Ampgard ductless AR medium-voltage motor control

How do arc absorbers work?

The Ampgard® ductless AR offers the same industry leading ratings and safety features as Ampgard AR, but uses a plenum containing arc absorbers instead of exhaust ducts. Gases created from the arc blasts are routed directly into the plenum and into the arc absorbers. These arc absorbers inside the plenum filter large particles and absorb the energy in the arc fault by-products. The filtered and cooled gases are then exhausted out of the plenum and into the room, eliminating the need for exhaust ducts and blast zones.

What standards does the Ampgard ductless AR meet for arc flash safety?

The ductless and ducted solutions are both certified to IEEE® C37.20.7-2017 for Type 2B construction, enhancing safety from the front, sides and rear of the enclosure even with the low-voltage control doors open. Both are rated to mitigate arc faults up to 50 kA for 0.5 seconds.

What are the space requirements?

The Ampgard ductless AR with arc absorbers has the same height and depth as Ampgard AR—127 inches H x 50 inches W (including horizontal bus and plenum). Configurations must have a minimum length of 108 inches. The top of the plenum must have a minimum ceiling clearance of 18 inches. No rear access is required, only front access. 3-inch clearance is required from the sides and rear of equipment.

Does one product—ductless or ducted—provide a safer solution over the other?

Both solutions provide the highest degree of protection, are tested and certified to IEEE C37.20.7-2017, and are able to withstand the effects of an internal arc fault of 50 kA for 0.5 seconds. However, ducted solutions do require an external blast zone, which increases the risk of exposure and injury for personnel who could potentially enter this area during an arc flash event.

What is C37.20.7?

C37.20.7, an IEEE standard, outlines certification procedures to protect personnel from arc-fault dangers. The 2017 revision added Annex I for Medium Voltage Motor Control Centers and requires testing  gear with an arc at the line-side fuse ferrules, where arc energy is highest, unlike the 2007 version that only required testing at the most likely point of arc occurrence, typically at the disconnect. The old standard left a risk of exposure to higher energy arcs than the gear was certified for, making the new criterial crucial for enhanced safety.

How does this Arc resistant gear compare to other Arc mitigation methods?

Arc mitigation methods, such as Arc Flash Detection Relays, Differential CTs and ARMS settings, can reduce the duration of an arc event but do not provide the same level of protection as equipment certified to C37.20.7. While these devices improve the detection time of an arc event, they still depend on a breaker to interrupt the fault. Once an arc flash is detected, it may take 3–5 cycles for the breaker to open— ample time for significant damage to occur. For the highest level of personnel protection C37.20.7 certified arc-resistant gear remains the most reliable safeguard.

What are the plenum installation requirements?

The plenum is pre-assembled and ships separately from the equipment. At the worksite, the plenum should be installed on the top of the equipment. Please refer to IB48088 for installation specifics.

Can I retrofit my existing arc-resistant gear to make it ductless?

Yes. To switch from ducted to ductless, you must seal or remove the exhaust ducts and replace the ducted plenum with an arc absorber plenum. Eaton Electrical Services & Systems (EESS) can help assess current installations and provide solutions. 

Can the same spare parts be used across ductless and ducted components?

Yes. We use the same starter components in ducted and ductless equipment types. The only difference in construction is the plenum.

Will this solution simplify the design of projects?

The Ampgard ductless AR with arc absorbers eliminates the need for exhaust ducts and blast zones. This makes project planning easier and more flexible, as there’s no need to match ducts to worksite layouts or designate blast zones. It allows for greater flexibility in floor plans, as the equipment will occupy less space on the floor and walls. Additionally, it eliminates the complexity and any potential complications of aligning the duct path to the worksite, meaning other equipment doesn’t need to be arranged around ductwork. Repeat designs can be used without considering site-specific requirements.

Would we expect to see installation times reduced?

Yes, this solution significantly reduces installation time.  Unlike ducted equipment, which requires on-site assembly and installation of exhaust ducts, the ductless system only requires installing the plenum at the worksite. This eliminates the extended timelines associated with hanging ductwork, installing brackets, and drilling ceilings and walls.

Are there design guides and instruction manuals available?

Yes. There are installation manuals and a design guide for Ampgard AR. 

Design guide: DG020002EN—7.2 kV Motor control (Ampgard AR)— medium-voltage, arc resistant

Instruction manuals: 

• IB48088—Instructions for Eaton’s 7.2 kV Ampgard AR (arc-resistant motor control center)
• IB48077E—Duct and plenum installation for Eaton 5/15 kV Type VacClad-W arc-resistant metal-clad switchgear and Ampgard arc-resistant motor control centers