Live parts inside enclosures

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Hello from Germany,

we build machinery for the tire industry. For customers in the USA we build the cabinets acc. UL and NEC regulations.

Each cabinet group have its own main switch. The cabinet doors are interlocked with this switch and can be defeated with a screw at the main switch handle.
At the front doors we have warning signs "ELECTRIC ARC FLASH HAZARD...." and "Autorized personnel only".

Each machine will be pre-checked by the german TUV according to UL regulations.
The TUV tester now told me to cover all transformers inside the cabinet with additional plastics to protect workers from direct contact.
The transformers are "open type", the terminals are fingersafe but the windings are lacquered.

And now the question:
Is it really nessescary to cover all parts inside a cabinet even if the cabinet doors are interlocked and the opening of the cabinet is only allowed to skilled workers?

My NFPA way:
6.2. Protection against direct contact

6.2.1 Protection by Insulation …..
not relevant
6.2.2 Protection by Enclosures
yes, it is mounted in a cabinet
6.2.2.1 Direct Contact from Outside…..
not relevant / no openings
6.2.3 Enclosure Interlocking
relevant / I have an interlock
6.2.3.1 Means shall be permitted to be provided for qualified persons….
relevant / fullfilled by main the switch and warning signs / operator manual
6.2.3.2 The Interlocking means shall …..
relevant / fullfilled by the kind of the main switch
6.2.3.3 Where provided with a defeat….
not relevant / no live parts inside the cabinet doors.
6.3.4 Enclosure Access
not relevant / for enclosures without main switch

No additional covers needed.....

Thanks in advance

Andreas
 
That's between you and your testing organization.

That panel needs the listing before the NEC will allow it to be installed.

Hm, no.....
The machines are not build in series. They and their cabinets are uniqe, just as our customers wants to have them....
They are not listed.
We build the machines and cabinets according to NEC / NFPA 70. We deliver them to the US and erect them.
After that the local AHJ inspect the complete machinery, a tire component building line, and (hopefully) issure an occupancy permit.

To support the AHJ we pre-check the machinery before we sent it to US by an independent testing organisation, the TUV.
We get a report with findings to solve.

And in this report I found the item written in the first topic.

I design cabinets for USA and Canada for at least 20 years. But no tester wants me to cover live parts inside a lockable cabinet.
Thats why I'm asking.

Andreas
 

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
There is no regulation here requiring that. Your design would meet our requirements, other than the fact that you will not apparently have an accepted NRTL listing of TUV does not accept your design. Not all states require it, but some do, which might get you in trouble some day.
 

kwired

Electron manager
Location
NE Nebraska
There are UL approved custom design shops that can build such control cabinets that don't have to follow NEC, but do have to get certified and follow applicable UL requirements with what they do build.

In the absence of having this certification, anyone can build a control cabinet - it just needs to meet NEC requirements if it is going to be inspected to NEC.

Having a listing means NEC doesn't apply to what is inside, the listing requirements cover that.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
Hello from Germany,

we build machinery for the tire industry. For customers in the USA we build the cabinets acc. UL and NEC regulations.

Each cabinet group have its own main switch. The cabinet doors are interlocked with this switch and can be defeated with a screw at the main switch handle.
At the front doors we have warning signs "ELECTRIC ARC FLASH HAZARD...." and "Autorized personnel only".

Each machine will be pre-checked by the german TUV according to UL regulations.
The TUV tester now told me to cover all transformers inside the cabinet with additional plastics to protect workers from direct contact.
The transformers are "open type", the terminals are fingersafe but the windings are lacquered.

If by "pre-checked" you mean TUV will be inspecting it and applying a UL label signifying it meets UL508a requirements, than you should be good to go.

While some people argue the semantics, the NEC does not actually apply to the innards of a control panel, although the control panel has to deal with NEC requirements such as for over current protection and disconnecting means for motors. If your panel meets UL 508a requirements, and has the listing sticker on it, you should be fine.

I will point out though that a UL508a control panel for an industrial machine such as what you are building has some additional requirements not required for general purpose UL508a control panels. These requirements are found in UL508a sections 65-67.
 

kwired

Electron manager
Location
NE Nebraska
If by "pre-checked" you mean TUV will be inspecting it and applying a UL label signifying it meets UL508a requirements, than you should be good to go.

If someone is inspecting and applying a UL label then it is a listed assembly. The same third party OP mentions is telling them to make some changes, so apparently some things they are doing do not meet the listing requirements.

I can not help with those requirements as much as I can with NEC requirements, but as I see it if there is a UL label, supposedly whoever puts it there is qualified to do so and the unit is listed, if not that label was fraudulently applied.

I could see some possible issues with the builder not being a certified UL shop and the fact they are relying on a third party to label it - don't know the rules there though.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
If someone is inspecting and applying a UL label then it is a listed assembly. The same third party OP mentions is telling them to make some changes, so apparently some things they are doing do not meet the listing requirements.

I can not help with those requirements as much as I can with NEC requirements, but as I see it if there is a UL label, supposedly whoever puts it there is qualified to do so and the unit is listed, if not that label was fraudulently applied.

I could see some possible issues with the builder not being a certified UL shop and the fact they are relying on a third party to label it - don't know the rules there though.

TUV is a qualified NRTL. They are allowed to field inspect things built by third parties not authorized to apply the label and label them.

My inclination is to do what they want so they will put the sticker on. It is not worth the time and trouble to argue over something this minor.
 

kwired

Electron manager
Location
NE Nebraska
TUV is a qualified NRTL. They are allowed to field inspect things built by third parties not authorized to apply the label and label them.

My inclination is to do what they want so they will put the sticker on. It is not worth the time and trouble to argue over something this minor.

Didn't know what TUV was, but agree otherwise, if you want the label you need to comply with those that put the label on it.
 
Good morning and thanks for all the answers!

we don't get a label or a sticker from TUV Germany, we just get a report that our construction is able to get a occupancy permit.
This report we hand over to the local AHJ. He can use it or not...
But our customers are the mayor tire brands. The local AHJ will be well trained to the machinary we deliver.

If the NRTL give us a label before we deliver the machinery we can't make any changings during commissioning without loosing the label.
And we have make a lot of changings we don't know during design, add customer machines, additional tools.

Back to the question:
The problem here is, that the TUV tester told me to cover all transformers inside the cabinet with an additional plastic sheet.
He founded this with NFPA70 "6.2. Protection against direct contact" without reading the following exceptions.
But the transformer vendor told me not to do so, I will get thermal problems.

Is there any regulation (NEC, NFPA, UL508A) that requires the covering of all live parts inside a cabinet locked by a main switch, only to open by tools by a trained worker?
It must be a new regulation. All the years before we delivered transfomers "as build" without complains.

The best answer so far:
Jraef:There is no regulation here requiring that. :D

Andreas
 

Besoeker

Senior Member
Location
UK
I don't know about Germany but, being part of the EU I would have thought that similar specs would apply.

All of the specicifications I have seen for quite a few years now and most are customer driven call for IP2X protection inside panels. Essentially it means that you can't sick your fingers on live parts. And most panel mounting are made to that degree of protection. Relays, PLC modules, DIN rail terminals......

Rowofterminals01_zps74948f3e.jpg
 

kwired

Electron manager
Location
NE Nebraska
Good morning and thanks for all the answers!

we don't get a label or a sticker from TUV Germany, we just get a report that our construction is able to get a occupancy permit.
This report we hand over to the local AHJ. He can use it or not...
But our customers are the mayor tire brands. The local AHJ will be well trained to the machinary we deliver.

If the NRTL give us a label before we deliver the machinery we can't make any changings during commissioning without loosing the label.
And we have make a lot of changings we don't know during design, add customer machines, additional tools.

Back to the question:
The problem here is, that the TUV tester told me to cover all transformers inside the cabinet with an additional plastic sheet.
He founded this with NFPA70 "6.2. Protection against direct contact" without reading the following exceptions.
But the transformer vendor told me not to do so, I will get thermal problems.

Is there any regulation (NEC, NFPA, UL508A) that requires the covering of all live parts inside a cabinet locked by a main switch, only to open by tools by a trained worker?
It must be a new regulation. All the years before we delivered transfomers "as build" without complains.

The best answer so far:
Jraef:There is no regulation here requiring that. :D

Andreas
You probably only need some sort of shield over transformer terminals to make them finger safe. Whoever makes your transformers probably has accessories that are designed to fit them.
 
Besoeker / kwired:
Yes, we have similar regulations and the transformer terminals are already fingersafe.
See the picture attached...

The TUV tester complains about the windings, they are lacquered.
If someone falls into the open cabinet while power is on, he can be hurt.

Andreas
 

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kwired

Electron manager
Location
NE Nebraska
Besoeker / kwired:
Yes, we have similar regulations and the transformer terminals are already fingersafe.
See the picture attached...

The TUV tester complains about the windings, they are lacquered.
If someone falls into the open cabinet while power is on, he can be hurt.

Andreas
If I jump out of a moving vehicle I may be hurt as well:roll:
 

just the cowboy

Inactive, Email Never Verified
Location
newburgh,ny
Wrong I think

Wrong I think

Besoeker / kwired:
Yes, we have similar regulations and the transformer terminals are already fingersafe.
See the picture attached...

The TUV tester complains about the windings, they are lacquered.
If someone falls into the open cabinet while power is on, he can be hurt.

Andreas

You can touch those lacquered winding and not get shocked, they ARE insulated. If not they would be shorted out to each other and not work.
 
Hi,

kwired: Hahaha, yes, but according to my tester you need a locking at your doors only able to be opened when the car stands still.

cowboy: have a look in the NFPA79 / 6.2.1 .....Paints, varnishes, lacquers, and similar products shall not be considered protection against electric shock.....

Andreas
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
Hi,

kwired: Hahaha, yes, but according to my tester you need a locking at your doors only able to be opened when the car stands still.

cowboy: have a look in the NFPA79 / 6.2.1 .....Paints, varnishes, lacquers, and similar products shall not be considered protection against electric shock.....

Andreas

NFPA79 is not part of UL508a though.
 
Hi Bob,

out of the Siemens Handbook for UL "http://www.automation.siemens.com/tip-static/dlc/en/Low-Voltage-Distribution-Boards/The_Secrets_of_UL_and_NFPA.pdf"

Which standard applies?
Before configuration, it is necessary to clarify which standard is applied in which application cases. When to use UL 508A? When to use NFPA 79? When to use both?
The requirements and interfaces of both standards are clearly set out with regard to most points. If requirements overlap, however, the standard with the higher
requirements in relation to the respective point must be applied.

I was thinking, if something is not regulated in UL508A I have to look into NFPA79....

Not correct?

Andreas
 

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
Hi,

kwired: Hahaha, yes, but according to my tester you need a locking at your doors only able to be opened when the car stands still.

cowboy: have a look in the NFPA79 / 6.2.1 .....Paints, varnishes, lacquers, and similar products shall not be considered protection against electric shock.....

Andreas

NFPA79 is not part of UL508a though.
The lacquer over the windings of a transformer is NOT the insulation of the windings, it is there to protect the insulation. The magnet wire itself is already insulated, otherwise it would just be a big mass of conductive material, not coils.

Regardless, as I said earlier, for North America, the issue of "touch safe" terminals inside of a live electrical panel is a moot point, because you are not allowed to enter a live electrical panel unless you have ALREADY defeated locking mechanisms, thereby indirectly indicating that you are a "qualified electrical worker" and that assumes that you know what you are doing. So once the door is open and parts are live, you must be taking the proper electrical safety precautions with regard to YOUR PPE (Personal Protective Equipment). Additional protection agains touching of live parts is prudent, but not MANDATORY.

But, again, if you are going for TUV certification, and TUV says they want to see it, you really have no choice.

If you are not getting a certification from TUV*, the issue of "letting the AHJ get trained on the equipment" is something that you are not understanding correctly in my opinion, and you are at risk for having your machines "red tagged" when a contractor attempts to install them here in the US. Not everywhere, for sure, but in MANY places here, that will be an issue.

*Paying for TUV to inspect the equipment and then not attaining a certification for it makes no economic sense to me either. I also think this might be something you are not correct about or are maybe unaware that behind the scenes, your sales dept. is providing the TUV certification to end users so that your machines meet the NRTL labeling requirements here in the US.
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
And just what is this insulation found on magnet wire if it is not lacquer?
It sounds like what is being said is that insulated magnet wire requires additional insulation and/or mechanical protection if it is used in a panel or for building wiring.
 
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