ANSI C84.1 RANGE A/B

[TWW]

The ANSI standard C84.1 designates voltage range A and B and service/utilization. The service/utilization is quite clear, however the service range A versus B is not clear as to how and when each apply. Probably written by committee.
An Airforce TM 5-811-1/AFJMAN indicates A is industrial (large loads) and B is residential (small loads). However if it would go to a court of law (in USA), what would/ (or is there an) be the definitive meaning, based on dialog extracted from this ANSI C84.1?

 

[busbar]

It seems unlikely that one range or another could be rigidly applied in litigation. The standard seems intended to be a “best effort” consensus document. §2.3 and §2.4 of C84.1-1995 seem self-explanatory and unambiguous.

ARI commentary: It must be recognized that, because of conditions beyond the control of the supplier or user, or both, there will be infrequent and limited periods when sustained voltages outside of Range B limits will occur. Utilization equipment may not operate satisfactorily under these conditions, and protective devices may operate to protect the equipment. When voltages occur outside the limits of Range B, prompt corrective action is recommended. The urgency for such action will depend upon many factors, such as the location and nature of load or circuits involved, and the magnitude and duration of the deviation beyond Range B limits.

 

[jghrist]

Further to busbar's response, from IEEE Std 141:

"Range B allows limited excursions of voltage outside the range A limits that necessarily result from practical design and operating conditions. When voltages are outside range A and inside range B, the corrective action should be taken within a reasonable time to restore service voltages to range A limits."

The application does not depend on the size or class of the customer.

 

[TWW]

From jghrist's comment
A design build project that yields Range B performance when operated at a level of line current that equals the current obtained using NEC 220 is not satisfactory under normally accepted practice. correct?

 

[busbar]

There is a code quote regarding adequacy …an installation that is essentially free from hazard but not necessarily efficient, convenient, or adequate for good service…

 

[TWW]

Therein above NEC-Art90-1(99) is why one uses ANSI C84.1 to from getting burned (contractually as opposed to the NEC literally). But in itself appears leaves the door open to marginal performance by including the B option. Why not just have one specification and leave it to that. It just another case of "let the buyer beware and oh, naivety is such an expensive thing."

 

[jghrist]

The NEC 220 loads are usually conservative, because the NEC is a safety, not a performance standard. If the contractor can show that loads will rarely exceed those that will result in range A voltages, you might have to accept the design unless the contract is more specific. I'd make sure that you have some recourse if you experience low voltages during peak normal loads after you start operation.

<<Blantant pitch for design-only Engineers follows>>

This is a problem with design-build; the designer has a large incentive to give you the minimum allowable.

 

[dpc]

No system should be designed for routine operation outside of the Class A range. The B range is intended for unusual temporary operating conditions.

 

[busbar]

Consensus documents are the result of committees, trying to satisfy all concerned. It's hard to expect much else.

Left to utilization-equipment manufacturers, it should be ±1%—but for utilities ±20% should be OK.