How to Set Your Humidistat When Using Heat in South Florida

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When that recent cold front rolled through South Florida, our phones lit up.

  • “Why isn’t my heat working?”
  • “The thermostat is on heat, but nothing’s happening.”
  • “It worked last year!”

In many cases, nothing was broken. The issue? The humidistat setting.

In South Florida, many homes have a humidistat connected to the HVAC system — and if it’s not set correctly during cooler weather, your heat may not run at all.

Let’s break down why this happens and exactly how to fix it.

What Is a Humidistat?

A humidistat measures indoor humidity levels and tells your system when to run based on moisture in the air.

In South Florida, humidistats are common because:

  • We deal with high humidity most of the year
  • Many systems are set up to control moisture
  • Some thermostats are tied directly to humidity settings

But here’s the catch… When temperatures drop and you switch to heat mode, the humidistat can prevent the system from turning on if it’s not set properly.

Why Your Heat Didn’t Work During the Cold Front

During cooler, drier weather, indoor humidity levels drop.

If your humidistat is set too low (for example, 30–40%), your system may think:

“Humidity is fine. No need to run.”

Even though you’ve set your thermostat to heat, the system may not engage because it’s prioritizing humidity settings.

The result? No heat — even though nothing is actually broken.

How to Set Your Humidistat When Using Heat (Step-by-Step)

Here’s exactly what to do:

Step 1: Locate Your Humidistat

It may be:

  • On the wall near your thermostat
  • Built into your thermostat
  • Inside a control panel near your air handler
  • If you’re unsure, check your thermostat settings menu for “Humidity” or “Dehumidify.”

Step 2: Switch Thermostat to HEAT Mode

  • Set your thermostat to HEAT, not AUTO.
  • Set your desired temperature (typically 68–72°F during cold snaps in South Florida).

Step 3: Adjust the Humidistat Setting

For heating season in South Florida:

  • Set the humidistat to OFF, if possible, or
  • Raise the humidity setting to around 55–60%

This allows the system to run heat without being restricted by low humidity levels. In cooler weather, indoor humidity naturally drops — and that’s okay. Your system doesn’t need to control moisture the same way it does in summer.

Step 4: Wait a Few Minutes

After adjusting settings, give your system 3–5 minutes. If set properly, the heat should engage. You should feel warm air coming from the vents shortly after.

Common Mistakes We Saw During the Cold Front

  • Humidistat set too low (30–40%)
  • System left in AUTO mode
  • Thermostat switched to heat but humidity control still active
  • Assuming the system was broken before checking settings

Most service calls turned out to be simple setting adjustments — not mechanical failures.

A Quick Reminder for South Florida Homeowners

We don’t use heat often here.

That means:

  • Settings get forgotten
  • Batteries die in thermostats
  • Humidistats stay set for summer

Before the next cold front hits, take a minute to check your settings. It can save you a service call.

When to Call a Professional

If you’ve:

  • Adjusted your humidistat
  • Confirmed thermostat is in HEAT mode
  • Checked breaker and batteries

And your heat still won’t turn on. Then it’s time to have a technician inspect the system.

Don’t Let a Setting Leave You in the Cold

South Florida may not see freezing temps often — but when we do, your system should be ready. If you’re unsure how your humidistat is set or want a quick system check before the next cold front, give us a call. We’re here to keep South Florida comfortable — year-round.

2026/03/09