Interpreting Diagrams Test Tips for the EEI TECH Battery

Interpreting Diagrams is the TECH test about reading a key. EEI's brochure says it measures the ability to use symbols and codes to locate objects on a map or diagram and to determine the object's status. That is the whole published description: no question count, no time limit. What it tells you is that the skill is lookup and status, not calculation — and that is very trainable.

What EEI does and does not publish

The TECH brochure names four tests and gives a count and time limit for Mechanical Concepts only. For Interpreting Diagrams it gives the one-sentence description above and an example. The Center for Energy Workforce Development's summary of the EEI batteries repeats the same description. LG&E and KU, which publishes the brochure, describes the skill area as the "ability to use symbols and codes to locate objects on a map or diagram or to determine an object's status".

Numbers you may see elsewhere — "nine questions in nine minutes" is a common one — are not in any brochure. They match EEI's practice exercises, which Entergy tells applicants are shorter than, and differ slightly from, the real tests. Our own timed run is 24 questions in 20 minutes; that is our practice pace, chosen to keep you moving, not a claim about the real test.

The two jobs in every question

Every question asks you to do one or both of these:

• Locate. Find an item from its number, its symbol or a grid reference. "In which square is item 37?" "Which item is in C4?"
• Determine status. Work out what state it is in from how it is drawn or coded. "Is valve V18 open?" "What does the tag on compressor 3 say about it?" On a switching diagram, status also means working out what is live: which loads are energized, which outlets get water.

Knowing which job a question is asking for stops you doing the other one by mistake. A locate question does not care about status; a status question usually needs you to locate first.

A routine that works

1. Read the key before the question. Every symbol and code you need is defined there. Our tag plans deliberately change their status codes from plan to plan, because the habit you want is reading the key every time, not remembering it.
2. Grid references: column, then row. C4 is column C, row 4. Put a finger on the column letter and slide down; most locate errors are a column off.
3. Status from the symbol, not the context. If the key says a filled symbol is out of service, a filled pump is out of service even if it sits in the middle of a busy line.
4. Trace paths back to a source. To decide whether a load is live, start at the load and walk back towards each supply. Stop at the first device that blocks the path. If every route is blocked, it is dead.
5. Know what blocks. A closed switch passes current and an open switch does not; an open valve passes water and a closed valve does not. That reversal catches people every time they move from an electrical diagram to a piping one.
6. Respect tags. When a diagram marks a device as tagged — do not operate — then a question about which device you could operate must ignore it, even if operating it would work.

Worked example: what is live?

Picture a two-supply one-line. Supply 1 feeds a bus through switch S14, which is closed. From that bus, switch S22 (open) goes to load L1, and switch S23 (closed) goes to load L2. Supply 2 feeds a second bus through S30, which is open, and that bus feeds L3 through S31, closed. A tie switch S40 joins the two buses and is closed.

Which loads are energized? L2 is: Supply 1 → S14 → S23 → L2, all closed. L1 is not: its only switch, S22, is open. L3 is too, but not from Supply 2 — S30 is open — it is fed from Supply 1 through the closed tie: Supply 1 → S14 → S40 → S31 → L3. That last path is the one most people miss. When you trace, try every route, including the tie.

Practice versions of exactly this, drawn rather than described, are in the Interpreting Diagrams demo, alongside grid maps and tag plans.

Speed without guessing

These questions feel slow at first because you are learning each diagram. They get fast for the same reason Graphic Arithmetic does: several questions hang off one diagram, so the time spent reading the key and orienting yourself is spent once. Spend it.

Then, per question: find, check the key, answer. If you catch yourself re-reading the whole diagram for every question, you skipped the orientation step. And because each question is about a specific item, a wrong answer is usually a misread rather than a misunderstanding — check the item number and the grid reference before anything else.

Where this fits in TECH

Interpreting Diagrams is one of four TECH tests, alongside Graphic Problem Solving, Mechanical Concepts and Reasoning from Rules. EEI combines the scores into one Overall Score and does not publish its range or any cut score. Our TECH practice covers all four, by question type; see what EEI publishes about TECH for the full picture.

Frequently asked questions

Do I need electrical or piping knowledge?

No. Everything you need — what each symbol means, what blocks current or water — is on the diagram or in its key. The skill is reading accurately, not trade knowledge.

How many Interpreting Diagrams questions are on TECH?

EEI does not publish a count or a time limit for this test. Figures you see elsewhere match EEI's shorter practice exercises.

Is it like Graphic Arithmetic?

It shares the habit of reading a drawing carefully, but there is no arithmetic. It is closer to map reading: find the item, read its status from the key.