New boiler, need new traps?

jreed

I've got a 6 month old boiler on a 2-pipe system. The old 19170's era boiler ran adequately, and we got adequate heat from all rads. But I eventually got too worried that the thing would up & die in mid-winter, so I replaced it. It's been making hot water via its coil/outboard tank combo just fine since spring. Now that we're heating, most rads get hot, but three don't. Let me lay out my theory & what I'm thinking of trying:



The system has two main branches. At the far end of one branch are three rads stacked above each other on first floor, second floor, third floor. None of these get hot, although other rads upstream on the same branch do. The supply pipe gets hot right to the rads, but not the rads themselves.



I thought the valves (Hoffman Adjustable Modulating) might be stuck/clogged, but I've disassembled & cleaned them all & they all work fine. They *were* properly adjusted for the size of each rad, but for now I have set them to full opening size in hopes of maybe getting a little flow thru them. It hasn't helped.



I've taken apart & looked at the thermostatic traps on each. I 'tested' them by blowing steam on them from one of those 'as seen on TV' steam cleaners with no visible effect. I've never replaced any of them, so they are decades old. I assume they are dead. They seem to have failed closed.



At the end of this branch (and the other one as well) is a cross-over to the return with another thermostatic trap. I assume this is dead too; it seems to be slightly open.



My first guess is that this end-of-branch vent/trap is bad, resulting in steam going up the return, resulting in trapped air & no heat.



There's more to the story, but enough for now.



Should I try:

(1) replace the end-of-branch trap

(2) replace that, and also the three rad traps above it

(3) replace all traps in the house at the same time

(4) something else?

BobC

New traps/

Let me say that I am not very familiar with 2 pipe steam, but when they changed out that boiler they probably banged the pipes pretty good. You should have a vent of some sort at the end of the dry return. All of that work on the pipes probably shook something off the inside of the pipe and may have partially clogged them. I'll bet that new boiler makes steam a lot faster than the old one did to so the vents may have to be more aggressive - just a guess.



For what it's worth I'd start at the boiler and look at air valves and any F&T traps that are closer in to where all the work was done, on the branch your having trouble with. Is there a single trap that is common to these problem radiators?Again I'm not very familiar with two pipe systems so this is just my best guess.



Bob

Jamie Hall

If...

that end of branch crossover trap is bad, it would more likely affect the whole system rather than just that one return -- but it is possible.  If it is failed open, the return where it comes in will be steam hot (best with an IR thermometer, but the eeyouch! test also works).  On the other hand, if a radiator trap is failed closed, and they do, the radiator won't heat (although it is quite possible that the steam riser to it may get hot).  Sometimes traps last for decades -- the ones in the building which I superintend have been there since 1930 -- and sometimes they don't; fortunately, replacing the innards is cheap and easy.



The steam from a steam cleaner isn't going to be hot enough to tell one way or the other.  However, if they are closed when they are cold, they aren't going to be any less closed when they are in the radiator!



So... my first inclination would be to replace the innards on those three and on the crossover trap and stop there and see how the thing works.



Bob's suggestion about vents is reasonable -- you may find that you are undervented with the new boiler.  That, however, won't make just one riser's worth of radiators quit.  So it is a separate problem; first things first.  (It's also an easy problem to fix, although much more expensive -- since you have crossover traps, the odds are that there is one main vent, near the boiler; you can replace it with one or more bigger ones without too much hassle).  But do the traps first.

jreed

further experimentation...

I let it run for a bit, long enough for the upstream rads to get hot, and the risers at the non-heating downstream three to get hot. The three rads got maybe a little bit warm, near the inlet. Hard for me to tell if that's from steam, or just conduction from the riser.



The crossover in the cellar near these three is, perhaps, working after all. Hot side hot, cold side cold, as judged by the grabbing-the-pipe test. Maybe it always has been, or maybe I knocked something loose, in a good way, when I inspected it.



Just for fun, I unscrewed the cover on the 1st floor unit's trap & took out the innards. Whooshing sound, which stopped when I blocked the hole with my finger. Bringing my face up close & unplugging the hole told me it was blowing air out, up the return pipe.



And this last part might be my imagination, but I thought at first I could feel air being blown (gently) out of the radiator, against the side of my finger, you know, as I had the hole in the bottom of the angle trap plugged. I also thought maybe the rad was starting to heat up a bit. But after several minutes, the radiator wasn't convincingly hot, so maybe it was all in my head.



I'll sleep on it...

Rod

Steam Traps

Hi - Be really careful when opening the system and testing for steam. Live steam can give you a very bad burn. Rather than using apart of your body, use a strip of newspaper hold it near the hole and watch for movement.

There are rebuild parts available for most steam traps, even the very old ones.

You might want to get an IR digital thermometer to check the steam traps. "Santa" brought me one last Christmas and it's really handy! It's a Ryobi Tek4 -Model RP 4030 available from Home Depot.

- Rod

jreed

update:

New valve innards are on order, I should have them next week. First I'll try replacing the cross-over at the end of the line that serves the three cold rads, then the traps in the rad themselves. Stand by.

turbobike

steam traps

I had a somewhat similar situation. Have an older home, and I've been here 30+ yrs, and NEVER replaced a steam trap. I wasn't really happy with the uneven heat at most of the radiators.

After reading a couple of Dan's books, I took the plunge and replaced all of the steam traps at the same time. The difference in the radiators outputs is like night & day !

So, for me, if your traps are that old, replacing them is a must, not a maybe.

jreed

Update #2

New cage units arrived. Budget didn't permit replacing all of them at once (which could be a mistake, I know, but whaddya gonna do?) so I replaced:

- end-of-line cross-over vent traps on all three supply branches (call them north, middle, and south)

- 1st and 3rd floor radiators at end of south branch. Intended to replace 2nd floor in this same 3-floor stack as well, but apparently I ordered the wrong unit.



And the results are:

Not much difference. All rads on middle branch heat fine. North branch has only two rads, and they are far away. They heat slowly, but they do heat, which is somewhat of an improvement. The three stacked rads at the end of the south branch (mentioned above) do not get hot, and their supply lines are very sluggish about getting hot. Other rads upstream on that same branch heat fine.



By "heat fine" I mean they get plenty hot, across all sections. I can't say whether they are operating exactly as intended - maybe they're heating too soon, for example - but they do get hot.



I was almost certain that the cross-over vent at the end of the south branch was the culprit, not venting & thus preventing the stack of three from getting steam. Was that a bad theory?



FYI: if I haven't mentioned it and it's not obvious, this is a two-pipe system with just the one vent to atmosphere, on the return line in the cellar near the boiler.

jreed

Would this be a stupid and/or dangerous test?

My theory is that the three stacked radiators on the end of the south branch are not venting well enough, even though the cross over vent at the end of that branch is new and therefore assumed to be OK.



What if I uncapped the trap on the third floor rad temporarily and took out the cage unit, leaving the trap wide open? That would serve as a vent for that stack, wouldn't it? Assuming that the cross-over is working, I would not get steam crossing over & backing up the return line, it seems to me. If I then fired up the boiler and the 3rd floor rad got hot (eventually sending steam out the radiator and into the uncapped trap, I suppose, which would mean it's time to shut off the boiler) it would suggest that I need additional venting on that stack.



Am I way off on the theory of operation here? Or is this just too stupid to try?



< Re-reading this, it does sound kind of stupid, but I'll leave it up for comment anyway. Not ashamed to be wrong, if I can get educated in the process.>

Jamie Hall

No, not stupid

potentially dangerous, though.  It would serve to find out if something about that stacked riser is the problem (is there any way you can put a vent on the top of that riser?).



Thing is, what you want to find out is if air comes out of the open trap, and if steam then rises normally in the riser.  That's great.  What you also want, though, is to shut the thing off before steam comes out of the open trap.  First place, live steam really really burns.  Second, if you do get steam coming out, it will do a nifty job of taking off the wallpaper, sogging up the wallboard, etc.



So... if you do do this, I'd suggest a before and after test: find out how long, if ever, it takes for stearm to reach the valve on the top radiator with the system as is.  Then take the trap apart as you suggest, and time it again.  If there is a substantial difference, then you at least know you need more venting on that riser, or the traps are bad, etc.  Otherwise, you've at least eliminated one more variable...

jreed

Update #3

Reps from the installer, the distributor, and Burnham took a look at the system this morning. Burnham rep has diagnosed the problem as incorrect near-boiler piping, leading to wet steam, leading to (I think he said) water in long horizontal runs cooling the steam before it could get to the rads, leading to poor heat distribution, and serious banging in one pipe. Also, dirty but not utterly filthy boiler water.



So, a tech will be back tomorrow to repipe & skim. The wise men all say that near-boiler piping can be critical, so we'll see if this fixes things.

jreed

Success!

It's been three weeks now, and all is well. Now I'm looking forward to collecting enough billing/usage data to see whether the new unit is significantly more efficient than the old one.



So, you've heard it before, but here's more evidence: doing the piping the way the mfr says is critical!