schizophrenic heating system - twin personalities

steamcurious

I keep exploring the heating system in my house and it gets

weirder and weirder.



The house was built in the early 1920s and was originally

piped as “vapor” or perhaps two-pipe steam system. However sometime in the past

90 years most of the house was converted to a one-pipe system. The exception is

the piping into a section of the house that includes an newer addition, and

that part of the house is piped as a sort of two-pipe system!. I just

discovered this, trying to figure out why that section of the house does not

heat very well now that the system is running at low pressure.



Details:



Most of the house is fed by two mains using a standard

parallel, up-feed arrangement with wet returns. This section is now running as

a standard one pipe system with vented radiators, etc. The addition is fed by a

2”main that was tapped to the near-boiler piping right before the two mains

split (the split giving rise to the two mains is piped correctly; the original

guys knew what they were doing). This 2” main makes a long run through a crawl

space (probably 40 or 50 feet), and then fans to feed 4 radiators. The

radiators do not have vents, but rather have their own return that is vented just

where the drip line turns down to connect to the bottom of the Hartford loop (please

see diagram).



To add insult to injury the 4 radiators in this run are

dissimilar. Two are standard cast iron radiators but the other two are tube and

fin radiators, the kind (I think) that are meant to work in hot water systems.

These two radiators are fed from the 2” main using ¾” pipe.



Needless to say the system does not work well. Originally

the boiler was set to run at around 10 pounds and it was very, very noisy. I

cleaned the returns and lowered the pressure and now it runs nice and quiet.

However the addition now gets very little heat! It seems to me the reason the

system was running at 10 pounds was to push steam through the weird piping

heating the addition. Does that make sense? Anyway, I thought I could help

things along by providing better venting for this run, but even with the vent

completely out, the heating of the addition is marginal at best. In fact, it

takes many a long time for steam to reach the vent in this run, several times

longer than it takes for it to reach the other air vents in the system.



So what would be the best way to deal with this situation? <span style="text-decoration:underline;">

</span>

TomM

questions

traps on the addition side?

Jamie Hall

The characteristics

including venting requirements etc. of two pipe vs. one pipe systems are sufficiently different to make good balancing really hard.



The usual suspects: are the steam mains insulated?  If not, do.  If there is insulation missing on that run to the two pipe system, you're probably out of luck until you get some on it.



Is the vent for the two pipe section big enough?  If not, that might help a little -- although where you tried it with the vent out, that probably isn't going to help much if any.



Raising your pressure isn't going to help a bit.  Steam doesn't push for beans -- it goes to low pressure, which is going to be where it can get, and where it is condensing fastest.  Which, at the moment, is the one pipe system radiators.



After that... can you slow the venting on the now one pipe system's radiators?  That just might help a lot.



Otherwise, some experimentation is in order.  Specifically, if you close the vents on the all the one pipe radiators (if you can), does the two pipe section heat OK?  If not, there is some sort of problem there which may need more trouble shooting.  If it does heat then, and slowing the venting on the one pipe radiators doesn't help enough, you may have to go with TRV vents on the one pipe system... 

jpf321

perhaps

perhaps a vent on the supply side of the 2-pipe would be helpful .. right now you are waiting on the steam to get all the rads to get steam-hot all across before you will see steam at the return side vent. forgetting about the time to get steam to the return vent, how are the rads heating in general? simultaneously? all across? and you are requiring venting through the rads to push air out the return side vent. i'm sure there's no harm in leaving it there, but i would consider one on the supply side as well.



what size is the current return side vent .. 50ft of 2" pipe could easily require a Gorton #2 + a Gorton #1 .. then it must vent all the rads .. then it must vent the return side to the vent .. that's quite a bit of work for a single vent on the return side.



calculate the amount of air that you are expecting to move through the current vent and see if it's adequate .. if not, add venting to the supply side (at least to handle the 50ft 2") as well as increasing venting at current return side vent (to handle the combined rads and the return run to the vent)



what size tap is the current vent on? 1/2" pipe will only support 2pcs of Gorton #2 .. if you need more venting than that, even leaving the hole open probably isn't going to help much .. maybe you need a 3/4" hole or 2holes-1/2 each.

steamcurious

Good ideas!

Thanks for the ideas.



In response to your questions.

1. The "addition" (2") main is insulated all the way through to the end.

2. There are no traps of any kind.



I agree that the problem is getting the steam moving through the "addition" run. However the fact that it moves very slowly even when I remove the air vent at the end of the run suggests to me that there are serious issues with resistance in the pipping. Is it possible that the returns are filling with condensate and that works as a plug? I do not know if the pitch is correct (or even what it should be for such a piping arrangement).



I like the idea of venting the supply side, it may even work. I will give that a try.



I am reluctant to slow down the venting of the two runs serving the main house as it will cool the rest of the house and may increase the energy cost.



What about making that run into a one-pipe system? at least the piping is relatively accessible..

Unknown

2 pipe system

Attached is a diagram of a 2 pipe system. Where there are traps in the drawing it will also work if instead of traps at the point where there are traps now piping then drops individually into a wet return. Venting location depends on whether there are traps and how they are arranged. You need traps/individual drips otherwise the system equalizes ("short circuits") pressure through the return. There is one more possibility with the radiators in that these could have orifices

- Rod

jpf321

plug in returns

i think you will only get a "plug" in returns if it is plugging access to the vent. if water is "stacking up" horizontal or is the horizontal which the vent is on is filling with water due to improper pitch.



again, do the math to determine your venting needs (supply, rads, return) .. and then vent properly.

Jamie Hall

It would

very much be worthwhile to check the pitch of that two pipe main -- the way it is piped, it has to pitch back to the boiler.



No traps on the radiators?  Eh?  What is keeping the steam (if it gets there!) from passing through the first radiator to fill -- probably one of the fin tubes -- and locking the rest of the radiators on that line out?  Better check on that.

jpf321

wouldn't

wouldn't the steam eventually fill all rads assuming the vent(s) were still open. i'm thinking of it as one great be radiator where the steam eventually fills all tubes/columns until the vent closes. i think dan mentioned that some systems are designed like this (the Dakota in NYC??) .. but this may also presume a vent on each rad.



jpf

Unknown

2 Pipe Steam Loop

I think adding vents is a waste of time at this point as first you have to determine what sort of 2 pipe configuration you're going to adopt as that decides where you need to put the vents.

Okay let's take this one step at a time. Let's tackle the mains firsts

1.Which way does the 2 inch steam main slope? (toward or away from the boiler?)

Is the slope on the steam main 1 " in  20 ft or better?

2. On the Return Main -the one with the vent -Which way does it slope?

Is this slope1 Inch in 20 ft or more



Wet Return-  Is there or could there be a wet return piping installed under these radiators?  (It would have to below the lowest boiler waterline level)



Could you upload some pictures of the radiators on this loop? I'm really interested in the inlets and outlets. 



This sort of thing is what I mentioned in one of your earlier posts in that you need to get you off boiler piping squared away first and then you'll be in a good position to replace your boiler.

- Rod

jpf321

yes i'm almost positive

yes i'm almost positive that Dan mentioned that "The Dakota" in NYC uses a "ladder" arrangement of 2-pipe where there is steam fully in the "returns" and "supplies" .. Dan? am I recalling correctly?



He showed a picture that there were main vents actually located outside above their roof (presumably on the supply side) .. i'm tempted to buy the book, http://books.google.com/books?id=OGEDiKOujjgC

Jamie Hall

If there are, indeed

neither traps nor individual radiator vents nor inlet restrictions on the radiators on the two pipe section, it's just not done right.  The type of two pipe system Dan mentioned is the original two pipe, and didn't have traps -- but did have vents on all the radiators, like a one pipe, and was, for all practical purposes, a one pipe system only with more pipes.  This is a possible modification. 



Inlet restrictions is another possibility, though.  Orifices on the radiator inlets -- have you checked that?  Or calibrated valves?  There are some excellent vapour systems which use that approach.  However, they really don't play well with conventional one pipe systems.  Because of the restrictions (which are there to keep steam from making it through the radiator -- they only admit enough steam to fill the radiator, and no more) they are very sensitive to pressure (never over 8 ounces) and they are, obviously, much slower than a single pipe radiator with a normal vent.

Charlie from wmass

I have inherited a system like you describe.

As luck would have it the customer had it installed before even my Father did their work. It has been a pain ever since it was installed. Running pipes back individually to the wet return in the basement and venting them individually marginally helps. It is noisy and not well balanced to our tastes but vastly improved to the customers experience before Da got there. The vents do not have a very long life due to the water hammer the system still has. Yes we had better options for a repair including traps. The budget would not allow for a proper repair. After 25 to 30 years of going through radiator vents the customer is still happy with the heat. Both my father and I are still shaking our heads.

steamcurious

One more observation

One more observation. Today I fired the boiler and listened as the steam started to make its way through the piping. I heard what seemed to me like gurgling, steam

frying to make its way through puddled condensate. The gurgling suggests to me impeded steam flow.



Remember that the entire run has one single vent, at the end, just before the vertical pipe leading to the Hartford loop. There are no steam traps or hidden returns. And the pipe and fin radiators are modern era, similar to the kind used in water heating baseboards. I get the impression that his was piped without too much though and using materials at hand as part of the addition.



In any case, many thank to all of you for the ideas and suggestions. I see how you guys are thinking about this. First figure out what is there - especially the pitches - and after correcting any pitches that may need it, see if venting will help. Thanks Rod for the suggestion about what tasks to prioritize.



I will get to work on that plan and post the results of the survey and suggested modifications.

Charlie from wmass

What plain are the heat emitters on?

are they all on the same floor or are they on different floors? Also remember the fin tubes and the radiators have very different latent heat characteristics. even with hot water it is a bad idea to mix them.

TomM

pics?

steamcurious, we'd be interested in seeing some pics.