Steam Vapor System

scottstp77

Here is the situation.  Installed a new boiler for custumer in winter of '07.  This was a 1912 two pipe steam vapor system.  Started as coal, then oil, then natural.  The original boiler was a spectacular looking round boiler with chrome trim everywhere!  Honeywell controls.  System is two pipe with no steam straps.  There were vents on the steam mains where they left the header and out to the system.  We installed a new boiler and repiped the near boiler piping to manufacturers instructions.  Added steam traps to the radiators and replaced all radiator air vents.  Pressuretrol is set as low as possible.  As you might have guessed, the system is banging away! Will changing out the pressuretrol to a vapor stat be sufficient?  Please help.

Jamie Hall

It certainly won't hurt

You don't say what kind of vapour system you are dealing with -- except that it doesn't use traps.  It really doesn't matter -- all of those systems were designed to run on very very low pressure -- typically no more than 6 to 8 ounces per square inch.  Anything over that, and you will get steam passing through some of the radiators.  So for starters, a vapourstat would be a good place to start.



Whether that does it for the banging is another question.  If the banging is right at the beginning of a cycle, it may not, as that is almost always condensate (or wet steam) carrying into the mains and runouts, and getting shoved around.  For that you will want to check that all the mains and runouts -- to the extent possible -- are insulated, and particularly that nothing has sagged.  It does happen.



On the other hand, if it is later in the cycle, lowering the pressure may help a lot, as the banging may be due to condensate rising too high in the returns (boiler pressure pushing it back out, effectively) and again getting caught somewhere and getting pushed around.



One step at a time...

Dave in QCA

Some additional thoughts

I agree with everything that Jamie has said, but have some additional comments and questions.



You say that there were no steam traps on the radiators, but you put new ones in.  What was there before?  Was it a valve? If a valve, what did it look like? A fitting with an orifice? 

You also say that you replaced all of the radiator vents.  Usually, actually always, you don't use vents with a 2 pipe system with traps.  How is the return piping from the radiators connected back to the system in the basement?   Is there a dry return piping system from the radiators?  Is it vented?  Or, is it simply a return line that drops to a wet return line?

Pictures would be of great help here.  Lots of them, all of the various connections listed above.

I suspect you may have created problems by installing traps where they don't belong.  You could be working with an old Moline Vacuum system.  They used valves on the outlet, and the had key fittings on them.  It also could be a simple 2 pipe, without traps, system.  Steam comes in through the inlet, air is vented through the rad vent, and condensate drops through a separate, non vented line to a wet return line in the basement. 

Dave in QCA

Welcome to Heating Help.com

I was getting ready to chastise you for not getting advice from here before you did the work on the system.  However, I see that you just joined today.  Welcome!

I am going to strongly recommend that you purchase and thoroughly read the publications available, particularly, "The Lost Art of Steam Heating"  It does a great job of explaining (with pictures) just about every type of steam or vapor system ever installed.  I bought my set about 6 months ago, and I still constantly refer back to them. 

Here is a link to a combo discount deal.  http://www.heatinghelp.com/products/Super-Deals/14/129/A-Steamy-Deal

Jamie Hall

That's what I get for being in a hurry...

I missed the bit where you said you'd added traps to the radiator outlets, and replaced the vents on the radiators.  There shouldn't be vents on the radiators -- they'll be nothing but trouble.  That is, if it really was a vapour system, which, in 1912 it almost certainly was (20 years earlier it might have been somethng else, but not in 1912).  After you do the pressure bit, the next thing I'd try -- the very next thing -- would be to at least turn all the radiator vents upside down so they can't function.



Are there main vents on the system?  You don't say, but they certainly should be there somewhere.



The steam traps on the radiators may not hurt anything, although if the pressures are right they won't help anything either -- they shouldn't be needed, unless someone has knuckleheaded the supply valves.

scottstp77

Steam vapor system clarifications

Thanks for all of your replies.  I spent some time today on the site with a service technician and I now have some clarification to do.  First is that this is a two pipe system.  When I first saw the project, there were air vents on the radiators, angle valves on the steam supply, and nothing on the return side of the radiator.  Just gravity back to the boiler.  The steam main pitches up to the end of the steam supply runs in the basement, all pitching back to the boiler, so no end of the main drip or anything like that.  On the return lines close to the boiler there are Hoffman #4 air vents.  The radiator vents were in rough shape so we replaced them the day we installed the boiler.  They are Hoffman 1A type.  So we installed this new boiler and during the first week or so of operation, we were struggling with water hammer.  My installer who had more experience with residential steam systems than any of us in the office, thought we should add steam traps because he thought that steam was passing through the radiators and getting into the return.  So we added the traps.  The noise seem to subside.  As part of taking out the old boiler, we had an abatement contractor clean all of the insulation off the piping as it was also in very tough shape.  Consequently, the mains were now uninsulated which we thought may be exacerbating our noise problem.  So now, all of the steam mains are re-insulated.  This homeowner also travels for extended periods of time and wanted to have an auto fill device installed.  So this installation is using a MM LWCO / Autofeeder combo. 

 Today we found that the water level was at the very top of the sight glass.  We dismantled the LWCO / Feeder and cleaned it, cleaned out the pig tail for the pressuretrol, closed the ball valve to the water feeder, and tested the system operation.  What we found was that with the ball valve to the autofeeder closed, the boiler would shut down several times on low water.  We added water very slowly until the boiler would re-start.  after finding what seemed to be the correct water level, one that did not kick in the LWCO but also one that would not flood the boiler when it shut down, we marked the gauge glass and left the autofeeder valved off.  We tested operation through several more cycles and everything seemed to work great.  No noise in the system at all.  All radiators heating. 

The problem is that the homeowner would like to have the autofeeder operational.  Again, with the autofeeder operational, the boiler is not getting condensate back fast enough and is going out on LWCO.  The feeder kicks in, and finally condensate comes back and before long, the boiler is flooded and water is getting up into steam mains creating the banging noise (or so we think!).  The Weil McLain installation manual talks about doing a timing test on the condensate return to see if a reservoir pipe is needed.  We have not done this, but intend to go back and do this test. 

We did not change out the pressuretrol today.  That seem to be working just fine.  Thoughts?

scottstp77

Publications!

Thanks, I will be sure to buy these tomorrow.  One set for the office and one for home!  We are a full service design build contractor with an annual sales in excess of thirty million dollars.  Three professional mechanical engineers on staff, but no one really knows anything about residential steam!  I come from the Boston area so I have been around the stuff, but not from a service or troubleshooting perspective.  I wish we had a few of the dead men still around!  Thanks for the advice.

Gordo

It May Help

if you remove the MM water feeder and install a Hydrolevel water feeder.  You can set a delay on the feeder from 30 sec to 10 min. and set how much it will feed per call from the LWCO.  It also keeps tract of how many times it feeds as a big plus.

scottstp77

Hydrolevel VXT

Excellent, thanks.  Based on what was happening today this would be very helpful. 

Jamie Hall

Slow returns

can be a nuisance.  That Hydrolevel VXT should take care of that problem very nicely.



You may find that when you are able to lower the pressure, part of the apparent slow return problem will go away.  I would still be inclined to change out to a vapourstat -- for two reasons.  I personally think they are somewhat more reliable at low pressures, even if you can reach the pressures you want with a pressuretrol (and as I noted earlier, that system probably should run on 8 ounces cutout -- which you can't possibly reach with a pressuretrol) and also the system may work better at the pressures it was designed for...



I'm still concerned about the vents on the radiators -- although my overall philosophy is that if it's working, don't fix it -- so if it's quiet, I'd say to leave it be.  With them in place you probably have adequate venting overall, although the response time may not be as even as it would be were they not there and you relied only on the main vents.  How is the balance between the radiators?  That would be my other concern -- that the close radiators might heat much faster, and much more completely, as they would be effectively stealing steam from the main through their vents...  But if it's ok, leave it be!