Really Old 2 pipe vapor system Short Cycling:

zippydw

Spent the day crawling all over this thing. I think you are right on the money about the evacuator.

I scraped alot of paint off the "carrot". It is a McDaniel Suction Tee. Doesn't look like anything in McDAniels current line.

I also found what looks like really antique traps at the take offs to the return mains (right below the bottom of the floor joists from each rad. Also, there is something that looks like a trap at the bottom outlet side of the big honking pipe where it connects into the wet return leading to the boiler.

One thing, at the end of one rear run, there is a 5' section of cast iron base board with no trap. COuld that be causing some of the short cycling and should I put a thermoostatic trap on it?

Then, I have looked everywhere. There are no air vents. At the top of one of the returns there looks like a relatively new pipe cap. should I put air vents on the returns with this type of system?

I an attaching a pdf sketch of the piping at my boiler if that helps.

Thanks for any help you can offer on this. I spent hte day wathching this run for 3 minutes. shut down for a half hour and run for three minutes. Repeat cycling.


S

Damian_2

Short cycling at really old 2 pipe vapr system-installment 1

OK. Who remembers my "big honking pipe" pix from last winter?

situation:
-2 pipe low pressure (actually vapor-someone called it "vapex", all dry returns. Have never found a trap anywhere on the system.
-1907 original system. McLein Weil boiler put in in 1950's.
-150,000 BTU input for 2000 square foot frame.
-no traps on returns. No vents at rads.
-Mix of column rads and narrow tube rads
-Can't locate vents or a F and T trap.
-But it does have this cute "big honking pipe" vertical with the returns tying into it that the wall had alot of ideas about as to what it did.
-5 year old McDonnel Miller low water cut off
-Last year got alot of great help about short cycling at 0 degrees outside temp.

Todays problems:
Short cycling at 20 degrees outside temp. Heat not catching up to tstat setting. TAkes forever to get steam after temp hits set point.

Appearance of alot of corrosion at bottom of Hartfor Loop into boiler. Same thing problem I had fixed about 5 years ago with the McDonald Miller.

Some More:

Last year it seemed that at very low temps an intermitent leak at the Low water cut-off was causing he thing to cut out. New sight glass, gaskets, vigil candles to dead old guys and I got through the winter. Never quite figured out what the "big honking pipe" did. But following Dan's sage advice...since it wasn't broke (anymore) don't fix it.

This year all the kids moved out. shut off alot of upstairs rads. Ones left on work just fine except for one that never worked anyway.

I am at a loss about the short cycling. All the rads get hot. Seemed to work fine in a test fire after doing site valve replacement in September.

I went back on the venting concept from last time. I have one pic of something on the return from one side of the house (house has one return main from the front, and another from the back that tie into the "big honking pipe")

On the rear house return there is some sort of bleeder contraption (photo attached. Is this some dead old guy's idea of a manual vent? The return for the front does not appear to have any vents. Need some advice on this.

Also, last night I found what looks like some cross-over valving and pipes between the supply and return ahead of all the rads that flow into the "big honking pipe".

I am wondering if the BHP is actually a primitive device to enhance vacuum in the system and act as a quasi condensate pump since it is about 4 inches in diameter and drops off to a 2 inch diameter at the bottom that flows into the boiler.

On the corrosion (photo attached)has anyone seen this and any ideas about what's causing the electrolysis?

I will have to post another forthe rest of teh photos since the server seems to limit the number of photos that can be attached

Damian_2

photos installment 2

rest of the photos. Any help is really appreciated

Bob W._3

zippydw:

"This year all the kids moved out. shut off alot of upstairs rads. Ones left on work just fine except for one that never worked anyway.

I am at a loss about the short cycling. All the rads get hot. Seemed to work fine in a test fire after doing site valve replacement in September. "

Question: To me (HO) it stands to reason that shutting off radiation alone could cause short cycling. Perhaps you should open up all the rad valves and see if the problem is cured. Just a thought.

Damian_2

Short cycling at really old 2 pipe vapr system

When I shut off the third floor and a couple of the bedrooms, I expected to get some hammer, especially if I ran the boiler a little cooler, say at 65 degrees. It's been really mild in Chicago through November.

From a problem solving logic your recommendation makes a great deal of sense to eliminate a change in the system state that coincided with the problem if that is the source of the short cycling.

What I haven't been able to get about the "why" is that while I am reducing EDR getting used, I am also closing off the rooms so I am reducing my area heated and corresponding heat loss through the exterior walls windows etc.

Since I am reducing the heating load, is this a case of giving the pressurtrol a little bump to lengthen the cycle a bit since I have reduced EDR working. so the cycle is adequate to meet the tstat setting?

Over the past 15 years, we've insulated about 80% of the walls and replaced about half the old windows. Calculated boiler load based on my last permit for an addition we built (separately heated-not on the boiler)was less than half of the boiler output assuming 65% efficiency.

I hate heating up 150 kbtuh for me, herself and her pooch (and the kids hamsters that they left us) while I am trying to get a handle on setting up for a boiler replacement. I have to address the question of how big the replacement boiler will be since the old dead guys probably seemed to have been pretty heavy handed in sizing the original.

Thanks for the advice. Really aprpeciated

Bob W._3

Zippydw, sorry I was not more specific. I meant open the rads just as a test to see if the problem stops. If so, you at least know what is causing it and can address it from there. Remember that your boiler is sized to the radiation in the home (or should have been) and when you cut down the EDR all you are doing is pushing too much steam into too small a system. Short cycling can't be helped. I know this from experience. We run a 450,000 BTU boiler that was sized to fill our 1079 sq. ft. of EDR. 300 sq. ft. is never used, and we are eliminating more yet. The only solution was to get a new boiler.

Bildo

try a vaporstat

Try installing a vaporstat instead of the pressuretrol. It looks like you have the pressuretrol set at zero. The pressuretrol you have is not accurate enough to be set that low.

Steamhead (in transit)

Looks like someone had a gauge on that return

that's what the pigtail and shutoff cock was for.

Was your house ever supplied from steam pipes under the street?

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Damian_2

Really Old 2 pipe vapor system Short Cycling:

Thanks Bob. I am on that track for next spring.

Herself is all over me because she wanted it done last summer. Someone told her that the new boilers suck less gas....

now if I can just figure how this thing is vented (aside from leaky old valves)

That started out as a joke but, as strange as this sounds this year is the first year in memory where I did not have at least one leak. Spent alot of time this summer tightening things up. System runs dead quiet. Maybe that's the problem....The leaks were actually venting the system!

Damian_2

Really Old 2 pipe vapor system Short Cycling:

No on the off board steam supply. original system appears to have been coal fired. My sense is that the Wclein Weil is acutally the third boiler in the house. Best I can get from the neighbors and old folks in the neighborhood, the house had alot of work in the 50's and maybe the 20's.

One second floor rad was removed. Found the pipe in the wall...no evidence of a trap at he bottom of the riser. They cut the pipe at the wall sill plate above the lateral.

You can tell on the valves. Some are the really old hand throttle valves. I just repack those and light more vigil candles. Then there are a bunch of newer ones standard steam valves. no orifices. Always on the supply side.

Damian_2

Really Old 2 pipe vapor system Short Cycling:

OK. The more I play with the current problem, I am thinking I may hav emore of a control issue.

Last night followed BobW's suggestion. Rads warmed up but the house did not budge above 60 with os temp of 18-20. Same as with the kids room rads shut.

So tomorrow I am just going to change out the Honeywell transformer on the gas valve. IT was under the location I had a problem last year with an intermittent sight valve leak under max load. Might have gotten corroded if anything dripped on it.

Any suggestions on how to guess a bottom setting for the vaporstat? I have used Holohans book on alot of things, but don't feel like taking a couple of days in setting up a sizing program in excel to back into a setting.

Actually the bottom limit is set about a fingernail thickness above zero.

Thanks for the suggestion

Christian Egli_2

The big honking pipe got me thinking...

Well, not to get too far off course... like someone else mentioned, what you have is probably an ejector, like a Richardson ejector.

The carrot stuck into your big pipe is the venturi jet fed by steam from the top. The gasses from the return main get sucked into this carrot by the lateral connection, next, everything gets shoved down into the big pipe. Water would cascade into the wet return, air would go out somewhere else, leftover steam would condense here or presumably go to the two radiators you seem to say are connected to the big mystery pipe. The abandoned pigtail was the hot spot to place a gauge for measuring return pressure and vacuum, to see how well the venturi ejector was working.

But you're having trouble heating up and some short cycling. This system is gasping for venting.

Does the ejector still work? Does it get hot during operation? Can you control the steam feed to it? What boiler pressure do you have?

More importantly, where does air leave from the big honking pipe? This is a very useful lead to follow.

Here is what I would consider doing if we determine the ejector is no longer functional: divert the horizontal pipe that comes into the carrot and plug it into a bunch of air vents. Here your air would leave the system.

It will be necessary to make some kind of assessment on your current lack of radiator traps and/or steam orifices.

On the other hand, maintaining and running the ejector (which has no moving parts) would most likely greatly improve end of main steam circulation and prevent air bound problems particularly during moderate heating and short cycling.

And if it gets cold where you live, you can still go hug your big honking pipe for warmth. What do you think?

Damian_2

Really Old 2 pipe vapor system Short Cycling

Thanks for letting me know what the pipe is and the configuration atteh top. I have had al;ot of people stand, scratch their chins and shake their heads about what it is.

I read about the Richardson ejectors in one of Holohans books. It's just that this system actually barely predates the ASHRAE technical document on some of the patents on 2 pipe systems. So I thought the the ejector concept was relatively newer. I have approached the thing with the attitude that the guy who installed it was a very creative "dead old guy".

Taking the questions from the top.

1. I did get up close and personal with the ejector and with a stethescope could hear water draining into it. It also is warm. Means something is happening. I just don't know how well and if it is doing what it is supposed to.

2. The gauge is an antique. But it looks like it runs just under 2 pounds.

3. I'd love to hook it up to air vents if I could find any. This is one of those systems that has no vents on the rads, and has a valve on the condensate side of the rad. Thinking that there is a main vent, I have crawled on top of the return pipes but have not found anything. Any ideas if there is an antique technique for venting that does not include a vent device would be appreciated.

This weekend out of sheer frustration and having to put up with my very non-mechanically inclined wife making pretty snide remarks about the process I was taking to think through this, I chose the "Standard American Auto Mechanic" method to problem solving that is made-fun of on Car Talk so much. I started replacing parts.

The system has two loops-one to the front of the house and one to the back. The loops serve rads on the first and second floors-generally stacked directly above each other. The front loop only has two rads on it-some mechanical genius removed the second floor rad to the master bedroom and cappped the pipe at the supply/return mains.The rear loop runs fine. (there is a small section of cast steam iron base board with no vents or trap asteh last rad. An it really gets hot when everything is workiing. The rad that is not working is the end rad on the first floor loop.

The non working rad has all the old valves. No orifice. I've looked.

Anyway. I replaced the gas valve -an obsolete honeywell V8200 something with a V8300 with integral regulator. Had alot of corrosion in the little terminal at the top of the old gas valve. The piper had located it right under the McDonnell Miller LWC and the sight valve. So it got leaked on alot when the LWC rusted out and failed about five years ago, and when the gaskets at the sight valve would leak every so often inder high pressure. I didn't pick up on that quickly because it was intermittant. I repiped it to get rid of the old maxitrol regulator and move it out of line of fire for future leaks. Kille two birds at once (gas valve and regulator).

I also replaced the thermostat that looked like it was old enough to have been Mr. Honeywell's demonstrator model when he founded his company. System fired up. Gas valve responds really well to the tstat. The old honeywell di not have a legible anticipator etting, so I set he new one at 1.2.

I did not notice the short cycling which may not mean much. I am in Chicago. We had a 40-ish degree os temp weekend with the tstat at 65. The short cycling occured at 0 degrees and below last winter (and did not seem to happen above 15). This fall it didn't short cycle when I test ran the system in october, but started a coulple of weeks ago when I kept the boiler on by at tstat setting of 60 degrees-not bad when os temps are between 50 and 55, but just cold enough to make everyone at home mad at me.

So far, temp held at 65 with a tsat setting of 65 with os temps in the mid 20s. no noticable short cycling. But I am taking the after noon off with noone home and will crank the thing up to say 74 and monitor the cycling. Then if it gets warm enough, I am going to pull that end of the run rad off line one pore time and take a look at the valves and supply pipe to see if I missed something. I keep hoping that there is a main vent stuck somewhere at the end of each loop.

Thanks for the time in responding.

Damian

Christian Egli_2

A hole in one

The air gets sucked out of your entire system by the ejector. You won't find any air hole or air vent up stream of the ejector.

Where there's got to be a big hole is downstream, after the ejector. That big honking pipe is where the ejected air gets thrown into, it then has to leave through a pipe that is wide open to the atmosphere.

There may or may not be a thermostatic vent that closes on steam.

This exhaust pipe probably opens to the atmosphere after going through a condensing radiator first. The pipe itself might then dissappear into the chimney where it would open into the flue (at subatmoshperic pressure).

Once you find the air hole, you can look, feel and smell what comes out.

zippydw

Really Old 2 pipe vapor system Short Cycling: Need more help

Thought the controls change had corrected. House holds at 65 degrees at 25 degree os temp, but won't do better no matter where the tstat is set. Still haven't found a vent pipe downstream of the ejector.

Thing runs for a few minutes cuts out for about 10. repeats cycle. Listened to evacuator. Water is dripping into it in steady flow.

did find a flue damper on the boiler to the chimney. Looks like a relatively new addition (w/in 20 years) Could this be causing pressure issues in the boiler?

zippydw

really old 2 pipe system

Spent the day crawling all over this thing. I think you are right on the money about the evacuator.

I scraped alot of paint off the "carrot". It is a McDaniel Suction Tee. Doesn't look like anything in McDAniels current line.

I also found what looks like really antique traps at the take offs to the return mains (right below the bottom of the floor joists from each rad. Also, there is something that looks like a trap at the bottom outlet side of the big honking pipe where it connects into the wet return leading to the boiler.

One thing, at the end of one rear run, there is a 5' section of cast iron base board with no trap. COuld that be causing some of the short cycling and should I put a thermoostatic trap on it?

Then, I have looked everywhere. There are no air vents. At the top of one of the returns there looks like a relatively new pipe cap. should I put air vents on the returns with this type of system?

I an attaching a pdf sketch of the piping at my boiler if that helps.

Thanks for any help you can offer on this. I spent hte day wathching this run for 3 minutes. shut down for a half hour and run for three minutes. Repeat cycling.


S

Damian_2

really old 2 pipe system-seems to be working much better

Christian-Hole in one is right. Thanks Put in a new Hoffman 75 on my front loop return (I discovered it conveniently end ran the evacuator). Also took Holohan's books advice and looked for caps where there should be vents.

Found on of those coming off a tee on the riser (piped exactly as bell and gosset says not to)

Redid the pipe. installed the vent.

Put in a new T-87 and the system seems to be really cooking.

One last question. Should I consider putting a Hoffman on the rear loop return that feeds into the evacuator? I have not found any vents leading to outside air, but the rads are heating very nicely.

Thanks to you and Bob W again for your patience and your help!

Christian Egli_2

While digesting all the turkeys

And while digesting all the info you supplied, here are a few more comments.

You have two rungs in your system. Starting from the boiler, you have the front loop and the rear loop, each with a necessary return connection to the boiler.

The front loop serves the radiators using a two pipe scheme, with no vents on the radiators. I haven't clearly understood what kind of radiator traps you have (this is an area for you to investigate further, much improvement will come from top shape traps)

This front loop needs an air hole. I believe you say you already found it and installed a Hoffman 75 (option 3 below).

To see if we followed the same path:

In picture Top of B. H. P. and on your schematic, we see a cap at the end of the front loop return (This is the second pipe labeled as front return on the schematic)

This is a key to your mystery. I would promptly open this cap. Air should come out of the front loop right here. Deal with the hole in either of three ways:

Is there any chance this capped hole once led to another capped hole on the rear return that feeds right into the lateral intake of the carrot-like ejector. Currently only the rear loop uses the ejector, but a bridge here would make the front loop use the ejector as well. Rebuild the bridge, option 1.

If you have thermostatic traps on the front radiators, then this capped hole should remain wide open to the atmosphere with no automatic vent on it (and you would need to guarantee low enough boiler pressure to prevent back up of stack water in the return from spilling out, measure the B dimension). Option 2.

The problem with adding a thermostatic air vent on top of thermostatic radiator traps appears when any one radiator trap goes bad. Because the air vent will hide the symptoms, you'll forget to fix the problem: you'll have banging and your whole system will seam to be on messed up.

If there are no thermostatic traps on the front loop but rather some orifice type control, then you would be better off with a large thermostatic air vent on the hole (or even a collection of vents). Option 3.

If you're not sure anymore, install a valve instead of the cap, so that you can manually vent your front loop as you watch air, then, perhaps, steam coming out. Meanwhile, check for traps on the radiators.

The rear loop.

It is power vented with the air ejector. Here, an end of steam main air vent might not help at all. I don't know that you say there is. None of the radiators should have any hole that opens to the atmosphere.

The ejected air gets out after passing through your big pipe and through what is labeled (incorrectly I think) as the first front loop return. This is no return at all, it is the evacuation duct for useless air and remnants of steam from the venturi jet action. Since steam is hot and valuable this pipe is insulated, as we see in picture Top of B. H. P., while your other returns are un-insulated.

To solve the mystery, I would look at where this pipe leads to. Probably a single radiator that condenses the scraps of steam coming down with the air. This radiator would need to have an open hole to the atmosphere. You need to find this hole and open it up. Then, everything should be as originally intended.

If necessary, anywhere on this incorrectly labeled front return , you could add a thermostatic air vent, starting right near the big pipe. This could make the job of the ejector a little easier on start up.

The important thing is to not add air vents on the rear return anywhere between the radiators and the ejector, this would feed the return with air flowing the wrong way through the air vent. The answer to your last question would be a definite no.

Oh, and with an ejector on the rear loop, I kind of would expect to have no thermostatic traps on the radiators, but rather an orifice control system which is not obvious to the naked eye. Check it out but you may have no need for traps on your rear loop.

Can you breathe any better now?

Damian_2

venting strategy you discussed

Christian- First, thanks for the patience and information about this. Yes...herself is getting much more patient with some progress being made.

Option 1. I will check again, but there is no additional connection at the Suction tee where a bridge could have been made.

Option 2. Part of the problem is that this thing is an an old "cellar" where partitions are masonry, there is a plaster ceiling and everything gets buried soon after it leaves the boiler. On the rear loop rads, there is something that resembles a very small in line trap right where each rad return comes throught the floor and turns to the takeoff to the supply main. I thought they were traps, but the there does not seem to be a temperature differential from one side to the other and the rads are working.

I thought the tee might have been somewhere a previous mechanical guy put an end of the line vent that got broken by the initial condensate charge on start up. Probably happened a few times, someone got sick of the vent sputtering and they capped it. I have managed alot of property maintenance mechancics and that would be their MO. They figured that if things became airbound, they could just open the cap as you suggest. No one left me those operating instructions!

Option 3. That was the one I found as the nicest fit to what I was seeing. And it seems to have worked at least to get the living room rad working and the second (end one) on the line heating up a bit.

Both of these rads have the original return valves. Last time I detached the end rad, the valves were gate valves and no orifice plate was there. I was going to play with the end run rad this weekend. I was going to check if the return valve was gummed up or not completely open. When looking for vents or the threaded hole for them, I found holes on the living room rad closed with a glorified set screw. The end of the line rad did not have any spot for a valve (which I thought was strange.) I will look for a hole and follow your suggestion if I find it.

On that insulate pipe I called a return. I thought that it was a return from a two story riser at the far side of the house. The rads on that riser are the hottest in the house. With what you said about a condensing rad, I am also going to check if the end rad has a hole in it for venting.

I am glad you advised me about not venting the rear return. I was getting on a roll with the heat returning to the front rads after putting in the Hoffman.

The heat is as even as its ever been in years.

I'll post whatever I find.

Steamhead (in transit)

Pics?

Love to see your rad return valves and those mystery devices in the rear rad returns.

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Damian_2

Valve and other Pics

I will post some digitals over the weekend.

The fitting at the rear rad looks like a small in-line trap. It seems like a God-awful place to put one since someone would have to pull apart alot of pipe to service them.

And with cracking into this old cast pipe, my best frends are a propane torch and 48" by 1" round piece of black pipe with a wrench jammed in it.

I guess that's where the phrase "pumping iron" originally came from :-)