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The readings, rules and reasoning behind 313A questions
Explanations of concepts that come up again and again, each tied to the work areas it belongs to and linked to its sources.
Superheat vs subcooling: what each reading tells you
Superheat reads the evaporator, subcooling reads the condenser. How to calculate both, which one to charge by, and how to read them together.
Read the article →September 21, 2026 · Area FUndercharge or restriction? Telling two starved evaporators apart
Low suction pressure and high superheat can mean a leak or a restriction. Subcooling and a temperature drop across the drier tell you which.
Read the article →September 21, 2026 · Area BReading a vacuum decay test: leak or moisture?
What a micron gauge is telling you after you valve off the pump, why the compound gauge can't, and how to set up an evacuation that finishes.
Read the article →September 21, 2026 · Area B + ETemperature glide, dew point and bubble point, explained
Why zeotropic blends like R-407C have two PT values, which one to use for superheat and subcooling, and why they must be charged as liquid.
Read the article →September 21, 2026 · Area BWhat Canada's Federal Halocarbon Regulations, 2022 actually say
A section-by-section summary of the rules on release, recovery, leak testing and charging, who they apply to, and where Ontario's own regulation takes over.
Read the article →September 21, 2026 · Area A + DA2L refrigerants: what the safety class means for the job
What the A and the 2L stand for, which common refrigerants are A2L, and what changes in tools, recovery and installation practice.
Read the article →September 21, 2026 · Area FIdentifying compressor terminals with an ohmmeter
How to find common, start and run on a single-phase compressor from three resistance readings, check the math, and test for a grounded winding.
Read the article →September 21, 2026 · All areasA 90-day 313A study plan built on the exam weights
How to spend study time in proportion to the Red Seal breakdown, find weak areas early, and use the last weeks for review instead of new material.
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