Two Pipe System Clarification

simon_skove

Two pipe steam/vapor system.

I need a refresher.

All things being dandy, boiler makes steam, steam fills the piping system (hopefully without too much loss due to cold pipes). As the steam reaches each radiator through the top valve at one end and fills the radiator, the air escapes through the bottom valve and heads down the dry returns back to the boiler and continues its escape through the large return vents back at the boiler.

There is no visible devise at any radiator to prevent the steam from following the air through all the dry return pipes and out the return main vents back down to the boiler.

This is a 1920's system with virtually no changes other than the boiler and the deletion of radiators. One that was on the ceiling in one of the rooms in the basement and one on the second floor landing.

My question is how did the steam stay in the radiators back when in 1925?

Steamhead

There are probably orificing devices in the radiator shutoff valves that keep the steam from reaching the rad return connections, as long as the boiler pressure does not exceed 4-8 ounces or so depending on who designed the system.

Or, there might be devices inside the radiator return elbows that you can't see without disconnecting the radiators. These kept the steam from reaching the dry returns.

Jamie Hall

and just to add to @Steamhead 's remark — provided that the orifice or regulating valve is correct, and the steam pressure is kept down where it belongs, all the steam which can get into the radiator is condensed by the radiator before it has a chance to escape. Simple and elegant.

109A_5

The thing that may be missing is a means to purge the air in the steam main efficiently, I see a water seal which will return any condensate in the main to the dry return but no path for the air. To me burning fuel to push air out of the main through the radiators is not helping with efficiency.

Purging the air in the main through the radiators may be a comparably slow method. As @Steamhead mentioned the radiator valve and any orifice on the return side of the radiator is used to slow down the flow rate.

simon_skove

Steamhead - showed you the pictrue above over 10 years ago. Based on the information I provided you determined this was a Tudor System.

Steamhead

https://forum.heatinghelp.com/discussion/comment/1905379#Comment_1905379

Your memory is better than mine….. Tudor it is.

simon_skove

So the Tudor System works based on not creating too much steam and it will condensate within the radiator?

109A_5

It appears with the Tudor system there is no dedicated means to purge the air from the main except through the radiators.

https://heatinghelp.com/systems-help-center/european-heating-systems-circa-1907/

https://heatinghelp.com/assets/documents/492.pdf

Steamhead

https://forum.heatinghelp.com/discussion/comment/1905388#Comment_1905388

That was not uncommon in the coal-fired days. Now we add main vents.

109A_5

https://forum.heatinghelp.com/discussion/comment/1905389#Comment_1905389

Yes, looking at the patent dates that would make sense.

simon_skove

The main vents you mentioned Steamhead are located where?

mattmia2

https://forum.heatinghelp.com/discussion/comment/1905391#Comment_1905391

they probably need to be added because someone converted the boiler to oil or gas then replaced the boiler but never added the vents.

with the coal boiler there was probably a device to equalize the pressure between the mains and returns and that won't work with the mains vented, that type of system needs a single vent on the return. the output of the coal boiler would vary depending on if it had just been stoked or if it had been burning for a while so there needed to be a way to automatically control the pressure across the radiator so the orifice could allow a known amount of steam in to the radiator

the amount of something that passes through an orifice is a function of the orifice size and the pressure.

since you are controlling the burner with a vaporstat, you can keep the pressure under control that way and you can have main vents.

simon_skove

I do have two locatioins at the ends of the dry return from "opposite" directions on the system. One side has a Gorton #2 - 1/2" and the other side has two of the biggest size vents made by the "other mfg"

Jamie Hall

https://forum.heatinghelp.com/discussion/comment/1905387#Comment_1905387

Exactly. But this is true not only of the Tudor system but is the true distinguishing characteristic of a vapour steam system as opposed to the general class of two pipe steam systems.

EBEBRATT-Ed

@simon_skove you need to keep the pressure low. Start the boiler from cold and when the supply pipe gets steam hot see how long it takes for rads to heat. If it take a long time you may need more venting. The vents on the mains should be on the steam line at the end of the mains before it drops to the loop seal

Jamie Hall

The alternative to steam line main vents is crossover traps to the returns. They both work.

Steamhead

https://forum.heatinghelp.com/discussion/comment/1905391#Comment_1905391

Near the ends of the steam mains, after the connections to the last radiators.

109A_5

https://forum.heatinghelp.com/discussion/comment/1905422#Comment_1905422

So far I don't see either in that system.

simon_skove

How hard is it to tap that 90 at the end of the steam main in that pic with a vent…what size vent?

EBEBRATT-Ed

@simon_skove length and diameter of the main decides the size of the vent. look around for a tapping first. You can tap the elbow 1/4" I wouldn't go larger than that to drill and tap.

Other options are:

1. to take the elbow off and put a tee in its place. There is a union in the drop pipe to help with this.

2. Or tap the tee that feeds the last radiator on the main

3. Take the radiator valve off the last rad fed from the main and put a tee where the valve is with a vent on it

Drilling and tapping the tee that feeds the last rad is probably the easiest if you can get a large enough vent on it.