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.

ariccio

Oh lord where do building management get their ideas? 

I love my super. He's a great guy and a good friend. But sometimes he perplexes me.

Among several reasons, he's said that the inlet valves on the radiators in our building (they're labeled Dunham) shouldn't be open partway, because (variously) they aren't designed to hold back pressure and that closing them part way could result in more banging.

Of course, they only change steam traps on cold radiators, so the system is wildly out of balance, with most never changed in people's entire lifetimes. Since some people are so overheated, people then shut the valves all the way off. Which, when a significant portion of the building shuts their steam inlet valves, probably worsens pressure problems.

Now that the building is replacing the 1960s boiler with a fancy new one, we're on a mobile boiler in the mean time. People are really friggin warm. One of my radiators got up to 235°F and started leaking steam. I think that means they're up to at least 5psi steam, if I understand the charts correctly.
Apparently other people are having problems with leaks. The faster firing boiler *probably* is amplifying all the problems if not entirely responsible.


I told them all of this could happen if we simply went to replace the "bad" old boiler without even considering addressing the steam traps, but nope, nobody listened, and I'm a bit embarrassed to say I find this affair kinda funny. But I'm too polite and like them too much to point and laugh and say "I told ya so!"

bburd

That mobile boiler is almost certainly set for a pressure much higher than it should be. Two psi should be the maximum for that type of system.

ChicagoCooperator

My mother lives in a mid/late 20's building and their fancy mechanical consulting, well, consultant, company (they may have done the boiler replacement design) told the board to tell Shareholders that they should only use the valves on their two pipe system (strangely, a lot of people had 'upgraded' their radiators to convectors, probably in the 50's and 60's to make their units more modern looking) for on and off rather than modulation. I rolled my eyes at that - the perfect example would be a brutally cold sunny day with a north wind - the south half of some units would be boiling, the north half of those units would be chilly w/o heat and the north wing cold - the whole point of two-pipe is adjustability. Their excuse, I mean reasoning, was balance or pressure....

My mother being elderly likes it warmer as did my father - they replaced most of their convectors with CI radiation and always keep the living room radiator off and don't have a bedroom radiator and she's never been cold in those rooms.

KC_Jones

I'm wondering how they sized the new boiler? I'd speculate it's oversized based on everything the OP is stating management is doing. And after the pretty new boiler, oversized, is installed and things still don't work, I wonder how the contractor then proposes to fix it?

Brace yourself for "its steam, it's old, that's how it is" which, BTW, is complete crap.