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GSHP power issues

I installed a 15 ton, a 10 ton unit and a five ton unit, for a residential home in 2007.  Over the last 1.5 yrs the homeowner found that randomly and not often, 3 times over 1.5 yrs., when the power went out and came back on the 10 ton units 70 amp breaker would blow.  The owner happened to be in the mech room when the power went out and observed when the power came back on, the breaker tripped.  When reset everything worked again.  I eventually got the electrician to replace the breaker with an 80 amp size(max.size  manufacture recommended). A month later the electrician was out doing more work and noticed the breaker was tripped again.  He then reset it and within 5 minutes it was tripped again.  By the way I did check the time delay jumper and verified it was in the on position and not in test mode.

I was then called out to the job.  The 10 ton unit has 2-5 ton compressors wired in parallel.  I test each one separatetly and found that compressor 1 had grounded windings, a failed capacitor and a fused closed contactor.  Compressor 2 had a locked rotor and failed capacitor.  I found the incoming voltage to be 247 V.  With the electrician we tested the power supply to make sure everything was grounded correctly and it was.   I spoke to the manufacturer and the good thing is that everything is warrantied.  They did ask we to disconnect the positive temperature resistor and recommeded I install a hardstart kit instead. 

But what is the real problem here.  It is a home in rural Colorado and I would not count out brown outs or spikes.  I know the hardstart kits will help but what about protecting against the power supply itself? 

Thanks for you input



Jeffrey
Jeffrey Campbell

Comments

  • don_9
    don_9 Member Posts: 395
    Power issue

    I would doubt that you have a power issue.I would be looking more for a liquid flood back issue at your compressor.When ever I come to a grounded or locked up compressor 9 out of 10 times the reason for the compressor demise was something to do with airflow or problem with the water distribution system.

    Being in colorado and i could only assume that your ground temps can get lower then design and if that the case then i would be checking safety, starting with the low pressure switch.
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,837
    I think he's using a large water feature (flowing pond) as his source.

    If it were me, I think I'd be deploying some power monitoring equipment to watch for droops and or surges. Check with your local power supplier, and if they don't have it, look into HOBO data loggers. Some times, the problem is not on the same property as the problem....



    You can also monitor loop field supply and returns to make certain there are not issues on the other side of the system as well...



    ME
    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • Simply Rad
    Simply Rad Member Posts: 165
    Power issues

    ME



    This is a different system I installed prior to the Srednciki project that you saw.  This is a slinky trench system.  The flow in the load is 30 gpm and load doesn't have a flow meter but I do have a pump that is sized approriately and I am going to pull it and check for rotation. THe compressor are two separate refridgerant circuits and we will check the levels when we install the new compressors.   The owner put me in contact with his  home automation company.  We had a long conversation about power and the struggles we have had over the years. He had alot of troubles in particular with his automation system in this house.   He is going to talk with the owner about monitoring the incoming voltage.  It just so happens that the homeowner was head of the finance department for GE for 35 yrs.  Great customer and good person.  Wish I had more like him. 
    Jeffrey Campbell
  • Simply Rad
    Simply Rad Member Posts: 165
    Power issues

    ME



    This is a different system I installed prior to the Srednciki project that you saw.  This is a slinky trench system.  The flow in the load is 30 gpm and load doesn't have a flow meter but I do have a pump that is sized approriately and I am going to pull it and check for rotation. THe compressor are two separate refridgerant circuits and we will check the levels when we install the new compressors.   The owner put me in contact with his  home automation company.  We had a long conversation about power and the struggles we have had over the years. He had alot of troubles in particular with his automation system in this house.   He is going to talk with the owner about monitoring the incoming voltage.  It just so happens that the homeowner was head of the finance department for GE for 35 yrs.  Great customer and good person.  Wish I had more like him. 
    Jeffrey Campbell
  • Simply Rad
    Simply Rad Member Posts: 165
    Loop Field

    I forgot to add that the loop field incoming temp is 35F and the return is 29F.  This year here in Colorado was a big test of the loop field.  Normally we have 2' of snow on the ground by Christmas.  This insulates the earth and the past years the loop has been running around 38-40F.  THis year the ground was not covered with snow until Feb so the frost line was deeper than normal.  There were alot of underground water line freezes this year.  By the way the loop is approximately 7 feet down. 
    Jeffrey Campbell
  • Techman
    Techman Member Posts: 2,144
    edited March 2012
    GSHP

    The load side GPM is only 30gpm? Should it be 2.25 -.3 gpm per ton? Can you install those "voltage monitoring/shutdown" device's on each compressor? Upon restart ,what keeps those 6 comps from starting all at once or in any combination of 2 comps starting and dropping the incoming voltage. Without a hard start device on the comp that line voltage doesn't stand much of a chance. Can you startup  all comps  ,one at a time until all 6 comps are running and record L1-L2 ,L1-G  , and L2-G each step of the way and start /run amps on both legs.With the in -warranty dead comps,it should be possible to get a "factory teardown report" to determine the cause of failure of the comps.
  • Simply Rad
    Simply Rad Member Posts: 165
    Techman

    The entire system is 15 tons.  I have 2 units a five ton and a ten ton(dual compressors) The faulty unit is the 10 ton which has 30 gpm or 3 gpm/ton.  I have a staging control, which uses PID logic to bring on the stages on at a time.  There are only 3-5 ton compressors. 



    Thanks



    Jeffrey  
    Jeffrey Campbell
  • Techman
    Techman Member Posts: 2,144
    GSHP

    Tks.!
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,837
    I forgot about that one Jeff....

    Shreddies left such a lasting impression on me, I forgot about your other big GSHP job.



    The surface influences you are seeing is one of the main reasons I am not a big fan of loop fields, as opposed to VBH's. Looks good on paper, but if you get into a drought condition, and the soil dries out, conductivity drops significantly. And then theres the encroaching frost line...



    I've never had any of these problems with VBH, tho I suppose they could occur.



    ME
    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • zacmobile
    zacmobile Member Posts: 211
    Power issues

    As ME said monitoring the incoming power would be very helpful in troubleshooting this issue. I've seen a lot of problems with GSHP's in rural areas due to inadequate/outdated power distribution systems that the utility swore up and down was top notch. If there is a dip in the incoming voltage on compressor start up the amperage draw will increase, possibly to the point of breaker tripping. But you should verify (or get an electrician to) that all connections are tight between the heat pumps and main service connection. On the heat pump end you could also try these: http://www.emersonclimate.com/en-US/products/electronics_compressors/Pages/securestart.aspx way better than a hard start, I have had good experiences with them.



    Good luck!
  • Harvey Ramer
    Harvey Ramer Member Posts: 2,215
    Some Electrical trouble shooting you could try.

    Turn off all power and check the voltage at the first disconnect or as close to the meter base as possible. Next turn on as many electrical appliances as you can to simulate a load. Check the amperage on both legs and check the voltage across both legs and then from each leg to neutral or ground.

    If the amperage is much higher on one leg then the other, relocate 120v breakers until the panel is balanced.

    If you suffer more than a 5% voltage drop under the simulated load you have a undersized transformer or an undersized service drop or a combination of both. The utility company must do the changeouts if this is the case.

    Low voltage will burn up a motor quicker than you can imagine. If you have brown-outs you could add some run-capaitors and a potential-relay. If the voltage drops below a cetain point the potential-relay redirects the current through the run-capacitors and boosts the voltage. Tricky business but it works.

    Some compressors are polarity sensitive. I don't think the ones you have are but it would be something to check. Typically a compressor that is polarity sensitive won't start at all if the poles are reversed.

    It would also be a good idea to put a lockout on the power to the unit. If the power goes off it disconnects the current and has to be manually reset when the power comes back on. Reason for that is, when the power comes back on everything across the whole grid is trying to start at one time and can cause severe voltage drops.



    Hope this helps.

    Keep us posted

    Harvey
    Ramer Mechanical
    ramermechanical.com
    To learn more about this professional, click here to visit their ad in Find A Contractor.
  • Simply Rad
    Simply Rad Member Posts: 165
    Working in progress

    Trying to get things replaced and back on line.  Once that happens I will post results.  Thanks for all the input.



    jeffrey
    Jeffrey Campbell
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