How do I qualify voltage's


I need some help, I am trying at the moment to develope a risk assessment document to replace having to test every socket in the plant when new applications/equipments are installed.

Basically at IQ level there is teat where you have to verify that for example the voltage coming into the equipment is 230V ± 10V (European Standard Voltage). Is there a way that I can write a document to explain that this does not need to be tested for each socket on the site as it is verified at the source level or something like that.

Has anyone come across any similar problem.

Any help would be greatly appreciated.



Hi Jimmy

What you are suffering from is not having qualified you electrical system infrastructure. You can’t build system and equipment qualifications and validation on an unqualified infrastructure. This may include compressed air supplies, vacuum supplies, electrical supplies, temperature & humidity, HVAC i.e. air flows, air changes, filtration etc.

I guess that measuring the voltage at the socket as part of IQ is a lot easier than qualifying your entire electrical system. But it doesn’t really tell you anything. What about spikes, brown outs, surges and all those VSDs putting harmonics onto your electrical wave form. Computers are better off with a UPS.

You have inadvertingly opened a can of worms

Hope this helps


Hello Jim,

I have experience with a similar issue. Perhaps I can shed some light here!

Your electrical requirement I assume comes from the company who manufactures the equipment. Wwith this being said, I would attach any documentation from the manufacturer that lists the specs to your IQ protocol as supporting evidence. In addition, I would run one test to ensure the voltage coming into the building(s) is a high enough. If you would like, you could run a test on one socket in each building if you really want to narrow it down.

However, the most important piece here is to list your minimum electrical requirement for each piece of equipment, as I ma sure they vary. In listing this system requirement, you can easily use the test to show the building has at least enough voltage to handle the equipment.

gokeeffe madea good point, Uninterrupted Power Supply (UPS) is an essential piece of the validation, as one must ensure the systems and equipment can continue functioning in the event of a power loss. BTW - You will want to run a test for the UPS too! :slight_smile:

I hope this helps!

Michael J. Gregor
Partner, ComplianceDoc

There are no such tests - the power supply into any plant will vary with the loading on the power station. In very bad circumstances (cold wintery evening at peak loading) it has been known for the mains power to drop to 200 volts ac.
So much for testing for 230 !!!
You must really read the 16th edition of the IEEE regulations.

Starting at your main power in to plant source.

The isolator for the circuit you are qualifying should be switch off, and its in coming voltage measured - the isolator must then be turned on and loaded to its maximum expected usage. The difference between loaded and unloaded voltages must not exceed 4%. (IEEE 16th section 4.3.11)

Where you have a supply in a remote area in a large facility it may well have passed down through a distribution system involving four , five, or more distribution boxes (isolators).

Each one of these is allowed the same volts drop between on load and off load. I would expect a serviceable system to drop about 2 volts per distribution leg. So if you are six boxes down the line expect to have lost at least 12 volts with all circuits active, with no single distribution box dropping more that 4% of its off-line input voltage.

Always check you are using the latest information from the IEEE. Never work from hearsay.

Alex Kennedy

There is another way. Contact a reputable and licenced electrical contractor to supply you with a certificate of compliance for your installations! That would in fact cover volt drop, c/breaker sizing (kA, voltage and Amperage) cascading systems, cable sizing and installation, etc.
With this you could measure your main incoming power supply over a period of say a week in summer and a week in winter. This would check for voltage variations, power factor correction (Cos θ) harmonics etc.

What voltage specs are being added to the URS for voltage if this has not yet been done??