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Fast return/slow return

delcrossv
delcrossv Member Posts: 40
edited October 4 in Strictly Steam
As you can see, my mother in law's system has two dry returns. I replaced 2 Dole #5's where one was clogged and the other was incredibly slow with B&J big mouths. Now I have the "fast" loop that does the outer rooms of the apartments heating really fast (GREAT!) but the second loop that does the interior bedrooms and baths has a pretty long lag before it gets hot.

To try to even things out a little, I put a 3/4 x 1/8 bushing on the "Fast" return vent with a stub of brass nipple. It's "better" but not timed perfectly.

Questions: Was this done on purpose to get the more exposed rooms heat first?- so should I leave it like this with a little "drag" on the fast loop?

Or, should I keep tweaking to get all the rads to get hot simultaneously? Might require an even slower vent (Have any recommendations for the next step down from a Big Mouth?)

Any other ideas to even things up?


Comments

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 9,678
    Looks like your on the right track.

    I would put some thermometers sprinkled around and see how even the temps are not worrying about which rads are hot and how much of them is hot unless those areas prove to be cooler

    Just keep tweaking and you will get there.

    Air and steam will take the path of least resistance. Venting the large main with a big mouth is giving that main less resistance. It could also be something in the way the steam mains are taken off the boiler that favors the larger main.

    Try to increase the venting on the smaller main rather than choking the bigger main....but you may have to choke the large one a little.

    Also check the mains for any water hammer? Is the system quiet? Check the piping pitch, a little water in the smaller main could kill the steam. Check to see if the vent on the smaller main is panting
    delcrossv
  • delcrossv
    delcrossv Member Posts: 40
    edited October 4
    The bedrooms are noticeably cooler- until the steam gets there.

    System is dead quiet no noise/ water hammer/gurgle anywhere.

    What do you mean by "panting" for the smaller main? Like breathing in & out panting? (???)

    The air from the fast main comes out quickly, the slow main I can barely feel it's working- keep checking to see the disc is open. I'll check pitch next time I'm there, but the slow loop rads do get hot- eventually.
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 9,678
    If you had water (condensate) lying in a steam main due to a sagging pipe the water will cause some steam to condense and the air vents will breath in and out "panting"

    If your system is quiet then that's probably not the issue.

    So on a normal call for heat does the slow main heat before the burner shuts down? Or does it only heat when you crank the stat way up?

    delcrossv
  • delcrossv
    delcrossv Member Posts: 40
    Can't tell yet, system only goes on if the stat is at 80+ due to the weather.
    Now that it's getting cooler, I can put the setpoint a degree or two above ambient and see what happens.
    Running full out, there's a lag
  • gfrbrookline
    gfrbrookline Member Posts: 648
    Some people would love to have this problem as they prefer the bedrooms to be cooler than the capital rooms. If it is a problem you can increase the size of the vents on the radiators on the cold/slow loop.
  • delcrossv
    delcrossv Member Posts: 40

    Some people would love to have this problem as they prefer the bedrooms to be cooler than the capital rooms. If it is a problem you can increase the size of the vents on the radiators on the cold/slow loop.

    True, if only the bathrooms weren't on the slow main (Brrr)
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 9,678
    @delcrossv

    Your problem is better than most. Usually all we here about is banging, leaking and crappy piping
    delcrossv
  • neilc
    neilc Member Posts: 1,345
    why not post a picture of the 2 mains as they come off the header,
    delcrossv
  • delcrossv
    delcrossv Member Posts: 40
    neilc said:

    why not post a picture of the 2 mains as they come off the header,

    Will do, tomorrow. Goes up to the ceiling, out about 6' and splits as a T. Can't tell sizes as everything is lagged (and I'm not messing with the lagging if I can avoid it). :#
  • delcrossv
    delcrossv Member Posts: 40
    edited October 5
    Now that I look at it, it's pretty obvious which main is favored.


    So, a little more throttling on the big (fast) main vent?
    I might fire it with no vent (open pipe) on the slow one to see if that helps. 

    Cheapo Chinese  water feed valve is leaking , so I have to attend to that first.

    More to come.  :D
  • gfrbrookline
    gfrbrookline Member Posts: 648
    Maybe not throttling the mains as much as adjusting the vents on the bathroom radiators. What do you currently have for vents on these radiators and what type of radiators do you have? Pics help. You might benefit from a faster vent in the bathroom and keeping the bedrooms cooler for sleeping purposes.
  • gfrbrookline
    gfrbrookline Member Posts: 648
    I think the last pic may have been you hinting at this but you will likely even things out greatly if you insulate your mains, which the first pic shows the boiler piping lacks. You are loosing a tremendous amount of your output into your basement instead of your living space and wasting fuel.
  • delcrossv
    delcrossv Member Posts: 40
    I think the last pic may have been you hinting at this but you will likely even things out greatly if you insulate your mains, which the first pic shows the boiler piping lacks. You are loosing a tremendous amount of your output into your basement instead of your living space and wasting fuel.

    ??? The mains are all lagged. The condensate returns next to the boiler aren't.  


  • delcrossv
    delcrossv Member Posts: 40
    Maybe not throttling the mains as much as adjusting the vents on the bathroom radiators. What do you currently have for vents on these radiators and what type of radiators do you have? Pics help. You might benefit from a faster vent in the bathroom and keeping the bedrooms cooler for sleeping purposes.
    If anything they're probably over vented. Hoffman 40s on 3 section column rads in the bathrooms. 

    It's not that the slow loop rads don't get hot, it's that they heat after the fast loop ones.
  • delcrossv
    delcrossv Member Posts: 40
    edited October 7
    @gfrbrookline
    Walked the line and there is a long bare section- in the basement on the other side of the building. It was a basement apartment at one time and that was the only source of heat there. As the thermostat for the building is there, I can insulate some of the line, but not all of it. Am I right that I should start closest to the boiler and work my way around?

    @EBEBRATT-Ed
    I ran an open pipe (no vent) test, and things were much improved. I put a cross and a couple of nipples since, if I figure correctly, 3 big mouths should be pretty close to an open 3/4 pipe. I'm gonna pull the choke off the fast line as it's just trapping stuff against the disc. That plus a little more lagging and I think it'll be as good as I can get it and still heat the basement (some).

    Thanks guys for the advice!
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 9,678
    @delcrossv

    Sounds like you have it under control...a little tweaking. Does the boiler build any gauge pressure? You might add a 0-5psi gauge in addition to the 0-30.

    And yes the steam will be less likely to go through the branch of the tee than the run.
    delcrossv
  • delcrossv
    delcrossv Member Posts: 40
    @EBEBRATT-Ed

    If I really get it going, runs at 1 psig per the 0-30 . Matches the pressuretrol (also set at 1psi).

    If I don't set the thermostat for a big jump in temperature for a long burn, maybe a couple of ounces then the t-stat reaches temp and shuts off. The steam was coming out of the open pipe at low pressure then the stat ended the cycle (setpoint 3 degrees above ambient)

    A 0-5 sounds like a good idea. :)
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 9,678
    Sounds like you have enough venting
    delcrossv
  • gfrbrookline
    gfrbrookline Member Posts: 648
    edited October 8
    @delcrossv Walked the line and there is a long bare section- in the basement on the other side of the building. It was a basement apartment at one time and that was the only source of heat there. As the thermostat for the building is there, I can insulate some of the line, but not all of it. Am I right that I should start closest to the boiler and work my way around?

    I would recommend insulating all of your mains as much as possible with 1" fiberglass, this will give you even steam distribution. If you have uninsulated pipes the steam will condense and turn back to water until the pipe heats up and the radiators will take much longer to see steam. This is likely your problem.

    Your thermostat should also be in a section of the house that is were the heat is evenly distributed. If it is on the side that is heating slowly now, as you have stated, you will likely have to make adjustments once you insulate the pipes.

    After you insulate you can look at the rad vents.

    With the current vents/insulation do the rads on the slow side get hot across the top and eventually heat through or are they just slow to get steam? If they heat across the top an eventually fill they are over vented, if they are just slow to heat and fill from section to section that is usually an insulation issue. The hoffman 40, .067cfm, is a very slow vent, the only slower fixed vent is the Gorton no. 4, .040cfm, so I don't think you are over venting the radiator.
    delcrossv
  • delcrossv
    delcrossv Member Posts: 40
    edited October 8
    @gfrbrookline They are just slow to heat section to section. Rear bedroom being the worst (end of the line). E.G. Front bedroom hot 6 sections, bathroom 2 1/2 sections, rear bedroom maybe 1section off whatever is in the line after the boiler stops firing. There's a wide open 1A on the rear bedroom rad. The branches to the various risers are also bare in the basement apartment, so I'll get those too.
    Out of town next week, so I'll update when I get the insulation in and retest.
  • gfrbrookline
    gfrbrookline Member Posts: 648
    www.buyinsulationproductstore.com is where many of us get out insulation. Much better than the box stores and has the 1" you need for steam.
    delcrossv
  • delcrossv
    delcrossv Member Posts: 40
    Thanks for the buyinsulationproducts tip. They were very helpful. Insulated about 20' of main and an equal amount of branches, leaving about 12' of main exposed. I have not, as yet insulated the fittings.

    Ran it with the setpoint about 3 degrees above ambient and it's "better" but the burner switches off before the steam gets to the end of the slow line. About 5 minutes later, the slow main catches up and it's hot.

    The slow main is pushing 19 rads (7 are 6 footers) and the fast one is pushing 11 - and the 11 are smaller. So probably half the load or less than the slow one.

    Nest step is to completely cover the main and get some insulating cement for the fittings. Worth it?

    Then I'm left with choking the fast main (either a Gorton #2 (50% slower than what's on there now) or a Hoffman 75 (50% of a #2). So crank it down with the Hoffman or half as fast with #2?

    The thermostat is is a bad place, just under the returns (insulated in that section) in the basement apartment. I'm thinking moving it 5-6 feet further away and off the common wall from the boiler room, might get me a longer cycle time. Any thoughts on that? I can't move it upstairs, so that's off the table.
  • gfrbrookline
    gfrbrookline Member Posts: 648
    edited 1:11AM
    People on the forum have had bad luck with Nest's on steam systems. You are better off with something like a Honeywell Vision Pro 8500 which lets you have several wireless sensors.

    I would start by adding the Big mouth from the fast main to the slow using a close nipple and a 90 and replace it with a Gorton No 2 so the steam doesn't favor the fast main as much.

    Also since the slow main is feeding a lot of radiators with large capacities the radiator vents could be part of the problem on both sides. You may need to slow down the radiators closer to the boiler and smaller radiators on both sides so the steam has a chance to reach the end rads on the slow side. If the radiator vents on the fast side are too aggressive they will rob steam from the slow side as steam takes the path of least resistance. Use the link below to find the proper vents for your radiators and include the runouts in your calculations as indicated in the opening paragraphs. I recommend gorton's or ventrite No. 1's, some like maid o mist, Hoffman 1A's are hard to adjust correctly. Just don't buy the junk from the big box stores.

    https://heatinghelp.com/assets/documents/Balancing-Steam-Systems-Using-a-Vent-Capacity-Chart-1.pdf.



    As for the fitting I would use fiberglass with PVC covers from the same place you ordered the insulation. They are very easy to install with tacks.