No Heat in Certain Sections of System

Hello,
I have a multifamily property that gets heated by a steam boiler system.

This system is controlled by a thermostat that reads outside temperature.
For the most part the entire system works fine, except every now and then, a radiator or a section of the building will not get heated even though the rest of the system is being heated.

In this situation, I have 2 radiators being fed by the same piping that do not get any steam. I have replaced the vent valves on each rediator and still do not get any steam. I have check the main pipe in the basement feeding these radiators and it is hot leaving the basement. The entire radiator is completly cold, even if I take the vent valve out, no steam gets to this radiator.

any idea what could be the problem???

 

Is it always the same one or two radiators or does it happen to different radiators at random?

If it is always the same radiator(s) then it could be a waterlogged radiator. Put a carpenter's level on the top of the radiator and see if the radiator slopes gently (about a half a bubble on a two-foot long level) downward towards the steam inlet. If not then you need to shim the radiator legs on the air vent end to achieve this gentle slope.

It could also be a defective hand valve on the steam inlet. Do these radiators have simple hand valves or are they thermostatic valves? If hand valves they must be either fully open or fully closed, you cannot adjust the heat by having the valve partially open.

 

Thanks for your reply.

In this case, it is the same radiator. As far as steam inlet valve, it is a hand valve.

I've made sure that the valve is completely open. Also, I have disconnected the radiator from the inlet hand valve to check if the radiator is the problem.
I do not get any steam even with the radiator disconnected and the hand valve completely open. I sense no heat below the hand valve (pipe feeding steam into the hand valve).

 

You are going to have to take the radiator valve apart. Do NOT do this unless the boiler is shut down and its temperature is below 160 degrees.

I think you will find the internal parts of the radiator valve have come loose from the valve stem and are blocking the steam from getting through the valve. If the valve is okay then there is something blocking the pipe between the boiler and the radiator.

One other possibility is that the "riser" pipe has an additional valve in it somewhere that has been closed. Perhaps in a utility closet or pipe chaseway.

 

Thanks again.

I will take this valve a part and hope that is the problem!

Can you explain what you mean by "riser" pipe? As far as I can tell, there is only one pipe coming and going out of this radiator.

 

The riser is the vertical piping from the basement to the radiator. Sometimes this pipe will serve more than one radiator on additional floors above each other.