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Electrical isolation questions for the Refrigeration and air conditioning (RAAC) specialist test

5 free questions on Electrical isolation, from section E. Specialist: HVACR – refrigeration and air conditioning. Every question is original and explains why each option is right or wrong.

Last verified against HSE guidance and the law ·How we write our questions

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Question 1

Easier ·Link to this question (question 1)

You are about to replace a compressor contactor on an air conditioning unit.

What must be done first?

Choose one answer.

  1. A. Work on it live, carefully
  2. B. Check it with your finger
  3. C. Make it dead and prove it dead
  4. D. Switch off at the unit and hope for the best
Show the answer and explanation

Answer: C

  • A. Wrong: Wrong. Don't work live if it can be avoided.
  • B. Wrong: Wrong. That could kill.
  • C. Right: Right. HSE says electricity supplies should be made dead and proved to be dead before work starts.
  • D. Wrong: Wrong. It must be proved dead.

Explanation

Make the supply dead, prove it dead, and stop it being switched back on.

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Question 2

Medium ·Link to this question (question 2)

A client asks you to fault-find on a live control panel because it is quicker.

What does HSE say?

Choose one answer.

  1. A. Live work is fine if you are quick
  2. B. Live work is fine on small units
  3. C. Live work is fine with rubber boots
  4. D. Avoid working live
Show the answer and explanation

Answer: D

  • A. Wrong: Wrong. Avoid live work.
  • B. Wrong: Wrong. Avoid live work.
  • C. Wrong: Wrong. Avoid live work.
  • D. Right: Right. HSE says electrical contractors should not work live if it can be avoided.

Explanation

Avoid live working. Make equipment dead before working on it.

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Question 3

Medium ·Link to this question (question 3)

You have isolated an air conditioning unit to work on it.

What should the method of isolation do?

Choose one answer.

  1. A. Stop it being switched back on
  2. B. Allow anyone to turn it on
  3. C. Leave the fuse in a drawer nearby
  4. D. Turn off only the display screen
Show the answer and explanation

Answer: A

  • A. Right: Right. HSE says the method of isolation should prevent inadvertent or deliberate re-energisation.
  • B. Wrong: Wrong. It should prevent re-energising.
  • C. Wrong: Wrong. It should prevent re-energising.
  • D. Wrong: Wrong. Isolate the supply.

Explanation

Isolation must stop anyone switching the supply back on, by accident or on purpose.

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Question 4

Medium ·Link to this question (question 4)

An apprentice asks if they can wire up a new condensing unit on their own.

What does HSE say?

Choose one answer.

  1. A. Anyone, if the client agrees
  2. B. Only trained, competent people
  3. C. Anyone, if they follow the wiring diagram on the lid
  4. D. Anyone over 18 can do it
Show the answer and explanation

Answer: B

  • A. Wrong: Wrong. Electrical work needs training and competence.
  • B. Right: Right. HSE says electrical work should only be done by those who are trained and competent to do it.
  • C. Wrong: Wrong. Electrical work needs training and competence.
  • D. Wrong: Wrong. Age is not competence.

Explanation

Electrical work must only be done by trained, competent people.

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Question 5

Medium ·Link to this question (question 5)

Other trades will be drilling and cutting near the existing electrics during an air conditioning refit.

What does HSE say?

Choose one answer.

  1. A. Tell the other trades to be careful, and nothing more
  2. B. Switch off the whole street
  3. C. Isolate the relevant parts
  4. D. Leave it live, so the lights stay on
Show the answer and explanation

Answer: C

  • A. Wrong: Wrong. Isolate the relevant parts.
  • B. Wrong: Wrong. Isolate the relevant parts.
  • C. Right: Right. HSE says where other trades' work could disturb or damage the existing system, isolate the relevant parts.
  • D. Wrong: Wrong. Isolate the relevant parts.

Explanation

Isolate parts of the electrical system that other trades' work could damage.

Study

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