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Riser is getting hot but rad is not.....would venting the riser solve this problem?

Esteamed experts,

I have a second floor radiator that is located exactly 2 floors above the boiler, the riser is the very first branch coming off the main (about 2 feet in from start of main).... it is a 1 inch riser about 12 feet in length...

The riser is heating up fast, but the radiator only heats up the first fin, until all the other radiators in the house are completely hot and have closed their vents, only then does it heat up completely....which most of the time means that the thermostat has already shut down the boiler...

The supply valve is working fine, piping and radiator are pitched correctly, radiator is not clogged and currently has a size D on it...(all checked out by a professional).

All other radiators on the 1st floor have either size 4 or 5 vents and all radiators on the 2nd floor have D vents...and they all heat up evenly around the same time

What is bugging me is that the riser is getting hot fast, but not the radiator....would adding a vent to the riser make a difference in this case?

Thanks !


    ALIGA Member Posts: 194
    edited December 2013
    Have u tried

    Removing the valve, and seeing if it heats up?
  • earhere
    earhere Member Posts: 7

    Still heats up very slowly though without a vent.
  • BobC
    BobC Member Posts: 5,473
    Steam can be finicky

    How slow does that valve inlet get hot compared to the other second floor valve inlets? Has this radiator always been like this? Are you sure the valve on this radiator is a steam valve, it it different than the other radiator valves?

    The D is an aggressive valve, maybe using a slower vent on the other second floor radiators would encourage this bad boy to behave. Since the boiler is cycling on pressure it seems you have the capacity it sounds like it's a matter of balance.

    Also be sure to check the takeoff from the main with a level for good slope.

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • earhere
    earhere Member Posts: 7

    Valve inlet gets warm at the same time as all the other radiators. Not sure if it always behaved badly as this is my first winter in this house. And yes, it's the same supply valve as all the others.

    I should also mention that when the radiator finally heats up completely, it sound like a lot of condensation is taking place, sounds like the inside is being washed with a water hose....but no water hammer.
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