Trouble with Slow Radiators and Dry Returns on One Pipe System

merikus

@neilc, any suggestions for a procedure of detaching and (potentially) cleaning the pigtail? My biggest fear is I mess something up and then don't have heat for days...

merikus

Thanks, @nicholas bonham-carter, @JUGHNE, and @Jamie Hall for the insights regarding the placement of the vents.

I'm trying a little "venting by geography" tonight by taking the vent off that really slow radiator and just watching it. It's heating up faster than any radiator in the house. I'm starting to think if I get a few quick vents that might help me get through the winter. Any suggestions for some quick vents? I've been told that the Vavivalve Heat Timer vents almost too fast, so maybe that would be an option.

Jamie Hall

You may not have to take the pigtail off. You might be able to unscrew the pressuretrol from the pigtail. You would have to take the wires off (take a picture or clearly label what wire goes where, and do this with the power off!). Do NOT be tempted to take the pressuretrol apart -- they're difficult to reassemble. Then see if you can run something stiff but flexy -- like a zip-tie -- through the pigtail. Or blow it out with compressed air.

On the vents -- which just popped up as I was typing the above! -- the heat timer might be just the ticket. As I think I mentioned above, though, there's no rule that says you couldn't stick a main vent on there to see what happened -- say a Gorton D or 1. I have a suspicion that that vent is acting essentially as a main vent...

merikus

@Jamie Hall, Yeah, for sure my radiator vents are acting as a main vent. Y'know, it's interesting, being completely new to steam, it almost sounds when I have the vent off like the system is "breathing," taking a breath in followed by a breath out. It's such a fascinating and cool method of heating--I'm finding I like it even more than heating by wood alone (something I did for many years).

I figure when I put all that venting on those 4 long run radiators that should help a lot. I realize I'm not technically doing the right thing by venting the radiators both on the pipe side and the other side, but I think in this one particular case, until I can get my main vents installed next summer, it should go a long way to helping this winter.

I already have my Gorton #2s ready to go, can't wait to get them installed.

Jamie Hall

While not technically right -- the bottom line is getting the air out sor the steam can get in, and there are times where and when for various reasons the best way to do that is to stick an extra vent on the inlet side of a radiator! Sometimes, like yours, on the radiator itself. Sometimes MacGyvered onto a T which somehow gets stuck on the top of the riser at the inlet valve.

If it works... go for it!

merikus

Thanks, @Jamie Hall. I had another question for you, @nicholas bonham-carter and @JUGHNE based on your conversation about the placement of my main vents.

I'm trying to understand the placement of these vents. I know the three of you recommend placing them at the end of my "dry returns" instead of at the end of the last radiator. Since high pressure always goes to low pressure, wouldn't placing these vents are the end of the "dry returns" rather than after the last radiator make it take longer for my radiators to come to pressure? Reason being that the pressure (which contains the steam/heat) would want to move towards the spot of lowest pressure, which is the main vent on each run. In theory, wouldn't that mean that the mains would come to temperature first, then the "dry returns," then the radiators (since pressure/steam would travel along the mains, then travel along the "dry returns" to get to the main vents, and then finally go out the small main vents on the radiators)? Or am I thinking about this entirely wrong? It sounds like based on the conversation the three of you are having that I'm thinking about this wrong, but I'd love to understand why.

Thank you!

Jamie Hall

Well, they'll probably answer to -- but the short answer is no. Consider: your radiators when the steam is coming up are at the same low pressure as the pipe wherever the main vent is located. As soon as air starts to move into a radiator -- or on down the main -- the pressure will rise at that point, but only slightly -- and only in accordance with the resistance of the vent. So if we consider the steam main at the point where a radiator takes off, the steam in there will "see" two paths to take: the radiator takeoff and the steam main. Ignoring the minor detail (?!?) of condensation in the pipes, the flow will split so that the pressure a very short distance away from that T in the main and in the takeoff is equal. If we consider the two extremes -- no venting on the main or no venting on the radiator -- what we find is that if there is no venting on the main, all the flow will go to the radiator. No venting on the radiator? All the flow goes to the main. In between? A split. The flow, in fact, will always split so that the total resistance from the point of split on either path is the same.

If one keeps this firmly in mind, it becomes really obvious why -- especi+--ally with one pipe systems -- changing the venting in any one location will affect the balance in the entire system. This is what makes balancing one pipe systems such fun...

Now this happily ignores the problem of condensing steam. If the pipes carrying steam -- whether they are steam mains or the extension of steam mains commonly, but incorrectly, referred to as dry returns -- aren't insulated, a good deal of condensation will occur in them before steam gets to where it is useful. This moves the point of atmospheric pressure, and thus the total resistance to flow from any other point in the system, which just adds to the fun. Insulate all piping where possible (risers are often impossible to insulate effectively) if that pipe carries steam -- and that includes the "dry returns" between the last radiator takeoff from a steam main and the location of the main vent (the rest of the "dry return" doesn't matter -- air can't get out of it, so very little steam will get into it)(actually an interesting argument can be made to suggest that not insulating those "dry returns" may actually speed up the arrival of steam at the more distant radiators, by effectively reducing the flow resistance in that length of pipe and thus moving the point of atmospheric pressure closer to the last takeoff. But in the long, that is wasteful of steam).

ethicalpaul

I couldn't quite follow all of @Jamie Hall 's answer, so this is not necessarily an argument against it.

But I would have no hesitation to putting a main vent anywhere after the last radiator's supply. Any part of the main after the last radiator can stay steam-free in my opinion.

And putting the main vent immediately after that last radiator's supply will let the main fill with usable steam faster, and will start to deliver steam faster to all the radiators.

Jamie Hall

Basically what I was saying, @ethicalpaul -- only your answer is neater and shorter!

ethicalpaul

OK thanks! I hate it when I don't agree with you because it almost always means I'm wrong

merikus

Thank you @Jamie Hall and @ethicalpaul. Jamie, your information regarding the impact of un-insulated pipes on this entire process was quite interesting as well. After reading your comment I actually went down to the basement and got some additional insulation in hard-to-insulate spots! I have a few really hard to insulate spots--I may try to get some smaller insulation (currently working with 1.5 inch) to get in those spots. But I figure if I have 90%+ of the system insulated that's a lot better than nothing.

I think the biggest challenge I have of putting the main vent right after the last radiator is that my "dry returns" are doubled up on each other on my two short runs, leaving no space right after the last radiator to put a vent. Looks like I'll have to put those vents in that spot at the end of the "dry return" run, though it sounds like that ultimately doesn't matter very much.

One of my main concerns with putting those vents there is the question of how to make sure that water isn't getting to those spots that I'm going to run the main vents. My friend the steam guru suggested I attached a clear plastic hose to my radiator drain, throw it over a joist, and see how high up my water is really getting when vents are open. Hopefully it's not getting so high as it is surging into those horizontals. At any rate, I need to calculate the Total Connected Load so I can have the tech downfire my burner.

ted_p

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merikus said:

Thanks, @ted_p! Here's the label of my boiler for the model number and other pertinent information.

Thanks @merikus!

Smith BB14 series

Haven't been able to find docs for it yet, but I'm still trying. Smith no longer has anything for it on their website.

I did happen upon this thread on The Wall, from 2002, shortly after the series was discontinued:
One of the Last H B Smith bb 14 I will install
It appears that they were well regarded, and their passing was mourned.

I'm hoping that @Steamhead will notice this, and chip-in with the merits and shortcomings of your boiler, as well as his expert opinion as to what you might be able to get away with in the way of down-firing. He frequently throws-in fascinating bits of history, too!

Just going by the ratings on the plate, that is a big fella for a single family house; 625 sq ft of EDR at the low end of the rated capacity!

Jamie Hall

Water should never get to your main vents! If it does, you have other problems.

merikus

@Jamie Hall, agreed--but I'm pretty sure I have other problems! My current main vent setup is terrible, and when I removed one of them to see if I could get the pipe to vent faster, water came spewing out of it like Old Faithful. Not quite sure why...

Jamie Hall

merikus said:

@Jamie Hall, agreed--but I'm pretty sure I have other problems! My current main vent setup is terrible, and when I removed one of them to see if I could get the pipe to vent faster, water came spewing out of it like Old Faithful. Not quite sure why...

So I recall. Not fun. But -- we really need to get that problem fixed before we can worry about much of anything else, eh?

merikus

@ted_p, thanks for the info about that boiler. Really appreciate it. It's nice hearing we have a solid workhorse down in the basement. I know when I bought the house the plumber who inspected it for us said it was a solid piece of equipment.

Being that you took a look at those specs I wanted to calculate my EDR for you and get your take on down firing. According to my calculations, I have an EDR of 612 sq. ft. EDR. Including the pickup factor of 1.33, I get 814 sq. ft. EDR. That said, I know that The Lost Art of Steam Heating Revisited suggests that 1.33 may not be enough for an old turn of the century system like mine. At a pickup factor of 1.5, I get 918 sq. ft. EDR.

How do I read that I=B=R net rating label on my boiler? If I understand The Lost Art correctly, that net rating should be calculated not with the pickup factor but rather with the radiator EDR alone, which means I'm right on target so long as I'm running at 1.7 GPH.

Of course, that leads to a question of how do I know what my boiler is running at. The only info I have is that "1.50 X 80B @ 140 PSI" is written on my boiler near the oil nozzle.

merikus

@Jamie Hall, agreed! Am hoping that I can figure out an option for downfiring the boiler that will help reduce how much it is surging. Also planning on doing that test with a clear hose to I can accurately visualize exactly how high up the water is getting, I think that will tell me a lot.

Jamie Hall

The EDR rating of the boiler already has the pickup factor included. So 612 EDR is the square foot EDR rating you are looking for on the boiler -- and the 1.70 gph firing rate should give that to you.

merikus

@Jamie Hall, how would I figure out if I'm firing at 1.70 gph?

Jamie Hall

Honestly, I've never gone into how the firing rate of a nozzle varies with pressure -- I don't play with burners. Control circuits, yes, boilers, yes. Pumps, yes. etc. But not burners. The 1.50 is the nominal flow rate of the nozzle that's on there -- at 100 psi. The 80B is the nozzle angle and type. The 140 psi is the pressure the burner is operating at -- and according to the handy dandy Delavan table that would give you a little less than 1.8 gallons per hour.

But -- hopefully someone who actually plays with burners will come up with a better answer.

merikus

@Jamie Hall that makes a lot of sense, thank you!

gfrbrookline

You have water coming out of you main vent ports because they are way too low on your returns, likely where the dry return turns into a wet return. They need to be above the 90 degree elbow above them where the dry turns into a wet return, ideally 18" back from the elbow and mounted 10-12" above the return pipe.

merikus

That is great advice, @gfrbrookline. Thank you!

gfrbrookline

mattmia2

It is likely the surging combined with the very uh...creative...header is causing liquid water to be pulled in to the mains with the steam and that water is coming to the returns in larger quantities than they can handle well and that is how water is getting to your vents. If you can solve the surging it will likely solve the water in the vents.

neilc

Jamie Hall said:

You may not have to take the pigtail off. You might be able to unscrew the pressuretrol from the pigtail. You would have to take the wires off (take a picture or clearly label what wire goes where, and do this with the power off!). Do NOT be tempted to take the pressuretrol apart -- they're difficult to reassemble. Then see if you can run something stiff but flexy -- like a zip-tie -- through the pigtail. Or blow it out with compressed air.
...

adding to what Jamie has here,
unwire the Ptrol,
and get a wrench on the flats under it that screw to the pigtail,
use another wrench or screw driver in the loop of the pigtail to back up the pigtail, not letting it torque(or snap) at the boiler,
you might be lucky and find things not cranked tight, tight,
run a wire or ziptye thru the pigtail, and try blowing thru it into the boiler,
add a little water back to the pigtail as you reassemble.