Is This Sufficient Venting For My Steam Main?

Unknown

I guess the real test is: Do you think it is venting satisfactorily?

One test you can do is remove the vents and time how quickly steam gets to the open vent hole. I'd put a nipple and a ball valve on the hole so you can shut it off when the steam reaches it or have someone standing by at the switch to kill the heat as soon as the steam reaches the vent hole. Just be careful as raw steam can give you a bad burn!

You can't get any faster venting than the open vent hole so that becomes the minimum achievable vent time. You then reinstall your vents and do the timing with the vents in place. If you are within a minute or so of the minimum achievable vent time, your venting is optimum.

Is the radiator on that last riser operating satisfactorily?
If so then you are fine. To quote one of the steam pros: "If it works, don't fix it!"

TonyBal_2

I Measured the Main and I Have These Vents . . .

I measured my steam main today. It is a 2 1/2 pipe that is 50 and 1/2 feet long when measured from the header, and the main makes two 45 degree turns.

The vents are one Hoffman 75 and three Gorton #1s. I have the Gill & Pajek e-book, which says a main of my length has 1.515 cubic feet of air to vent. At one ounce of pressure, my venting capacity with the vents I have is 1.49 CFM, and at 3 oz increases to 3.06 CFM.

So according to these numbers, the main should vent in a little bit more than one minute with one ounce of pressure from the boiler? Is that how I interpret these numbers? Am I correct that this is adequate? Does the answer depend at all on the number of lines that feed off of the main?

The only unusual set up with the vents is that the Hoffman is all the way at the end of the main, about two inches past the last riser. The three Gorton vents are on a tree located several inches before that last riser. I don't know how much this matters.

Thanks so much.

TonyBal_2

Here's Why I'm Asking . . .

My only concern is that my radiator valves begin to whistle and/or hiss about 25 minutes after the steam hits the radiator after a cold start when the rads are about 60% or so hot, which others say can be a symptom of insufficient venting of the main and risers. I get this symptom on all of the rads in my apt except one rad that I keep turned off to keep the temp comfortable. Sometimes the whistling/hissing sounds like there is moisture in the air valves, although none of them is spitting moisture. This sympton also occurs on cycles after a cold start up, but much sooner.

I live on the second floor of a four story building, and the steam hits the radiators at the farthest point from the boiler about 11 or 12 minutes after the boiler starts up from a cold start. I would estimate that the steam doesn't take more than a few more minutes to travel up the rest of the riser, which means the steam gets to the furthest point in the building in 15 minutes or so from a cold start up. I don't know how long it takes my boiler, a Burnham IN 11, to make steam, so I don't know how long it is taking the steam to travel after steam is produced.

My next step is to try to figure out how much air has to be vented from each riser for the steam to hit the radiators.

And to answer your question, the rads fed by the riser furthest from the boiler do get hot. If I have a problem it is that my apt gets overheated, and I'm trying to figure out how best to balance the rads to reduce overheating. Right now, all of my rads have Gorton 6 valves on them.

nicholas bonham-carter

overheated apt.

seems like your steam arrival is acceptable. the overheating may have more to do with the thermostat location.are the rads in the t-stat area as well vented as yours? how about heatloss in that area compared to yours?--nbc

Brad White_203

I am thinking that

your mains are properly vented, full and hence vent no more. Thus it is up to your radiator vent (the "caboose") to finish the job.

Because it slows to get only 60% of the radiator hot when (as I gather; the others are properly and fully hot), you might consider going to a Gorton "D" on that slower radiator.

For whatever reason, it needs better breathing.

My $0.02 from a distance.

FJL

My Rads Get Fully Hot

All of my rads got all the way hot. What happens before they get all the way hot is that they hiss. They seem to hiss, on a cold start up, after about 60% of the radiator is hot, and they hiss until the rads get fully hot and close up (assuming that the t-stat is still calling for heat). This symptom is common to all of the radiators in my apt. I'm just trying to figure out why they hiss when they do, and what to make of it.

The more immediate problem is an overheating problem. We use the Honeywell VisionPro t-stat with a remote sensor in the apt on the top floor, which is the fourth floor. I presume that a top floor apt loses heat more quickly than the other apts in the building. We had installed the sensor in that apt becuase the residents there had complained of insufficient heat, and we wanted to make sure that that apt got a sufficient amount of heat.

The problem w/this set-up is that the more often the boiler cycles during the course of the day, the greater the temp differential between my apt and the apt with the sensor. My apt get progressively warmer during the course of the day.

I guess I now have to figure out whether I can reduce or eliminate the overheating by changing the venting rates of the rads in each apt, such as by increasing the venting on the top floor and slowing the venting in my apt, or whether a thermostatic controlled valve is what I need.

I read on another thread here, however, that a thermostaic controlled valve is the last option to use when everthing else is running smoothly -- the "cherry" on top of the sundae -- and I wonder whether I first need to find out why my current valves are hissing and sounding like they have some moisture in them.

Is it possible that I can eliminate the hissing by reducing the pressure below what I use now, which is 16 ounces and 4 ounces? I forget with is cut in and cut out.

mel rowe

Homeowner with lots of unwanted experience with hissing vents. I've had this problem, mostly in the past now, due to a variety of things. When I first moved into this old house, the hissing was due to the Pressuretrol being set too high. Also,I found a lot of valves were bad and did not close up completely. After working on these things, and getting a new boiler installed, I still had a problem with wet steam, due to boiler overcapacity and high steam velocity causing wet steam. In your case I think I would make sure the vents are working right, maybe by buying a new one and trying it on a rad that is normally noisy. FWIW

Brad White_203

TRV's

Mad Dog was right to call them the Cherry on the Sundae- but that does not make them the last resort.

In an ideal world, you would not need them. All radiators would heat at the same time and the sun would not hit in a way that bothers you. Also the radiators would match their room's heat losses exactly.

That overheating problem you have is not going away. I am an advocate of what works and TRV's properly applied, work. Why wait?

TonyBal_2

Which TRVs?

I think a TRV is the way to go. Which you recommend? Many like to Macon OPSK, but they are pricey. But if they work, I guess it is worth it.

Thanks for the help.

Brad White_191

Define

"pricey" but without mentioning a dollar figure. I have found them to be comparable to others but remember, you need a vacuum breaker and straight-pattern vent.

Yes, the OPSK's are what I personally prefer but shop around and see. Just make sure that you have comparable features.

TonyBal_2

Pricey

Pricey = three figures. I'll look around. I'm not sure what a straight-pattern vent is, but I'll see what I can find out w/google. Thanks for your help here. It is very much appreciated.