Float switch
A safety switch in the drain pan or condensate pump that interrupts operation when water rises above a set level. Because it cuts the call for cooling rather than the whole unit, a tripped float switch shows up as a system that will run in fan mode but not cool.
Also called safety switch, overflow switch
What does a float switch do?
A float switch is a water level safety in the drain pan or condensate pump. When water rises past its trip point it interrupts the cooling call, stopping the system before the pan overflows.
Float switch: how it works
A small buoyant float rides on the water in the pan and opens contacts in the control circuit when it rises. Because it interrupts the cooling call rather than mains power, the display can stay lit and the fan can keep running. That response separates the condition from a power fault.
Where you meet the term
- In a system that blows air but produces no cooling, with no fault code shown.
- In an installation over a finished ceiling, where a secondary pan and switch are required for exactly this reason.
- In a condensate pump, where the same principle protects against the pump failing rather than the drain blocking.
How to check it
- Look for standing water in the pan. Water sitting in the pan while the drain discharges nothing outside confirms the switch is doing its job and the drain is the problem. Owner check
- Clear the drain, then let the level fall. The switch resets itself when the water goes down. Bypassing it to restore cooling removes the only thing stopping a ceiling leak. Technician
Float switch: what it is not
- A tripped float switch is not the fault. It is the protection working, and the drain path is where the fault actually is.
- Bypassing the switch to get cooling back does not fix anything and removes the protection that was preventing water damage.
Float switch questions
Why does my system run but not cool with no error code?
A float switch interrupts the cooling call directly rather than reporting to the board, so many systems show nothing. Standing water in the drain pan alongside that symptom is the confirming observation.
Does a float switch reset itself?
Yes, once the water level falls back below the trip point. If cooling returns and then stops again, the drain has not actually been cleared.
Do all systems have one?
Not all, though they are standard where a leak would damage a finished space, and building rules in many places require a secondary pan and switch for units above ceilings.
Where this definition comes from
Written from manufacturer support article material held in the HVAC Bench evidence record. Where a document limits a definition to certain models, that limit is repeated here rather than generalised across a brand.
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