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 · 12:20AM

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?

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

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