Flow switch lockouts--over 100 in 6 weeks

Discussion in 'Maintenance and Troubleshooting' started by Lockedout, Feb 8, 2012.

  1. Lockedout

    Lockedout New Member

    I've had a geothermal system for just over a year that has never worked properly. I've read through many posts to try to find some similar problems and solutions before my installation contractor tries to fix it for the 7th time is 6 weeks. My situation seemed very similar to wmdgeo but the posts ended on 12-28-10 so I don't know how that problem was resolved. I'll provide as much info as I have:

    We live in central NY--Syracuse area in a 3200 sf home--half of the construction is from 1850's (with new pumped in insulation) and the other half is post 1992 and well insulated. In December 2010 we installed a 6-ton 2 stage water to water Enertech Geocomfort heat pump with 4 Geocomfort air handlers and a desuperheater function to provide hydronic heating in a new basement floor. The closed horizontal loop field was installed in August and sat pressurized for 4 months--no pressure loss. The loop field has 6 - 150 ft long coiled 3/4 inch lines of tubing that join together into a 1.5 inch trunk line that comes into the non-pressurized flow center. (total length about 5200ft) It is buried at 6-8 ft.

    Our first electric bill last January was 4 times anything we had ever had because the system was running on mostly auxillary power because the heat pump was locking out. The contractor was out almost every week to bleed air out of the lines or clean the flow center pumps. Finally in late March the system started running consistently--but now I think it was because the temperature was warm and not because the system was fixed. The contractor had to come back in May to switch the system manually to cooling mode by jumping something (?) in the thermostats and disconnecting the auxillary heaters. Cooling worked great all summer and heating worked until temperatures finally dropped around Christmas. About a week before the lockouts began--some glycol mixure started oozing from the non-pressurized flow center.

    Since Dec 27, the heat pump has locked out on the Flow Switch indicator light over 100 times. The contractor has been here 7 times and performed the following services. (I apologize if I don't know the proper term and provide a description instead)

    -Added glycol to protect the system to 10 degrees--I'll try to find percentage
    -purged air out of system using external high pressure pump to 100 psi with flow center disconnected
    --cleaned grit out of flowcenter pumps
    -replaced HBX --cpu (wouldn't come on after reset anymore)
    -replaced 2 lower flow pumps with one larger one on the "load in" line to reduce pressure. Pressure was over 450 psi and then dropped to below 400 psi. High pressure has never locked out the heat pump
    --checked all electrical connections and reconnected auxillary heat
    --replaced flow switches on last visit---has run out of things to replace

    He tells me EWT settles at about 38 degrees and LWT is about 33. The flow rate is around 13-14 gpm and he is considering installing another pump to increase the flow rate. The system has run no more than 4 hours without locking out for the last week. I usually hear it shudder to a stop--dimming the house lights--and then it will lock out on the next heating cycle. The setpoint is 118 degrees, but it rarely makes it to the setpoint without the heatpump stopping in stage 2 (by itself) and then turning back on in 5 minutes. I'm not going to provide energy cost info at this time because I just want to know how to get the system to work---I'm on auxillary back-up at night unless I get up every two hours to reset the system.

    I paid another certified contractor to come in and evaluate the system 10 days ago. He believes it is the mix in the loop field---not the heat pump itself. I'm sorry to make this so lengthy, but it actually is a summary! It has not been a good new year. Any advise is greatly appreciated. Thank you---Lockedout
  2. Bergy

    Bergy Member Industry Professional Forum Leader

    What is the model # of your heat pump?

  3. jrh

    jrh Member

    Do you have p/t ports?
    Has Flow been verified on the Load side as well?

    You might want to drop the setpoint also. See if 110 will satisfy the thermostats.
  4. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    2 things jump out at me.
    1) flow rate for closed loop should be ~3gpm/ton
    2) glycol is harder to pump to begin with protecting to 10F will make it worse
  5. Lockedout

    Lockedout New Member

    Model # and p/t ports

    Bergy and jrh--

    The model # is GWT070A11AAACSS. Forgot to mention that on one of the last 6 visits p/t ports were installed--but my contractor doesn't seem to use them when he tests the system. He puts the probe into the insulation right against the pipe?? I think he told me he thought it was more accurate--but we've had soooo many conversations that I'm not quite sure. I can ask him about the flow on the load side and get back to you.

    My thermostat settings and set point have been adjusted just about every time the contractor has been here. When the unit was first installed the setpoint was 125---I know now that was too high. Two weeks ago he dropped it to 106 to see if that would help. The only thing that changed was instead of the compressor turning itself off (not locking out, but taking a 5 minute break) at 110-115, it was taking a break at 96-104 and then eventually locking out. Always with the flow switch indicator. I've been keeping the thermostats on the first floor at 65-67 and the second floor at 64. Until they reconnected the aux heat---I was using a new high efficiency wood burning stove to warm the house. The aux heaters were disconnected because they were blowing heat while the A/C was running.

    The only thing that has kept the system from locking out has been the warm weather. We had two days in the high 50s that melted all of our snow and the next day--although the temp dropped the unit ran for 36 hours straight. The loop field is in full sun.

    Waiting to hear back from my contractor on his plan for tomorrow. Thanks for your interest.
  6. Lockedout

    Lockedout New Member

    Flow rate

    AMI Contracting--

    So does that mean the flow rate should be more like 18 gpm?

    You are correct about the addition of glycol--the lockouts have increased from every 4-12 hours to an average of about 3 hours since more glycol was added. I've been keeping a log of every lockout. I obviously can't reset it when I am not here, but otherwise it's pretty accurate.

    Do you have a suggestion for what the mix should be? I've read some discussions about glycol vs. methanol or ethanol. The installation manual recommends (at least 4 times) to use deionized water when using glycol. I know they used my tap water--could this be part of the problem? Thanks for your interest.
  7. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    First things first.
    Make sure your source side is good. While 13-14 gpm flow is not great, it is not catastrophic either. How are the temps and flow measured? Check the antifreeze or have them checked. A lot of the supply houses sell glycol solutions which have 60% glycol and 40% rust inhibitors. Then they mix it as the book tells them, assuming 100% glycol. Your LWT is right at the point where the coil could start freezing up. Chances are that if the switches are OK and the problem persist even after they have been replaced, that indeed you have a flow issue. They would not go off at 13-14 gpm. Check the loop pressure after lockout.

    Let us know.
  8. Bergy

    Bergy Member Industry Professional Forum Leader

    A GWT070 is a Compass Water to Water unit. There are TWO flow switches in your heat pump. There is a water flow switch for the source (loop) side and there is one for the load (water) side. The flow switch lock-out LED will not show if the source side, or the load side, switch is opening. P/T ports are REQUIRED on both the source side and the load side. water flows MUST be balanced between the two sides if the heat pump is to operate properly. The ONLY way to know if the unit is operating within specs is through the P/T ports. A pressure gauge and thermometer are needed to gather pressures and temperatures, which in turn are used to find GPM's and calculate the Heat of Extraction/ Rejection.

    Do you have any photo's you could post of the install?

  9. johnny1720

    johnny1720 Member

    I guess my first question is did you pay this installer? Also it sounds very strange that the aux heat is trying to run during cooling mode.

    How many installs has this guy done?
  10. Lockedout

    Lockedout New Member

    Request for pictures

    Bergy and docjenser--
    I've attached 3 pictures for you. One of the entire mess including buffer tank and hot water heater. A closer view of the flow center connections and ports and one of the manifold feeding the 5 zones---4 air handlers and 1 radiant basement floor.

    When you say "flows MUST be balanced" does that mean equal? Or do you have an equation that I need to check. Just to verify---both flow switches were replaced last Friday--the system now locks out more than ever--but it has also been in the 20s-30s almost all week. The only light that goes on is the upper flow switch indicator.

    My contractor will be here tomorrow--what numbers do I need to gather from him? I can see I need EWT and LWT also a pressure reading from both ports. I also need to have him provide the gycol % along with the type of glycol he is using. And loop pressure after lockout. Anything else?

    Docjenser--to answer your question he has been hooking up a flowmeter (clear plastic tubing) through the flowcenter to measure the gpm there. I'm not sure if you mean freezing up literally--but I've never felt anything but heat coming out of the unit when it locks out--there is nothing iced up as I've read in some other posts.

    I hope the pictures are helpful--I'll get the numbers to you tomorrow. Thanks again.
  11. Lockedout

    Lockedout New Member

    Aux heat during cooling

    Yes--I did pay the installer in full when the heat pump and all ductwork and airhandlers were installed and running. I didn't know until I received my first electricity bill how poorly it was actually running. He is obligated to provide the first year of service without charge and is doing so although we are both unhappy with the amount of time he has spent here.

    One of the problems with the installation of the aux heat units---if I understand it correctly--was that 2 of the heaters were wired to come on everytime the air handler came on--no wonder my bills were outrageous. Rather than fix the problem in the spring--they disconnected the aux heat---and said they would fix it before heating season. They were finally reconnected in late January---on the 4th visit.

    Don't know whether you were just being facetious, but he said he does 30 installs a year---I don't know that he actually finishes any of them, however.
  12. dgbair

    dgbair Just a hobby Forum Leader

    Is that really all 3/4" piping?

    Why does the loop header looks like it's all connect via 3/4" piping? Do you really have 5 loops all being feed into the flowcenter via a common 3/4" pipe?
  13. Bergy

    Bergy Member Industry Professional Forum Leader

    With a non-pressureized flow center source GPM is measured at the flow center with a flow meter. You should have 18 GPM flowing through the source side AND 18 GPM through the load side. They does not appear to be any P/T ports on the load side so knowing the flow rate is not possible. I must say, the workmanship leaves something to be desired... :(

    From your photos...
    The unit should set on a pad, not up on blocks. the space below the unit becomes a resonance chamber makeing the unit louder than needed.

    I only see one electric tank for your domestic hot water. Twin tanks are recommendedfor better effieciencies from the desuperheater.

    This is a small combo unit we did several years ago... Bergy

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  14. geoxne

    geoxne Active Member Forum Leader

    The load and source flow switches on the GWT are wired in series to the control board. It should be determined which side is faulting to determine whether it is a source or load issue causing the lockout.

    Source Side-
    Has been addressed with a flow meter and though a bit low should not be a lockout issue.

    Load Side-
    Has not been addressed. The lack of P/T ports on the load side will make DeltaP and DeltaT diagnostics difficult. However, I would get the load side temperatures in and out by surface probe (with no airhandlers calling you only want to be pumping the tank).

    -DeltaT should be in the 5 to 7F range at those temperatures. If over 10F I would suspect flow issues (pump size and/or restrictive piping)

    -Load in temp should be within a couple degrees of the HBX controls sensed temperature. If not the sensor is in the wrong place.

    I suspect 6 tons of geo through a waterheater with 3/4" tappings (and even smaller dip tube) is pushing it. Also, a true buffer tank has 4 appropriately sized tappings to provide hydraulic separation between the Geo and the airhandlers. This piping scheme can work (I have done it successfully myself) but you have to understand that the flow rates through the geo load side will change depending on if and how many airhandlers are being pumped at the time.
  15. Lockedout

    Lockedout New Member

    dgbair, Bergy and geonxe--

    Thanks for all of this information and pics--although a little upsetting. Nice copper!

    dgbair--the connection into the flowcenter is 1 3/8".

    Bergy--I did point out to the installer that the install manual said the unit should be placed on a pad. He said they use the feet instead of pads and they are acceptable. Not the whole truth apparently.

    We do only have 1 hot electric hot water tank and 1 buffer tank. Do I really need another?

    geoxne--I will provide your info to the contractor this morning and provide his response later. It's over my head!

    The only defense I can offer for my contractor is that he had to work around the completion of an addition to our house. He did get the radiant floor in the slab on time and could have saved himself much time and trouble had he not delayed the install 6 weeks forcing him into the heart of heating season---so that we were unable to remove the heating oil tank and boiler from the basement until he had a new unit. That said, his placement choices for the new equipment were limited and it is a little tight where installed in the oldest part of the basement.

    Thanks again for your help.
  16. Lockedout

    Lockedout New Member


    My contractor was here all day today. He separated the flow into the buffer tank (as suggested by geoxne) by installing and closing a cutoff valve for the airhandlers and piping the Geo directly into the tank. He also made electric corrections to simplify the system. He agrees that there should be a p/t port on the load side--said pressure drop was 4 (does that make sense). Verified EWT and LWT at 38 and 31. He also removed some glycol because he thought it might be around 35% and wanted it lower. He will test mix again next week. The repiping dropped the internal pressure below 400psi from about 425. I didn't get the pressure after lockout.

    Unfortunately the system just locked out again. I've already called him and he plans to replace the pump on the source side with a larger one. We are both frustrated and disappointed. He insists he has NEVER had this much trouble with any install before. My house is really 2 houses (old and new) put together with 2 stories each--thus the need for 4 air handlers.

    Here is the weird thing about his work today. He could not get the system to lock out in 3.5 hours---and I haven't been able to keep it on for more than 3 hours all week. The outside temps were similar to yesterday when it was locking out every 1-2 hours. The only thing that was different was the unit's cover was off, so...he put it back on and it locked out within 45 minutes. Could excessive heat inside the cabinet be tripping the flow switch somehow?? The unit does a strange shudder before it stops and then the flow light comes on about 30 seconds later. I'm just a homeowner...but i have to wonder if the compressor stopping prematurely for some other reason is causing the flow indicator to light because there is no flow? I told him I'm leaving the cover off for the night to see how it runs.

    Anyone? Any ideas? Thanks.
  17. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    I have been watching this thread

    since it was posted.

    I do not think your posts here do much more than get you upset. I hope you are not treating your contractor to the emotions I see you venting here.

    Some of the best folks in this business are trying to help you, but I never hear any positive after the rants.

    The flow is imperative to the system's successful operation. One must be able to measure what the flow really is. That requires instrumentation. Buy that.

    Leave the door off.

    The noise you describe is what happens when a scroll compressor is unhappy and trips it's internal high head temperature/pressure safety. The safety is a self resetting switch, (until it wears out). So when it cools down things start working. What you describe points to low flow of water on the supply side, (loop field). You knew that already.

    There are two additional things I would do before allowing a guy that is trying to help you buy a new bigger pump.

    Test the thermostor that locks out the system. It is easy to test with an ohm meter.

    Make sure that the thermistor is placed in the correct location. Even in America machines can be built by people with hangovers.

    My guess. The machine is wrong. That is why we have lemon laws for cars. I would like to see real flow numbers. If you all get stuck or upset call me. 440.223.0840.

  18. Lockedout

    Lockedout New Member

    My apologies...

    Dear Mr. Custis--
    As I said I am just a homeowner, a frustrated one---looking to HELP my contractor fix the problems my system is having. I provided him with this log yesterday. I even hired a second contractor--at my expense-- in an attempt to diagnose the problem. I treat him and his employees with no disrespect. Please accept my apoligies for displaying emotion. I didn't realize I was ranting---my intention was to answer the questions that were asked of me with some explanation. I appreciate all of the advice and comments provided. I will leave out any editorial.

    Yesterday, my contractor said the flow was 13.5 gpm and he was hoping to increase that with the removal of some of the glycol and replacement with water. He will test again early next week.

    When you say to test the thermistor---do you mean the flow switchs that he just replaced? He said they are both working correctly. The two he removed were corroded and rusty.

    I do have some positive information to report. The system has not locked out since I removed the cover last night. The outside temp was 16 degrees--coldest temps all week. Does this still point to the scroll compressor or something else electrical going on?

    As we watched it yesterday---with the cover on---the compressor would stop suddenly--well below the temp setpoint and with a pressure of 400-425 psi---and then the flow switch would lock out after 30 seconds. Is it sensing that the flow has stopped midcycle and is acting correctly? Is it possible that excessive heat is building up inside the cabinet and forcing some kind of electric short?

    I'll forward your additional comments from yesterday to my contractor.

    Again, thank you for your help.
  19. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    "Docjenser--to answer your question he has been hooking up a flowmeter (clear plastic tubing) through the flowcenter to measure the gpm there. I'm not sure if you mean freezing up literally--but I've never felt anything but heat coming out of the unit when it locks out--there is nothing iced up as I've read in some other posts."

    I was afraid the source coil would be frozen from the inside, yes literally, no way you would know from the outside. Then obviously is not enough flow and the flow switch would shot off the unit. Your installer needs to confirm the correct antifreeze concentration with a refractometer.
    Your installer does not seem to have much experience. When I see a single tank setup for the desuperheater (without a buffer tank), which is inefficient to the point that the desuperheater will almost never turn on and contribute to hot water generation, it tells me that your installer has not understood the concept how the DSH works.

    Given your flow and delta T on the source side, you end have with a heat extraction of 39,235 BTU/h, which is right on target fro a 6 ton unit, and tells me that your refrigerant cycle and your loop are performing fine. Only thing which needs to be done is to verify the glycol concentration. 13.5 gpm shouldnot cause your problem, your heatpump is designed to run with 9 gpm with open loop systems. The threshold for the flowswitch to not allow the unit to turn on is 1 gpm/ton, so 6 gpm. You are way above that. No exchange of pumps on the source side will help you with your problem.

    Next on the list is the flow and delta T on the load side. On the load side, the flow should be 9 gpm, the manufacturers usually spec a delta t around 10-12 F (I disagree with Bergy here). Your Grundfos 26-99 should be able to do this. What is the diameter of the piping, especially the elbows, between the heatpump and the hydronic buffer tank? Your installis a bit on the messy side, so I would check this next.

    The second most common reason for high pressure you see (400+ is high) is an over charge (too much refrigerant). Check the load side first (flow, delta T) and only then check the charge.
    Last edited: Feb 11, 2012
  20. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    I'm troubled by some inconsistencies, though I may be reading too much into some earlier posts:

    "I usually hear it shudder to a stop--dimming the house lights" That plus Mark Custis comment on scroll compressor internal overload, and then the 30 second delay until the low flow light annunciates makes me wonder if there is a problem on the refrigerant side.

    Lights should not dim as a compressor turns off.

    Let me start by saying I have no experience with this brand, but a system low on refrigerant charge can trip low teperature lockouts. A severely undercharged system can lead to an overheated compressor since it is refrigerant flow that cools the compressor.

    I would NOT expect low loop fluid flow to cause a compressor overload fault - indeed, reduced source side flow / temp in heating mode tends to UNLOAD the compressor - it gathers less heat and does less work, reducing its load and current.

    Has charge and refrigerant operating conditions been verified? Has compressor current been measured? How about measuring compressor discharge temperature? It is possible that operating with cover off provides just enough cooling to the compressor shell to stave off the internal overload or other high temperature interlock.

    Some systems use a low temperature switch on the REFRIGERANT line leaving the heat exchanger but report that as a low water flow error, when it can in fact be a low charge problem - confounding to debug!

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