Molded-Case Circuit Breakers (MCCB) vs. Supplementary Protector

[deruth]

We manufacture a semiconductor wafer metrology tool, for installation in fabs in the USA, Europe, and Japan. Thus we must meet not only NEC, but CE requirements (machine directive, low-voltage directive), and SEMI S2/S8 safety guidelines. (Not sure if they are all pertinent to my question, but I mention it for completeness).

I'm trying to determine if our equipment is required to have a MCCB (molded case circuit breaker) at the AC-facility inlet to the tool, versus using a supplementary protector. Currently we are using an Altech V-EA "Miniature Circuit Breaker", model 2DU20 (20 Amp). The manufacture has confirmed that this is a Supplementary Protector, and NOT a MCCB.

In our design, the AC facility power (either 120 VAC or 230VAC, single phase), comes into our machine, is routed directly to this Altech supplementary protector, before being routed directly to our power-distribution box (PDU). The PDU is jumpered for either 120 or 230VAC input, provides EMO/EPO and remote on/off capability, and also has a step-down torroidal transformer with a 120VAC secondary, to provide 120VAC for distribution throughout our tool, via multiple 120VAC fused outlets.

The PDU provides fused power to multiple devices, including computer and lamp power supplies, a robot controller, an AC blower motor, and an AC impeller motor.

My Questions:
1) Is it acceptable to be using a supplementary protector in this application? Or should we be using a MCCB to be compliant with NEC and/or Low-Voltage Directive codes?

2) Do the NEC and/or Low-Voltage Directive codes require having Ground-Fault Protection in the tool in conjunction with the main circuit breaker, and if so can a MCCB provide the Ground-Fault Protection?

Thanks in advance for any insights you can offer.

 

[rbulsara]

NEC is merely a Code or a Standard for installation of electrical systems. NEC (or NFPA of which NEC is part of) does not 'certify' or test or appove OEM equipment or assembly.

Equivalent of CE would be say UL or ETL, the agencies who cerify or 'lable' the equipment or OEM assembly. However it is not necesary by law to have a UL listing in order to sell soemthing in the US market, but won't sell well without them. NEC and most local regulations however require a 'Listing' or 'Cerification' by a testing agency such as UL or ETL.

Having mentioned this, to your question of NEC:

1) NEC requires a over curernt protection in form of circuit breaker or a fuse at the origin of the circuit. (I am not sure NEC addresses minature circuit breakers (MCC)). I guess what the manufacturer is saying that the MCB is just a local disconnect (supplementary) not a short circuit or overload protection device. But if the manufacturer itself says'it is a supplimentary protection device, I would say you need a fuse or a MCCB protecting feeder condutors to your assembly. This MCCB can be and will be at the panelboard where this service originates and which you will have in any case.

If the MCB is not readily accecible, some codes and OSHA regulations may require a readily acceible local disconncet within sight of the tool machine.

2) NEC does not require a ground fault protection to permanetly installed individual equipment. However you can get MCCB with ground fault sensing buit into it to protect operators from a shock hazard (called GFCI in the USA, same as ELCB in europe I guess). You have to test this properly as GFCI or ELCB are prone to nuisance trips if not applied correctly.

 

[jbartos]

Suggestions marked ///\\deruth (Mechanical) Oct 6, 2003
We manufacture a semiconductor wafer metrology tool, for installation in fabs in the USA, Europe, and Japan. Thus we must meet not only NEC, but CE requirements (machine directive, low-voltage directive), and SEMI S2/S8 safety guidelines. (Not sure if they are all pertinent to my question, but I mention it for completeness).
///What about the product bearing some testing laboratory label(s), e.g. UL, FM, etc.? Have you been looking into this one?\\
I'm trying to determine if our equipment is required to have a MCCB (molded case circuit breaker) at the AC-facility inlet to the tool, versus using a supplementary protector. Currently we are using an Altech V-EA "Miniature Circuit Breaker", model 2DU20 (20 Amp). The manufacture has confirmed that this is a Supplementary Protector, and NOT a MCCB.
///This might be determined by the testing and certifying laboratory. It is difficult to address this without seeing the schematic and wiring diagrams.\\
In our design, the AC facility power (either 120 VAC or 230VAC, single phase), comes into our machine, is routed directly to this Altech supplementary protector, before being routed directly to our power-distribution box (PDU). The PDU is jumpered for either 120 or 230VAC input, provides EMO/EPO and remote on/off capability, and also has a step-down torroidal transformer with a 120VAC secondary, to provide 120VAC for distribution throughout our tool, via multiple 120VAC fused outlets.
///This is where the electrical power consumption, short circuit level, safety, grounding, etc. begin to surface. The supplementary protectors are meant to be downstream protectors from MCCB or fuses with relatively small loads to protect and under relatively low short circuit currents.\\The PDU provides fused power to multiple devices, including computer and lamp power supplies, a robot controller, an AC blower motor, and an AC impeller motor.
///This suggests an MCCB or Fuse protection rather than MCB, unless the electrical consumption is relatively low.\\My Questions:
1) Is it acceptable to be using a supplementary protector in this application? Or should we be using a MCCB to be compliant with NEC and/or Low-Voltage Directive codes?
///It depends, MCCB will be safer than MCB but the MCB may suffice.\\2) Do the NEC and/or Low-Voltage Directive codes require having Ground-Fault Protection
///Yes, when it comes to the equipment grounding, if covered by conductive metals. Ground fault circuit interrupter (circuit breaker) is considered safer than a regular circuit breaker; especially, when it comes to wet locations, and various conductive metallic surfaces around the machine/tool.\\ in the tool in conjunction with the main circuit breaker, and if so can a MCCB provide the Ground-Fault Protection?
///Yes, it has to be GFI circuit breaker.
There may be some similar product discussed or documented on Web.\\\

 

[jbartos]

Suggestion: Visit

http://www.ktec.org/

http://www.ab.com/industrialcontrols/products/c_protection/supplementary_protection.html

for:
Allowing 10 to 20 times let through energy than normal MCCB. Therefore, these devices protect downstream equipment more sensitively.

 

[HydroInspector]

UL 489
Applications Requiring
Branch Circuit Protection
UL 489
Protects conductors entering the OEM equipment.
This required UL 489 device may be provided integral
to the OEM equipment or be external as part of the
distribution system. May act as branch circuit
protection if it protects the conductor to the utilization
equipment.
UL 489
Required to protect convenience receptacle circuits
(internal or external).
UL 489
Required to protect an external load circuit leaving the
equipment.
UL 489
Required for motors in the equipment.
UL 489
HACR equipment (Heating, Air Conditioning, and
Refrigeration).

UL 1077
Applications Permitting
Supplementary Protectors
UL 1077
Supplements or provides additional protection
for sensitive electronics inside the equipment.
UL 1077
Used on the load side of branch circuit protection to
protect criteria or sensitive internal circuitry such as:
_ Computers and microprocessors
_ Communications equipment
_ Electronic controllers
_ Power supplies
_ Many other types of equipment.
UL 1077
Permitted for protection of motor control circuits
NEC 430-72, unless transformers are in circuit,
then UL 489.

Tony Moscioni
Electrical Inspector
Electrical Safety Authority