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Expansion tank retro-fit?

BruceLundeen
BruceLundeen Member Posts: 7
in Strictly Steam
Here is a picture of a steam boiler I got a recent call on. The expansion tank had rusted through and the boiler was off on low water.
First, what do you think of the hot water expansion tank, and second, how it is connected to the system? Behind the boiler there was an vertical ASME tank the same size but I could not tell if it had just been taken out or was waiting to be put in, so I brazed up the hole. It is cold here in Minnesota and there is no time for hunting down a new tank.
My guess is that the new boiler we see held less water and the boiler would go off on low water before the condensate got back.
However, I can't get my head around why they didn't connect the expansion tank to the Hartford Loop, or if that would work. I don't remember if the outlet of the tank was below the Hartford Loop or not.
I have told the homeowner that the tank needs to be replaced- and soon. I tried to get across that LWCO's should be used only when they supervised. The boiler has two them, both probe-types, and one of them is a commercial type with a manual reset.


Comments

  • MilanD
    MilanD Member Posts: 1,160
    Do you have more pics and in better resolution? The only setup I've seen has this tank pressurised and with a connection to the main from the top, and bottom into a wet return before Hartford loop. This would be done to increase water volume for the boiler.

    Is this house shaped unusually? How long is the wet return from the last rad to boiler? Seems like someone tried to increase condensate volume but didn't quite do it correctly with a vent there on an unpressurized tank. Also looks like the header is really low... I wonder if it had something to do with that. Obviously, this works, so whatever you do, pipe it in the same way before getting yourself into owning it after the fact.

    If you look at Weil McLane PEG boiler manual, piping for extra tank on page 19, it'll tell you how it should be piped ideally. Again, I wonder if it has something to do with low header and the fact the system would suck water up, so instead of repiping the header, someone added the tank. Just make sure to not change any other settings. What is the op pressure set at?
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,858
    I think your assumption is correct. It is being used as a "range tank" due to the returns holding back so much water. Bandaid fix at best. Need to replace he wet returns and do away with the range tank.

    ME

    There was an error rendering this rich post.

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 16,255
    It looks like a surge tank use to increase the boiler waeter content
  • DanHolohan
    DanHolohan Member, Moderator, Administrator Posts: 16,596
    I think Ed's right. That's a dopey thing they did in the '80s to try to make up for the low-water content of the steam boilers back then.
    Retired and loving it.
  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,578
    Milan is uite right in noticing the nonstandard reservoir tank’s lack of an upper connection to the equalizer. With just a Hoffman 75, or 76 vent, it may act in reverse, sucking water out of the boiler at shutdown, instead! In addition the tank may be mounted too high above the water line to work properly.
    Lack of main venting capacity may also allow the vacuum to hold up the condensate, which happened to me before I learned the Black Arts of Steam Heating from Dan’s LAOSH!
    Keep the pressure low in such a case to avoid hiding a lot of water stacking up in the wet returns.
    If I can find the correct instructions for the Weil reservoir tank installation, I will post a link later.—NBC

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