Question 1

What are the FCU and condenser?

Accepted Answer

The FCU is the indoor unit in the room. The condenser is the outdoor unit. Room BTU tells you the likely FCU size. Condenser rating tells you what the outdoor unit can support.

Question 2

What does System 1, 2, 3, or 4 mean?

Accepted Answer

The number is the FCU connection count. System 3 means one condenser connected to three indoor units. It doesn't prove that the condenser can support every FCU mix, or cool all rooms strongly at the same time.

Question 3

How should I read the recommended condenser size?

Accepted Answer

Treat it as the outdoor capacity target to ask about, not a confirmed model. Your quote should still show the brand, outdoor model, rated capacity, and supported FCU combination.

Question 4

Why can condenser size be lower than total indoor BTU?

Accepted Answer

Multi-split systems often connect more indoor BTU than the outdoor unit can deliver at once, because rooms aren't always used together. That works for staggered use. If many rooms run together, ask for a condenser closer to that combined load.

Question 5

When should I step up the room BTU estimate?

Accepted Answer

Step up or confirm on site when the room gets strong afternoon sun, sits on the top floor, has large glass, has a high ceiling, or opens into another space. These raise cooling load even when floor size looks normal.

Question 6

What should I check when a quote says System 3 or System 4?

Accepted Answer

Ask for the indoor FCU sizes, brand, outdoor condenser model, rated capacity, and supported FCU combination. Compare those details against the room BTU and condenser target from the planner.

Question 7

When should I ask for two condensers instead of one?

Accepted Answer

Ask when a large living room, open kitchen, high-ceiling area, or 24k+ FCU needs to run together with bedrooms. One condenser is compact, but two condensers cool unlike loads more reliably.

Question 8

What installation details affect the final setup?

Accepted Answer

Condenser location, ledge or bracket condition, HDB electrical loading, power route, piping route, drainage fall, beams, trunking path, and service access all shift the setup. A floor plan helps us confirm this after the BTU estimate.

Question 9

What changes if this is a replacement?

Accepted Answer

BTU still starts from room size. Replacement adds one more question: can the existing piping, drainage, trunking, bracket or ledge, power point, and old FCU/condenser pairing be reused safely?

Question 10

What should I send for a useful setup check?

Accepted Answer

Send room sizes, ceiling height if unusual, which rooms run together, and a floor plan or clear room photos. For a replacement, add photos of the existing indoor units, condenser, trunking, drainage route, and the quote.

Aircon BTU calculator

Size each room. Then check the condenser.

Setup and site-check questions