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what size sidearm should i need.

dan simon
dan simon Member Posts: 2
I have an apartment complex. I will be replacing my boiler and will in the next 2 years attaching a sidearm for my hot water. I am curious what size in gallons I will need. I Have 4 units( 8 baths, 8 kitchens and a 1 washer laundry room.)
All are currently supplied by 1 100 gallon gas water heater. We have never had a problem with hot water at any time of the day with what we have. Cost is the main concern of mine in this replacement. I dont know exactly how a heating contracter would determine the size neccessary for the building. I was recommended a size by my contractor, but with what I understand about the gallons of water heated per hour in comparing gas with boiler I seems that the size might be excessive.


  • Brad White
    Brad White Member Posts: 2,398
    Fixture Units

    The way I was taught (before software and perhaps other modern methods) was the Fixture Unit method proulgated by the American Society of Plumbing Engineers (ASPE), not to be confused with the Canadian Territories Plumbing Engineers (CANTPE). :)

    Each fixture is given a value roughly proportional to the amount of hot water it uses.

    These numbers are added then compared to what is known as Hunter's Curve (this is not a type of archery equipment; don't make the same mistake others have made! ;)

    Hunter's Curve allows for diversity, that is, an allowance that all fixtures will not be drawing all at once and that the more fixtures you have connected, the fewer as a total percentage will draw at any one time.

    In other words, a single apartment may have simultaneous shower, laundry and possibly dishwashing activities, but a half-dozen such apartments are less likely to be doing all things in each unit at the same time. Thus a single apartment will have a greater demand percentage than a larger complex.

    I do not have my tables handy otherwise would spot you some better advice. But my point here is that you should ask to see your contractor's methods and assumptions both in GPM and GPH rates regardless of the type of system you choose to use finally.

    Burnham and other companies may have tables available on their web sites for you to cross-check too.
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"

    -Ernie White, my Dad
  • Steamhead (in transit)
    Steamhead (in transit) Member Posts: 6,688
    First cost

    or operating cost? If I were you I'd make the latter my prime consideration. Energy costs are only going up.

    Instead of a side-arm, to have the heating boiler also heat the hot faucet water I'd go with an indirect tank. Whereas the side-arm must be kept hot all the time, the indirect will store a tankful of hot water for a long time without losing much heat if no one is using hot water. This means that during the summer, the boiler probably wouldn't have to fire at all in the wee hours when no one is likely to use hot water.

    Another advantage of the indirect is that it has more heat-transfer surface than the side-arm (or direct-fired tank). This means the boiler won't have to work as hard to heat a given quantity of water.

    And some commercial-type indirects carry a 15-year limited warranty. I don't know of any side-arm units with this.

    On the Triangle Tube website, there is a rule-of-thumb sizing page that tells me, based on what you've posted, that their TR-60 commercial indirect should work well in your building.

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  • Glenn Sossin_2
    Glenn Sossin_2 Member Posts: 592
    Agree w/ Steamhead

    Indirect is the way to go. Theres another factor that didn't get raised so far. You have a 100 gal water heater. That will allow 2 or 3 showers at the same time and no one would probably notice anything.

    Try 3 showers simultaineously with a side arm heater and you may see a whole different story - especially assuming you are going to use a tempering valve. As your draw of hot water increases, so will the pressure drop through the side arm heater. On a large peak demand, the pressure on the hot side could drop a few psi and the cold side could overrun the hot inlet on the tempering valve and then people are getting a flash of cold water when they're expecting hot water. I had this happen to me on a job. Installing checks on the hot and cold inlets would help prevent this but I'll think you'll have the potential for occassional unstable water temps and pressure drops.

    As Steamhead said, go with the indirect.
  • Maine Doug_60
    Maine Doug_60 Member Posts: 12
    Depends on what

    city you live in. For Baltimore, a 9mm sidearm is probably sufficient. Some prefer a bit heavier, my son has a 45.
  • Brad White
    Brad White Member Posts: 2,398
    Of course

    you are both talking about "heaters".

    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"

    -Ernie White, my Dad

  • I'm partial to my .32 actually...
  • Brad White
    Brad White Member Posts: 2,398

    That would not scare a squirrel. :)
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"

    -Ernie White, my Dad
  • Glenn Sossin_2
    Glenn Sossin_2 Member Posts: 592

    I fired one of these at a range in PA several years back. Boy Clint made it look easy.
  • Ed_26
    Ed_26 Member Posts: 284

    12 gauge is the way to go.. pump or semi... takes care of all nasties.

  • Weezbo
    Weezbo Member Posts: 6,232
    a 460 would provide a Heck of a Blast *~/:)

    once brandished ,...i think you would be in Plenty of Hot Water :)

    other wise a Triangle Tube might be your best value...

  • Works pretty good on mice though... :)
  • Glen
    Glen Member Posts: 855
    It did not take long -

    for this conversation to enjoy the effects of the double entendre. Unfortunately - in Canada we are not allowed to do that - unless at a fully supported firing range. As with any sidearm - size does matter - hence the original question. :-)
  • Aidan (UK)
    Aidan (UK) Member Posts: 290
    what size sidearm should i need.

    .455 Webley & Scott.
    What else?
  • Perry_3
    Perry_3 Member Posts: 498
    But it depends on the applications...

    Just like everything else. The sidearm must be sized to the application.

    In some cases a 22LR deringer is perfect... In others a 50 Caliber Desert Eagle is barely adequate.

    My "compromise" general purpose sidearm which is adequate for most situations I expect is a 40 S&W.

    Given a specific situation.... and I may well chose something else.

  • Perry_3
    Perry_3 Member Posts: 498
    For the true sidearm enthusiest: 50 Cal BMG Pistol

    They are rare.... But it does a job no other handgun can do.


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