounds. They are all sourced from the building main 13.8 Kv and substations. All grounds are tied back to the main substation. It makes no difference. Your control panel needs a disconnect for each source.

[mactec54]

We routinely build control panels for production lines with multiple power sources and grounds. They are all sourced from the building main 13.8 Kv and substations. All grounds are tied back to the main substation. It makes no difference. Your control panel needs a disconnect for each source.

"Routinely build control panels" the last control box you used I recall you brought it already made for your hobby machine

[wmgeorge]

"Routinely build control panels" the last control box you used I recall you brought it already made for your hobby machine

Before I retired and started drawing the bucks for not working… just being a hobby guy. Yes even my hobby panels are wired to Code. We wired some pretty good sized industrial plants.

Looks like Al and I did the same work.

[Al_The_Man]

Looks like Al and I did the same work.

Could be.
Mostly retro fits, PLC control panels and CNC retro fits with Fanuc and Mitsubishi, designed a few custom ones with Galil motion cards, which are a pleasure to use.
Al.

[wmgeorge]

Could be.
Mostly retro fits, PLC control panels and CNC retro fits with Fanuc and Mitsubishi, designed a few custom ones with Galil motion cards, which are a pleasure to use.
Al.

Not the same. I installed and wired production lines, moved old junk machines at times into the modern world. Plus new stuff also, some PLCs. some solid state control systems as prototypes and just a lot of MCC wiring to machines and tying in interlocks and the like. At the time I was working under a very strict Master Electrician. Later on I was the sole electrician for second shift production. Loved every minute of my electrical work. Later got into Commercial HVAC/R work specialized in controls.

[millhouse_]

This is it now:

[Al_The_Man]

This is it now:

I see you are already using the DIN rail GND terminals!
Some cable trough would have neaten'd it up a little!
Max.

[RCaffin]

Not mentioned yet is the function of a Ground wire - why have one? There are two reasons, and really two different sorts of ground wires.

The first is safety. If something exciting goes wrong, you want the Ground wire to be able to handle as much current as the Active can supply which might be 30 - 40 A. This is why you often see instructions that the ground wire should never be smaller. Note this well.

The second reason for a 'Ground' wire is to serve as a screen, to block EMI or radiated interference. For instance, you should Earth the screen around your spindle PS cable. In general, the Ground wire from such a screen does not need to carry 30 A. Within reasonable limits of distance, quite light electronics hookup or signal wire is adequate for the screening. I won't go into the fact that high-frequency interference usually sits on the exterior of a copper conductor anyhow.

The tricky bit can be when there is a risk of a Mains fault to a low-voltage power supply lead. This is a bit of a cross-over case. In practice, we usually use slightly more than 'light electronics hook-up wire' for this.

My 2c.
Cheers
Roger

[wmgeorge]

The equipment grounding wire is required by electrical code for safety, and sized to the main power input source, the EMI drain is a bonus. Yes your shields should be grounded to this ground as your metal cabinets are also.

To clear up confusion, the DC and signal power negative
( - ) should not be tied to equipment ground unless instructed (?) as its not the same thing as it carries voltage.

[Al_The_Man]

To clear up confusion, the DC and signal power negative
( - ) should not be tied to equipment ground unless instructed (?) as its not the same thing as it carries voltage.

Yeah, there is two thoughts on this, some practice never grounding the power commons of different sections of equipment, IOW keep all power separate, and the opposing view on grounding at all times if it is possible.
I have always prescribed to the latter, whether the equipment supplier has decreed it or not.
I know of a few instances here in the past where posters have had 'noise' issues caused by false triggering of inputs due to injection of noise which can be inductive or capacitively coupled. Such problems were cured after grounding all power common.
There is also a practice that was outlined in a Siemens paper covering the importance of something called equi-potential bonding, this ensures that all metallic parts of a machine are at the same ground potential, this practice virtually eliminates the occurrence of Ground Loops.
The above has so far kept me in good stead!
Al.