Contact Info
When working properly, your boiler’s radiators should be uniform to the touch at every point. From top to bottom, left to right, there is generally the same temperature. Though heat is lost from the water to keep your rooms warm, it doesn’t have that level of effect to keep different parts of the radiator at different temperatures. If you notice the top is colder than the bottom or the bottom is colder than the top, there is an issue to sort out. The likely cause is trapped air. But fortunately, there is another solution to fix this issue than boiler replacement. And in this post, we will be putting together all the information about this particular issue.
It will educate you on why your radiator is cold at the top and warm at the bottom. It will also help you fix this issue immediately.
Boiler radiators are metal fixtures that receive warm water from the central boiler and warm the home by distributing heat throughout the home evenly. It features fins or hollow columns that maximize the surface area and release the heat effectively. The working mechanism of a boiler is pretty straightforward. The system uses fuel or electricity to turn water into steam. This steam then flows into the metal pipes distributed throughout the entire building, reaching every room. The heat from the steam is transferred to the surroundings as it flows. The cold water, after releasing all its heat to the surroundings, returns to the boiler, where it is heated again to make the rooms warm again. This cycle continues until you turn the boiler off.
This is the question we often hear in Pennsylvania. Many homeowners are not aware if their radiator temperature is not even. Here is how you can confirm it.
The simple DIY test is a touch test. Turn the boiler on and keep it running for 15 to 20 minutes. After that, touch the radiator at the bottom and then at the top. If you notice that the bottom is warmer than the top, the problem is confirmed. Putting your palm on the warmer radiator metal is sometimes risky, as it can lead to skin burn issues. This is where we recommend putting a wet cloth near the bottom and then near the top. If the bottom makes the cloth dry but the top fails to remove its moisture, the issue is confirmed. When the boiler has just started, the heat might be only at the bottom end and still climbing toward the top, so you may notice the top is colder. This is why we always recommend testing after the boiler has been working for at least 15 to 20 minutes.
The most common cause of a radiator that is cold at the top and hot at the bottom is trapped air. The bubbles add air to the water stream. Once entered, this air moves upward as it is 900 times lighter than the water. The water stays toward the lower end; the air stays toward the top end. As the water is warm, the bottom region feels hot to the touch. As the air is not as warm as the water, it feels colder to the touch or fails to dry the wet clothes.
The solution is pretty straightforward but requires a careful approach. You have to release that trapped air. First, turn the system off and wait for 20 to 30 minutes so the water inside gets cold. Now, find the bleed valve. It is a tiny valve, usually sitting near the end of the radiator. In many cases, this valve needs an opening key, but sometimes you can open it with a screwdriver as well. Pick the opening key or screwdriver, depending on the requirements, and turn the valve slightly in the clockwise direction until you hear the hissing sound. This is a good sound for you, as it shows the trapped air is being released outside. As the air moves outside, the water behind moves into that place, climbing upward. Be close to the valve; once you notice water coming out, close the valve immediately. This is all you need to do.
Turn the boiler on, wait for 20 minutes, and check if both ends are equally warm now.
Lehigh HVAC has been serving Pennsylvania with expert boiler repair services for 11 years. We fix almost all makes and models, from minor repairs to bigger replacement projects. Contact us at 484-961-7044 for service bookings.
