Unequal steam radiator heating

@manus0142 0142
What do the air vents on the main steam distribution lines look like? Can you take pictures? Most likely you have insufficient air venting volume and installing several more main air vents will allow steam move through the system faster.

What is your pressuretrol on boiler set to? Can you take a picture of that? If the pressure is set too high it will slow down the distribution of steam throughout the system.

Hello @manus0142,
If I understand your post correctly, a few years back it all worked fine. So to me the question is what has changed between then and when the performance significantly diminished. As others have mentioned, possibly the main vent is now plugged up or stuck closed. Could the return for that main be plugged up trapping condensate water where it should not be ? Did the house settle some more, pipe supports dilapidated, pipe pitch has changed.

Is it a one pipe system ?

yellowdog said:

i am definitely not a steam expert, but this doesnt sound right to me.

"If the pressure is set too high it will slow down the distribution of steam throughout the system"

Well, it isn't quite right -- but it's sort of right. It's a good deal more complicated than that, but ...

But it's often moving slower because it's already everywhere so moving faster wouldn't make any difference.

Or in the case of a really oversized system that builds pressure before the radiators even see steam, it's already moving as fast as the radiator venting will allow it, so it isn't going any slower than it would otherwise. In this scenario the steam is moving faster the higher the pressure is since it's going to push the air out of the way faster than it would at low pressure.

The statement is quite misleading and weird IMO. I think it's used to try to convince people that raising the operating pressure of their boiler is useless, and that is very true but I would use other arguments for that.

To try to make amends for this diversion, to the OP I would say don't use that company if they actually thought that replacing a steam pipe would help your steam distribution. It's like repaving your driveway when your car won't start.

The main venting that others mentioned is highly suspect here.

yellowdog said:

i am definitely not a steam expert, but this doesnt sound right to me.

"If the pressure is set too high it will slow down the distribution of steam throughout the system"

High pressure creates wet steam by increasing the density of water vapor compacted by pressure which slows down the steam moving through the system along with creating other problems.

Instead of trying to create higher pressure at the boiler compared to the lower pressure of the atmosphere at the exits of the air vents, it is better to create more exit capacity at the air vents. You want to create lower pressure at the ends of the system (vents) rather than trying to increase pressure at the entrance(boiler).

Picture you have a full subway train with doors on both sides. People are trying to get on a center platform, while others are trying to get off the opposite side of the platform. Does shoving people on the center platform harder onto the train get people off the train faster or create bunching (increased density) inside the train that makes it harder for the people trying to get off the train to leave? If you don't shove people (not increasing pressure at the boiler), and the opposite side of the train has nice big doors for everyone onboard to GET OUT quickly (what sufficient air vents do), suddenly the flow of passengers goes much more smoothly. Does that make sense?

Slow steam distribution almost always is because there's insufficient exit capacity for air (venting) so that steam gets trapped behind it in traffic. Increasing the 'traffic' (pressure leading to denser steam) isn't going to fix the exit capacity problem, but will make the 'traffic' problem worse because you are trying to solve for the wrong end of the equation.

Big Ed_4 said:

The pressure is used to tell the burner to shut down when the system is full of steam .

Seems to me that is only true on a poorly designed or poorly maintained residential systems. Here, even on a 2 degree Fahrenheit day my pressure never went over 2 inches of Water Column or 1.156 Oz. I kind of wished it got colder out so I could see the pressure increase or the system just not keeping up with the heat loss. Even at 2 degrees Fahrenheit the Boiler seemed to only run at about 55 - 60% duty cycle, with only the thermostat terminating the burn.

How far along the misbehaving steam main does steam actually get? It should get hot right to the vent on that main quite quickly. If not, the "main" vent (yours are both almost certainly too small) may not be operating properly.

If the steam seems to stop dead in the main, there may be a problem with a sag in that main. Check that the main is properly pitched for its full length. There may be other reasons, but that's an easy one to start with.

Oh well. As I said, that's the easy one. However, if steam makes it to a certain point in a system, and never gets beyond that point, there is something about that point. Which sounds obvious. One thing to remember is that eventually -- though it may take a lot of time -- even a pipe with a cap on the end -- no vent or anything --will warm up. If steam can reach it.

A complete block in a main is very unusual. However, if for some reason there is trapped water, that counts.

Can you take a picture -- maybe a couple from different angles -- of the point at which steam stops?