Air venting question

HenryT

It seems that the verdict is to vent your main FAST and your radiators SLOW.

If this is true, and we are putting a small vent (gordon 6) on a huge radiator, is hissing normal?

If i have adequate main venting (just assuming) and i was told to vent by big radiator slow (b/c it is in same room of t-stat and set back of 3 degrees cause hammer in radiator due to fast venting), is hissing normal?

THanks!!

BobC

vent hissing

Did installing the Gorton #6 stop the banging?



Some hissing is normal, that is the air being released from the vent. It will be released over a longer time because the venting rate is slow. That large radiator should now come up to temperature slower.



Bob

Big-Al_2

Maybe

If your boiler is oversized, like mine is, then no matter what you do, at least a couple of the radiator vents will hiss.  With an ideally sized boiler, pressure will build so slowly that the radiator vents will be very quiet until all the air is vented.  If your boiler is a little big, then no matter how well you have things vented, the pressure will build fast enough that last radiator vents to close are going to be venting quickly enough to hiss.  Setting your pressure limit switch low will only help to a point.  Even a few ounces of pressure will produce an audible hiss from most radiator vents. 

HenryT

Thanks all

Big Al. so you currently cycle on pressure? my unit shuts on and off like 30 times before i reach my t-stat temp.  im talking if i raise the t-stat by 3-4 degrees, the unit constantly shuts on and off...

BobC

Typical cycle

My boiler is oversized by at least two to one, but it works to well to put out to pasture (14 years old). I am running it at low pressure and have downfired it about as far as I can and it still cycles on and off about 6-10 times before satisfying thermostat.



The attached PDF shows a typical cycle from last winter. At that time I was running it at 16oz and it had a 1.25 nozzle in the oil burner.



Bob

Big-Al_2

I'm not sure anymore

As empty nesters, three years ago my wife and I bought a hulking wreck of what once was a stately old house.  It came with dangerous wiring, non-working plumbing, crumbling plaster, threadbare carpets, cracked windows, a leaking roof, missing radiators . . . and all sorts of other old house charm.  On the good side, It was priced right, is in a wonderful location, and it came with a recently replaced steam boiler. . . albeit oversized.   Now I have plenty to keep me busy in my spare time.  Plaster dust is good for you, right? 



Coming up from a 7 degree setback, my boiler used to cycle dozens of times before the T-Stat was satisfied.  That was with a 144,000 BTU output boiler hooked to about 60,000 BTU of radiation.  Even after adding an antler of Hoffman 75's on the main, the radiator vents made quite a racket.  Since we bought the house, I've added three radiators, downfired the boiler by 10%, and lately stopped setting back the stat so cold at night.  I haven't actually re-calculated where I'm at, boiler vs. load, but the vents are quite a bit quieter this year.  I still have four upstairs rooms without radiators, so if I ever figure out where to route the piping, I may eventually be able to add enough radiation to balance out the system.

rcrit

twin house?

Your house sounds a twin of mine. When I moved in the second floor windows were all held open by Tinkertoy rods because none of them operated properly. I made a nice mobile with all the parts I found.



Your situation reminds me of a question I've often had. At my old house I had hot water heat which was fine for the most part. When I added a 400 sq ft addition with radiant flooring heat my existing boiler was sufficient (and I even had a mixing valve to add cold water to keep the radiant zone temps around 110). Now who knows, maybe it was severely over-sized in the first place, I now know way more about steam than I ever did about hot water.



So what does a steam homeowner do if they add an addition. Is it typical to have to budget another few thousand bucks to replace the boiler to meet the demand when adding onto the house? I suppose it would affect any homeowner whether they have furnace or boiler, perhaps I just lucked out.

nicholas bonham-carter

is hissing normal?

yet another of life's imponderable questions, such as the activities of bears in the woods, water-tightness of  crab digestive tracts under water, etc.

when you vent your mains adequately, there should be no hissing from the radiator vents. this applies to the shutdown part of the cycle, where air is sucked back into the system as well as during firing where air is being let out. if i heard hissing, or whistling, i would check my gorton #2's-all 18 of them on 6 dry returns feeding from 55 radiators!

i would also check my pressure. right now my air has been let out at the point where it has reached 2 oz.--nbc

Big-Al_2

Not Necessarily

NBC: Saying that adequate main venting will cure noisy radiator vents will only frustrate people who are already stuck with oversized boilers.  Obviously, inadequate main vents would force more air out of the radiator vents, but beyond a certain point, main venting alone won't compensate for an oversized boiler.  On the advice of people on this forum I wasted hundreds of dollars on extra main vents that didn't do squat.  I finally realized that my radiator vents are silent until well after the main vents close anyway, so the system is beyond the point where adding more main venting will make a bit of difference.  In fact, most of my radiator vents are quiet until time the system is about 3/4 full of steam. By then the boiler is making steam so much faster that the radiators can condense it that pressure starts building, and the radiator vents start to vent audibly.  Sure, I could put a Vaporstat on my boiler and turn the boiler pressure down, but since it's on/off and not a modulating unit, it would just make the short cycling worse.  The only way I'm going to silence my vents is with a smaller boiler or a bigger load.



As far as the whistling during shutdown . . . unless you have a really sensitive vacuum breaker in the boiler room, whatever vent cools off and opens first is going to make the  noise, and that's probably going to be on the coldest radiator.

BobC

Hiss

Your system must be like mine. Ive got a 14 year old Burnham v75 that's rated for 596 sq ft of steam feeding 200 sq ft of EDR. The boiler cuts out at 10 oz and back in at 4 oz and I'm firing at 1.1 vs the 1.35 gal per hour that the boiler is rated for - I'll probably reduce that to 1.0 gal per hour. The pipes are insulated and the main vents in less than two minutes.



Besides saddled with an over sizedboiler my main is only 10 feet long. It circles the chimney and seven 12 to 22 ft leaders go off to feed the radiators. My setback is 3-4 degrees. The Hoffman 1a's hiss while the steam is coming up and during the cycling caused by that oversized boiler. The hissing isn't loud and I've gotten used to it now so if it stopped, I'd probably go looking for what broke.



Maybe I should offer to sell steam to my neighbors?



Bob

HenryT

Thanks

Al, it only takes you 23 mins to reach desired temp?

Mine takes 23 mins to get steam to main, then to heat my house the thing would run about 1- 1/2 hours for temp to get up to 3-4 degrees.  My pipes are uninsulated (cardinal sin). I will plan to insulate them.

If you downfire your boiler, why didnt you downfire to fit your load?

Big-Al_2

Burnham Downfire Instructions

I would have gone down more, but the Burnham factory people recommended that the maximum I should downfire the boiler was 10%.  I'm not sure why.  The IN-6 has ribbon burners, and maybe they have a limited operating window.  I went to the next size down in gas orifices, and that gave me the 10%.  Eventually, I'll add another radiator or three . . . if I ever feel rich.



And . . . no . . . from a cold start after an overnight setback, it might take close to twenty minutes for all the iron to get hot . . . and another twenty minutes to satisfy the t-stat . . . but then, it might take an hour or so for the next call for heat.

BobC

Time

It takes 23 minutes of boiler run time to satisfy the thermostat, that is 40+ minutes overall but any time it's not firing is not costing me money. Insulating the pipes lengthened the "off time" because i wasn't loosing heat and condensing steam in the basement pipes.



My oil burner is firing at about 80% of the boilers rating, I'm going to go down to a 1 gal / hr nozzle next time after I've seen some real cold weather to see if there is any problem with fully heating on a design day. Most seem to think that going below 75% with oil probably isn't worth it. Now with the smaller nozzle (1.1 gal / hr0 I get steam to the end of the main in about 8-1/2 minutes from a cold start.

nicholas bonham-carter

venting discussions

i guess the key is low pressure and proper sizing as well as main vents; or am i going deaf. i certainly used to have noisy vents before placing my big order for more gortons.

as for over-sizing, our previous boiler was under-sized, to avoid some of the extra safety features needed over 1,000,000 btu. we certainly had hissing vents on the rads, and completely inadequate main vents; along with over-pressure. now they are silent, and without any back pressure 2-6 oz. does the job.--nbc