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Extra equalizing loop??

jono
jono Member Posts: 8
Seems like this piping doesn't make sense, or is it just me?

In the picture, on the top right is the far end of the steam main, and to its left is the dry return. The smaller branch top-left is a vent. On the bottom leading the the right is the wet return.

So my question: why would the steam main be connected to the return here? There is normal Hartford/equalizing loop piping near-boiler, so this is not that. Seems to me that this line should be trapped if it's there at all.

Additionally, as best as I can tell, this end of the "wet" return is dry, or partially dry, unless the boiler level is pretty high. So I suspect steam is getting into the return here.

Overall, the system heats well. What doesn't seem right is that the pressuretrol doesn't cycle after the system gets hot. Usually, when it's starting from relatively cold, it will cycle off at 1.5# after a while. But when it cycles back on it might build a little pressure, but eventually it drifts to zero and stays there for as long as I've been willing to turn the house into a sauna. Again it heats well, but I think I'm probably losing efficiency. And I think it has something to do with the steam piped into the return.

Does any of this add up? Thanks much!

Comments

  • Jamie Hall
    Jamie Hall Member Posts: 22,875
    That wet return MUST be wet for the system to function properly. No ifs, and, buts or maybes.

    You are quite correct in thinking that steam can go down that drip, across the wet return and back into the dry return. It's not supposed to do that.

    You need to lower that wet return so that it is, in fact, below the boiler static water level. Ideally by at least 6 inches.

    If you can't lower the wet return for some reason, you could put in a false water line.

    The function of that drip from the steam main is to take condensate from the steam main and return it to the boiler.

    You can also spend some time mumbling under your breath about the knucklehead who put in a boiler without matching the water line to the original.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • vaporvac
    vaporvac Member Posts: 1,520
    Do you have a two-pipe vaporvacuum system? If so, that could be the vacuum equalizer. It's necessary and should remain "as-is". Mine has exactly the same, but the wet return must be wet. Sounds as if @Jamie Hall is correct that someone didn't take the water line into consideration when replacing the boiler.

    p.s. Once all the air is expelled, the boiler shouldn't build pressure. That's normal and actually desired as far as I know.
    Two-pipe Trane vaporvacuum system; 1466 edr
    Twinned, staged Slantfin TR50s piped into 4" header with Riello G400 burners; 240K lead, 200K lag Btus. Controlled by Taco Relay and Honeywell RTH6580WF
  • Steamhead
    Steamhead Member Posts: 16,710
    The old coal-fired boiler's water line was higher than that wet return. Either lower it or use a False Water Line to keep it wet.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • jono
    jono Member Posts: 8
    Thanks all, appreciate the helpful responses.

    Jamie, consider the muttering done. Good tip.

    Pretty sure it's a normal two-pipe system, but I guess I might not know how to spot a vaporvacuum system. Anything else to look for?

    Last question about the wet return. Nothing else, other than what's in the picture, connects to the wet return. The radiators all connect to the dry return. What would happen if I put a trap on the drip? Seems like that would do as well as a loop seal to keep steam from going back up the dry return. I haven't noticed any water hammer so that's not a concern so far.

    Thanks again.
  • Fred
    Fred Member Posts: 8,542
    Not sure what problem you are trying to fix. You have no hammer, low pressure (which is exactly what you want to see), the system heats well, what's the issue? Many of us, with single pipe, parallel flow systems have steam mains that, after the last radiator run-out turn into a dry returns and either loop back towards the boiler and eventually drops into a wet return or end at some location and then have a drip leg that drops into a wet return. Make sure your wet return is below the water line and you are good, unless there are other symptoms.
    Also, not sure what you mean by the Pressuretrol will not cycle and the pressure never builds back up. Pressuretrols are there, more as a safety device to ensure the boiler does'nt build pressure beyond a safe level. They are only engaged when a boiler is over-sized and produces more steam/pressure than the radiators can condense (again a control device) or when it is very cold outside and the boiler runs for long periods or when you create a sauna (artificially causing the boiler to run for extended periods).
    I'm guessing your wet return(s) are below the water line or you'd have some significant water hammer.
    If you want to decrease the distance the steam flow past the last radiator run-out, move the main vents closer to that last radiator run-out. It's not going to create any significant added effeciency for you (it looks like those mains aren't that long anyway).
  • jono
    jono Member Posts: 8
    Well, it seems that my only problem is that this end of the wet return is dry, based on it being about 3" higher than normal water level. However, I'm now thinking that condensate might stack high enough to seal off the drip once things heat up.

    I'm fairly certain steam is getting into the returns, at least at first, because I can feel the heat spread outwardly from where the drip connects. The vent branch gets steam-hot, so I'm wondering if this is shutting the vent prematurely. But yeah, there aren't any other overt signs that this is the case.

    Also, I do get a bit of water hammer, usually during cold starts, but it's in the dry returns, not the wet.

    The mains are pretty long actually, a loop around the basement. The dry return header parallels the steam main, also a loop. The picture is showing a corner approximately opposite where the boiler is -- both lines tee off just above frame.

    I have experience working with steam systems, but none with heating/low-pressure since buying this house about a year ago. So this is as much just trying to figure out how things work (I'm now addicted to reading this site) as it is fixing the problem.

    I'm curious why there would be a wet return that goes the length of the basement, when nothing else connects to it. The dry return header circles the basement, so you could drop down from it anywhere. Why run the wet line as far as possible instead of a few feet from the boiler? I'm sure it's something to do with how the original boiler (guessing coal?) worked, or maybe one of the many things the dead men knew that I don't.

    Anyway, like Fred said, bottom-line things are working reasonably well, so I'm debating if it's worth the effort to lower the wet return or build a false water line (cosmetic issues in a finished basement). Adding a trap to the drip line from the mains would be pretty easy though, and seems like it would solve the problem. That was my first instinct, but then again, I still don't know what I don't know.
  • Fred
    Fred Member Posts: 8,542
    If that wet return is actually 3" above the nornal water level of the boiler, you do need to either drop the wet return down or use the false water line.
    The antler that the vent is mounted on will get steam hot. That heat is what closes the vent. Once the steam is at that point, the air has been expeled.
  • vaporvac
    vaporvac Member Posts: 1,520
    Any chance you could post some more pics of the basement and near boiler piping as well as a couple of a typical rad? The wet returns must stay wet, but other than that, I'd be reluctant to change the original piping without know what it does or did. I'm just betting this is a vacuum system from the extra equalizer. What do your pressures do when the burners go off?
    Two-pipe Trane vaporvacuum system; 1466 edr
    Twinned, staged Slantfin TR50s piped into 4" header with Riello G400 burners; 240K lead, 200K lag Btus. Controlled by Taco Relay and Honeywell RTH6580WF
  • jono
    jono Member Posts: 8
    Fred- The vent is on the return side, not the steam side, so I don't think live steam should be getting to it, that is if the wet return pipe were forming a loop seal. On startup, the return piping within a few feet of this drip will get as hot as the mains, but the rest of the returns are still cool. That couldn't be by design, could it?

    Vaporvac- Yes, I'd love to have you look at some more pictures. I'll get on that shortly.

    As to the pressure, once the system is warm it stays at zero, which I gather from you guys is good. I'd have to get a compound gage to find out if there's ever vacuum. I'm not sure if the vent would allow that.
  • jono
    jono Member Posts: 8
    Pictures... Home was built in the 20s FYI.

    Typical rad:


    I'm planning to replace the traps in the summer; some look like original equipment. Speaking of, I haven't looked hard yet, but seems like an angled one like this might be hard to find:


    Looking away from our original picture. The steam and dry return go all the way around the basement like such. The wet return slopes downward along one side of the basement and turns the corner to where the boiler is. Thinking the only reason it's so long is to allow the condensate drip at the far end of the mains.


    Vent:


    Boiler. None of the near-boiler piping was insulated when I inherited it, hence the ugly insulating project in progress.


    Other side:


    Hartford loop:


    Anything else you want to see?
  • vaporvac
    vaporvac Member Posts: 1,520
    edited January 2016
    Those are not traps per se and are integral to your system. You apparently have a Mouat system which is great for you, but be sure to maintain low pressures. Here's some info, but there's a lot more in the library on this site. https://heatinghelp.com/systems-help-center/mouat-water-seal-movie/
    https://heatinghelp.com/heating-museum/mouat-vapor-system/
    https://heatinghelp.com/heating-museum/1927-proposal-for-a-mouat-vapor-heating-system/
    This should get you started.
    BTW, can you read any markings on your vent to help ID it. My pressure gauge that came with my boiler registers vacuum. Yours doesn't?
    Two-pipe Trane vaporvacuum system; 1466 edr
    Twinned, staged Slantfin TR50s piped into 4" header with Riello G400 burners; 240K lead, 200K lag Btus. Controlled by Taco Relay and Honeywell RTH6580WF
  • Fred
    Fred Member Posts: 8,542
    That vent is a Hoffman #75
  • vaporvac
    vaporvac Member Posts: 1,520
    Thanks @Fred. @jono , is that rad valve representative? Do any look like the originals? I understand that the Mouat system was VERY low pressure, but not a vacuum system, so I hope others will pipe in on the extra equalizer. Perhaps the changeover from coal required a slightly different set-up. Anyway, I doubt it's causing a problem and may be solving one.
    Two-pipe Trane vaporvacuum system; 1466 edr
    Twinned, staged Slantfin TR50s piped into 4" header with Riello G400 burners; 240K lead, 200K lag Btus. Controlled by Taco Relay and Honeywell RTH6580WF
  • jono
    jono Member Posts: 8
    Wow, eureka! Looks like I have a lot to read up on.

    The drawing in the magazine clip is exactly what I have, down to the drip line (equalizer) next to the vent.

    Yes, there are some original fractional valves. Seems that the non-original valves should be throttled more, because the seals are definitely blowing by.

    Not all of the rads have the Mouat seals either though. There are some more familiar bellows traps too.

    So it's a hodgepodge at this point I guess.

    Now I'm wondering if I should replace the pressuretrol with a "vaporstat" or something that can maintain lower pressure. Right now it's set as low as it goes, 0.5 to 1.5. Or would that end up cycling the boiler too much?
  • Fred
    Fred Member Posts: 8,542
    With that system, a Vaporstat would be of huge value!
  • vaporvac
    vaporvac Member Posts: 1,520
    How does your measured rad EDR compare to the sq ft of steam on your boiler plate? That may help determine how well a Vstat would work. p.s. you can repack valves depending. I think the originals are "packless" and the replacements may just be the handle. It's hard to tell.
    Two-pipe Trane vaporvacuum system; 1466 edr
    Twinned, staged Slantfin TR50s piped into 4" header with Riello G400 burners; 240K lead, 200K lag Btus. Controlled by Taco Relay and Honeywell RTH6580WF
  • jono
    jono Member Posts: 8
    Well, I haven't calculated the EDR yet. Guess that would be good to do.

    Any recommendations on vaporstat model, if I went that way?
  • Fred
    Fred Member Posts: 8,542
    The 0 - 16 oz, model #L408J1009 from Honeywell is the one many of us use.
  • SteamCoffee
    SteamCoffee Member Posts: 123
    edited January 2016
    IIRC Mouat system was 3 oz., the Safety Valve shut things off at 9oz. Or seals won't work properly. Had a very cool system to keep the pressure low, pretty sure if was vapor only, not vac...
  • jono
    jono Member Posts: 8
    Thanks everyone for the help. I certainly have something to go on now.

    Decided first thing I'll have to do is fix the waterline in the wet return, as everyone has told me I must do. Hopefully that will keep steam from getting to the vent and shutting it, and the system will maintain low pressure on its own. If necessary I'll add a vaporstat.

    Latest question: for the rads that have thermostatic traps on them, what's the best thing - purchasable in 2015 - to use going forward? Fortunately that's only 3 out of 16 rads (guessing these were added later on).