Any reason not to use the supply valve to fine-tune temperature in 2 pipe system?

geeklain

Hi,

I live in a big apartment building (~250 units) built in the late 50s in NYC. The heating system seems to be a 2-pipe steam system to my untrained eye. There is a supply valve on one side of the convector and a steam trap on the other side. From what I heard most everything is still the original system design from the 50s (boiler and other parts).




The super and the management have been telling the tenants to not control the temperature in their apartment by partially closing the supply valves. They tell us that the valves should be fully closed or fully open. This sounds a lot like recommendations for 1-pipe steam systems but we have a 2-pipe system.

Is there any reason why they would tell us that? how does a partially closed valve impact a 2 pipe steam system (good or bad)?

Thanks

Jamie Hall

On a two pipe system, you can use the supply valve to control the heat output from the radiator. In fact, unless I am much mistaken, that supply valve had a throttling device on it...

@Steamhead would know immediately what it was.

Gordo

That appears to be what is called either a "SWRF-B" or a "SWRF-A" valve, currently made by MEPCO, the successor company to Dunham. Not sure if you have a 3/4" or the 1/2" version.

It is indeed for a two pipe system and is indeed adjustable.

The kicker is, that it is essentially two valves in one. The plastic handle part is for on-off control, and there is another part which is only supposed to be accessible for metering adjustment via a special pin-type spanner wrench available from MEPCO at an exorbitant cost.

JohnNY

Tell your building they need a tutorial since they seem to know just enough about steam to cause a problem.
Just a suggestion.

geeklain

Thanks guys!

I'll talk to the building management. I'll see what they have to say about this.

Bonus question: would it be easy to replace those valves with TRVs?
Apart from the cost of the parts and labor, any technical reason not to upgrade? (like pressure, etc)

Jamie Hall

If you don't want to get fancy, it's permissible ( ) to set the on-off handle part way. Won't hurt anything. It's not the finest control -- tends to be pretty on or pretty off -- but it works.

The valves could be replaced with TRVs, but it would be a pretty extensive project. Depending on how the boiler is controlled, though, TRVs can result in some rather fierce short cycling.