faulty steam radiators? steam heat CPH?

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Heating and Air Conditioning January 28, 2014 at 1:54 pm

faulty steam radiators? steam heat CPH?

We have a steam heat system in a three story detached house. Newish gas boiler, and we’ve had several notable heat guys come out and make a few recommendations to tweak the system. Nothing quite does the trick, though. Basically, the front of building just doesn’t heat up properly. All the radiators in the front usually fail to heat up 100%. Two of the radiators seem to get blazing hot valves, while the radiators heat up so slowly. This seems odd to me. Could the radiators themselves be faulty or need work somehow? The air vents are clear and properly placed, they are pitched correctly, and the air vents have been balanced–or an attempt to do so has been made (replaced nearly all using various sized Grotons–very small on the other side of the bldg and very large on the front side). Valves are turned wide open. I never hear anyone saying that the problem could actually be the radiators themselves. Is this ever the case?

I thought perhaps it was short-cycling, so I just changed the thermosat setting to 1 CPH (it was set at 5, I realized!). So, short-cycling isn’t a problem now. But I wonder this, even though I keep reading that steam systems should be set at 1 CPH: when it is super cold out, is it possible that 1 CPH is TOO FEW, as in, the house cools down to quickly for only 1 CPH (especially since it is a detached house and the windows aren’t great)?

Thanks in advance!

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Sorry to hear about problems your having, My guy has done repairs for many of my customers and they are very happy, if you wish to get his contact infor send me an e mail and i would gladly provide you with his contact. coresolutionsnyc@gmail.com

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Why don’t you just try running 2 cph for a day?

It would be nice if you could perform an EDR calculation on the system and compare it to the output of your boiler. Start there.

Or, you could call metalwork’s “guy” like he posts in every thread without naming him or giving his phone number. Nothing shady happening there!

Hilarious. I’m cracking up! Does his “guy” also do free estimates?

I wonder what kind of radiator repairs a “guy” does.
I thought I would just try 2 CPH, but I am an owner who doesn’t actually live in the bldg, so it would be hard for me to assess. I just know the tenants complain that the radiators on one side don’t heat properly, and when I am there to check, it’s quite true — back is blazing hot while front is not. The part I am most curious about is why the valves on some of the radiators get blazing hot while the radiator itself barely heats up. What could that mean??

Front not heating sounds like a main vent issue. Radiators not heating yet valve is hot is a venting issue. Air is trapped in your radiator. Install a real vent like a Hoffman #40, lower your steam pressure to 2# and throw those shitty Gorton vents in the trash. Or give them to the guy.

steam_man, curious about the physics here – what’s actually happening that makes a valve get hot but not the rad upstream of it? surely only escaping steam can make that valve hot, and that steam had to pass through the radiator to get there?

steam man, what sized gorton is a hoffman #40 equivalent to? and how about thermostatic valves? i always wonder why they aren’t more common than just choosing different size vents for different radiators…

also, I’ve got one Gorton #2 on my main on the cold side of the building. Do you ever put TWO of them on that side? (The Gorton website says “install one or more at the end of the long main”…) If that’s possible to do, kinda seems like a logical idea, if the whole front side of the house is not heating up enough. I’ve got all Gorton size 4 and 5’s on the warm side of the house and C and D’s on the cold side…

A Hoffman 40 vents cfm at a rate between the Gorton 4 and 5 models.


deano, if I read this right, the ‘valve’ is the shutoff before the radiator. It gets hot because enough steam builds up to there, but the radiator may have a stuck or too-small vent, so not much heat develops

Thanks, MP. And CMU, that’s what I would have figured too, but the air vents are size Ds and clear (new last year, and I checked them again this year)…

what size is the tapping on the main vent? If you are venting out of less than a 3/4 inch tapping then you are not getting the full benefit of a main vent. And yes, you an stack them in a tree to provide more venting. Personally I think thermostatic valves are a nightmare…you are letting your tenants continually unbalance the system and cause endless headaches.

Ok this was sort of the case in my building. I spent a couple of days with a temperature gun watching the radiators warm up The rear risers cooked up faster than the front.

I added more venting to the main. Since the front of our cellar is draftier and more vulnerable to the elements I also wrapped the run of the main in the cellar. I ordered very wide insulation and was very diligent. After this I was able to then balance the dents.

It’s all about pressure differential. High pressure moves into low pressure zones. If you have air filling the radiator with nowhere to go, the higher pressure steam cannot enter. Simple. Vent the air, now the steam can move in. Sometimes more than one vent is required on a radiator.

Mains. Insulate them and vent them based upon the main volume. More than one main vent may be required so use tees and nipples. Use a Hoffman 4A.

So helpful, thanks, everone. I’ll focus on more venting on the main then! eman, i thought groton 2s only come in 1/2″… Your comment about stacking them in a tree led me to a little research that led me to this venting handbook, which gets rave reviews on various heating forums: http://www.heatinghelp.com/products/Steam-Heating-Books/25/146/Balancing-Steam-Systems-Using-a-Vent-Capacity-Chart-by-Gerry-Gill-and-Steve-Pajek I’m gonna get it. But in the mean time, would you add ONE more vent to the main, or TWO? Any harm in just going with two more…?
Thanks for pointing me in the direction.

cmu – thanks: of course! i must be dyslexic about valve vs. vent and keep forgetting they’re two very different things. duh.

It depends on the time spread between the front and rear risers heating up. Start with one more, see if the front and rear heat at the same amount of time…if not add one more, ad infinitum

eman, or all, forgive this very ignorant question, but I’m reading that venting manual/chart I linked above (it is brilliant! is this something many of you professionals use?), and I realize that I am confused about the term “tapping.” I thought it meant the diameter of the hole that the vent screws into. But I just read this, and it makes it sound like “tapping” refers to the diameter of the pipe?? My horizontal main line–the diameter of the pipe itself–is 2″…

Here they are talking about their suggestion to take off the main vent, firing the boiler, and timing how long it takes for the steam to get from the boiler to the open hole, then trying to add enough main vents to match that speed.

“Consider a 3/4″ pipe tapping for example. If you want to achieve the same speed as you would get from that open pipe, then you have to be able to vent the same amount of cubic feet, right? So, if an open, 3/4″ pipe can vent 9.5 cubic feet per minute (at 3 ounces of pressure from the boiler), then your starting point would be either to use four Gorton #2 air vents, or 10 Hoffman #75 air vents, or 23 Ventrite #77 air vents.”

And then they go on to explain that a 1/2″ pipe will have limited venting capacity no matter how many vents you put on it (“In short, using more than two Gorton #2 air vents on a 1/2″ pipe would be a waste of time and money”), etc, which made me think of your question above, eman…

They seem to use “tapping” and “pipe” interchangeably. But it can’t be that a main pipe would be that narrow…?? They must just mean the hole that the vent screws into?? But if so, every time you add a vent, you create a new hole, so why would the venting capacity be limited…? Again, sorry to be dense here.

I’ll obviously get a professional to do this, but I want to know what to actually ask for. I’ve had a couple of the “best” heat guys here already to assess the system, and none has ever suggested more than one vent on the main…

This is all craziness. Look. Enough knocking your brains out. Here’s what you do:

1. Install a Hoffman #75 on a 3/4″ nipple 15″ back from the end of the main on a nipple 6″ (minimum) up from the center of the main.

2. Install a strainer vertically before the main vent.

3. File your book away and don’t look at it anymore.

4. If the above (1 & 2) aren’t possible, get as close as you can to what I told you.

5. Call it a day, because now you just did what every pro would have done if they came to your house.

well, you say enough knocking my brains out, but frankly, i’ve spent so much money on “heating assessments” and fixes by “heating experts” — to no avail! literally. the things that have actually helped AT ALL were things I ended up learning and doing myself, fixes that none of the heating experts who have come out ever even mentioned… At any rate, your advice, steam man, sounds good, so thanks.

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