1 pipe steam system: radiators are hot despite thermostatic valves on vents

nielsbot

Hi--

We have a 4 unit building w single pipe steam heat. (8 radiators, 2 per unit). 2 (maybe 3) units have thermostatic valves installed on the radiator vents. In my unit even with the valves set to their minimum, the radiators still get decently warm. I would have expected more control over the temperature? It's an issue with both radiators. Any suggestions for what could be going on?

I lowered the boiler pressure to 1.5

Thanks so much...

Jamie Hall

Decently warm? Or steam hot? There is a real difference. The problem is that some steam will make it into the radiator even if there is essentially no venting at all. Not much -- but some. The difficulty with one pipe steam is that one really can't turn the radiator valve itself off, since the vast majority of them aren't leak tight against steam, and condensate will build inside the radiator and give other problems, so the only real control is the venting.

You could, however, try taking the vent off completely and substituting a pipe plug. You'd sacrifice control that way (it's not exactly handy -- "I'm cold! Where'd I put that wrench?") but if you really want the absolute minimum of heat from the radiator...

JUGHNE

Do you have a reliable gauge that will confirm the pressure you assume you are operating at?
A plugged pigtail will fool both your gauge and control.

nicholas bonham-carter

Or turn the vent upside down.
TRV's are essentially a band aid to give you time to balance the system, with good main venting, and low pressure, verified by a 0-3 psi gauge. Probably you could start with Big Mouth vents on each dry return, and keep adding them until the backpressure is under 2 ounces.
If your main venting is adequate, the radiators will all receive steam within a couple of minutes of each other. Use slower radiator vents such as the Hoffman 40--NBC