Single pipe steam. Inlet side hot. Vent side cold. Should radiator fins all heat up at same time?

CoachBoilermaker · October 15

Single pipe steam.
Turned the thermostat heat up to 80*F.
Ran the boiler for 20 mins. then checked each radiator.

In general, on most radiators, the inlet side was hot, and the vent side was still cold.
How long should it take for the heat to reach the last fin next to the vent?

After 20 mins, I then turned off the heat. Did I need to wait longer?

BR #1: Inlet side hot. Vent side cold. Vent quiet.
BR #2: Inlet side hissing/sputtering. Inlet side hot. Vent side hot. Vent quiet.
BR #3: Inlet side warm. Vent side very cold. Vent hissing.
LR: Inlet side hot. Vent side very cold. Vent quiet.
DR: Inlet side hot. Vent side barely warm. Vent hissing.
Kitchen: Radiator encased by kitchen nook bench. I feel heat coming out.

I also checked the main vent in the basement.
Main pipe was hot before and after the main vent riser, which was also hot.
So, I think main vent is working?

Video:
https://drive.google.com/file/d/1fUElS_m0TpL7A70b6Dag-QdvXb0bFSU0/view

ethicalpaul · October 15

Here are my thoughts:

20 minutes isn't very long from a cold start. It takes time to heat the water to boiling. It might take around an hour for the whole radiator to get hot
The pipe side definitely should get hot first
The heat will travel across to the vent side depending on the speed and condition of the vent
You shouldn't hear any gurgling, it can be a sign of water trapped in a poorly-pitched pipe, or broken valve
Some vents will be silent. You really should only hear a slight, gentle hissing sound of air escaping. Sputtering isn't good, but might not be too big a deal…it might just be a little condensate in the vent.
You want to check the main vent during that first 20 minutes to see if it is letting out air and then not letting out steam

EdTheHeaterMan · October 15

Sounds like you may need some new vents. Also you may need some boiler room maintenance.

To be clear about how the radiators actually heat. if you have a cold start, that means everything is room temperature, the boiler and pipes and radiators above the water line will be filled with AIR. Air and steam don't mix. If you could see it in a bottle, and the steam was Red and the air was Blue, it would look like a Red gas (the steam) would have a line where the Steam ends and the air, a Blue gas, starts. Just like vegetable Oil and tap Water in a glass are separate.

Now you start the burner and put your hand on the header pipe where it exits the boiler. It will stay cool to the touch until the boiler starts to make steam. Then you will feel a rapid change in temperature as the steam reaches that point in the piping. Now move quickly down the main pipe away from the boiler and feel that pipe. Cool to the touch while it is pushing air out of the way. Then very hot when the steam gets to that point. Quickly move further down the pipe and feel the cool pipe and then it becomes a hot pipe.

This keeps happening until all the air is out of the pipes and radiators. If your vents are not letting the air out at a balanced rate, so each room gets heated at about the same time, then your vents need to be changed to vents that will let the air out slower on the radiators that get hot too fast and let the air out faster on the radiators the don't get hot fast enough.

That is easier said than done in some homes, on some systems.

Wait a little longer to see if everything works itself out.

Another thing to remember is that most steam systems were installed when Coal was King in the heating industry. Coal boilers did not have thermostats. They had people that put coal in then by hand. So the fire did not turn on and off like a gas or oil burner does today. The heat was always on. More in the winter because you might put 3 shovel fulls in the boiler every few hours. Less in the spring and fall, because you might even let the flame actually die out in the afternoon so the house doesn't overheat. You learned how to keep up with the weather when you operated a coal fired boiler.

CoachBoilermaker · October 15

My concern with replacing the radiator vents is what if they break off? Then the entire heating system is not usable at all due to the steam spewing out of the broken vent hole. Is replacing old radiator vents best left to a professional? Makes me feel stupid as I've been working on cars for years and have a garage full of tools. LOL.

ethicalpaul · October 15

I haven't had one break off that I couldn't get out. If you're a car guy you should be OK but if in doubt, call a pro. It's certainly easier than a bolt breaking off in a head. Even not a very good plumber should be able to handle it. You might have to tell them which brand of vent to use, or buy it yourself and have them install it so they don't buy some garbage.

CoachBoilermaker · October 15

https://forum.heatinghelp.com/discussion/comment/1814328#Comment_1814328

Is it a cold start for tankless coil? Regardless, the inlet side was very hot. How long should it take for the steam to reach the other side of the radiator? A few seconds, a few minutes, an hour? How long does vent side stay cold until I know something is wrong?

CoachBoilermaker · October 15

Is there a brand of vent I should get? Variable vent?

ethicalpaul · October 15

Let me quote myself:

It might take around an hour for the whole radiator to get hot

As long as sections of the radiator are getting hot, nothing is wrong. How fast they get hot is up to the vent.

CoachBoilermaker · October 15

https://forum.heatinghelp.com/discussion/comment/1814338#Comment_1814338

To clarify, if the vents were stuck closed, would NONE of the radiator get hot? Are you saying that since the inlet side fins are hot, this implies the vents are not stuck closed, but are simply just venting slowly? If the vent was totally stuck closed, the steam would never reach the inlet side fins in the first place?

ethicalpaul · October 15

Yes, if the vent was failed completely closed, even the air in the supply pipe (runout) wouldn't get out of the way to let steam by.

People turn a vent upside-down which for most vents makes them close, to "shut off" a radiator

Jamie Hall · October 15

https://forum.heatinghelp.com/discussion/comment/1814346#Comment_1814346

Pretty much. You might get a little heat on the inlet pipe, and a few — maybe two or three — sections — at the end of a really long run when the pressure got to 2 pounds or so.

And as has been said, 20 minutes from a cold start it just getting going. Give it a little time.

Steamhead · October 15

@CoachBoilermaker , are the hotter rads (BR #2, for example) located closer to the boiler?

RTW · October 15

Wouldnt hurt to first: 1) boil the vents in white vinegar for about five (5) minutes and see if that resolves issues before spending significant amount of money on replacing all vents, 2) It's a good idea to periodically boil vents anyway as preventive maintenance. Lastly, I have one pipe steam that works excellent mainly due to routine annual maintenance ( by qualified tech) and occasional inspections / boiling of vents

Regards,

RTW

STEAM DOCTOR · October 15

Get an 1/8" easy-out and 1/4" drill and tap set and some 1/4"-1/8" black bushings. Just in case.

ethicalpaul · October 15

☝️☝️☝️ All those taps above should be NPT I'm sure @STEAM DOCTOR implied

CoachBoilermaker · October 15

https://forum.heatinghelp.com/discussion/comment/1814338#Comment_1814338

The frustrating part about internet research is when you get conflicting information.

On another thread, I see this: Keep in mind that the pipe end of the radiator will show heat before the vent end. In a matter of minutes, they should even out.

vs.

It might take around an hour for the whole radiator to get hot

ethicalpaul · October 15

<shrug> my radiators do not even out. The heat travels across them during a call for heat and it takes some time to do that. As I said, it depends on the venting.

Here's a faster one than mine. You can time yours.

https://www.youtube.com/watch?v=JBVZLhtqFvQ

Grallert · October 15

The goal is not to heat the radiators up completely. The goal is to satisfy the thermostat. So if you were to set the thermostat to 70 will the space reach that set point? There might be a number of things happening or nothing at all. I would set the thermostat to a temperature you want like 68 or 70 and let it rip. This could take some time to take the curse off the radiators. You might find that not all the sections of all the radiators get hot before the thermostat is satisficed. That's ok. You then might find that on a design day all the sections on all the rads do heat up.

delcrossv · October 15

https://forum.heatinghelp.com/discussion/198166/single-pipe-steam-inlet-side-hot-vent-side-cold-should-radiator-fins-all-heat-up-at-same-time

BR#2 needs the packing nut on the valve tightened (a little). Just until the hissing stops.

BR#3 and DR may need a faster vent.

Vents should be hand snug. Careful use of teflon tape (dont get any in port to vent) is recommended.

On startup (pipe cold) check to see if main vent is emitting air. Once the pipe is hot the vent should be closed.

As @Grallert says:

The goal is not to heat the radiators up completely. The goal is to satisfy the thermostat.

CoachBoilermaker · October 15

https://forum.heatinghelp.com/discussion/comment/1814398#Comment_1814398

So that video is 10 minutes to fully heat across the radiator.

Mine was on for 20-25 mins. and not even close to the video progress.

And he says, "We need a new 1A", implying the radiator is not even working correctly.

CoachBoilermaker · October 15

https://forum.heatinghelp.com/discussion/comment/1814399#Comment_1814399

Understood. I set my thermostat to 80*F.

After 20-25 mins. some of the vent side fins were cold to the touch.

Wouldn't the goal also be to heat all fins, actually, to help reach the 80*F target, which was not attained yet

CoachBoilermaker · October 15

https://forum.heatinghelp.com/discussion/comment/1814398#Comment_1814398

Your radiators never even out, despite having new vents, I assume?

How can this happen if steam is what causes the vent to close.

This implies steam has reached the very last vent fin.

Are you sure your vents are working?

ethicalpaul · October 15

Sorry, I meant they don't "even out" without filling with steam. If they completely fill with steam, yes they even out at full heat.

I'm sure my vents are working 🙃

ChrisJ · October 15

On a typical winter day all of mine will get heat to the inlet valves of the radiators (pipe side) within 3-4 minutes and they all start heating within a few seconds of eachother. In extreme cold they get steam in 90 seconds. This balancing took a lot of effort, but it is possible. On a cold start 20 minutes is normal.

The radiators will not get the vents hot in less than 30-40 minutes of constant running. Most of the time my vents are room temperature and only a few sections heat. Even on really cold days the vent side bottom of my radiators will tend to be cool.

This cheesy picture shows the area that tends not to heat on mine during normal use even on really cold days. It just never runs long enough to work that last bit of air out.

Steamhead · October 15

@CoachBoilermaker , some radiators will behave like that if there were made without push-nipple connections at the top of the radiator sections. This does confuse some folks. Post some pics of your rads so we can have a look.

CoachBoilermaker · October 16

https://forum.heatinghelp.com/discussion/comment/1814426#Comment_1814426

Once your inlet fin gets hot, how long does it take for the other side vent fin to get hot?

1 minute? 20 minutes? 1 hour?

KC_Jones · October 16

There is no predicted time, so the answer is, the appropriate amount for how your system is set up. That could be minutes, an hour, or never.

It’s akin to asking how big is a box.

There are tons of variables that influence it. Boiler output to system size, vent size, main venting size, style of radiator, size of radiator.

I have a boiler that is sized to radiation with zero pickup so mine heat really slowly, slower typically equates to greater comfort as it flattens out the swings between firings. If you have an oversized boiler with higher output it might go faster, or if it’s drastically oversized and bangs off the pressure safety like crazy it could go slower.

And finally, I’ve done a lot with my system and quite intimate with it, I couldn’t tell you how long mine take because I’ve simply never timed them. I can’t really think of a reason it matters. I have aggressive main venting to fill the mains first, that takes about 3 minutes on a warm system. After that all the radiators have steams available to them and heat at the rate needed to keep a particular room at the temperature I desire. Some are much faster than others, in general the upstairs goes slower to keep it cooler which is what the family likes. My master bedroom is 8 sections and I’m not sure if the 4th section has heated…ever. I just don’t need heat there so it’s set up to go very slow. When it’s mild I don’t think it ever heats past the first section.

You are trying to satisfy the thermostat not fill radiators. Adjust venting to make things even as you want and satisfy the thermostat. As Chris said above, his radiators are oversized for his house so fully filling them would overheat the house, even when it’s at or below design temp.

mattmich · October 16

Unless it's brutally cold outside, my radiators provide enough heat when partially warm to satisfy the thermostat. When it's negative degrees out, that's when everything gets hot, and until then, pressure won't come into it. As long as you have steam condensing somewhere in the system, there won't be even a pound of pressure.

I have a large radiator (~50 sq ft) early on the main, and even a Maidomist #4 (smallest orifice available) is too big. That radiator gets really hot before any heat reaches the later ones. I put a toothpick in the vent hole and the next cycle, not even the inlet got hot. That's how sensitive radiators are to venting.

FWIW I bought a Varivent so I can hopefully balance better. I'm not really doing much until it gets cold so I can have realistic conditions.

cheers -m

EdTheHeaterMan · October 16

In order to make it easier for all of the folks here to be on the same page, including the seasoned professionals all the way up to the first time steam system owner, I would like to clarify the terms that may be misunderstood when I see them used incorrectly. This is not to be demeaning in any way, I just believe that when you know the correct term for something, it is easier for all those reading this conversation to eliminate any confusion.

When @CoachBoilermaker uses the term Fin or Fins, I believe they are actually referring to a radiator section. The term Fin usually refers to the thin sheet metal sections of a convector or a baseboard radiator that increases the heating surface area of a piece of pipe that is holding the hot steam or water as shown here:

Screenshot 2024-10-16 at 10.30.32 AM.png

In these photos above, the left photo is a copper pipe with aluminum fins that are enclosed in a metal housing designed to cause air currents to flow across the fins and pipe to cause convection heat to enter the room. Item #6 are the Fins.

On the right photo is a cast iron radiator that has no fins. There are 16 sections that make up that radiator. 14 intermediate sections and 2 end sections with legs so the radiator can be installed as a free standing radiator in the room that will be heated by the radiator.

CoachBoilermaker · October 17

Did another test tonight.

The 60 foot main took 10 mins to heat all the way around. I followed the heat as it moved through the main. That was neat to feel the pipe heat up.

Here are the results of the radiator performance and vents:

35 mins after boiler turned on

BR #1
Never any vent sound
Only 3 or 4 sections are hot (total 8)

BR #2
Vent sound stopped
All sections hot (7 of 7)

BR #3
Vent sound still on
All sections hot (17 of 17)

LR
Never any vent sound
Slowly getting hotter (11 sections of 20 are hot)

DR
Vent sound still on
All sections hot (16 of 16)

CoachBoilermaker · October 17

BR#3 and DR: Should vent sound stop once the last section at vent is hot?

BR#1 and LR: If there was never any venting sound, and radiator was only half filled, is vent bad or good?

ChrisJ · October 17

The actual timing is moot.

As long as you're venting fast enough that there's near zero backpressure (You can tell this by noise from vents, they should be very very quiet) and the house heats evenly, it's correct.

The point is, no, the radiators should not heat all the way across except under extreme conditions.

Grallert · October 17

You have two spaces were the vents are hissing and the radiators are fully hot?. I would consider changing these vents. The vents should stop venting when confronted with steam. Hold a cold spoon up to the vents in question and see if they are allowing steam to pass. You'll likely see condensation on the cold surface indicating a stuck or failed vent.

If the other radiators are not satisficing the thermostat it's time to have a look at those. Are they venting air? Sometimes a little tap with the handle of a screw drive or something will loosen up the stuck mechanism inside. Try this with vents that fail to close when they see steam. This is often a process and requires some measure of patience, even for a pro. If you replace any vents the the balancing process starts over, takes a while sometimes. You'll get it. Give it time.

CoachBoilermaker · October 19

Update:

Recall the DR vent that was still venting audibly after 40 mins, and all radiator sections were hot. When I removed the vent, I could blow air when upright, and vent would close tight when held upside-down. Can a vent appear to work properly and close during a manual blow test, but not work under actual operation?

CoachBoilermaker · October 19

Update:

The LR vent hole was painted on the backside. Blowing into it, it does let air out, but very tight/slow. The new Hoffman 1A blows much more freely, even at the 1-slow setting. This must explain why the LR radiator was so slow to fill up.

Huge thanks to you guys in helping me and giving me the support and confidence to diagnose and troubleshoot.

ethicalpaul · October 19

to answer your question, almost anything is possible in a vent. The only sure fire way to test it is to apply steam to see if it closes.

You can of course test if it passes air with your breath

bburd · October 19

Note that even if a radiator section is steam-hot at the top, there may still be air near the bottom of the section that is keeping the vent open. Steam will tend to rise to the top of the radiator, especially if the sections are connected across the top; cooler air will tend to sink the bottom.

What you should never see in a system that is working correctly is steam (technically water vapor since it will condense as soon as it escapes) coming out of an air vent.

Steamhead · October 19

That vent looks like a Gorton D, which is too big for all but the largest radiators.

Can you post pics of your rads and tell us what vents are on them?

CoachBoilermaker · October 19

https://forum.heatinghelp.com/discussion/comment/1814523#Comment_1814523

KC, what type of vents do you use to balance your radiators? Vary the vent speed.

CoachBoilermaker · October 19

https://forum.heatinghelp.com/discussion/comment/1815197#Comment_1815197

Damn, you're good. I think the painted one is indeed a Gorton D. I compared it to the vent on BR #1.

I'll get you some pics, but some of the vents are hidden by the metal radiator enclosure.

For now:

BR #1
8 sections
19" (W) x 22" (H)

BR #2
7 sections
17" (W) x 38" (H)

BR #3 / Primary BR
17 sections
45" (W) x 25" (H)

LR
20 sections
50" (W) x 21" (H)

DR
16 sections
40" (W) x 26" (H)

CoachBoilermaker · October 19

I spend most of the time in the LR.

Thermostat is in LR.

BR #1 & BR #2 empty. Sleep in BR #3.

Single pipe steam. Inlet side hot. Vent side cold. Should radiator fins all heat up at same time?

Comments

Categories