What Can Stop A Radiator From Getting Hot?

FXProglJr

Hi everyone,

I've put up a few posts before - thanks for your help - I made quite a few changes in main venting, pressure settings and return piping, but I'm still grappling with the problem of much more heat getting to the 2nd floor in my 2 family, 2 story (+ basement) house.

Now I think I've found the problem, but am not sure what's happening.

All of the 1st floor radiators were only getting to 140-150*F. (That apt. was vacant for a while so I had free access - I didn't check the 2nd fl radiators). The thermostat is on the 1st floor, so the furnace was running until the 1st floor reached the set temp - by which time the 2nd floor was 4*-8* hotter.

I've attached a layout of the mains in the basement and a layout of radiators on the 1st floor.

I started by removing the main vents (one at a time) to make sure that steam was getting to each end of each main - it was.

Then I removed the Maid-O-Mist air vent from a radiator on the 1st floor and replaced it with a nipple and small ball valve. When the steam came up, I manually let the air out of the radiator and, sure enough, that radiator got up to 200*F. I thought I solved the problem.

So - I removed the Maid-O-Mist valve (that had a very large vent opening) from radiator #1 - the biggest radiator in the apartment. I was surprised to find it quite full of water. Anyway, I replaced it with a new Maid-O-Mist valve with a much smaller vent hole. That radiator now reaches 200*F when the steam comes up.

Then I went to the bath room radiator that had some old, adjustable air vent on it. I turned the adjustment back and forth a few times and now that radiator also gets up to 200*F.

BUT - the remaining 3 radiators won't get past 150*F even with new vents (and I've tried several different makes/models). It seems that the vents close before the radiators get hot.

Does anyone have any ideas??

Jamie Hall

I'm sure you've done this, but... the first place I'd look at this point is the runouts from the mains to those problem radiators. Any sags? Correct pitch? Then I'd make sure that the valves on those radiators were fully open...

But as I as I'm sure that you've done that!

Mark N

If you have tube rads that have push nipples across the top of each section. It is possible that if you vent the rad too fast the steam will short circuit across the top and shut off the vent. The rad then doesn't fully heat. Most people just check the top and say the rad has heated all the way across, but never feel the bottom which is cold.

Steamhead

Mark N said:

If you have tube rads that have push nipples across the top of each section. It is possible that if you vent the rad too fast the steam will short circuit across the top and shut off the vent. The rad then doesn't fully heat. Most people just check the top and say the rad has heated all the way across, but never feel the bottom which is cold.

It can also short-circuit across the bottom on some rads, then rise into the vent and close it. This happens frequently on the original American Corto rads with 2" section spacing. Feel across the bottom of the rad to see if this is happening.

I usually cure this with slower venting, but it seems you've already tried that. Some radiator shutoff valves with very small throats will aggravate this too, since they cause the steam to leave the valve in a jet that shoots across the bottom of the rad.

Post some pics of the problem rads- let's have a look.

FXProglJr

Thanks for all the thoughts

Yes, the valves are all the way open; all the problem radiators are pitched correctly; The runouts back to the main seem to be sloped properly (one of the radiators was banging a few years back, but raising it 3/4" or so solved that problem), but I'll try raising them all a bit more and let you all know if that helps (unfortunately I need to leave town for a while due to a family emergency and won't be able to get to this before I leave).

Radiator #1, the one that now gets up to 195*-200*F, it that temp across the entire top and bottom. The radiators that only make it to 140*-150* seem to be that temp across the top, bottom and middle. All of the radiators look like the attached

Abracadabra

Wet steam? Post pics of near boiler piping?

You probably need more venting than the Gorton #1s

FXProglJr

Here's a photo of the near boiler piping. Originally there were two coal furnaces in this house. Back in the 1950's, they were replaced with a single oil fired furnace. And that one was replaced with a new Peerless in the mid 1990's. The installers changed as little as possible of the original piping.

The riser is 2", the header is 4", the pipe that goes from the header back to the bottom of the boiler is 1-1/4", the mains are all 1-1/2", the run-outs to individual radiators are 1" and the condensate returns are 1"

There are now 5 Gorton #1's venting the mains. I happened to be in the basement when the boiler fired up. So I went to the end of the basement and held one main in each hand. It took a few minutes, but they started to get hot, they both got really hot really fast. I don't think venting of mains is causing this problem

Captain Who

1) Steam not making it to the portion of the main where THAT PARTICULAR radiator takeoff is located. I notice you have some possibly undesirable bull Tees in your mains.

2) Condensate blockage in radiators and runners due to insufficient pitch, too small pipe, sag in pipe, sediment accumulation

3) Problem with the venting on that radiator. Vent closing too soon or blocked or too small orifice. Check with a mirror to see if there is fogging and if so, does the fogging end before the rad is heated all the way across?

4) I think sometimes it is a good idea to have 2 vents (appropriately sized) on those radiators with the push nipples across the top. Put one at the top and the other one at the standard location towards the bottom.

Captain Who

5) Other radiators on that main stealing the steam, ie. improperly balanced vents or too large vents. Best to vent radiators slowly and mains rapidly.

FXProglJr

thanks for your thoughts:

Steam not making it to the portion of the main where THAT PARTICULAR radiator takeoff is located. I notice you have some possibly undesirable bull Tees in your mains. - I've tried removing the air vents and inserting nipples and ball valves in these radiators - the steam is making it to the radiator - I can open the ball valve and get the radiators hot

2) Condensate blockage in radiators and runners due to insufficient pitch, too small pipe, sag in pipe, sediment accumulation ---- last summer I pulled one of these radiators . The radiator inside appeared clean. then I and ran a snake down the runner - it came out clean so I don't think there is any sediment in the runner. I'll try raising the radiators a bit more to improve the pitch in the runners, but that will have to wait a while - I'll let you know if this helps. As for the runners being too small - I have a few similar 2 fam, 2 story houses on this street. All the runners are 1"...none has a problem of radiators not getting up to 195*F

Problem with the venting on that radiator. Vent closing too soon or blocked or too small orifice. Check with a mirror to see if there is fogging and if so, does the fogging end before the rad is heated all the way across - I've tried several different size Maid-O-Mist vent sizes as well as several different make vents (Victor, Vari-Vent, etc). they all seem to close before the radiator gets hot and I can't figure out why that happens...but, if I manually vent these radiators, I can get them up to 200*F - any ideas here?

I think sometimes it is a good idea to have 2 vents (appropriately sized) on those radiators with the push nipples across the top. Put one at the top and the other one at the standard location towards the bottom. ------ Now this something I had not thought about - I'll give it a try and let you know (But, then again, all these radiators used to get very hot and I haven't changed anything - except it's now many years later)

Captain Who

FXProglJr said:

Now this something I had not thought about - I'll give it a try and let you know (But, then again, all these radiators used to get very hot and I haven't changed anything - except it's now many years later)

You REALLY haven't changed anything? When you first noticed the problem was it a "snap" change or a gradual change that took a while for you to realize there was a problem?

What about 5) above?

I think especially when you have bull tees in the main or runners you can get some pretty strange situations where the steam just decides to take a path of least resistance (especially wet steam) and it is necessary to do something drastic to change that, like you putting the ball valve on with the open pipe.

FXProglJr

Since Grandpa passed, this has been a rental w/ 2 apartments. As I said earlier, the thermostat is on the 1st floor, so that apt. is always at the set temp. When asked, the upstairs tenant always said the heat was "fine". It wasn't until she moved out (after 25 yrs) and I was getting the apt ready for the next tenant that I found out it was way too hot up there and I don't know how long it's been that way. At that point (last winter/spring) I replaced all the radiator air vents on the 2nd floor with slow ( very small hole) vents and all the vents on the 1st floor with fast (large hole) vents.

Since that time, I've been learning from all of you here and did quite a few things like:
reduced the pressure
added insulation to the mains
checked the ph of the boiler water
"skimmed" the boiler
re-piped the returns to bring them down to the floor before getting connected to the equalizer

Despite all of the above, when heating season began this year, it seems there's still more heat getting to the upstairs radiators.

And now, the only thing I can find that's obviously not right is that the air vents on the downstairs radiators close before the radiator is hot. And that seems to happen no matter which make/model/size I try

Captain Who

Varivalves may be best here because they don't close until 160-165 (sometimes even higher). When you say the vents "seem" to close before the radiator is hot all the way across, are you sure they are closed? Perhaps the other radiators are robbing the steam like I said in 5). Could be a changing situation as the whole system heats up. That's why I suggested using the mirror to check for fogging.

FXProglJr

well....I said "seem" to close because, if I listen closely, I can hear them close (sure, after a while, I can hear them open for a sec or 2, but then close again). And, I don't think the other radiators are robbing these - I have another pressure gauge installed near the end of the main where these radiators are installed and it follows the same pressure as the gauge at the boiler.

I tried a vari-vent and it didn't make any difference

Captain Who

6) I would suggest that you keep decreasing the orifice sizes on the rads that are heating up until the ones that are not start to get their fair share of steam. There's an unusual flow situation going on here. You have the static pressure at the end of the main but the steam is being drawn elsewhere.

7) Perhaps the main vent is closing too soon and you just have compressed air at the takeoff to the troubled rads and not steam. Temp is the key to the presence of steam or not, not pressure.

Captain Who

I missed your 1st before the last post about the mains getting hot. Do they get hot at the base of the vents? I assume so. Maybe you can scratch 7) off then. I looked at the photo of your near boiler piping. That header is massive but you have the takeoffs to the mains in between the two risers from the boiler. That's a definite no no.

Captain Who

oops......3rd before last........whatever

Captain Who

oops again......after looking at the photo again I think what I thought was a second riser is actually your equalizer, which means it all looks good as far as I can tell as far as the header goes, but I don't think that Tee in the main is such a good thing at all.

Fred

Have you checked the vents on the second floor? Are they larger vents that the ones on the firsst floor? Steam is going to take the path of least resistance, the fact tht those radiator runs are longer, that will gine the second floor some advantage already (long verticles that the steam can compress the air more than the shorter first floor runs). Try slowing the second floor radiator vents down and see what happens. That may make steam more readily available to those Rads on the firsst floor.

Captain Who

We're missing the information of where the radiators (especially the problem ones on the 1st floor) are physically located on your Basement Piping Diagram.

FXProglJr

The vents on all the radiators on the 2nd floor are new Maid-O-Mist with the very smallest hole available (I think it's #4 - 0.040").

And attached is a diagram of where the radiators are located (Pl's note that my earlier dwg of the mains showed 2 Gorton #1's on one end of the 2nd floor main - that was wrong - they're on the 1st floor main).

Remember when I first measured temps, all the 1st floor radiators were only getting to 140*-150*F. I replaced the air vent on rad. #1 with a new Maid-O-Mist with a #5 vent opening (next to the smallest available) and now that rad. gets to 200*F. And I jiggled the adjustment on the adjustable vent on rad #3 and now it also gets to 195*F

But, no matter what I try with the remaining rads, they only get to 150* or so

Abracadabra

FXProglJr said:

The vents on all the radiators on the 2nd floor are new Maid-O-Mist with the very smallest hole available (I think it's #4 - 0.040")

What's on the 1st floor rads?

Fred

Do you know what the total sq. ft of EDR is for both the first and second floor? Does that reasonably match the Sq. ft. of steam the boiler is rated for? This could be a rare case where the boiler might be under-sized a bit.
Also, I think you said you lowered the Pressuretrol settings. Have you actually watched the boiler to see if it is saying in that pressure range? Too much pressure will affect steam delivery.
One final thought, on a couple occassions here recently, posters have had similar issues and the problem turned out to be partially blocked or corroded gas lines. Have you checked the gas pressure/flow into that boiler? Have you had anyone look at the boiler burner and clean/tune/adjust it in the past couple years? It is possible that the burner (without cleaning/tuning) or gas supply just won't support the boiler rating.

FXProglJr

oh...sorry...here's the diagram. In order to simplify the dwg, I removed the 2nd floor mains and returns

FXProglJr

yes, I've checked the radiator EDR's and furnace capacity.
They are:
1st floor 5 radiators - 141EDR -
- 2nd floor - 6 radiators - 177
Furnace rating - 471

I have the pressuretrol set as low as it will go. I've been watxching it and it consistently cuts out at 1.65# and back in at 0.3#

The boiler is oil fired and cleaned, adjusted and maintained by my oil delivery people once each year

Fred

Are the run -outs to those radiators insulated? Are they in a colder part of the basement/crawl space? Are you comfortable that your oil delivery people really test and tune the burner? I'm sure I don't need to say That boiler is about 50% over-sized. (but I will anyway)

Captain Who

So is the first floor radiator's main the one that is closest to the equalizer on the header or closer to the riser from the boiler? I'm a little worried about how close that first takeoff is to the riser, despite the large size of the header.

Captain Who

Your Basement Piping Diagram shows only 1 Gorton #1 on the long run (after the tee) of the 1st floor main, but your Radiator Location Diagram shows 2 of them at the end of that long run. What is the exact lengths of each of the main runs to the vent locations? I'm thinking that your main venting is definitely on the small size and the diameter of the mains is on the small size so there is more pipe friction. A Gorton #1 is pretty anemic.

Which radiators are the ones that are not heating on the first floor.......I mean which numbers on your diagram?

Are the main vents definitely located after the last radiators? Your diagram doesn't show the exact location of the vents relative to the radiator takeoffs.

FXProglJr

The runouts to the radiators are not insulated - but they do get very hot - too hot to touch.

The 1st floor radiators (except #3) have Maid-O-Mist air vents...I've tried all different sizes.....Radiator nos 2,4 &5 don't get much past 150*F no matter what type or size vent I try (unless I manually let the air out) . When I changed the air vent on rad #1 to a new Maid-O-Mist No5, it started getting up to 195*-200* (but the others didn't enen with new vents) and rad#3 has an old adjustable vent that I fiddles with and now that radiator gets 195*F

Each end of each main ends in a tee with the air vent(s) on top and condensate return on the bottom/ The tap for rad#5 is just before the tee and the tap for rad#4 is from another tee between the main vent and the tee mentioned earlier in this paragraph -see attached).

And, yes I stand by the maintenance people to watch what they're doing every year as I ask them to explain just what they're doing.

oh, and sorry about the confusion...I made an error on the first basement diagram I posted. the main for the first floor has the 2 Gorton #1's

Fred

It looks like somewhere along the line, someone has bushed the inlet side of that radiator down to the ssize of the valve. Are they all like that or just the ones that aren't getting as hot? Could they be holding enough water in the bottom of those radiators to condense the steam as it enters the radiators?

FXProglJr

Capt. Who - the main near the equalizer goes to the 1st floor.

Fred - yes, the inlet of the radiator has been bushed down to fit the valve. The mains are all 1-1/2" and the runouts to the radiators are all 1". The valves are all for 1" pipe........I don't think water remains in any radiator as they are all pitched to the valve. But I'll try tilting them a bit more to make sure. That, raising the entire radiator (to increase the pitch in the runouts) and adding another vent to each radiator really have my interest.

But it'll need to wait until I return from FLA (my only brother got rear ended by an 18 wheeler and isn't doing well and needs some help) So I'm off to a warmer climate. I'll be back on this problem when I return and let you all know how I make out.

FXProglJr

ok....I'm back and have been tinkering....(If you remember, we got radiator #1 and #3 to get up to 195* when the steam comes up by changing/adjusting their individual air vent) Now I've been working on radiator #4 (kitchen). First I tried raising the radiator another 3/4" - no change....then tilting it a bit more toward the inlet - no change.....then I removed the plug in the existing hole on upper portion of the last section above the existing air vent (boy - that was a job!) and installed another air vent. Now, that radiator gets a bit warmer, but not as hot as radiator #s 1 and 3, before both vents close. And I should note that the bottom and last section now get up to 175* while the center and steam entry parts remain in the 120* - 140* range.

And more ideas/suggestions to try?

BobC

Steam will always go the easiest route, you have to make everything else a bit harder so the steam goes where you want it to.

Have you gone over the piping to be sure you don't have a sag anywhere in the piping? Any water sitting in a sag will collapse steam and it may not bang like you would expect it might.

Make a list the radiators and their EDR, the vents on the radiators, the length of pipe between the main and each radiator. Do all the other radiators get hot at about the same time?

Bob

Fred

BobC said:

Steam will always go the easiest route, you have to make everything else a bit harder so the steam goes where you want it to.

Have you gone over the piping to be sure you don't have a sag anywhere in the piping? Any water sitting in a sag will collapse steam and it may not bang like you would expect it might.

Make a list the radiators and their EDR, the vents on the radiators, the length of pipe between the main and each radiator. Do all the other radiators get hot at about the same time?

Bob

He has 1-1/2" mains and 1" run outs to the radiators. Most of us have run-outs equal to his main. My suspicion is that those mains can only carry so much steam and it feeds whichever radiators it can get to. Those 1" run-outs (and the 1-1/2" main for that matter) just don't allow much room for return condensate either.
Is the problem radiator(s) on the main that has the largest number of radiators?

Mark N

Sounds like he short circuiting across the top of the rad. Most likely caused by the new vent he installed at the top of the last section. That is why the center is warm. It makes no sense that the last section would be hotter than the first(he calls it steam entry part).

FXProglJr

yes guys...I agree (and I'm not trying to be difficult here, just trying to understand what's happening), but steam is available at this radiator (if I remove one of the vents and replace it with a nipple and small ball valve and let the air out until I see steam, I can get this radiator up to 200*). So - I'm back to the question - why would the air vent (or after I installed a 2nd vent, why would both vents) close before the radiator is completely hot?

Mark N

The vent doesn't know if the rad completely heated or not it just closes when steam hits it. Have you tried a slow vent on this rad like a Hoffman 40?

neilc

so without looking for your other posts,
what pressure you running at?

Fred

FXProglJr said:

yes guys...I agree (and I'm not trying to be difficult here, just trying to understand what's happening), but steam is available at this radiator (if I remove one of the vents and replace it with a nipple and small ball valve and let the air out until I see steam, I can get this radiator up to 200*). So - I'm back to the question - why would the air vent (or after I installed a 2nd vent, why would both vents) close before the radiator is completely hot?

Take that vent off of the top of that radiator. I don't know why anyone suggested that to begin with. For some reason, steam is hitting the vents on the other end of the radiator before going through the remainder of the radiator. Is this radiator the same as the others or was it added at some point? This isn't an old Hot water radiator is it? Some of them can't be used for steam.
EDIT: I hate to bring it up again and I know you said all the radiators are bushed down to 1" but is it possible the radiator in question is holding a little more water in the bottom of it than the others, because of that bushing? Steam will condense when it come in contact with water, even though it may not bang or hammer. Sorry if I'm frustrating you but that bushing is almost always problematic. With the valve off, the steam can rush past the water but with the valve on, it moves slow enough to condense.

FXProglJr

Bob C- there doesn't appear to be any dips...the last few feet of the main for the 1st floor is level (I need to go back with a water level to check for sure) - There is no banging and, if I hold onto the pipes, I can feel the steam arrive and move all the way to the ends of the mains and then proceed up the last run out. (When the steam arrives the pipe get way to hot to hold onto very fast and the heat progresses along the main at about 5 sec. per foot of travel). The list of radiators you asked for is attached (the problem is the same no matter what make or model vent I use). I have not checked to see that they all get hot at the same time.

Fred - Yes, the problem radiators are on the section of main with the most radiators - but don't forget - when I started looking at this, radiator nos. 1 and 3 also didn't heat past 140*. This was corrected by changing/fiddling with their air vents. Also, don't forget that I have a 1" condensate return that runs from the underside of each end of each main back to the equalizer. I have no idea what an "old hot water radiator" looks like but this one (see attached) looks like the same style as all the other ones in the building. I don't know how to check to see if this radiator is holding more water then any of the others - guess that will have to wait for the spring.

Mark N - steam "short circuiting" certainly is a possibility - but why would it happen and how can check for or stop it. Don't forget, I've tried quite a few different makes of air vents as well as all the different orifice sizes and even tried adding a second vent. Nothing makes any difference.

But, I did just return from the building. Last night I tried changing the lower air vent to an old, adjustable vent (marked 1A, but I couldn't read the mfg. name) and the upper air vent to a Gorton #5 and today after the steam came up that radiator was at 160* almost all the way across (the very first section - where the steam enters - was at 120*). That's hotter then this radiator has been since I started. So I tried opening the adjustable vent a bit more and changing the Gorton #5 to a Gorton #6 (slightly larger hole). Can't wait to see if there's any change tomorrow.

Oh...and I should mention that many of the air valves I remove have water in them that did not drain back into the radiator. Is that a problem?

Fred

Looks like its always been a steam radiator. You do realize that the nature of a steam system, and the way it works for all of us, is that all radiators don't always get hot all the way across and they don't all heat at the same rate, right? Most of us have radiators that only heat all the way across on the coldest of days (0 and below) when the boiler runs for extended periods of time.
The amount of heat you will get out of any particular radiator is going to be driven by the boiler run time, the size vent on that radiator and the actual size of the radiator itself. A larger raadiator has more mass to heat and will take longer than a smaller radiator.
I have reread your original posts several times and I am concluding that you want/expect all radiators to heat to equal temps with each cycle. Not the way steam works. When the Thermostat says it is satisfied (in the room it is located), the system says "I don't care where the other radiators are temp wise, I'm done for this cycle".
If you want to test the full heating capacity of all the radiators at any given time, you will hve to set the Thermostat to a temp that lets the boiler run for at least a couple hours.