Cassette Leaking After Heavy Rain: Float Switch Missed Load

A cassette leaks after heavy rain and the safety device is called useless. Whether it failed or was asked for the impossible.

By Team Snowflake | Updated 24 Aug 2026

Teaching case based on recurring Snowflake service patterns; identifying details are combined.

How this presents

Staining on a ceiling below a unit that does shut itself down when the pan fills. The shutdown happens reliably every time. Damage appears anyway, and it follows periods of heavy rain rather than heavy use.

Setup: LG Cassette4-6 yearsCondoDowntown Core
Misread as: A safety device that has failed, leaving the property with no protection at all.
Check first: Whether the damage follows heavy rain rather than heavy use

What else produces this

A device that operates every time is not a failed device, so testing it again answers nothing. What matters is the gap between the water reaching the trigger level and the water reaching the edge, measured against how fast it is arriving. Under ordinary conditions that gap is comfortable. Under a rate the arrangement was never sized for, the pan reaches its edge before the shutdown has taken effect, and the sequence is correct throughout.

A shutdown occurring reliably every time removes the protective device from suspicion.
Damage following heavy rain rather than heavy use points at an inflow the drainage was never sized for.
Water entering the drain path from outside during rain adds to what the coil produces.
A pan reaching its edge before the shutdown takes effect explains damage sitting alongside working protection.

Why it happens

A shutdown stops the unit producing more water. It does nothing about water already in the pan or arriving from elsewhere, and it takes time to have any effect at all. Where rain finds its way into the drain path, the inflow rate is far higher than anything the coil produces, so the level rises faster than the sequence was designed for. Everything operates correctly and the ceiling still gets wet.

What resolution involves

Rain is kept out of the drain path, at the outlet or wherever it is entering, so the protection is never asked to handle a rate it cannot. The distinction is worth holding onto generally. Protection that operates late is not a faulty device, it is an inflow that was never anticipated, and replacing the device changes nothing about that.

How to tell it worked

Behaviour during heavy rain rather than a bench test of the shutdown itself. The device passes any test put to it; what has to be proven is that the pan no longer fills faster than the shutdown can help.

Before you approve a quote

Correct but late is still a wet ceiling

A device that operates every time is not the fault. Test the rate of inflow instead.
A shutdown stops production. It does not remove water already there or arriving from elsewhere.
Damage that follows the weather rather than usage points at water entering from outside.

Questions this case answers

Ceiling cassette drips only during heavy rain: is the drain clogged?

Probably not. Rain entering the drain path from outside adds to what the coil produces, and that inflow can outpace the drainage even when the line is clear; the unit's shutdown still operates every time.

What is a float switch and how can it cause a leak?

It is the device that stops the unit when the drain pan fills. It does not cause the leak itself: the shutdown takes time, and rainwater arriving from outside can reach the pan edge before that shutdown takes effect.

Does a leaking cassette mean the drain pan has cracked?

No, not necessarily. Here the pan was sound and the shutdown reliable; the damage came from rain entering the drain path faster than the shutdown could compensate for.

Can a leak that only happens in a storm be reproduced during a visit?

Not by itself. The device is already doing what it was made to do, and a newer one operates at the same level with the same limits. What has to change is how fast the water arrives.

Describe your situation

Tell us what’s going on. Symptoms, setup, photos, anything we should know. We’ll assess and come back with the right next step.

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