Washington Bosch SM60 freeze error -- closed loop

Discussion in 'Maintenance and Troubleshooting' started by Burnhaven, Dec 25, 2019.

  1. gsmith22

    gsmith22 Active Member Forum Leader

    the photo of the pipe in post #12 is definitely HDPE pipe. zooming in on the photo in post #9 it looks like you have a close header but I can't tell if it was site built or pre-fabricated. Site built would mean lots of joints between short pipe sections and T fittings so lots of opportunities for leaks because there are lots of fusion connections. I would tend to think pre-fabricated headers would be more immune to a leak but anything can happen. Fusion connections aren't rocket science but there is a process to follow - you hold the pipe and the fitting it is going to connect into against a hot iron at the same time heating/melting the outside of the pipe and inside of the fitting. Then you take them off the iron and press the pipe and fitting together allowing it to cool. Its like connecting pvc pipe but instead of using primer and cement you are using heat via the iron.

    If it was my system, I think I would have them re-pressurize the loop first without the stop leak and see if it stays pressurized. If it stays pressurized, then that would indicate something along the lines of what ChrisJ was talking about - blockage in a section of the loop that was never originally purged of air that recently became unblocked adding a bunch of air to the overall loop. If it doesn't stay pressurized, that would indicate a leak somewhere in the system outside (I'm assuming you would see the leak if it was in the pipe in your basement). Then re-pressurize with stop leak and see if that allows it to stay pressurized (ie maybe the leak is small enough to get clogged by the stop leak). If that works, you may want to consider converting to a non-pressurized pump system so to keep internal system pressure as low as possible at the now clogged leak point. If the stop leak doesn't work, I would probably then go and dig up the manifold, tear it apart, and separately pressurize each section of pipe and see what holds pressure and what doesn't attempting to isolate the problem to one of the slinky loops, the manifold, or the pipe leading to/from the house.
    Burnhaven likes this.
  2. gsmith22

    gsmith22 Active Member Forum Leader

    Assuming you use the system to air condition, that would mean that whatever is causing your problem, had to have changed recently (ie since summer) or else the unit would have locked out then too as it uses the same loop to push heat to the ground
    Burnhaven likes this.
  3. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    While I can appreciate all the input here, why the rush to a complicated problem? Service 101, loop lost pressure does not mean it is empty. The technician should have attempted to goose the loop pressure to re start circulation and gathered data based on the result of that. Adding stop leak to a loop prior to attempting goosing the pressure is ill advised.
  4. gsmith22

    gsmith22 Active Member Forum Leader

    Agreed, I recommend that first too to verify it does or does not remain pressurized upon refill before going down the stop leak route
  5. Burnhaven

    Burnhaven New Member

    So to re-pressurize they need to show up with a flush cart? And the testing would be done with air or water? ( not glycol that might just leak out again, if that's what actually happened)

    Can you elaborate on the scenario where during initial construction, one loop never filled up and just contained air? In this scenario if fluid eventually ( recently ) got into that loop, it would make the system appear to be empty ( when in fact still 3/4 full ), and of course that air is now somewhere else in the system.

    We haven't looked in the crawl space. If the larger send/return pipes are attached to the Bosch unit itself in the mech closet, then those would have had to burst somewhere in the 25 feet or so between the mech closet and the front foundation where the large pipes exit.
  6. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    Goosing the system can be done via the PT ports on the unit, or the purge port on the flow center. It is normally done with a rubber hose and a needle adapter using your domestic water. There are also small hand pumps to accomplish the same result. It can be done with the purge cart as well, but is a pita when compared to other methods if system can be re started via just goosing.
  7. Burnhaven

    Burnhaven New Member

    Thanks again. We're certain we had cooling in August. No one here seems to know if we've had heat since October, where the auxiliary heat wasn't on. We're in a "combined household" with the two grandparents ( wife and me ) in an apartment on one end and my son and family living in the remainder. My son has been dealing with Barron Heating here in Bellingham, WA, which is the local authorized Bosch service company.
    Total sq footage ~ 3800 sq ft with the six ton Bosch unit servicing all. Two weekends ago I believe my son turned off the aux heat and ran the system. We wondered why our wood stove in our apartment wasn't getting us very warm so I checked the temp of the air coming out of the vents coming from the Bosch units and it was 60 def F. Without outside air temps at 50 or less, does this tell me some "loop heating" had to be taking place?

    On 12/16 my son told me "We noticed it was running on auxiliary heat most of the time last week so I changed the aux heat lockout temp from 50 degrees down to 30"
    That's when I noticed the 60 deg air from the vents. He then changed that setting back up to 40. Later that week we got the "freeze error" showing on the unit screen and scheduled the hvac tech visit.
    The Barron hvac tech came out last Friday for an "initial evaluation."

    Based on this troubleshooting info from the manual,

    "If heat pump is connected to a closed
    loop with antifreeze check that the “FREEZE 1"
    resistor on the UPM board has been cut to set
    the unit to antifreeze mode" We've never cut this resistor -- I'll have to visit the mech closet myself to check it

    "If temperature drops
    below or remains at freeze limit trip for 30 seconds,
    the controller will shut down the compressor and
    enter into a soft lockout condition. The default
    freeze limit trip is 26°F, however this can be
    changed to 15°F by cutting the R30 or Freeze1
    resistor located on top of DIP switch SW1"

    FreezeLockout Troubleshoot From manual.jpg

    Freeze 1 resistor.jpg
  8. Burnhaven

    Burnhaven New Member

    Techs were back today and the report is a hole in the pump housing. It looks like the SM Bosch units had a ten-year warranty but I haven't heard yet if the loops are dry or not. ( not free to refill with partial antifreeze )

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