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Why Is My Radiator Not Getting Hot?

When winter rolled around and I decided it was time to start up my radiator, I was faced with an unexpected issue: the radiator was not heating up. I began to wonder what the issue could be. So, I did some research to find out why my radiator is not getting hot.

So, why is my radiator not getting hot? If the radiator is not getting hot, it likely is failing to properly circulate water. This could be as a result of air in the system, faulty valves, debris or other malfunctions. There are many telltale signs that help to troubleshoot a radiator and suggest what the specific problem may be, and fixing them can often be done without a call to the plumber.

Though less popular than in years past, radiators are still present in many people’s homes today. A properly functioning system is an excellent source of heat. However, there are a few common small faults that can occur within an otherwise healthy radiator system that should be addressed to ensure a system functions at its best. By familiarizing yourself with the radiator and understanding how it creates and radiates heat in the first place, you can better troubleshoot your radiator to get right to the source of what is causing it to not heat up.

Why Is My Radiator Not Getting Hot?

What Causes Radiators to Not Heat?

Radiators work by circulating hot water or steam throughout a system of tubes and fins, thus radiating the heat throughout the space they occupy. The central boiler is responsible for heating the water while the units that sit within the rooms are responsible for dispersing the heat created by the boiler. If for some reason the radiator or any part of the system cannot circulate the water or steam, some or all of the radiator may feel cool to the touch, resulting in an improperly heated room.

Oftentimes, a radiator can become dirty and simply needs thorough cleaning to get back to a top-tier operating shape. Though your specific unit may be different, many radiators can simply be removed from the home and flushed out using a hose. This will break loose the debris that is hindering the water or steam flow and allow the radiator to efficiently circulate it throughout the entirety of the unit.

Another common problem with a radiator is its tendency to harbor trapped air at the top of the unit. This can occur after the system sits unused for a period of time, such as over the summer. A good way to identify this problem is by allowing your radiator to heat up and then using your hand to check for cool spots. If you find that the top of the radiator feels cool, it likely has built up a column of air that needs to be cleared. Many units have an air purge near the top that allows the system to be opened to clear the air. However, some units have an automated valve that senses the air and purges it, then shuts off once it senses the steam or water. Though this is a fairly common problem with radiators, if you find that it is happening often, there is likely a greater problem within the system that should be addressed.

Trouble Shooting Tips to Your Radiator Working Again

Bleed Air From Your Radiator

Bleeding the air from a radiator is often a simple, quick way to get your radiator up and running quickly and ensure your house is nice and warm. The trapped air column will rise to the top of the radiator, resulting in coolness to the touch at the top of the unit and heat at the bottom. To remove this air from inside the radiator, it has to be bled out. The majority of radiators will have a bleeder valve at the top of the unit. To purge the air, you simply open the bleeder valve with the necessary tool, let the air out, and close the valve once water or steam starts to come out.

For this reason, your unit should be turned on and up to temperature before bleeding. This is also why you should only open the valve enough to hear a slight hiss of air, as to not burn yourself once the water or steam starts to come out. Once the air has all bled and you have tightened the valve, give your system a few minutes and check the radiator top once more. If the radiator is warm to the touch, you have successfully removed the air. If not, you likely need to bleed more air or possibly flush the system of debris.

Flush Your Radiator System

If your radiator is not fully coming to temperature, it may be a result of a blockage somewhere in the system. The good news is that these blockages are not as serious as they sound, and with a little work you will have your home comfortable in no time. Blockages often happen as a result of rust or other deterioration within the unit itself. For this reason, blockages are not as common in sealed, pressurized units, but pose problems in open-vent systems. Thankfully, open-vent systems are easily flushed.

To flush an open-vent system, simply use a store-bought liquid additive for flushing radiators. Follow the manufacturer’s instructions and completely drain the system once the product has run its course. Refill the radiator and monitor its performance. If the debris was considerably built up, it may require a second flush to reach peak performance. If you have a sealed system, you will likely benefit from hiring a professional to flush the system.

Related Questions

Do I have a Pressurized or Non-Pressurized System? 

When it comes to radiators, not all are created equally. In fact, there are a wide variety of differences that could occur from system to system, and it is important to know what kind of system you have. One of the biggest differences between systems is whether it is pressurized or non-pressurized, also referred to as an open-vent system. A pressurized system is as the name suggests, sealed and under pressure. No air, water, or steam is coming or going. Because of the makeup of these systems, they are a little harder to address when they collect buildup. However, when compared to an open-vent system, a pressurized radiator is far less likely to buildup debris as a result of contaminants.

Open-vent systems often have more of an issue with debris caused by their open design. However, these non-pressurized systems typically just require a sludge removing additive to run through the entirety of the system to clear the debris. Once the sludge remover has done its job, the homeowner simply needs to drain the dirty water and refill the tank.

Are radiators dangerous? 

No! This may come as a surprise to many people, but radiator heat systems are actually incredibly safe. They may look a little daunting and archaic, but radiators do not pose much of a safety threat to their surroundings. Because they radiate heat, some types such as cast iron can get hot to the touch. However, other models such as ceramic radiators do not. No open flame means minimal risk of fire, however, it is still advised that homeowners to not drape flammable materials like drying clothes over the heating unit itself. Freestanding radiators are also surprisingly safe when compared to their space heater counterparts and even feature built-in tilt sensors that shut the system off if it falls over.

Are radiators energy efficient?

It may come as a shock to homeowners, but radiators are a surprisingly energy-efficient way to heat a home. That is if the system is properly set up and all lines are insulated. Because radiators heat a room long after the water inside has been heated, the heat is long-lasting, consistent, and comfortable. This is what makes cast-iron radiators a popular choice. Much like cast-iron cookware, a cast-iron radiator takes longer to heat up, but once it’s hot, stays hot for an extended period of time.

Can you replace an old radiator with a new one?

Many people are surprised to find out that you can still buy and install radiator systems in a new home. Though radiators are old technology that is no longer the standard option for the modern home, many people desire the function and form they offer and so they buy radiators online. One main advantage of a radiator over a forced air unit is the quiet operation. Homeowners also enjoy the added comfort of the humidity of the air and so many buy radiators online. If you are wanting to replace your old radiator, contact a HVAC Installation expert.

Written By

Hi there! My name is Matt and I write for Expert Home Report. I enjoy writing about everything related to home improvement, home tips and DIY. In my spare time, I'm either spending time with my family, doing a DIY project or learning a new skill.