Alright, I need some sleep...

Steam_Starter

I am dog tired from last two nights! Being woken up by rad in B/R hiss, then clang, then quiet...3 mins later; hiss, then clang, then quiet.  The hissing goes on for about 8 secs then stops.  As the system heats the hissing period gets smaller and then stops. 



All of the rads in the house get fully hot, gentle hiss, no issues. 



Focusing on my BR rad, it is pitched properly to the valve, the valve is fully open so I thought it was a venting issue.  I vented my main with everything I have on an antler: 1 x hoffman 75, 3 x gorton #1, 3 x gorton #2.  The main is about 45 feet long x 2.5 inches including risers and headers.  Vent antler is on a 3/4" riser 5" long at end of main (just after riser(s) for second floor.)  I really have no more room in the bsmt ceiling bay for more vents. 



I changed out the vent on this rad to others that I have and they all do the same thing.  Hiss, clang, stop.  A minute later, hiss, clang stop.



PT is set to 1.5 out / .5 in.  Accurate 3 PSI gauge.



I am wondering if I still need more venting as air from the main is still being forced out of the rad?



Thoughts from the pros?

nicholas bonham-carter

Sudden water-hammer

Was everything quiet last season? Can you watch the gauge for the whole cycle, and see if there is a spike in pressure, coinciding with the hammering? While the mains are venting, the back-pressure should be very low-is that the case? The pigtail could be clogged so that your actual cut out pressure is much higher than you think. A gauge on the radiator would show you the true pressure, and give you something to look at when you are rudely awoken! It could be put on a tee between radiator and vent.

Could the antler be pitched down instead of up, so that it collects enough water to impede the venting?--NBC

Steam_Starter

Hmmm....

NBC,



So many questions; so much to think about!  One by one...



Was everything quiet last season?



It really started at end of season; that's why I went crazy with venting...



Can you watch the gauge for the whole

cycle, and see if there is a spike in pressure, coinciding with the

hammering?



I can do that, good idea...just drop a cellphone near the rad and listen in on my wifes phone while I am in bsmt...(Yes, its that loud!)



While the mains are venting, the back-pressure should be very

low-is that the case?

Yes, BP barely registers on gauge till antler gets hot; first thing I checked...



The pigtail could be clogged so that your actual

cut out pressure is much higher than you think. A gauge on the radiator

would show you the true pressure, and give you something to look at when

you are rudely awoken! It could be put on a tee between radiator and

vent.



Awesome idea....I'm going to do that and see what I come up with. (But why would it only be on one rad balking?  The take offs for this rad and the one in my sons room are within 8" of each other...)





Could the antler be pitched down instead of up, so that it collects enough water to impede the venting?



Looks like antler is pitched proper way...checked with torpedo level (and as per other thread here I flipped it to confirm level was dead on...)

Steam_Starter

Oops....

One more thing...



The clang on the rad really sounds mechanical....like the vent is slamming shut after opening.



Pressure check on rad should tell me more...



JLG

Big-Al_2

Oversized Boiler

I had the same problem for years.  I added lots of main venting.  It didn't help much.  The radiator vents wouldn't make noise until after the main vents closed anyway.  Even the biggest main vents vents flow exactly  the same amount of air as smaller ones once they are closed.  Zero.



I switched over the upstairs (bedroom floor) ones to bimetal radiator vents instead of the alcohol-filled snap-action style.   (I prefer Maid-O-Mist, but the Gorton units are similar.) That helped quite a bit. They were fairly quiet. They would still open and close a bit, but at least they didn't clang shut.  The alcohol filled ones (i.e. Hoffman 40) are actually designed to clang shut.



The biggest problem seemed to be an oversized boiler that would build steam too quickly.  It doesn't take much pressure for radiator vents to hiss, so lowering your pressure limit switch may not do too much either.  Last year I swapped out the orifices in my burner to reduce the output by 10%, and I added a radiator.  That helped quite a bit.   This year I replaced the boiler with a smaller (correct sized) one.  Now my vents are virtually  silent.  The radiators all fill with steam more gradually and the vents don't have to open and close repeatedly because the steam doesnt get ahead of the air anymore.  Unless I'm coming off of a deep setback, the thermostat is often satisfied before all the radiators are completely hot, so many of the radiator vents don't even have to close.   (If I let the boiler run long enough, it eventually builds pressure, but that doesn't happen on normal cycles anymore.)  

Steam_Starter

Big Al....makes big sense!

Now that you mention it, the boiler is oversized by about 15% based on my EDR (man, I learned a lot on this site!)



And now that you mention it, that's EXACTLY what is happening....the rad doesn't start clanging until AFTER the main vents are closed.



Since there is nothing I can do right now re: swap out of boiler, I am going to try the non-alcohol rad vent route!



Thanks!  Keep you posted...

Rod

Vent Tester

Hi- What size are you radiator vents?  You may want to try a slower vent. Attached is a picture of the system I use to test radiator vent operation. It also allows me to test how the radiator will operate:

1. With no vent.- Tests how a large capacity vent will perform.

2, Using a large orifice vent you can use the ball valve to throttle it down to see if a slower vent will work better /be quieter.

3. To check the main vent operation (though I like Crash's gauge on the "antler" setup better for testing main vents) you will generally see a pressure spike when the main vents close.

- Rod

Steam_Starter

Common sense dictates....

Well came home tonight and tore into the rad...changed the air valve to maid-o-mist and surprisingly I found condensate in the hoffman I took off..a lot of it.  Looks like it was full.



Checked the pitch of the rad again and it was 1/4 of a bubble on target slope to the valve.  Used the two quarters I had in my pocket and gave it a little more pitch just for sake of good order.  Too warm now to fire up boiler.  I will hit the thread when it chills out and advise where I stand.



Question:  should there be condensate in the air valve?



JLG

Steam_Starter

No bustin' Z's....

Well that did it!



Just a moderate hissing out of the rad when I adjusted pitch and changed to Maid-o-Mist.



Silence.....and sleep.



Thanks to all for the advice.



JLG

Big-Al_2

Fantastic!

That's great!  I'm glad to hear it.



I've got a different problem now that I changed out the boiler.  My wife just told me that she always thought that the sound of the vents hissing and closing was reassuring and old fashioned.  She misses the steam system sounds she had gotten used to and she wants them back.  Oh well. No good deed goes unpunished, eh?  The old boiler has already hit the scrap yard. She'll adapt.  Eventually.  I hope . . . .

Steam_Starter

Big Al...

I can relate to her...the sound is soothing as long as it doesn't sound like someone whacking the rad with a screwdriver!  (Especially soothing with a NE blow of 30-40 mph and snow drifts outside in the 10 degree weather!)



Thanks again...

crash2009

Antler Gauge

This one is installed and operating full time.  The vaporstat is set to shut down the boiler at 8 ounces.  This gauge never sees more than that.  Most of the time, it reads what you see here, 1.5 ounces.

Big-Al_2

Not mine.

Hmmm.  My alcohol-filled vents didn't sound like that . . . more like a coffee can getting shot with a BB gun. Maybe I had a different brand. :-)