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Expansion tank

what about seismic bracing? I mean, a few strategic cables to minimize the accelleration forces during a tremor can go a long way.

In our state (MA) we are in Seismic Zone 2, (a notch below California -in that respect only) and this is done routinely.

The second question would be, if the existing structure cannot accomodate a little sway bracing, do you really want a 15,000 lb. (assuming half-full) overhead tank in the first place?

My last questions would be, is that capacity tank a typo or if accurate, are 3000 gallons really needed? If your system volume and pressure can be checked, your bladder tank scenario might be easier to swallow.

My $0.02



  • Rich_34
    Rich_34 Member Posts: 5
    Expansion tanks

    OK I have another one. I work in a facility 40,000 sq. ft 2 Weil Mclain Boilkers (don't have the model info but at leastr 180000 btu's input) The expansion tank is cieling mounted and well go figure this is Alaska and we have well you know Quakes. Hey can I relocate the tank on the floor? It's oh 300 g's. We don't own the building so I don't want to splurge on a bladder tank... Alright then!
  • Scott04
    Scott04 Member Posts: 69

    You can't mount the tanks lower than the boilers. The air will always rise to the highest level. There is a seperator that takes the air from the system and directs it towards the tank. From that point it has to go up!

  • Ken_40
    Ken_40 Member Posts: 1,320
    Scott's probably correct...

    And he is rightfully assuming the expansion tank also has air "collection" specialty fittings attached, allowing the tank to serve two purposes: a place for an air cushion, and a place for air scavenging.

    If however, his assumptions are incorrect, you can mount the expansion tanks anywhere you want, but you must pipe them (or better yet, the boiler blocks themselves) to overcome the air elimination aspect of all hydronic systems.

    Are there "speacialty" fittings for air elimination inserted or installed on the exp. tank?
  • Expansion Tanks

    I agree with Scott on this one, to a point. You can put the tank on the floor next to the boiler but, if you want to recover any system air in the tank, it wont be able to bubble-up into it. The system air separates as the water is heated in the boiler, you`ll likely need a separator that will allow this air to vent to atmosphere, if you do it this way.
  • Tim_33
    Tim_33 Member Posts: 83
    I disagree..

    that the expansion tank has to be higher than the boilers. That is true only if it is a "standard", i.e. non-bladder type of industrial/commercial expansion tank, which is what is installed in this instance. If you have this type of vessel that is not located at the highest point in the boiler room part of the system, it will become water-logged and as an expansion tank, useless. IF you need to put the expansion tank on the floor, that can be done with a bladder type of tank, such as the B&G B200. So you can't just relocate the existing tank, but you can install a floor mounted, vertical bladder tank.
  • Tim

    Many guy`s used the boiler itself as an air separator, done this way, the "standard" tank had to be higher than the boiler. But it`s not "written in stone" that it must be like that. Oh sure, without proper "air migration fittings" this type of tank still waterlogs no matter where it is. Proper piping technics must be adhered-to as to its take-off, and boiler tie-in points, but it can be done. I wonder what the "old guys" did before bladder tanks became popular.
  • Tim_33
    Tim_33 Member Posts: 83
    What the old guys

    did was put the tank as high as possible in the boiler room so that air would be trapped and provide room for thermal expansion of the water and a place for air separated out of solution to go. With a site glass to show level, a steel tank near the ceiling of a boiler room was an indicator of the system health. A stable system maintained a very consitent level range in the expansion tank.

    Using a boiler as an "air separator" is new one, for me at least, I have never heard of that "practice". I have also never heard of or seen a high tank, improperly piped systems being excluded here, becoming water logged, unless it was leaking and "self vented".
  • Tim

    I know we are getting off the subject here, but remember, I`m talking "older systems". If you could get your hands on an older Trane heating manual, they actually describe A fitting the installer made-up to separate the air from the water, using the internal space of the boiler as the actual separator. it always went on the top, or upper back of the boiler in conjunction with the systems outlet. The only reason the tank was mounted above, was so the air(separated by this), could bubble up into it. I very seldom see a sight glass on a tank.
    Ps- This manual I speak of was published in the early 60`s

  • Randy Calvi
    Randy Calvi Member Posts: 14
    Expansion tank - gravity system

    Looking for advice... I have a client with a gravity, cast iron radiator system. Older boiler, but in good repair and everything works OK. System has an old riveted tank in the attic, vented through the roof. Unit looks OK, but has a little bit of corrosion and water scaling on one end. It doesn't look like a leak to me, more like maybe some condensation (it's not wet). Client would like to replace the existing expansion tank for peace of mind. Is there a proper way to add a modern, diaphragm type tank to this system without closing it up or pressurizing it? If so, is it possible to place it in the attic where the existing one is? It seems to me, that putting a new tank in, teed to the vent line and de-pressurized might work, but I'm a little hesitant of that being the right solution. Thoughts, ideas or suggestions? Thanks much.
  • Brad White_119
    Brad White_119 Member Posts: 11

    You may want to post this as a new thread, otherwise it may get lost in this one.

This discussion has been closed.