HVAC: Cycle and Service

What is in this deck

With this deck you learn the refrigeration cycle and how it is diagnosed: superheat, subcooling, airflow, heat pumps and the service discipline that prevents callbacks.

Four steps and two measurements explain most of what a technician does: compress, condense, expand, evaporate, and then superheat and subcooling to say what is happening inside.

101 cards on that and what follows from it. Why high superheat with low subcooling is a low charge and the reverse is an overcharge. What a restriction does that a low charge does not. Why a dirty condenser raises head pressure and a dirty filter freezes a coil. Then airflow, which is where half of all complaints actually live, heat pumps and defrost, gas heat and flame rectification, and the service discipline that ends callbacks: measure before, measure after, write it down.

Venting refrigerant is a federal offence, and the certification required to buy it comes from an approved programme rather than from a deck.

The categories decide what comes up: start with “Airflow” alone and add the rest when you are ready.

What you learn

• The cycle, and what each component is actually for
• Superheat and subcooling, and what each one diagnoses
• Low charge, overcharge and restriction told apart
• Airflow, static pressure, CFM per ton and short cycling
• Heat pumps, defrost, gas heat and the controls

The categories

18 categories sort the 101 cards. You can filter by category and take on what is due right now.

1. Airflow
2. Comfort
3. Controls
4. Cycle
5. Design
6. Diagnosis
7. Efficiency
8. Electrical
9. Heat pumps
10. Heating
11. Measurement
12. Refrigerants
13. Refrigeration
14. Regulation
15. Safety
16. Service
17. Systems
18. Theory

Learning with Qardbox

You see a card, you think, you turn it over and say whether you knew it. A round asks nothing more of you, and how the app works out the next date from that is on the page about FSRS-6.

What sits comes back less often, what wobbles comes back soon. You set a daily goal, and when nothing is due the app tells you exactly that instead of inventing work for you. How a round goes is shown on the learning page.

Everything stays on your device. No account, no sign-up, no ads. After the purchase the deck sits in your library like any other subject and can be studied, reordered and extended just like your own.

What it costs, and what it doesn’t

Qardbox itself costs nothing, and it stays that way. Every function is there from the start, with no subscription, no ads and no tiers; what that rests on is on the page about what it costs.

Your own cards stay unlimited, and decks from friends or from the family you read in without a limit, from a file as well. You do not need this deck in order to learn with Qardbox.

It is a shortcut: 101 checked cards for €0.99, once, with Family Sharing. The work you would otherwise do is already done. The App Store shows the price in your currency.