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UL Standards: Inspection & evaluation

Mark Lindsay, Director at Product Approvals Ltd. contributes to the UL series by sharing his expert knowledge of UL inspection and evaluation

Field Evaluation and NFPA 79

Unlike Canada the requirement for NRTL (Nationally Recognised test laboratory) approval is not mandatory. However, the vast majority of your potential customers are very likely to require and request it due to their own internal health and safety requirements.

The US is very litigious, and companies need to protect themselves. There is a practice in the US whereby for insurance reasons, companies employ an AHJ (Authority Having Jurisdiction). An AHJ visits their works and reviews all manner of details including the installation and use of electrical equipment.

If the equipment has been reviewed by an NRTL to the correct standard, then this is a tick in the box and the auditor moves on to the next area.

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How do you obtain NRTL approval?

There are two potential routes to obtaining NRTL approval on a machine:

A field evaluation of a machine would involve a review and testing against the requirements of NFPA 79 – Electrical Standard for Industrial Machinery. This is quite involved but if incorporated from the outset, the process can be managed. A common misconception is that building a machine with all UL approved parts allows for the UL mark to be applied. This is not the case.

Inspection and evaluation

A large part of the machine which attracts a lot of attention during the inspection is the control panel – this part will be evaluated in accordance with UL508a which again is quite involved but if incorporated from the outset can be managed and designed correctly to avoid potential cost down the line. However, if the control panel has been built by an approved UL Panel Builder and has the UL mark this is a tick in the box and the auditor will move on to the next aspect.

A field evaluation inspection of a machine must be carried out in the US as NFPA 70 (US wiring Regulations) is also looked at. If the machine does not meet the requirements, then the machine is ‘Red Tagged’ which means that power cannot be applied until it is brought up to specification and re-valuated. This of course incurs cost and time.

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One potential issue is that the machine does not have the correct gauge wire, this is because the US require much larger gauge wire than we would use in the UK. If the incorrect wire size is used, then the machine will need to be rewired in the correct size before the unit can be re-evaluated and marked.

If you’ve been following this blog series then you’ll notice an obvious link between all of its considerations – the effect of getting UL wrong and the importance of speaking to the right people in the know before moving forward on growth initiatives into US markets.

Having an understanding of the processes encompassing inspection and evaluation is a major facet to the right UL practice for machine builders and OEMs and hopefully, the information here alleviates that concern which is often overlooked when converting European builds to US ready machines or looking to expand into the US with new build considerations altogether.

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