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Expansion Tank Question

EBEBRATT-Ed
EBEBRATT-Ed Member Posts: 10,225
I looked at a job that has a compression tank (no bladder) piped into the system off the air scoop (no problem so far). There is a tee in the tank piping between the air scoop and the tank. The branch from this tee runs over and is piped into the tops of three boilers. In effect when all these valves are open (as they are) the expansion tank is connected to the system in 4 locations (3 boilers and the air scoop) All the boilers are piped into 1 common system.

In addition another large zone was added (4" pipe) and a second expansion tank (bladder type) was added to the system piped to yet a different location.

In my opinion the expansion tank(s) should be piped together and then only one connection should be made to the system at the air scoop which is correctly installed in the suction side of the pumps. I think the boiler connections should be eliminated.

Also can you mix compression tanks and expansion tanks on the same job?? It dosen't seem right.

Thanks,
Ed

Comments

  • Steamhead (in transit)
    Steamhead (in transit) Member Posts: 6,688
    Answers

    1- there should be only ONE "point of no pressure change"- at the air separator. Those boiler connections may have been done to take advantage of built-in air separators, but those only work well on single-boiler jobs.

    2- Yes, you can mix the two types. I've done it when I had to. The rule for the plain steel tank would still apply: NO automatic air vents!

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  • Rich Kontny_3
    Rich Kontny_3 Member Posts: 562
    No Auto Air Vents

    Steamhead,

    It just so happens that my home office is in the boiler room of our church's parish center. I installed the two boiler system in this building about 6 years ago. I used all Taco pumps and accessories and the air scoop "Taco" has a 1/2"FIP connection on the bottom that is piped to a floor mount compression (bladder) tank. The top 1/8" FIP has a Braukmann automatic air vent. I have never had a single air problem with this system or the air vent.

    I agree with everything you said about the built in boiler air scoops etc but I wonder why you don't recommend the auto-air device???

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    Rich K.
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 10,225


    I think Steamhead ment that your not supposed to use automatic air vents with a non bladder tank. They are ok with a bladder type tank.

    ED
  • Steamhead (in transit)
    Steamhead (in transit) Member Posts: 6,688
    That is correct

    if all you have on the system are bladder tanks, auto air vents are the way to go. But if the two tank types are mixed, do not use these vents.

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  • Rich Kontny_3
    Rich Kontny_3 Member Posts: 562
    Makes sense to me...

    had a brain cramp (or perhaps a senior moment :)
    The conventional tank would be subject to water logging with an air vent on the scoop (is that correct?) or am I still missing something??

    Rich
  • Ken D.
    Ken D. Member Posts: 836
    Expansion tank

    With a conventional tank, it should be piped so any separated air from the boiler goes into the tank where it is wanted and needed.
This discussion has been closed.