Heating Stuck On? Here’s Why

In today’s issue of, “why won’t my things work?” we’re talking about your home’s HVAC system again. Today’s particular problem is that the heating in your home has turned on and simply won’t turn off. Luckily, DreamyHome is the source of just about any type of fix you could need, so we’ll get your home back to its proper temperature in no time flat. If your heating is stuck on, there are a few things to look for before calling for help.

The most common causes for heating stuck on are a defective thermostat, faulty water checking system (if you use a boiler or radiator), a clogged air filter, or a bad primary controller.

Now yeah, those are words – but what do they mean? Keep reading to find out.

Why Is My Heating Stuck On?

Now there are (as mentioned above), several things that could cause this to happen. We’ll break them all down in detail in just a moment, but let’s recap. The problem could lie in your:

  1. Thermostat
  2. Boiler’s water checking system
  3. Or its primary controller

So let’s get into it and figure out exactly what is causing your heating issues, shall we?

Thermostat

This is by far the most likely source of the issue. There are a few things you should be examining to make sure that the thermostat isn’t the source of your problem. For more information on troubleshooting a faulty thermostat, go to our “Thermostat Not Clicking” article, located here.

Location

An oft-overlooked cause of thermostat shenaniganry is its location in your home. Your thermostat functions by detecting the temperature of where it is and sending that information to your heating system. This, in turn, informs the heater how much hot or cold air to pump in to reach the desired temperature.

If you’ve got your thermostat located in direct, consistent sunlight or near an entryway, it may be getting improper information. Consider moving your thermostat to a more thermally-neutral area and see if your heat turns off and on regularly again.

Replacing the Thermostat

Nobody wants to hear this, but it’s one of the first things most HVAC engineers will recommend. Now always do the above steps and go through what’s mentioned in the above article before just fully replacing the device. But, if push comes to shove and you’re in need of a new thermostat, take a look at our guide to the best wireless thermostats available today.

Settings & Batteries

Depending on the device, you’ll often have the ability to preprogram temperature settings on most modern thermostats. Now you likely have fiddled with them until they’re where you want, but it can’t hurt to check, so do me a favour. Walk over to your thermostat and take a look at the settings. Have they changed, reset to factory defaullts, or disappeared entirely?

It’s likely that your batteries (if it’s battery-powered) are dead or dying. If your thermostat is wired into the home’s electrical system, go take a look at the breaker – it could have flipped and power cycled the device, causing the settings to change or disappear.

If this is the case, replace the batteries, flip the breaker switch, and see if it’s changed anything.

Boiler Water Checking System

This does ecactly what the name implies – it checks the water levels in your boiler and circulates it to where it’s needed. If a part breaks (most commonly the check valve), it won’t stop pumping hot water through your home, meaning the heat won’t stop. The only way to fix this is to replace the faulty part(s), often with the help of an HVAC engineer.

If you really want to see if this is the issue yourself, you can check a video guide here on YouTube.

If you are not a licencsed boiler engineer, you should not do this without help. I am not knowledgable enough to walk you through how to do this, and you’re likely not knowledgeable enough to perform this check properly.

Primary Controller

Now, again, I’m not a licensed HVAC engineer. While I can learn how to troubleshoot issues, I cannot and will not walk people through how to perform complicated checks such as the one needed here.

With that said, one of the first things most HVAC engineers will check if you compain about having your heating stuck on is the primary controller. This is what manages the majority of water in the boiler and, by extension, heat in your home. If it fails, it will continuously pump heat through your home, similar to a fault in the water checking system.

Furnace Air Filter

Now this is for those with a furnace rather than boiler. Just like with all things that use an air filter, your furnace’s air filter needs to be replaced regularly (~every three months or so). If it’s clogged and dirty, it won’t function properly. When clogged, a furnace’s air filter will prevent your furnace from getting the air it needs. This will simultaneously make it work harder to do the same thing, and make it harder to detect when it needs to turn off.

To replace an air filter, do the following:

  1. Locate your furnace air filter. They are generally located inside the blower compartment.
    1. Before beginning anything else, turn off power at the breaker to your furnace and consult the owner’s guide. This will tell you where to look and what model air filter you’ll need.
  2. This step changes depending on the type of furnace:

Up Flow Furnace

These furnaces have a flow of upward air inside. The filter for these is generally located in the blower compartment int he bottom door, next to the cold air return. You’ll need to remove both the top and bottom doors, ensuring that the bottom door (upon reinstallation) engages the safety switch. If it doesn’t, the furnace won’t turn on at all.

Down Flow Furnace

The opposite to an up flow furnace. The filter for these is generally located in the upper blower compartment with a V-shaped filter. In other words, these generally take two filters. Just as above( but reversed), ensure the top door activates the safety switch upon reinstallation.

Horizontal Furnace

These are super easy to replace, as horizontal furnaces usually have a slide-out rack for the filter built in.

HEPA Style Furnace

Similar to the horizontal furnace, this is a very easy fix. You generally just need to open the filter cover and slide in the new one (after removing the old one, obviously).

Air Movers/Handlers

These are common in warm, humid environments, though not so much in colder areas. These generally have a rack built in with a filter, just like the horizontal furnace. If you didn’t replace the filters before, ensure you don’t have two filters in place. This is a common mistake that leads to poor performance and air flow (and a worse bill).

Final Thoughts

If your heating is stuck on, there are a lot of things to take into account. Your first stop should always be the thermostat – read our linked article above for more information on troubleshooting thermostats. After you’re positive that it’s not the thermostat, there are a lot of fixed you’ll need an HVAC engineer to address, with one exception.

If you have a furnace, try replacing its filters and reactivating the heat – that may solve things. If not, turn off your heat at the main breaker and call an HVAC engineer to take a look. This will save you money on the exorbitant heating bill you’d otherwise recieve and give your home a bit to cool off.

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About the Author Harry Thompson

Involved in home renovations throughout his life, Harry is an expert in everything to do with home and garden DIY. In his spare time, he enjoys cooking and tending to his garden.