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Steam Venting or Firing Rate

As I see it from this conversation, the application of a u-shaped trap is really to create a wet return which is the seal you seek. Terry can correct me if I mis-understand, but the prohibition on using a "master trap" is not to use a mechanical (Float and Thermostatic) trap as the end of return device.

Remember that dry returns are really steam mains in disguise before they drop below the waterline. Once they do that, they are wet returns, never to see steam again, one hopes :)

Comments

  • Steve Garson_6
    Steve Garson_6 Member Posts: 35
    Condensate Tanks and Boiler Feeder - Steam blasting out of vent

    Now that we've had our first real heating day, this steam system that I have been improving was fired up yesterday while I timed the heating. I need to know if these times are OK. This is a wood frame building that is roughly 100'x75':

    1. Cold start to steam reading main vents: 10 minutes.
    2. Radiator valves hot: most in 10 to 12 minutes
    3. First radiator section warm.: 15 minutes
    4. Last radiator section 200* : 60 minutes

    The boiler is a Smith 19-6 section. It's fired at 3.5GPH, but has a capacity to fire at 6GPH.

    Do I need larger air vents on the radiators? Is this timing OK? Since it was a cold start, the pipes had to rise from a temp of 50*.

    Thoughts?
  • How long

    did it take from the time the boiler was started until it started generating steam?

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  • Steve Garson_2
    Steve Garson_2 Member Posts: 708
    Steam and Receiving tank

    Around six minutes. A new point to add: Once the system was really steaming (one hour) steam started shooting out of the receiving tank vent at a furious rate. We upped the firing rate from 2.5gph to 3.5gph before the start of this season.

    The oil company said they need to add a trap before the receiving tank to block the steam. The system never had one, but I guess with the lower firing rate, the steam never reached the receiving tank. The wet return has 1-1/2 inch pipe. There are no traps anywhere. This is a one-pipe steam system.

    Is the oil company correct in their solution? I'm guessing that this might have something to do with the delay of steam reaching the farthest radiators and the system not shutting down on pressure.

    The boiler does have insulation and covers, just not in the photo. Receiving tank is on t he left. Also, when the float on the low water switch starts the pump, the boiler always fills two inches above the "normal" line. But the device is mounted with the line in the casting installed in line with the correct water line.
    Steve from Denver, CO
  • ttekushan_3
    ttekushan_3 Member Posts: 958
    I might add

    the problem is that you have a vented receiver at all. You shouldn't need it. Normally, the pressure is equalized between the return and the supply at the boiler, so the wet returns stay wet. This is as god intended for single pipe steam. You now have a wide open line at the end of the return. The wet return, whose outlet into the vented tank is very low, is being blown clear of water. This has nothing to do with your firing rate, or at least your firing rate seems right on but this problem is a function of the "redesign" that someone had done along the line.

    Don't put in the master trap. The master trap will still allow the wet returns to fill with steam. Sometimes a trap is used in large systems at the end of the steam main with a condensate receiver located remotely rather than at the boiler. You really don't have this need.

    Next year, pipe the return as a traditional hartford loop. [easy for me to say, right?!]

    But right now (and always, as far as I'm concerned) get a vaporstat to control steam pressure and get the pressure as low as possible that is consistent with good heat distribution. It won't slow the initial progress of the steam, but it will prevent the pressure from rising to the "blow the water out of the wet return" level. I would think that system would heat well and more efficiently on, say, 6 to 8 ounces of steam pressure. This should prevent steam from forcing the water clear of the return.

    Any other thoughts out there? [steamhead? :-)]
    terry
  • Steve Garson_2
    Steve Garson_2 Member Posts: 708


    The heating tech said that if he installed a simple U-shape piped trap, it would prevent the steam from exiting the return. If I shouldn't have him do that, please confirm.

    As far as pressure, I running at around 1 psi.

    I am curious if this system would work without the receiving tank, but it take a long time for condensate to reach the boiler, so my guess is the boiler would shut down on low water.
    Steve from Denver, CO
  • ttekushan_3
    ttekushan_3 Member Posts: 958
    Hi Brad

    I guess it comes down to the fact that the master trap as described won't do much until the wet return already has become dry.

    With regard to the U, I'm presuming what's meant here is an inverted U placed in the wet return before the tank, creating a higher water line in the return system, as Brad mentioned.

    An inverted U will work. What's the boiler pressure when the steam escapes? A vaporstat's always a nice efficiency booster for steam systems.

    BTW, watch the height of that inverted U. If too high, you my find a brand new water hammer at the end of the steam main if the water rises high enough in the returns. Figure 1 lb of pressure equates to about 22 inches of water lift.

    Now I'm off to look at a steam system thats squirting water out of the first floor radiator vents and shaking the building. I hear the tenants are frightened! I LOVE jobs like this! One day I'll work up the nerve to arrive on site in a wizard's cap:-)
    terry
  • Chris Kuzila
    Chris Kuzila Member Posts: 11


    How many seasons have you had this system? Did you calculate the radiation? From the picture, is that that wet return on the left, on the ground? Then it's full of water to the two 90's above the tank? 24"? That's a bit of pressure to blow that dry.
  • Brad White_203
    Brad White_203 Member Posts: 506
    All because of U

    Hi Terry

    I agree, the depth of the U is not so important but that the rise coming out of it ought not be much! (Unintentional False Waterline anyone?) But at least provide that passive seal.

    And no master traps, that much is clear... Thanks Terry.

    Brad
  • Steve Garson_2
    Steve Garson_2 Member Posts: 708


    Ten seasons. But this is the first season where I am managing the facility infrastructure.

    EDR is 823 before the pickup factor. If you assume 1.33, the total EDR is 1100 square feet of radiation.

    You raise a very good point. Yes, that pipe is the wet return and since it does have the 90* elbow, that should work as a trap. But it isn't 24 inches. The service tech said that he would need to raise the tank six inches. Does that make sense?

    I just lowered the pressure to .5 psi. Can you explain the two pressuretrols? The one on the left is a PA404A-1009, which appears to be a safety cut-out. I set this to .5 psi. The one on the right is a L404 C1147 which I set to .5 psi, as well. Should the PA404 be set higher, since it is a safety?

    The distance from the floor to the elbow of tank is 26". The distance from the floor water line of the boiler is 46".

    Some more photos.
    Steve from Denver, CO
  • Steve Garson_6
    Steve Garson_6 Member Posts: 35
    Do I need a tank?

    Is it possible that this system doesn't even need the tank? The EDR has been reduced by perhaps 15% since it was designed as a result of radiators being removed over the years as space was converted to hot air.

    How can I determine this? Should I shut off the valve from the tank and see how much water appears in the watch glass before the low water shut-off shuts off the burner? Or will this burn out the pump motor?
  • Chris Kuzila
    Chris Kuzila Member Posts: 11


    Which float switch does what?
  • Steve Garson_6
    Steve Garson_6 Member Posts: 35


    I just checked the specs on the pressuretrol used on this boiler. It's an L404C that apparently has a minimum of 2psi pressure. So I assume that even if I set it lower, it will run to 2 psi. If the pipe to the tank is only rises 24-inches, then 2-psi would be pushing above that water column.

    Sounds like vaportrol my might be my solution and just run it at .5psi, which shouldn't push the 24-inch water column.

    Can someone confirm that my logic makes sense; or not?
  • Chris Kuzila
    Chris Kuzila Member Posts: 11


    My earlier post concerning floats was asked to make sure the pump is wire to the proper switch, from the picture, it seems all wires run to the same junction box. You said when the pump hits, the boiler fills two inches above the water line. Yes, the vaportrol makes sense.
This discussion has been closed.