Hot pipes in the city - temperature and noise of the condensate line of a two-pipe steam system

fmdsf

A pipe that once was hot, is no longer hot.

A noise once in the air, is no longer there.

I live in an older San Francisco high-rise building. A large boiler in the basement provides steam heat via a two-pipe steam system. The heating system is generally very quiet. It wasn’t until I had my condo remodeled that I began to hear radiator pipe noise.

In an attempt to reduce the radiator pipe noise, the building plumber made adjustments to the building’s boiler. I believe that he lowered the pressure.

With the new boiler settings, the radiator pipe noise has been much reduced. I’ve noticed, however, that a building pipe that used to get hot, no longer gets hot. This pipe runs vertically through the building. I have access to the pipe because the wall in my condo has been opened up as a result of noise investigations that my contractor has done. I think that the pipe is a condensate line.

I’m wondering, now, should the pipe be hot or should it not? It once was hot (before the boiler was adjusted). If it should not be hot, why was it once hot? If it should be hot, why, now (after the boiler was adjusted), is it not?

I’m concerned that the radiator pipe noise may be associated with this pipe’s temperature, and that the noise could return if the pipe’s temperature, once again, becomes elevated.

Are there any ideas from the community?

JUGHNE

Could you post pictures of the inlet valves and the outlet devices on the end of your radiators? Close ups to read any labeling and then far away to include both ends.

fmdsf

Jughne, I will post the photos that you've requested, but, before doing that, I'm posting a photo of the pipe to which I referred. It's about 2" in diameter and runs vertically in the wall of my condo.

Regarding the radiators in my unit, they are not the original cast iron versions. They have been replaced with more modern radiators and are under thermostatic control. The inlet valves are made by Danfoss. See attached photos of inlet valve and trap.

By the way, regarding "noise" from the radiators, I recall hearing only short-term noise when there are initially turning on or after they have turned off.

Do you have any ideas about the questions I originally asked about the pipe?

Jamie Hall

Mind you, this is a guess. But the guess is that the pipe in question is a return, and that is was hot -- which it really shouldn't have been, if it is a return (warm perhaps, hot no) because one or more traps on it were being bypassed or had partly failed. And that lowering the pressure means that that isn't happening any more.

But, as I say, that's a guess.

JUGHNE

I would second Jamie's idea. They must have lowered the steam pressure which kept excess steam from blowing thru someone's failed traps above you. Your trap is on the right hand end of the convector pictured above. It should only pass air and warm condensate into the return pipes......but stop steam from going thru.
As for noise your convectors may have "tinged" and "pinged" as they heat up and cool off. The hot vertical condensate pipe would move thru expansion and possibly be rubbing where the pipe passes thru the holes in floor and/or ceiling. The renovation could have wedged a floor plate or such tight to the pipe and caused the rubbing.
It would be interesting to know what the pressure was previously. The mantra here is that lower is always better as far as steam pressure goes.
There is a maximum pressure that your new radiator valve can handle. Is the entire building equipped with these TRV's?

fmdsf

> Is the entire building equipped with these TRV's?

I expect a good bit of variability as to what is used throughout the building. Some condos have recently remodeled, some have not been remodeled in decades.

I'll see whether I can find out about the actual before/after settings for the boiler. What would be considered high pressure, though, and what would be considered low pressure?

By the way, thanks for the input/discussion thus far.

JUGHNE

The controlling device for pressure may go up to 9PSI and may be adjusted down only to 2PSI. Lower is almost always better .

If some units have not been worked on for years then there are radiator traps that would be suspects for passing the steam that might be causing the overheated return line. Neighbors with bad traps can wreck the new traps of others. "Good traps make for good neighbors" (also applies to fences in ranchland).

Jamie Hall

A more exact answer on pressure: the cutoff pressure for the boiler should definitely not be over 2 psi for most heating systems (there are some exceptions, but I doubt that you have any of them). Anything much over that can cause quite a variety of interesting problems, some of which are not at all obvious. Consider: even the Empire State Building runs on less pressure than that!

fmdsf

Okay, I got some photos of before/after settings for the boiler . See the attached images, and note the descriptive file names.

Comments?

JUGHNE

The left one is the main operating control it is set as low as possible, I have had the mechanism fall apart inside to where it would not turn on.

The middle one is the high limit. It has a manual reset lever on the top which if opens is meant to get your attention. (no heat....something needs attention by a pro.)

The right one is either a two stage or burner modulation control. I have one on a system that I need to investigate further. Maybe someone here could give us all a review.
We would need more pictures of the burner and from far back of all piping abound boiler.

fmdsf

I got another photo ... see attached.

By the way, with respect to the following earlier comment:

"Neighbors with bad traps can wreck the new traps of others. "

What's the mechanism? How does it happen?

Thanks.

nicholas bonham-carter

A malfunctioning trap can let steam out into the returns, and cause other neighboring traps to close prematurely, upsetting the balance of the system.
There may be additional traps called crossovers, which should be checked as well, as they too can upset the system if they are not working.
None of these repairs are so expensive as to be worth ignoring, when fuel costs and comfort levels are taken into account.
That system should operate with mere ounces of pressure, controlled by vaporstats, and verified by a 0-15 ounce gauge.--NBC