Help Diagnosing Potential Blocked Pipe

a3inverter

Greetings all.

Trying to diagnose why one of my radiators (second floor, 2 pipe radiator, second to last off the main) is not getting as hot as the others - to quite a large degree. All other radiators are working fine, putting out nice, even heat.

We recently moved this radiator to this bedroom (was out in the hallway prior and got nice and toasty out there) because we determined that at some point, the radiators were switched (this bedroom was unused so the previous owner put the smaller hall unit into the bedroom).

This bedroom's radiator used to be last off the main (previous owner had altered the piping such that the radiator in the room with the thermostat (on the first floor) was FIRST off the main, forcing this bedroom's radiator to be LAST. I restored the original configuration a month ago.

I have verified good flow through the air valve, I know the radiator itself is not blocked (again, it worked fine in it's previous location) and it does get WARM, but not HOT (like the others do).

The supply to this radiator has some horizontal runs (goes up the soil stack chase then across to the bedroom) so perhaps that is where the issue lies.

Any thoughts on how I can diagnose/test/troubleshoot?

KC_Jones

Start simple. Are all pipes pitched back towards the supply? You didn't create any traps when you redid the pipe work? Is the vent on the radiator working properly? To test you can remove the vent while the system is running and see how it heats. What type of vent is on the radiator? The speed of the vent can dictate how fast it heats. Is it possible it is heating so slowly that the thermostat kicks the system off before it heats fully? Some pictures of the radiator and associated piping you are talking about could help greatly in diagnosis.

Fred

You say this radiator has 2 pipes so I'm assumming this is a 2 pipe steam system. Did you raise or lower either one of those pipes to reconnect this radiator? If you did you probably changed the pitch of the piping where you can't see it (under the floor). that may be trapping water. You will need to raise that radiator. Are their traps on the piping? If so, there may be an orifice inside that trap that is too small for the larger radiator, you may need to also switch the orifice. If both radiators worked before you switched them, I doubt that the piping has a blockage in it, unless its water.

a3inverter

My responses:
1. Regarding pipe pitch, these pipes travel inside the wall, then straight down the soil stack chase to the main in the basement.
2. The piping I redid was not related to this specific radiator - the modifications made the radiator in the room with the thermostat LAST instead of FIRST.
3. I took the vent apart yesterday and it was pretty well plugged. Cleaned it up and it passes air fine now.
4. Don't have the vent in front of me, but it is likely original to the house (1930) and is adjustable. I have it full open. I have a Maid O' Mist (sp?) with a pretty big vent on it that I can try.
5. Regarding the thermostat turning off the heat before this radiator warms up: This was my initial troubleshooting step...and now the radiator in the room with the thermostat is the last one off the main, just after the problem radiator. The heat definitely stays on longer now and warms up the house better...just not this one room.

I will see if I can take some pics, however with the piping being in the wall, not sure how helpful it will be.

Thanks

KC_Jones

lol Fred I missed the 2 pipe comment. *facepalm* Pictures would still be good.

a3inverter

@Fred:
2 pipe radiators on second floor, 2 pipe radiators converted to 1 pipe on the first floor (I have no idea why - something done before I bought the house)

I measured the height of the connections on the 2 radiators that were swapped and there were the same, thus no change in pitch.

Not sure I mentioned it in my initial post, but this moving of radiators and changing of pipe routing was done because this problem radiator never got hot before. The smaller radiator (which I moved out into the hall...it's original location when the house was built) is working just fine in it's present location.

All signs really point to the supply line, the problem is that 90% of it is behind the wall.

Fred

LOL!

KC_Jones

hmmm Is it a 2 pipe radiator? With an air vent? Pictures of the radiator itself might help given your descriptions. Keep in mind sometimes a modification anywhere in these systems can effect some completely different part, never assume your modification has nothing to do with the problem. Hopefully with some pictures of piping and rads that will help. Also pictures of how the piping was modified would be good.

KC_Jones

I think it has been mentioned on this site many times. A true blockage in a steam main or takeoff is a fairly rare occurrence. It would be good to look into other things before assuming blockage. a 2 pipe and 1 pipe hybrid system?! That is different. They might have converted because they didn't know how to fix a problem, like a bad trap or something. Keep in mind for the most part Geography isn't the only factor for speed of heating. The venting rate controls this much more than geography does IMHO. I have the rad closest to my boiler heating slower than any rad in the house...on purpose. My most remote rad heats fully first. It's about venting and control not necessarily geography. I only mention this because you talk about redoing piping for speed of heating and in all likelihood that wasn't necessary.

a3inverter

It is an exact replica of this one (each of the bedrooms has one of these...same size...master has 2 of them)

Fred

Pictures are a must at this point. Are you sure that problem radiator is original to this system? Could someone have acquired and put a hot water radiator on your steam system? If the problem moved with the radiator, that radiator is suspect, not the piping.

a3inverter

The modifications I made were to 1) set things back to original 2) potentially improve heating and 3) to remove 12 foot long copper (!) pipe that ran across my workshop area and kept banging me in the head

a3inverter

@Fred - sorry if I wasn't clear. The problem didn't move with the radiator, the problem stayed with the room, regardless of radiator.

Fred

I think I see the problem. It looks like the vent is on the same end as the steam supply. If thats the case, that radiator needs to be turned around so that the vent is on the drain side to allow the steam to push all the air out accross the radiator from end to end. on second look, I can't tell which side is the supply side and which side is the drain side. Are all the 2 pipe radiators piped at both bottom ends? I would have expected to see the steam side piped at the top and the drain side piped at the bottom. Steam is going to take the path of least resistance and it would seem to me that steam would travel across the bottom of this radiator and into the drain pipe. Somebody else will have to chime in on this one.

a3inverter

@Fred - the side opposite the vent warms up first. And the elbow on that side gets hot and the elbow on the vent side does not. I take this to mean the steam is coming in the end opposite the vent, but could be wrong.

KC_Jones

@Fred correct me if I am wrong, the easiest way to tell proper orientation is the return pipe should be slightly smaller than the supply? On 2 pipe air vent they can be really close in size, but I thought the return was always just a bit smaller. Trying to remember from Dan's book. lol

Fred

KC, I would expect the return pipe to be smaller but from the pic, they both look the same size to me???

a3inverter

@Fred:

Are you sure that problem radiator is original to this system? Could someone have acquired and put a hot water radiator on your steam system?

I can't be sure the radiators are original...but all the other radiators in all the other locations are working very well. Not sure if these are hot water radiators or not.

@KC:

Agree that a blocked pipe seems to be a rare occurrence...that's why I put it last in terms of troubleshooting

KC_Jones

In my mind if the supply pipe is getting hot (steam hot) then you are getting steam there, but can't get it through the radiator. It still sounds like a vent issue. It could be a vent issue in another room though. Do you know if this radiator shares a takeoff with another radiator? Sometimes another rad with better venting can rob a radiator on the same pipe. I recall reading a story about 2 radiators off a tee and one vented so much better the other one stayed cold, even in the same room.

Fred

That's my take too, KC. or the steam is running right across the bottom of that radiator and down the return OR the elbow is only mildly hot because a horizontal pipe is filled with condensed water (pitched the wrong way) preventing steam from getting through.

a3inverter

Thanks for the insights guys. I will do some testing tonight with my electronic thermometer to see what is getting the most heat. Will also investigate the Tee possibility and separately try a different (bigger) air valve.

KC_Jones

If it is possibly another rad robbing the steam you could also try turning other rads off. The easiest way to do that (if you don't know) is to turn the vent upside down that closes it off.

Abracadabra

The picture doesn't make sense to me. I see a radiator, with two pipes, no trap, and an air vent. Are both pipes supply? Is one a return? If one is a return, where's the trap?

a3inverter

Abracadabra said:

The picture doesn't make sense to me. I see a radiator, with two pipes, no trap, and an air vent. Are both pipes supply? Is one a return? If one is a return, where's the trap?

I recall someone from The Wall suggesting that I may have a "vapor" system. In such a system the elbow has an internal trap (pic on page 53 of "We Got Steam Heat").

a3inverter

Pics for your viewing pleasure...left side is the steam supply, right side is the return. All the rads on the second floor are this 2 pipe configuration and only the problem one doesn't work.

Replaced the Vent Rite #1 with a Maid O' Mist #6

ChrisJ

So the questions are:

1: Was this originally a 2 pipe system that needs air vents on the radiators? I recall this type of system existing, but how can you tell if it should be or not?

2: What's going on that we can't see? I highly doubt a pipe is clogged.

Can you supply pictures of the piping around the boiler as well as any exposed piping in the basement?

a3inverter

ChrisJ said:

So the questions are:

1: Was this originally a 2 pipe system that needs air vents on the radiators? I recall this type of system existing, but how can you tell if it should be or not?

No idea.

ChrisJ said:

2: What's going on that we can't see? I highly doubt a pipe is clogged.

Can you supply pictures of the piping around the boiler as well as any exposed piping in the basement?

The only difference with the piping to this specific radiator is that it goes up a wider chase (shared with plumbing) than the others that go to the second floor. House is symmetrical - the piping to the second floor radiators at the front of the house and go up on either side of the front foyer. No tee, nothing fancy. And the one that goes up the right side of the foyer cranks out the heat.

a3inverter

a3inverter said:

ChrisJ said:

So the questions are:

1: Was this originally a 2 pipe system that needs air vents on the radiators? I recall this type of system existing, but how can you tell if it should be or not?

To expand on my response here, the entire system was originally a 2 pipe system. On the first floor, one can see a patched hole in the floor on the opposite side of each radiator from the present supply pipe. I don't know why they would have changed it.

On the second floor, all the radiators are 2 pipe and are have air vents.

ChrisJ said:

ChrisJ said:

2: What's going on that we can't see? I highly doubt a pipe is clogged.

Can you supply pictures of the piping around the boiler as well as any exposed piping in the basement?

The only difference with the piping to this specific radiator is that it goes up a wider chase (shared with plumbing) than the others that go to the second floor. House is symmetrical - the piping to the second floor radiators at the front of the house and go up on either side of the front foyer. No tee, nothing fancy. And the one that goes up the right side of the foyer cranks out the heat.