What Could Be Causing Radiator to Expel Less Heat?

Answered by Brett ~ September 28, 2011 ~ No Comments

My home has three floors, each with it's own radiator. However, the third floor doesn't seem to get all the heat that the first two floors do. Why is this happening?

Larysa D. ~ Boise, ID

Brett Kulina

Larysa, one possible reason why the radiator on your home's top floor is not heating up could be that the system's pressure valve is set too low, which would inhibit the hot water from reaching the upper most radiator. Many pressure valves are factory set at around 12 psi, but oftentimes that setting it is too low for homes with more than two levels. Increasing the pressure within your home's heat system to around 18 psi may be a possible solution to your problem.

Another common problem that can cause a cold radiator is air trapped within the radiator coils. The air is created by the constant heating and cooling of the water in the system, and when the air bubbles come together they can create a cold spot (air does not conduct heat as well as water). The simple fix for this problem is to bleed the radiator system, which releases the trapped air. Most radiators have a bleed valve that is opened with a bleed key, and once opened you can actually hear the air escaping out of the valve. After all the air is released from the bleed valve, water will start to flow out, which is the indicator that the system has been fully purged. Do not bleed your home's radiator when the water in the system is hot!

If your home's heat system is older, but has been upgraded with the addition of a water circulation pump, then there is a chance that your upper most radiator has a flow restrictor in its supply valve, which might need to be removed. These flow restrictors were sometimes installed in a home's upper most radiator when the system relied on gravity and heat to circulate the hot water. Because hot water immediately rises to the highest point in a closed system, restricting the water flow to the upper most radiator prevents it from getting too hot. When a circulation pump is added to an older heat system, then there is no need for the restrictor valve, because the pump now evenly distributes the hot water throughout the entire system.

An annual maintenance inspection of your home's heat system is probably not a bad idea, as an HVAC contractor can usually trouble shoot these types of problems rather quickly. With winter on its way, you want your home's heat system running efficiently as possible.

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