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  1. #1
    Join Date
    Jan 2003
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    USA
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    "Low voltage" cabling

    I would love to find this contractor.

    So boiler room comb fans. Two fans, two boilers. Asked to look at why one fan is not running with both boilers are running. No prints, asbuilts, anything just a pile of crap in a boiler room.

    Name:  HV Wiring.jpg
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    Look in the 6x6 box under the fan, relay and current sensor. No big deal. Push the relay in, fan starts. Got power, motor works...dust crap storm comes out. Hasn't ran in forever. Lets follow the free air BS cable and see what's controlling it.

    Wire goes maybe 6' to a 4sq box. Open that up...

    Name:  HC Wiring Box.jpg
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    Wow, box of wire nuts splicing everything to everything else. Fine, 2 conductor driving relay spliced into a 6 conductor down to the boiler. 15' down from this, another 4sq on the side of the boiler. Full of splices again as they switch over to THHN and enter the burner head. In the boiler head, the pair spliced yet again because its not long enough. WTF?!?!? Figured out in all their splices they dropped the neutral to the relay along the way...

    Then the kicker... Boiler controls are mainly 120v and so is the relay driving the comb fan. This is all riding on a 6 conductor cable for 15' with the BMS S/S, modulation and status points. Nice touch with the 3' of THHN at the end, only to mix everything on LV cable after that.

    That aside, under what reality does splicing everything at every box make any financial sense? Free wire scraps? Even then, the labor cost to do so would be killer.

    Hackery at its finest.
    Propagating the formula. http://www.noagendashow.com/

  2. #2
    Join Date
    Aug 2015
    Location
    Buffalo,NY
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    821
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    Had a similar call to this a few weeks ago. Although it was a different problem a lot of the same things in your pictures.
    2 Laars boilers with a Tekmar 8 zone. Each boiler has 2 stages. Boilers alternate lead lag every 2 days. So boilers are staged 1-4 and comb air is 5&6. Had mechanical problems with both boilers I fixed. But then one of the boilers would not fire from the tekmar control. Found a bad delay relay. Then on top of all that this was a green house with building Automation for the mixing valves for the zones. Oh and no schematic at all accept the boilers themselves. Both boilers are 1,200,000 BTU each.







    Sent from my iPhone using Tapatalk

  3. #3
    Join Date
    Jan 2003
    Location
    USA
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    Thread Starter
    ahh.

    Stab an eye out with #2 pencil.

    At least you have some labels above the relays. These guys left nothing. There are only so many dealers of X/Y brand in the area where this site is. Narrowing down the players won't take much, though hard to pin on anyone. Over the counter controls, this is the crap you get.

    Vendor X, put in Tekmar and they wrote a setpoint to it, documented in the panel. They had tons of spare I/O but didn't take ON/OFF control of the modulating boilers. Aka, we can't program anything like that. So they installed a tekmar, wrote a setpoint to that and it staged modulating boilers with a fixed 170F setpoint. Cycled like crazy, no respect to return minimum on non-condesing boilers, stack is rotted out. Vendor Y came in after or before that. Hard to tell because pump S/S is on Vendor X but speed on Vendor Y. Comb fan status on Vendor Y, but S/S is hard wired to boilers.

    Pay me now, or pay me later..or please don't call.
    Last edited by orion242; 12-27-2018 at 11:20 PM.
    Propagating the formula. http://www.noagendashow.com/

  4. #4
    Join Date
    Jan 2012
    Location
    Broomall, PA
    Posts
    2,369
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    It's wired like that so only he can 'fix' it. Although if he can without notes/diagram, he's the world's greatest.
    I'd probably have to spend the rest of my life there trying to figure that out.
    Uh...Google it yourself!

  5. #5
    Join Date
    Mar 2005
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    time for an omni
    Keep it simple to keep it cool!

  6. #6
    Join Date
    Oct 2010
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    A lot of boiler work gets done on an emergency basis , just get it goin kind of thing “we'll get back to it later”

  7. #7
    Join Date
    Mar 2013
    Location
    Billington Heights, NY
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    the soap and paper towel dispensers are nice

  8. #8
    Join Date
    Jan 2007
    Location
    Mn the state where absolutey nothing is allowed
    Posts
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    Quote Originally Posted by HVAC_Marc View Post
    the soap and paper towel dispensers are nice
    thats so you can wash your hands of the mess.

    you know sometimes a wire cutter is your best friend
    my boss thinks its possible to repeal the laws of physics

  9. Likes Metalman0880, HVAC_Marc liked this post
  10. #9
    Join Date
    Aug 2011
    Location
    Denver PA
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    48
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    The best thing to do with that is rip out all of the wiring and start from scratch.

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