Sarco “Boiler Return Trap”

Mike_Sheppard

Does anyone have old literature on this? Can anyone explain what this is doing and how it operates? Pictures attached

Edit: I now understand what it does. It is not working anymore.

Edit: Yes I know the near boiler piping is completely wrong. When they installed the boiler they removed one of the two risers from the boiler, and piped the two take offs on the opposite side of the riser from the equalizer. All 100% welded, no swing joints.

Larry Weingarten

Hi Mike, I found this off The Wall. https://heatinghelp.com/assets/documents/58.pdf Might it help?

Yours, Larry

Mike_Sheppard

@Larry Weingarten

VERY helpful! Thank you! I managed to find some other info online and now understand it.

Now I’m wondering if the thing is even working anymore!

Mike_Sheppard

My next question is, can these still be purchased? I am assuming not. So the system would have to be converted to a feedwater unit. This mechanical pump is only serving two returns. The other 3 returns just go right into the boiler through the Hartford loop, I guess they have enough head to overcome the boiler pressure.

The Sarco mechanical pump is bad, it lets steam in and vents it right back out the other side into the return air vent. Which closes the two air vents and doesn’t let those two returns vent. Boiler is also short cycling and the air vents in the other returns have been venting for over an hour now, I’m assuming they are massively undersized. The water is returning quickly enough and is feeding make up water to the boiler.

I will try to draw a diagram of this system later and post it up.

Steamhead

Not so fast. This is a Vapor system.

This device is called a "Boiler Return Trap", though in reality it functions as a pressure-powered pump. It was installed to make sure condensate from the dry returns could get back to the boiler if the boiler's pressure got too high, say 8-12 ounces or so.

I bet when you trace out the returns, you'll find that the Return Trap only serves the dry returns from the radiators, but not the returns from the ends of the steam mains. This is because (but not always) the steam mains are dripped straight into the returns without using traps. Therefore they have leftover steam pressure to help the condensate return. Dry returns do not have this leftover pressure so they need the Return Trap to assist. See chapter 15 of "Lost Art" for a detailed discussion of this. Note that if you trace out the returns and find something different from what I've described, the picture will change.

I believe Barnes & Jones can still supply return traps (called "Condensators") and maybe others can too. But with modern controls, you don't need one. Change the Pressuretrol to a Vaporstat set to 8 ounces or so, remove the failed Return Trap and its two check valves, vent the heck out of the dry returns by changing the two Hoffman vents to Gorton #2 vents, and watch how much better it works.

Then there's that messed-up near-boiler piping..............

Mike_Sheppard

@Steamhead thank you for the info. I’m not sure how to go about tracing steam pipes. Pretty much everything is in the ground. They have one apartment dug up behind the boiler room right now so I can see those lines. That return line does come from radiators and tees into one other condensate return that goes to this return trap. The other three (that don’t go to the return trap) all come back from the same area as the dug up return line that I can see. I had the boiler running for an hour and a half yesterday and those return lines never got hotter than 190 degrees. The two returns that I know came back from radiators never heated. Not a single bit of condensate came back on those. But the building is still complaining about overheating. If the three returns that aren’t going to the return trap are just main drips, wouldn’t they be hotter and the building not heating?

This is going to give me a headache I can already tell.

Edit: so at 8 ounces, the condensate should be able to return without the need of a return trap? They have a 16oz vaporstat right now, set for 10 but it cuts out at 2psi....

Edit - I’m just thinking out loud here making my brain hurt. If the mains did have traps on the drips, wouldn’t it make more sense to tee all the returns together instead of running five separate returns to the boiler room? Which makes me think those in fact are not trapped mains because they are all run separately. But if the two returns that go to the return trap are never getting hot, how is the building overheating? They have the condensate return sensor for the Tekmar control strapped to the three possible main returns. It heats up very quickly, only a few minutes and it’s 180 degrees. But even after an hour and a half of nonstop running it never exceeded 190.

GBart

If it doesn't seem to work call Sarco direct, I see nothing regarding that part anymore, generally all of those types of pumps are designed for X amount of cycles, say 1.2 million for example, after that the inner workings are expected to have too much wear to cycle anymore and from my experience it is easier to get the entire guts than to try and rebuild one.

GBart

They could at least know the specifications for that pump and recommend a replacement.

Mike_Sheppard

I think I’d prefer removing it completely and trying what Steamhead is suggesting if it would work.

GBart

The Dead Men built it........don't mess with the Dead Men

jumper

GBart said:

The Dead Men built it........don't mess with the Dead Men

How do we know that it hasn't been messed with already? I'd try SteamHead's suggestion.

Mike_Sheppard

100 years have gone by. I’m sure it has been messed with! Haha.

I’m going to go back next week now that I understand how this is working. I can physically measure the distance from the normal boiler water level to the dry return and see if operating at 8oz will work for this.

Going to look through Lost Art again tonight and make sure I’m 100% understanding this.

I need to figure out how to verify that the three returns that come back from the building that do not go to the return trap are indeed main drips with no traps. That’s he only way it could make sense, they come back at the same level as the two returns that use the return trap. So the only way that water could have returned to the boiler is if there was steam behind it. So what Steamhead has to be correct but I need to be able to physically verify that.

I’m hoping I can talk them in to changing the near boiler piping too.

Jackmartin

I am commenting with all due respect —- that Postive Return Trap is original it was put there for a reason the two returns coming to it did not have enough A dimension to enter against boiler pressure. Sprax Sarco makes PRT still and they work on the exact same principle as the one you have. I would suggest looking at the name plate on the PRT it is original to the installation. The reason it is overheating is the Tekmar placement —- ask yourself if I was condensate and I ran through the earth buried would I not loss my heat to the ground . Delta T hot goes to cold. Replace the PRT and reconfigure your temperature control position or better yet run it like a steam system off the Vapostats and do not worry about return water temperature this is steam not hot-water. The dead men did things using the law of physics ,hot goes to cold,more pressure more heat, and if you are not getting water out of the return lines to your PRT where is it going , evaporation? No, you have stated the returns are buried, and if there is one thing you can bet your pension on ,after thirty years, every buried return is leaking .That return trap is in all likelihood ,over sixty years old.The returns are ethier leaking or have become earth, they no longer exist. My deceased father in law was a surgeon and his pet peeve was as he put it “ why do people look for Peacocks when the problem is sparrows” what he meant was, the most obvious cause of the problem is usually correct. Occam’s razor tells us simplicity is always the correct interpretation. All the best and Hug your kids they are the future, Jack Canada

Mike_Sheppard

@Steamhead or anyone else, please correct me if I am wrong.

The problem here is the “A” dimension is too small correct? So a boiler return trap was used to force these two returns into the boiler. So with 8oz cut out, half a PSI, we would need about 14 inches minimum for it to work without the boiler return trap, right? I am going to measure it next week and see. I’m fairly certain there is well over 14 inches, probably double that or more, between the water line and the returns. The boiler is not original, I’m wondering if the original boiler was a firebox or something that had a higher water level. Starting to feel optimistic about this one.

Mike_Sheppard

@Jackmartin they are buried, but they’re buried in a troth or whatever you’d like to call it. I wish I had taken pictures. I got to see about 30 feet of this under-slab piping and it was in surprisingly good shape. One of the two returns that comes to the positive return trap is coming from the second floor, and is not underground at all.

Now that I am thinking about it, be old boiler was likely a coal firebox boiler. There is a coal room behind the boiler, and the small boiler room is two stories tall, which would lead me to believe that the old boiler was tall and had a much higher water line. The water level is at about my check level in this boiler, and the returns are about 2 feet above my head. And I’m 6’3. I’ll measure next week but I’m going to guess 30ish inches for A dimension with this boiler.

Edit: I am by no means wanting to just remove stuff and not properly fix the system. I want to fix the system as best as possible and if that means putting a new PRT back in, that’s what I will have done. But I do want to make sure it is actually still needed. If it’s not needed anymore because of a different water level then i’d prefer to remove it as Steamhead is suggesting.

Also want to take a moment to thank all of you guys. The wealth of knowdlege is amazing.

Jamie Hall

Something to remember, @Mike_Sheppard , and @Jackmartin -- this system was likely to have been coal at one time. One of the problems with coal was that if the pressure started to get too high, you couldn't just turn off the fire. Therefore a whole range of really ingenious gadgets were invented -- of which this Sparco is an example --which arranged things, one way or another, so that if the pressure did go too high the return water could get back to the boiler -- or at least not get out to wander in the dry returns.

Nowadays, however, we are blessed with vapourstats which accomplish the same purpose by shutting off the burner when the pressure gets too high --which is typically 8 ounces. If you conscientiously set the vapourstat properly, the ingenious gadgets become redundant. Generally they do no harm if left in the system, but you don't really need them.

If they aren't working, however, and you do let the pressure get too high, a surprising variety of evils will affect your system.

@Jackmartin 's comment on the return temperature sensor as a control is spot on. In most vapour systems, if they are working properly, the returns -- buried or not -- will never get to even approach steam temperature (often not even much over 100). Leaking steam traps or drips which have been dewatered by someone lowering the water level in the boiler, though, will allow steam to get in there, and then you can get high temperatures.

Mike_Sheppard

@Jamie Hall

The three returns that do not go to this boiler return trap, are likely returns from the mains like Steamhead said. I have to verify that somehow next time I am there. But the reason I believe he is right is because they do get hot very quickly. All three of them reached 190 degrees in several minutes after the boiler begins making steam - this is where they have the condensate sensor located. The two returns coming back to the boiler return trap never get hot. These are the ones coming back from the radiators. But somehow a few people in the building are still complaining about being too hot, and they’ve had heat all winter. I do believe the boiler is taking on some, small amount, of water from make-up, but not much. I will test this next time as well by shutting the make up off. I’m beginning to wonder if Jack may be on to something with the returns leaking under the slab after heating the radiators. The main level return I don’t believe is actually buried though and the other one that also doesn’t get hot comes down from the second floor.

Just read through the section in Dan’s book again about this style system and think I have a good starting point now for figuring this out.

Jamie Hall

You could well be right, @Mike_Sheppard . Are those three returns vented in some way? Maybe you said... but in that case it's more a matter of nomenclature than anything else -- which can trip us all up when we are working through the web! I always think of a pipe which is connected to the boiler at one to get live steam as a steam main -- even after the last takeoff. A return, to my way of thinking, is isolated from the live steam -- maybe through a trap (for instance a crossover trap or something like that, or just by the radiation) -- and which, therefore, is never supposed to be exposed to steam if everything is operating as it should. It's a dry return -- and must be vented somehow -- if it's above the water line. A dry return -- and usually the steam mains -- will all drip into a wet return.

I make the distinction at least partly because of pressure considerations. A steam main will operate, once things get going, at boiler pressure or nearly so for its full length. A dry return, however, should be at or very close to atmospheric pressure at all times -- hence the need for it to be elevated above the water line far enough so that boiler pressure cannot back water into it (don't have to worry about that with a steam main) and hence, also, the need for the gadgetry in the old days to protect it if the pressure gets too high.

Steamhead

That "condensate sensor" a.k.a. "Steam Established sensor" is definitely in the wrong place. You want it at the end of the longest steam main or, if at all possible, at or near the top of the furthest riser from the boiler. With this placement, and proper air venting, it will tell the control (Tekmar or Heat-Timer) that steam is about to enter the radiators. From that point, the control will adjust the remaining time of the "on" cycle according to the outdoor temperature.

It is not necessary to heat the radiators fully on a mild day. This just causes overheating and wasted fuel.

GBart

I wonder how an Intellidyne Steam control would work on something like this or any steam, I have not tried any except the hydronic controls.

Any opinions on them?

GBart

Never mind, just read the spec's, system must maintain 1.5psi??
Input rating greater than 2.5 million BTU / hour?

https://www.necsenergy.com/solution/intellidyne-boiler-control.html

Mike_Sheppard

Here’s a picture of what the system is. I believe this is identical to what I am dealing with. Although rather than the ends of the steam mains being vented with traps into the return main, they are just vented with air vents. There are three of these end of steam mains but only two return mains. And only two steam supplies going to the building.

The three end of steam mains make sense because they do not go to the boiler return trap (as in the picture) since they have the leftover steam pressure behind them and adequate “A” dimension.

What I need to measure is the “B” dimension. Off the top of my heat I’m going to guess there is probably about three feet there, 36 inches. So if I can keep the cut out under 1-1/4 psi the boiler return trap could be removed. Need measure actual dimensions though to be sure. Also need to figure out what the cut in should be to ensure there is still steam at the furthest radiator.

Will have an update on this later this week hopefully!

Steamhead

That's Dunham's version, straight out of Lost Art.

On your system, vent the heck out of those steam mains. Measure the length and diameter of each steam main and we can tell you what you need.

Your 'B' dimension is measured between the boiler's highest possible water level, and the lowest dry return pipe before it drops toward the Return Trap. Allow 30 inches per pound of steam pressure.

I'd start by setting the Vaporstat's cut-in at about half it's cut-out pressure, and see how that works.

Mike_Sheppard

I need to get a lower range pressure gauge. It has a 16oz vaporstat now but the 0-30 psi gauge on it shuts off at 3psi with the vaporstat set to 16. I’ll put a proper range gauge on it and see what the issue is.

@Steamhead do you think those steam main returns aren’t trapped? That’s what recall it saying in the book. Would make sense that they don’t go to the boiler return trap.

I have no idea how I’m going to measure lengths of anything with everything under the floor and in the walls. This should be challenging.

GBart

GBart said:

The Dead Men built it........don't mess with the Dead Men

that was sarcasm

Mike_Sheppard

UPDATE: Went back today.

Last time I was there I shut the steam supply off to the boiler return trap. It was allowing steam in and steam out at the same time through both of the top valves. Which was closing the air vents in the return main on top of the air eliminator. The two radiator returns were now getting hot. And they were complaining about the building overheating. I figured if the pressure was low enough the water would return to the boiler without the boiler return trap, which is why I shut it off to test that theory.

I measured the “B” dimension. The distance between the highest possible water line and the bottom of the lowest dry return, and it was 30.5 inches.

The boiler is short cycling like crazy because all of the air vents are undersized. The boiler cycles probably 10 times over 20 minutes before the air is out of the steam main returns.

I tried to explain all this to the property management and they got mad and said “just adjust the control to make it less hot” and hung up on me. So that’s that I guess. I wrote it up and emailed to them about the NBP being wrong, and as much detail about everything else I could. But I guess if they don’t want to do it then they don’t want to do it. Gotta love DC. They’ll probably hire another contractor to come do something “cheap” and mess it all up.

Oh well, I tried. Thank you all for the input. Learned a lot from this one. Boiler is running at 14oz cut out and 8 cut in. Trying to maintain enough pressure to keep the furthest radiator full of steam while keeping the pressure low to allow condensate back in.

jumper

>>I tried to explain all this to the property management and they got mad and said “just adjust the control to make it less hot” and hung up on me. So that’s that I guess. I wrote it up and emailed to them about the NBP being wrong, and as much detail about everything else I could. But I guess if they don’t want to do it then they don’t want to do it. Gotta love DC. They’ll probably hire another contractor to come do something “cheap” and mess it all up.<<

That's a dissonance I suffered from. On one hand one can send a letter explaining the situation and stating work is a best effort no guarantee situation. On other hand one can run for the hills. Latter is wiser; former is nicer.

Mike_Sheppard

@jumper the latter is what I do. I try to do it in a nice way. I try to make it look like I’m actually trying to help them rather then just milk them for money. I show them manuals and references and as much as I can to back up what I’m saying because 99% of the time the people I have to convince know absolutely nothing about what we do.

I had another one today that I went back to. Went on this install behind a competitor company. They installed a boiler completely wrong. Like everything you could have done wrong, they did it. I got it running as best as possible given the situation, and used the manual and other references to show them proof. They agreed with me but said they don’t want to do the work. Their Lochinvar boiler will not last more than a year but they’re not worried about it.

jumper

Hey,Mike, have you ever heard that no good deed remains unpunished? Kidding but....it's pretty sad when building owner calls to say that he should have listened to you. Now he's spent his money,he's all messed up,and he asks you what to do now? This site is fill of knuckle headed disasters.

Mike_Sheppard

It is for sure. But we can only try I guess.

Off note, just calculated the steam velocity leaving this boiler. It's supposed to have two tapping but they only used one. 1,000,000 btu/hr boiler. 5 inch riser. Approximately 52fps steam velocity through that one riser. And the two steam supplies are piped on the opposite side of the header from the equalizer. I'm sure they got some nice wet steam. I'm sure that's contributing to the short cycling as well.

Mike_Sheppard

Was just given more information about this situation.

Called back again and said building is still overheating.

But this time they mentioned that another contractor had replaced some of the main steam supply piping and risers.

The plot thickens.

Mike_Sheppard

Would I be right in assuming the main that goes out on floor one serves floor 1 and 2, while the main that goes up through the ceiling probably serves floors 3 an 4?

Steamhead

Is the building overheating consistently, that is, all areas too hot with none too cold or at normal temperature?

Mike_Sheppard

@Steamhead I am trying to get that info out of them. Originally they told me it was one person complaining. Then they told me it was everyone in the building complaining that, I quote: “their radiators are so hot that they’re smelling a burning smell”.

Mike_Sheppard

Here are three pictures they sent me of the piping that was replaced. It’s hard to tell by the picture, but there is one steam main, one condensate return, and 3 steam main returns down there. It appears that they replaced one steam main return and the one condensate return. It also appears that that one radiator there gets it’s steam off the steam main return rather than the main itself. Does that sound normal? I guess maybe it’s like that so those close radiators don’t heat too quickly? That radiator in the picture is physically the closest one to the boiler in the entire building. The boiler room is right behind that wall where the pipes go through after the radiator.

Mike_Sheppard

Here is what is happening in each apartment in the building.