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  1. #1

    Buderus GB142-45 instead of GB142-24...

    Hi all,

    I've been reading this forum for a few months while I was scoping out my options for replacing a Ye Olde boiler from an 1890's New England cottage. Finally decided on a Buderus GB142.

    I was sized for a GB142-24 by the one contractor who really seemed comfortable with these units. So, I went with him and today's the install day. Unit's on the wall & I notice that the badge reads "GB142-45", which is two sizes up. Turns out the supply house screwed up & I get to keep the 45.

    The contractor assures me that the AFUE will not be affected, but I've always heard that these GB units run more efficiently if they're slightly underscaled. Any opinions? Should I just be happy?

    tx,

    dh

  2. #2
    Join Date
    Nov 2004
    Posts
    977
    I'd have to disagree on running most efficiently if they're undersized. They work most efficiently when they are PROPERLY sized.

    You said it is 2 sizes up. That is correct, but you should take a closer look. The 45 is TWICE the output of a 24. You can set the output so it will not go to full capacity, but you can't adjust the bottom end of where it will modulate.

    I believe you will have short cycling issues. You will also have efficiency issues in the spring and fall, when the boiler will modulate down to low fire. Yes, the -45 is rated at about the same AFUE efficiency as the 24, 30 and 60, but system efficiency will be in the toilet. Jeez-o-petes'..the 45 is a monster compared to the 24..and nobody noticed? I always wonder what the rest of the engineering is like if they can't get the most basic item correct.

    Try starting a post on here about someone installing a forced air furnace twice the size it needed to be. Yes, the 45 is a more expensive boiler that needs bigger pipes and bigger pumps, but that doesn't make it OK to leave in place. It's not like you wanted a 32 oz pepsi and they threw in a 64 oz at the same price. Doesn't work like that. If your house needs a 24, that is what should be installed.

  3. #3
    Join Date
    Dec 2007
    Location
    East central Indiana
    Posts
    477
    Quote Originally Posted by sprintmj19 View Post
    ...Try starting a post on here about someone installing a forced air furnace twice the size it needed to be...
    I once "corrected" one such problem by capping burners, changing DI motor, adding runs, putting on a smaller blower, etc. One of my first service calls.

    HO was pisssssed, had to redo it like it was: 120,000 furnace in 1 bdrm house.

  4. #4
    Join Date
    Feb 2008
    Location
    Massachusetts
    Posts
    701
    Quote Originally Posted by sprintmj19 View Post
    I'd have to disagree on running most efficiently if they're undersized. They work most efficiently when they are PROPERLY sized.

    You said it is 2 sizes up. That is correct, but you should take a closer look. The 45 is TWICE the output of a 24. You can set the output so it will not go to full capacity, but you can't adjust the bottom end of where it will modulate.

    I believe you will have short cycling issues. You will also have efficiency issues in the spring and fall, when the boiler will modulate down to low fire. Yes, the -45 is rated at about the same AFUE efficiency as the 24, 30 and 60, but system efficiency will be in the toilet. Jeez-o-petes'..the 45 is a monster compared to the 24..and nobody noticed? I always wonder what the rest of the engineering is like if they can't get the most basic item correct.

    Try starting a post on here about someone installing a forced air furnace twice the size it needed to be. Yes, the 45 is a more expensive boiler that needs bigger pipes and bigger pumps, but that doesn't make it OK to leave in place. It's not like you wanted a 32 oz pepsi and they threw in a 64 oz at the same price. Doesn't work like that. If your house needs a 24, that is what should be installed.
    I couldn't agree more.

  5. #5
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,069
    Quote Originally Posted by sprintmj19 View Post
    I'd have to disagree on running most efficiently if they're undersized. They work most efficiently when they are PROPERLY sized.

    You said it is 2 sizes up. That is correct, but you should take a closer look. The 45 is TWICE the output of a 24. You can set the output so it will not go to full capacity, but you can't adjust the bottom end of where it will modulate.

    I believe you will have short cycling issues. You will also have efficiency issues in the spring and fall, when the boiler will modulate down to low fire. Yes, the -45 is rated at about the same AFUE efficiency as the 24, 30 and 60, but system efficiency will be in the toilet. Jeez-o-petes'..the 45 is a monster compared to the 24..and nobody noticed? I always wonder what the rest of the engineering is like if they can't get the most basic item correct.

    Try starting a post on here about someone installing a forced air furnace twice the size it needed to be. Yes, the 45 is a more expensive boiler that needs bigger pipes and bigger pumps, but that doesn't make it OK to leave in place. It's not like you wanted a 32 oz pepsi and they threw in a 64 oz at the same price. Doesn't work like that. If your house needs a 24, that is what should be installed.
    I think you covered all the bases.
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  6. #6

    resolved

    Well, after telling my contractor about my reservations he sent his buderus rep out my house to discuss it. The rep arrived with a -24 and the crew just swapped them out. They only had the -45 hanging on the wall, so no gas/water/electrical hookup yet. I feel much better about this setup - and really impressed with the contractor. He was fully prepared to do whatever I decided on, and that's rare.

    Thanks,

    dh

  7. #7
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,166
    Great to hear! We installed the wrong unit a few years ago. Only it was 1/2 the size! We corrected fast!

  8. #8

    Confused AM10 Module mounts upside down in a GB142???

    Hi,

    I'm preparing to wire my Buderus GB142 and I'm scratching my head. The AM10 (outdoor temp. sensor) is shown in the manual as mounting inside the unit using a "rams horn" & clasp type mounting. But if you assemble them that way - which is the only way it'll fit - the unit is upside down.

    Surely it's not meant to go in upside down.... ???

    dh

  9. #9
    Join Date
    Nov 2004
    Posts
    977
    I thought there was a contractor installing this? What does he say?

  10. #10
    The contractor installed the unit & hooked up water/gas, but jobs out the electrical. I'm comfortable with wiring, so I told him I'd take care of it. The schematic is pretty straight forward - it's just the orientation of this thing that looks screwy. I'll post some pic's tomorrow....

  11. #11
    Just heard back from Buderus. They said that when the AM10 module is mounted in the GB142 it is upside down. The image in the manual is incorrect.

    IMHO, the manual is correct (how it should be). They screwed up making the parts - you can't convince me the germans INTENDED for the LCD to be upside down to the user. Frustrating.

    dh

  12. #12
    Join Date
    Jul 2008
    Location
    Pittsburgh PA
    Posts
    37
    Quote Originally Posted by declanhalpin View Post
    Just heard back from Buderus. They said that when the AM10 module is mounted in the GB142 it is upside down. The image in the manual is incorrect.

    IMHO, the manual is correct (how it should be). They screwed up making the parts - you can't convince me the germans INTENDED for the LCD to be upside down to the user. Frustrating.

    dh
    I went through that myself last month on my first GB-142 install. It was driving me nuts trying to figure out how the AM10 was supposed to be mounted!!! I call my supplier and he said upside down. And I said.... you ------ kidding me right?.....nope Other than that....it's sweet......
    What was I thinking??? I never do that again!!!

  13. #13
    Yeah - seriously! I guess you could leave it in that enclosre it comes with and mount it on the wall, but sheesh....

    Another weird AM10 thing is that the GB142 manual shows a different WIRING than the AM10 manual. The RC terminal on the AM10 is shown connecting to either the boiler bus ("white plug on black wiring harness), or the wiring terminal strip inside the boiler (to the right). Turns out they both go to the same place & you only use the harness if the AM10 is going inside the boiler. Another little bit of excitement to my day...

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