Help with system type

Buster

We went on an estimate for a steam boiler replacement and I'm not sure what type of system this is. It is 2pipe with no traps on the radiators. I have attached some pics of the device in the return that I have not come across before. Any help is appreciated.

mattmia2

If there are no traps it is a vapor system of some sort, it will be much happier if you carefully size the boiler to produce just as much steam as the radiators can condense and put a vapor stat on it to keep the pressure very low. What controls are on the radiators? Do they have vents?

Hopefully someone knows specifically what this system is.

KC_Jones

@Steamhead always seems to be the system encyclopedia around here, let's see if he has anything to say.

Buster

We are waiting for them to get the covers off so we can measure the radiators. Adjustable supply valves and no vents on radiators. 2 Main vents at the end of the 2 dry returns just before they drop down in the the device in question.

mattmia2

Is there or perhaps was there at one time steam piped in to the device in question as well? Maybe it is some version of a steam powered boiler return pump.

Buster

Not that I can tell

Chris_L

Where is this home located? Was it on district steam at one time?
That was the business of the American District Steam Company, whose name is on the tag. See: https://en.wikipedia.org/wiki/Holly_Steam_Combination_Company

As for what that device does or did, I haven't a clue.

Buster

Not a District steam house. It's a farm house on 700+ acres 

clammy

I believe that’s a broomwell air eliminator return trap and if memory serves it usually had a line off the steam side feeds where the plug is now . That was most likely removed when a newer boiler using oil or gas was installed over firing w coal. Also check the return fitting on the radiators and make sure that there isn’t a water seal type trap if that is not present and even if it is you should derate your edr figures by33% to guarantee that the boiler is first off not oversized which will help prevent short cycling and also ensures that your boiler will not have the ability to completely fill every radiator w steam and have steam pass through your non trapped radiator and pressurize your dry return stopping any and all steam distribution due to zero pressure diff . As other stated you gotta keep your pressure very low maybe 4 to 7 ounces . So it gotta be a vaporstat ,take a close look at the existing main vents most likely hoffmann76 vapor vacuume if she can still hold a vacuume then replace w the same , Be sure your new boiler water line is going to be high enough that you do not lose any water seal which the older boilers higher water line may have covered if you do lose water seals out in the system then a false water line may be your fix . On a side note on your replacement boiler if it comes w a cycle guard lwco please remove it and install a non cycling type and take a look at the possibility of a 2 stage gas valve to curb any short cycling that’s kinda common w running pressures in ounces . These type of vapor system need dry steam to perform and operate properly so the best near boiler piping should be observed and respected which translates to both tappings being used header to be sized larger then the combined area of the mains it is suppling . Depending on btu size a min of a 2 inch equilizer and full port return inlets no bushings . Sorry to what seams like a rant but I see a lot of guys mess up on 2 pipe systems and the home owners get the short end of the stick until some squares it away . It’s great to see you seeking advice its more then most would due . Peace and good luck clammy

Buster

Good info clammy ,Thanks

Steamhead

KC_Jones said:

@Steamhead always seems to be the system encyclopedia around here, let's see if he has anything to say.

It's an ADSCO system. @Chris_L had the idea, but that company was involved with non-district systems as well.

This system used orifices in the radiator inlet valves to restrict the amount of steam to the amount the radiators could condense without steam getting into the returns.

The device with a tall sight-glass is a float-operated damper regulator, similar to those used in the Broomell, VECO and other similar systems.

See chapter 15 of Lost Art for more.

@Buster , where are you located?

Buster

Thanks @steamhead! It mentions the boiler would be oversized by 50 percent. What was the reason behind that? We are in Ashburn Va.

Steamhead

Might want to see if @Dan Foley comes out that far- his company is in Lorton.

Not sure why they oversized the boilers back then- but there's no reason for us to do the same.

mattmia2

Coal boilers were oversize so they could be hand fired in such a way that they would burn for a long time. Maybe this is what is being referred to?