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Weird Board Lockout

Discussion in 'Commercial' started by suBcooled, Oct 15, 2011.

  1. suBcooled

    suBcooled New Member

    Messages:
    24
    I had a no cooling call this evening at a bar. I had never been here before wasn't familiar with the layout, so I got acquainted with the systems for a minute and figured out which unit was down. It was a 7.5 ton York gas pack. ZH090N10B4CAA4B. 460V, 3ph. It was locked out, with just the blower running. LED gave 9 flashes, which translated to an Ignition failure or high limit open. I counted the flashes a few more times to make sure I was counting right. I checked the HLS for the hell of it, and it was closed, as I expected. I killed the disco and fired it back up. After the 5 minute delay, compressor 1 started, then a few seconds later compressor 2 fired as well.

    CKT1 was running 275 on the head (discharge, not LL) 110 suction. Running 15*SH and 9*SC. Compressor drawing 4.5Amps. CKT2 running 290 on the head and 110 suction, 22*SH 14*SC. Compressor drawing 4.4Amps. Ambient temp was 75*, 6%RH. I monitored operation for about an hour and made my normal checks throughout, and there wasn't a hiccup. I'm a bit mystified about what caused it to lock out. If it happened once, surely it'll happen again, and I was hoping to catch it while I was there.

    It was real dark out at this point, so I scheduled to return. I want to look a bit into why CKT2 was running a bit higher on the head as well, that was about 20 over ambient, while CKT1 was 15 over.

    Any of you guys have any advice on where to look about the board locking out? I couldn't imagine that the high limit was opening up, it's only been in the 80's here, and the switch is L165-30 (I have seen them open up in the resi units the attic during the summer's here, so the blower never shuts off). For the hell of it, I pulled a wire off the limit switch and the compressors immediately shut down and the LED gave the same 9 flashes, same as before. You think it may be the limit switch? Maybe vibration has compromised the integrity of the switch. It's probably staring me in the face, but this is the end of a 12 hour day and I'm beat.

    Here's a pic of the unit, up on the roof in the dark.
     

    Attached Files:

  2. Lurk

    Lurk New Member

    Messages:
    3,760
    i'm not familiar with that unit,

    but "ignition failure" OR "high limit open" seems like a pretty retarded diagnostic code.

    wtf

    the board doesn't know the difference between an ignition failure and limit switch opening?

    anyway, isn't it possible that somebody had inadvertantly kicked it into heat mode whenever and it may have just been a simple ignition failure? did you fire it in heat and see what happened? microamps?
     
  3. suBcooled

    suBcooled New Member

    Messages:
    24
    I was wondering that as well, but the stat's had lock boxes over them, and the owner insisted that no one had touched them. I probably should've fired the heat for a minute, but didn't want to fill the bar/restaurant with that 'heat smell', because I'm sure the heat hasn't been run in quite some time. When I go back it'll be early in the day, and I doubt there will be any people in the bar, so I'll cycle the heat and see if there is sufficient microamps on FS. I am fairly certain the heat wasn't run though.

    I agree about the diag code being retarded. I guess they're leaving it up to the tech to figure out which is the current issue!

    Thanks for the input!
     
  4. Lurk

    Lurk New Member

    Messages:
    3,760
    i agree.

    but it wouldn't be the first time a business owner had no idea what-in-the-hell his employees were up to.

    and, all you need is four or five seconds of flame to check signal and see it either lockout or not lockout. you can kill it then long before that smell circulates. just a thought, but i totally understand. also, it never hurts to "wiggle" wires. i can not tell you how many problems i've solved by "wiggling" wires. ;) especially if it looks like intermittent issues with switches (circuits) opening.
     
  5. otto

    otto Bakery Chef

    Messages:
    19,866
    Location:
    in a van down by the river
    A loose disk in a snap disc limit, loose wire. I would guess one of those. Happy Hunting.
     
  6. otto

    otto Bakery Chef

    Messages:
    19,866
    Location:
    in a van down by the river
    You would think that a heat failure shouldn't lock out the A/C also.
    Not terribly familiar with York model numbers, is this a heat pump?
     
  7. suBcooled

    suBcooled New Member

    Messages:
    24
    I wouldn't have thought that a heat failure would lock out the A/C either, that's what has me confused. This unit is gas heat.

    That's why I pulled one of the wires off the limit switch while the A/C was running, to see if it would lock out, and it did immediately. I have no idea why an open limit switch would lock out the compressors, but I confirmed that it does by disconnecting the limit switch during A/C operation.

    I too am unfamiliar with this unit. I've worked on boatloads of residential York systems, but not so much on the commercial side. This is the first time I've worked on this particular style York.
     
  8. suBcooled

    suBcooled New Member

    Messages:
    24
    You're right, I could just fire the heat for a few seconds to see if it starts up alright, and check the microamps then drop it out. I definitely hear ya on the 'wiggling' wires, that certainly can help track down an intermittent loose connection or loose pin in a plug. I'm sure I'll find it when I get back out there with a fresh mind, rather than at the end of a 12 hour shift on a roof in the dark!

    Thanks again for all the input guys, I'm off to bed now. 3am here on the west coast and I have to be back at work at noon. Got to love how whacked out my sleep schedule gets when I work 12-9 (which never ends up being 9 because I always get some catastrophe call at 8:45 that will take me 2-3 hours to repair)
     
  9. otto

    otto Bakery Chef

    Messages:
    19,866
    Location:
    in a van down by the river
    Carrier RTU's have a rollout snap disc that will open and cause a heating lockout, they open when they get old and the crappy design vibrates the unit which vibrates the snap disc.

    Anyway, good night.
     
  10. suBcooled

    suBcooled New Member

    Messages:
    24
    Thanks, I will definitely be sure to sure to take a closer look at that.

    Sent from my PG86100 using Tapatalk