Radiator Very Slow To Heat

Yanks2009

It's been a while since I last posted. I've always found this site to be extremely helpful



I have a one-pipe gas steam system. My heating has generally been working pretty well . Almost all of the radiators heat fairly quickly. However, one radiator in our master bedroom (there are two radiators in the room) takes a very long time to heat. I can also hear water flowing through the radiator.



I've made sure that the radiator is tilted and have tried replacing the vent, using faster vents This has reduced hissing but hasn't helped much to speed up the heating process. I have also replaced the 4 main vents with new Gorton #1 vents.



Any advice on how I should troubleshoot this issue would be greatly appreciated.

jpf321

a few things ..

i suppose it goes without saying that your radiator valve on that one needs to be fully opened .. i figured i mention the obvious first ..



do you have other rads further down the line than this one that heat up faster?

do you have a (long) horizontal pipe that feeds this rad? (perhaps the pitch on that needs checking as well)

are you sufficiently balanced and vented? have a look at the venting worksheet in my signature to help you to determine this.

what is the EDR of that rad compared to others that are heating fast? are they all exactly or nearly the same size?

when you say you have tried a larger vent..what size are you referring to?

what is the EDR of that rad?

Yanks2009

Cold Rad

Thanks for your response.



I do have another radiator down the line which is getting hot, and it's approximately the same size. The radiator in the attic is also working fine. The other radiator located in the same room is on the same wall, only about 10 feet away.



The radiator is located on the second floor, so a riser would feed the radiator...I do not believe there is a long horizontal pipe upstairs, but i could be wrong.



I will need to look into the venting...I have maid-o-mist type C vents on the other radiators, which seem to be working fine. I attempted to use a maid-o-mist type D (the fastest venting one they have) on this radiator, but it did not help. For now, I purchased one of those cheap adjustable vents from home depot for the radiator in question, and keeping it in the "open" position seems to have helped somewhat.



If I measured correctly, the EDR size of the radiator is 29.37 sq feet.



Thanks for your help.

jpf321

do the vents..

which you have on hand all pass the "blow test" ..

FYI, a Maid-o-Mist D is just about equal to a Gorton D (i'm sure that's by design)

The fastest vent out there is the Heat-Timer Varivent at Full-Open setting...about 80% faster than the "D".



I'm now curioius about the other rad "on the same wall" .. are they each fed, do you think, by different risers? If not, then there must be horizontal pipe somewhere between them.



You may want to try rigging a ball-valve at the end of an 1/8" nipple .. this will allow you to test the system with an "open pipe" and then close it (the ball valve) down when the steam arrives. Taking it a few steps further .. you can add a low pressure gauge as well...and further .. stick a vent on the end later for "vent testing" .. Rod recently posted a PDF image of such a setup...

Yanks2009

Thanks

I think you're right, there must be a horizontal pipe connecting the two radiators because I don't see separate risers in the basement ceiling...thanks for the suggestion, the odd thing is that at one point, this radiator was working.  This is my first winter in the house, and I recently replaced all of the vents on the radiators, as well as the main vents...could this be a balancing issue?

jpf321

perhaps...

i'm only speaking out of conjecture here .. when you same that it "used to work" what were the outside temps at the time .. i suspect they were higher .. in which case that imaginary horizontal pipe may not have been as cold as it may be now .. allowing the steam to "make it" to the final rad...now that it's colder, that pipe may be a bottleneck .. does any part of the cold rad get hot? does it have its own supply valve? is the supply valve hot? is the valve fully opened?



it could be a balancing issue .. if you suspect a horizontal pipe, you may want to treat both rads + horiz. pipe as a single unit and only vent the final rad (with a properly sized vent for both) ..



if at all possible, you may want to try to insulate that imaginary horizontal, and be sure it's properly pitched.



if you turn off the supply valve to the first (hot) radiator, does the 2nd cold radiator then get hot? that would be an excellent test to check for horiz pipe and whether it's a question of the first rad taking all the steam.



don't forget that if there is a pipe joining the 2 rads .. the first rad is condensing and dripping condensate back into the pipe supposedly trying to send steam into the 2nd rad .. so the dripping condensate could be interfering with the steam supply to the 2nd...i believe the proper way to join two rads in series would to be to feed the 2nd rad from the outlet end of the 1st rad .. rather than to join them in parallel.

Unknown

Starving Radiator

Fast venting on the radiators can sometimes get you into trouble.  There is an old adage of "Vents the mains fast, the radiators more slowly".  With fast vents the other radiator maybe hogging all the available steam.  Steam travels from an area of high pressure to an area of low pressure and will flow to the area of greater differential. If one radiator gets steam first, when this steam starts condensing (a cubic foot of steam condenses instantly to a cubic inch of water) this creates vacuum and a resulting a huge pressure differential. Since the pipe was sized to provide steam for one radiator, guess who gets the steam?!

As jpf 321 mentioned, turn off the "hog" radiator and see what that does. If the other radiator then gets hot,"hogging" is your problem and slowing down the hog radiator should help.

Other possibilities - On the cold radiator itself make sure you don't overdo the slope as too much slope can cause problems. It needs just enough slope to "encourage" the condensate to flow out the inlet pipe. Also the lateral pipe connecting the cold radiator may not have enough pitch. Some times there is a bit of slack in the piping and you can raise the whole radiator a bit and shim it up. Raise it evenly at first and then add the extra shimming to slope the radiator towartds the inlet pipe. Radiators are heavy! Use a short piece of 2/4 (with blocks) as a lever.  Even a slight bit of increase in elevation can make a big difference. - Rod

Yanks2009

Cold Radiator

Thanks to both of you for your help.

When the problem radiator was working, it was warmer out...both radiators have their own supply valves.  I will try closing the valve on the radiator that is working tonight..this should at least (hopefully) answer some questions.

Now that you mention pitch, a thought just occurred to me.  I recently had new carpeting installed in the room.  Is it possible that the pitch of the horizontal pipe was thrown off when I reconnected the supply line to the radiator, due to the increased height of the padding and carpeting? Maybe pitching the radiator is exacerbating this problem...

Unknown

Slow Radiator

Warmer weather means slower condensing in the "hog" radiator and therefore less vacuum and less demand for steam. Play around with them and you should be able to work out  a "fix" - Rod

Yanks2009

Still no luck

So I tried closing the valve on the "hog" radiator to no avail.  Both radiators are cold.  The supply line below the valve of the problematic radiator is hot...it's just that steam isn't filling the radiator...any other suggestions?

Yanks2009

Progress

Well, I tried a couple of different vents and also played around with the pitch, and it seems to have helped.  I reduced the pitch and used a faster venting vent, and the radiator got hot.  I then opened the valve to the other radiator, which warmed up pretty quickly.  The next test will be to see if both radiators heat up at the same time when I turn the heat on.

jpf321

good to hear ..

glad to hear that a new vent helped to heat the problem rad. if the supply was hot going into the rad but the rad was not, then the next suggestion would have been clean/change the vent. let us know how it goes. 

mike jones_2

steam system nuances

rod, props on explaining with such a clear example.  even after reading dan's books, it sometimes takes an answer to an actual problem to really catch the learning curve.  your explanation is like the visual experiment in science class that u remember for a long time because it all ties together.  thank u for explaining why the vacuum problem is caused by the venting so clearly.



i overstand why u dont want the vent at the top of a radiator. we have a radiator with the vent in the middle of the last section rather than 1/3 from top.  could this be part of why the radiator does not get as hot as the others?  we did give this the fastest vent in the building,  d sized, and even insulated the wall the radiator sits against to reduce condensate, and of course the pipes.  we will try to raise the branch pitch if it can be done without risking breakage. thanks again!

arches

joining two rads....

There's a section in LOASH on the proper way to join two rads in series on a one pipe system (i don't have it handy at the moment). Joining the 2nd rad from the outlet of the 1st isn't kosher. Each radiator is supposed to be attached to a (properly pitched) horizontal pipe via its own supply valve.