Two Pipe Guidance

tommyoil

Went to a two pipe steam job. Measured out at 84,300 BTU with a 175,000 PEG 50 in place. Near boiler piping NG. 10 column rads. Asbestos covered mains disappear into finished basement ceiling. Rads have graduated supply valves that have the name "Adsco" stamped on the sides. Made all valves functional to the point that I at least know that they are open all the way. 3 of 10 valves are a mess but again, they are open. 5 of the 10 rads get half hot (the top half) the bottom half is cold. There is a union ell at the return side of the rads similar to that of a Richardson type union ell. Those ells on the non-functioning rads are also ice cold. The other 5 rads are BLASTING HOT and seem to be functioning. Now comes the part I've never seen.... Supplies split to front and back of the house, returns do the same EXCEPT where the returns reach the boiler room, before they drop to the boiler, there is a common 1-1/2" tee which ultimately disappears into the wall to the second floor. When I traced it to the attic(third floor) it went out the side of the house where its was happily blowing steam to the great outdoors. There are no traps of any kind throughout the system and there are no vents (besides the open 1-1/2")anywhere either. I CAN tell you that both the LWCO and feeder work because in three hours I watched them operate multiple times. Initial complaint is not enough heat because of the 1/2 hot rads but after questioning Mr. Owner needless to say his fuel bills are astronomical and the water bill is not much better. Heres my questions... 1) Are the union ells operating along the lines of a Richardson system or a Mouat type? They are currently painted shut and before I cracked one open I wanted to know what was what. And 2)What do I do with that open 1-1/2 out the side of the house. I was skeptical about just capping it as I didn't want to cause some reaction and make matters worse elsewhere. I'd like to get everything hot for them all while saving them some fuel dollars. We KNOW the PEG 50 is oversized with some near boiler issues. Trying right now to address the 1/2 hot rads and open steam line to the birds. Where do we go from here. Thanks.

Steamhead (in transit)

The ADSCO is basically

an Orifice Vapor system. It is described in Lost Art as having plain return elbows. Therefore the radiator shutoffs are orificed to keep the steam out of the dry return.

First thing to do is install a Vaporstat. Set it to 8 ounces or so. Then set each valve so it lets enough steam thru to fill the rad about 80%.

It might not be a bad idea to install a surface aquastat at the tee where the vent pipe connects to the dry returns. This can be wired to stop the burner if steam gets that far.

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Mad Dog_2

Great idea Frank.....

Mad Dog

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tommyoil

So....

That attic vent needs to be open and not capped as I was sent to the job to do? I was initially sent there because another tech told H.O that each of the rad valves were no good and needed to be replaced. I was sent with a box of 3/4" rad valves and told to relace all of them and to cap the open steam pipe. Some of the valves ARE NOT Adsco valves(already) but standard rad valves and if I recall correctly those are the ones that work. The bathroom valve recently was replaced by others and its fully hot. Is it improper to change those Adscos to standard valves? I'm a little confused as to why only the top halves of some rads are hot. If the ells are standard ells then why aren't the bottoms hot? Are they "airbound" by steam entering the dry returns? Also, the Adsco describes a condensate reciever which is not there anymore if in fact it was ever there. Do I need to compensate for that? And what are the "special fittings" they refer to in higher pressure systems? I'll order thr vaporstat today. Does the surface mount aqua stat need to be reverse acting?

Jamie Hall

no surprise...

Steamhead is right.

First thing to do you are doing: get the pressure down. That is critical in any vapour system.

However, you have a another problem: those valves which were replaced probably don't have orifices in them! The orifices were critical to this type of system, in that they only allowed as much steam to pass as could be condensed by the radiator. In your present situation, those nice hot radiators are getting more steam than they need, and that is getting into the dry return a sailing merrily out the vent -- which is what that pipe to the attic is.

That vent pipe is fine. Next project is to throttle the various radiators so that each one gets only enough steam to get it hot. The outlet elbow should not be hot; Warm, perhaps, but not hot. If it is hot, close the radiator valve some and try again (not all radiator valves throttle nicely... one can hope that these do).

Radiators which are getting half hot aren't really a problem, and I wouldn't worry about them until you get the radiators which are really really hot throttled down.

May take some tinkering, but after a while you'll have a lovely vapour system, and the water and heating bills should come down nicely. Just warn the owner to keep his hands off the radiator valves once you get them set!

Paul Fredricks_9

This whole thread is so cool!

I'm not very up to speed on 2 pipes, but can't you put a main vent or 3 on the Tee that goes to the outside? Or do you need to keep that pressure down at all costs?

Steamhead (in transit)

That's correct

steam in the dry returns interferes with circulation. If the dry returns have steam in them, they are not at zero pressure, and the air from the other rads can't flow into them.

You can use orifice disks on standard rad valves, or get orificing replacement valves from MEPCO or Barnes & Jones. These valves aren't cheap, but are the proper parts for the job.

The condensate receiver on the ADSCO simply served as a collection point and low-pressure gauge. You shouldn't need to allow for it- just install a 30-ounce gauge and a Vaporstat.

The surface aquastat is a direct-acting, open-on-rise unit. A SPDT type will work too if properly wired.

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tommyoil

That was my next question.....

Even though the vent pipe to the attic is wide open, how is the system allowed to build any pressure at all? Is there actually ounces of pressure already in the returns despite the open vent piping? In which case if pressure is not allowed to build up, what difference would any "stat" make be it vapor or pressure. If your suggesting that there is defacto ounces of pressure available simply by having steam already present in the returns then I understand. I just dont understand how any pressure is available at all with the open piping to the outside. This certainly is a bit different than single pipe. And just let me say at this point THANK YOU guys for all your help and suggestions and Dan for giving us all access to all your expertise. My customer and I appreciate the time you take to lend a hand. I'm sure I will have more questions but I will cross one bridge at a time.

Paul Fredricks_9

Hey Tommy

Just for fun, can you take some pictures? I'd be interested in seeing what the valves and all look like.

tommyoil

I did already Paul

But I just got the camera the day before. As soon as I can I will.

tommyoil

The other thing is this....

175,000 BTU in an 84,300 application. How will I address the short cycling aside from replacing the boiler. Can I somehow skate by this season without doing that too? Possible remove some burner bars?