If you have cast iron radiators that heat your home what is wrong with some of the upstairs radiators if they get half hot and some don't get hot at all?

Answer 1

Answer

There might be air trapped in the radiator, try bleeding.

It's usually a flow problem. If the valves on all of the radiators are wide open, the steam will flow through the path of least resistance, often leaving some of the radiators lacking for heat. Try turning down the flow on some of the hotter radiators. You will need to spend a little time adjusting the flow... assuming that you have flow adjusting valves on the radiators. These old cast iron radiators have sections that are bolted together. Each section has a gasket to keep the steam or hot water INSIDE the radiator. Of course these old radiators collect rust over the years unless you are very careful and scientific about your water chemistry (most folks are not). You probably have a plugged hole in one of the gaskets between the section of the radiator that is getting hot and the section that is not getting hot. This "cold" section is being bypassed and not receiving any flow.