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Single Pipe Steam Main Return Temperature - Warm? Hot?

Could someone please explain the basics of the temperature for Main return. I am observing room temperature pipe even when the supply mains are scorching hot. I believe the 2" main makes a loop totaling ~60-80ft ft. I am getting some plumbers say that the return pipe will be at most "warm", but not hot.
Is steam ever supposed to make it to the return or by that time all the latent heat juice is out and its all warm'ish.
Is steam ever supposed to make it to the return or by that time all the latent heat juice is out and its all warm'ish.
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Comments
if the majority of the radiators are heated most or all of the way across it's likely the return piping will be quite hot, perhaps even close to steam temperature.
Under most conditions I'd expect them to be fairly cool though. My wet return gets very hot if it's below zero out but is usually barely warm.
If you're talking about a dry return (not along the floor) it also depends on where the main vents are. If the main vents are at the end of that return which many are, that entire return will be filled with steam and very hot.
A true return -- dry or wet should never be steam hot, vents or no vents. If a system is really cranking -- long runs etc. -- a wet return may indeed become warm, but really should never be really hot. A dry return should never be more than warm.
There are two pipe systems -- such as most vapour systems -- which have all the venting at the end of the dry returns at the boiler. However, they have crossover traps from the steam mains to the dry returns. In those systems, the dry return is never more than warm, and usually cool.
All two pipe systems must have vents on the dry return, whether they have crossover traps or not.
The most confusing systems are one pipe parallel flow systems. They too may have all their venting right at the boiler, at the end of the pipe before it drops to return the condensate. If they do, that pipe is not, technically, a return -- it is still a steam main, even though it is past the last radiator runout. In such a system, that pipe will indeed be steam hot right up to the very last vent.
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.
Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
Yes it is a dry return, vent is at the elbow before the pipe dips down to go back into the boiler.
So if I remove the main vent at this spot for test purposes and run the boiler, should i expect to see steam come of out? (path of least resistance)
But please be very careful. That steam can cause severe burns extremely fast.
New England SteamWorks
Service, Installation, & Restoration of Steam Heating Systems
newenglandsteamworks.com
I have a very similar setup as you. At one point my dry return, which ends approximately 2 feet from my boiler, didn't have any venting. It would only get slightly warm.
I have since added 2 gorton #2's and now that return gets steam hot. So I would agree with the others that running with it open at the end of the return should get steam heading there.
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.
Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
Tracing the pipe is a mystery as it is inaccessible once it leaves the boiler room. Maybe if we can capture some aliens they can help trace it.
Could radiator venting in 1st and 2nd floor be an issue which is making the steam not travel all the way to the main vent?
However, you wouldn't see any pressure at the boiler if it was and you said you were seeing 1.5 PSI.