Reading a rule precisely

You can find the right rule and still get the question wrong. It happens when you read the rule the way you read a newspaper: quickly, for the general idea. Rules are not written for the general idea. They are written so that every word does a job, and the jobs are often hidden in small words such as shall, may, not less than, except and or. This lesson teaches a way of reading rules that catches those words every time.

Denise calls it reading like an inspector. An inspector who writes a deficiency has to be able to point to the exact words that the installation does not meet, so inspectors learn to read rules as a series of conditions and consequences. Candidates who learn the same habit stop losing marks on the questions that are designed to separate careful readers from fast ones.

To practise without reproducing the Code, this lesson uses invented rules. They are written in a style similar to the Code but are not Code text and must not be used for real work. Once you have the method, apply it to real rules in your own copy.

The words that decide outcomes

A small vocabulary carries most of the meaning in any rule. Learn exactly what each word does. Shall creates an obligation: the thing must be done. Shall not creates a prohibition. Permitted, or may, creates a permission: you are allowed to do the thing, but you do not have to. Except introduces a case that is taken out of the main requirement. Unless introduces a condition under which the requirement does not apply. Where introduces a condition under which the requirement does apply.

The difference between shall and may is tested constantly. If a rule says a method is permitted, an installation that uses a different method may still comply, as long as it meets the requirements that apply to it. If a rule says a method shall be used, the alternative does not comply. A question that asks whether something is required, versus whether it is allowed, is testing exactly this distinction.

Limits: not less than, not more than, and the boundaries

Numerical limits use phrases such as not less than, not more than, at least, not exceeding and greater than. These phrases decide what happens at the boundary. A value that equals a not-less-than limit complies. A value that equals a greater-than requirement does not. When a question gives a value exactly on the boundary, the wording of the rule is the whole answer.

Lists of items: and versus or

Many subrules break into items (a), (b), (c). Whether all of the items must be met or any one of them is enough depends on the word that joins them, normally placed at the end of the second-last item. If it is and, every item must be met. If it is or, meeting any one item is sufficient. The joining word is easy to miss because it sits at the end of a line, often half a page below the start of the list. Train your eye to look for it before you read the items.

Lists can also be nested. An item can contain sub-items with their own joining word. A requirement might say that conditions (a) and (b) must both be met, where (b) itself can be met in either of two ways, (i) or (ii). Draw the structure as a small tree when a list is complicated. It takes twenty seconds and prevents misreading.

Exceptions and their position

Exceptions can appear in several places: within the same subrule, as a later subrule of the same rule, in a different rule that says notwithstanding, or in a supplementary section. A careful reader looks for all four. The common failure is to read subrule (1), find the requirement, and stop, when subrule (3) contains a permission that covers exactly the installation in the question. As Lesson 2 suggested, glance to the end of the rule before deciding.

A method for any rule

Here is the method in full. First, read the whole rule once, quickly, to see its shape: how many subrules, any lists, any cross-references. Second, identify the requirement words: shall, shall not, permitted. Third, mark the conditions: where, unless, except and any defined terms. Fourth, check lists for and or or. Fifth, follow cross-references and check for exceptions elsewhere. Sixth, apply the rule to the facts of the question, condition by condition. Only then pick the answer.

Practice with invented rules

The following rules are invented for practice. They are written in a Code-like style so you can apply the method, but they are not from the Code.

The second example shows why you must read to the end. A candidate who stops after subrule (1) marks the storage room gizmo as non-compliant. The exam writer will have put that answer in the choices on purpose.

Priya writes the logic of Practice Rule P-1 as a small function. Turning a rule into code forces you to decide exactly what each word means, and it shows instantly whether a set of facts meets the rule.

def practice_rule_p1(accessible, only_splices, on_drawings):
    # Invented rule for practice, not Code text.
    if accessible:
        return 'complies with subrule (1)'
    if only_splices and on_drawings:
        return 'complies by the permission in subrule (2)'
    return 'does not comply'

cases = [
    ('box above lift-out ceiling tile', True, False, False),
    ('concealed, splices only, on drawings', False, True, True),
    ('concealed, splices and relay, on drawings', False, False, True),
    ('concealed, splices only, not on drawings', False, True, False),
]
for name, acc, splices, drawings in cases:
    print(name.ljust(44), '->', practice_rule_p1(acc, splices, drawings))

box above lift-out ceiling tile              -> complies with subrule (1)
concealed, splices only, on drawings         -> complies by the permission in subrule (2)
concealed, splices and relay, on drawings    -> does not comply
concealed, splices only, not on drawings     -> does not comply

Reading the question as carefully as the rule

Exam questions are written with the same care as the rules, and the same method applies. Underline what the question asks: is it asking what is required, what is permitted, what is the minimum, or what does not comply? Note every fact that could trigger a condition: the location, the voltage, the type of building, whether equipment is accessible, whether it is a dwelling. A detail that seems like scene-setting is often the condition that switches a rule on or off.

Reading real rules

The invented rules in this lesson are deliberately simple. Real rules are longer, with more subrules, more cross-references and more defined terms. The method still works; it just takes a little longer the first few times. Choose three long rules from the sections you use most, perhaps the dwelling-unit demand load rule, a receptacle rule from Section 26 and a grounding rule from Section 10, and work through each one with the six steps. Draw the list structure as a tree. Mark the requirement words and conditions in pencil in your study notes, not in your exam book.

Then write a short scenario for each rule that the rule clearly covers, one it clearly does not, and one that sits on a boundary. Swap scenarios with a study partner and decide each one. Priya and Marcus do this every week, and they find that the boundary scenarios generate the best arguments. When they disagree, they go back to the wording, check the definitions and the Appendix B note, and usually find the word they had each read differently. Those arguments are exactly the thinking an exam question demands, done in advance, without the clock running.