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Thread: Newby seeking guidance BW GX-2-25S6BN vs GX-1-55S6BN

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    DIY Junior Member ap's Avatar
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    Default Newby seeking guidance BW GX-2-25S6BN vs GX-1-55S6BN

    Have been lurking and based on this site I have decided to replace my 20 year old Ruud 50gal rental gas water heater with one of the BW GX series. But trying to make sure I choose the right one. So far the old 50 gal. tank seems to be adequate (but I think its useful life must be near an end) ... the next tank will be required to handle my two children (9 and 11) into teenage (and later?) years so I am anticipating some increase in demand.

    The 25 gallon unit would seem to be more efficient (2 inch vs 1 inch insulation) and presumably I am not heating a lot of water when not in use. This would seem to mean some saving - not sure how much though.

    I am worried that if I buy the 25gal unit - I may regret this later and need (?) the 55gal unit


    There is a well known sizing chart on BW site that suggested the right tank size... although so far I can't seem to find a combination that recommends either of the GX tanks. A quick call to BW and the sales staff endorsed the 25gallon unit. I accept the fact I know very little about this and would happily take that recommendation but it seemed a little counter intuitive.

    Incidentally should I be concerned about ventilation given that the tank will occupy the same location as the current one - adjacent my gas furnace that is also atmospheric venting (that is to say it is Direct Vent exhaust but draws combustion air from inside the house)


    Any help/suggestions on the right size unit, relative efficiency (and combustion air demand) gratefully accepted
    thanks!


    (great site!)
    Last edited by ap; 03-08-2010 at 01:17 PM.

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    DIY Junior Member ap's Avatar
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    Does anybody know??

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    Retired Defense Industry Engineer jadnashua's Avatar
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    Both of those models seem to be optimized for high altitiude use. They also have larger burners than typical lower output devices. Being natural draft, this means it will be using interior air for combustion (and going out the flue), so, you may not be able to put it in the same place as a lower output version. Are you at high altitude? I couldn't find those on the BW site, but did find them via google. You may also need a larger flue.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Junior Member ap's Avatar
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    Thanks .. I currently have a 4" flue and I am at 650 ft MSL according to a nearby airport ... Often thought about the inside air consumption for combustion ... It occurs to me that the clothes dryer, furnace and stove vent in conjunction with the water heater might draw more inside air than advisable ... I wonder if either of the "GX" tanks might push it over the edge - whatever that "edge" is.....I was considering an HRV at one point but was told that it might not help too much as they exhaust as much as they draw. unfortunatley there is not a lot of room to plumb a air inlet for the central heating furnace which is in the same room as the water heater,

    The guys licensed to install these tanks don't seem to be too concerned (or is that lack of awareness??) of the possible issue as it is never identified by them when I shop around.

  5. #5
    Retired Defense Industry Engineer jadnashua's Avatar
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    Many installation manuals list the minimum volume required to enable the thing to work. This assumes your house has 'normal' leaks. Today, many people are trying to plug any leaks they can. This means that unless the burner is closed combustion (it draws its own combustion air from outside), all of those burners are sucking unconditioned air in through cracks in the house, and exhausting your conditioned air out the flue after it is used during combustion...very inefficient. When you add everything together, it can be a real problem.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Junior Member ap's Avatar
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    very inefficient. When you add everything together, it can be a real problem.
    that makes a lot of sense - I wish I was more knowledgeable though. I know I have moderately leaky home (mid '80's construction) but I still have three CO sensor alarms just to ensure I am not creating a problem for myself. But here in Canada ... windows stay closed for quite a while in the winter and at least the furnace and clothes dryer run fairly constantly

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