WF Premier2 ATV 4.5ton HELP

Discussion in 'Maintenance and Troubleshooting' started by geo_jon, Jan 24, 2012.

  1. geo_jon

    geo_jon New Member

    At my wits end. Have done EVERYTHING I can think of for this 16 year old unit.
    In it's lifetime, it has had new compressor, new air coil, new coax, txv, and filter, in
    addition to fixing the ecm blower twice.

    At this point, I feel that the refrigeration circuit is doing what it is suppose to. For anyone curious, just about anything you would want to know about my unit is available real time (updated every 2min) at:

    http://jade.mw.net:19980/pic/wf2.html

    Last weekend, I checked pressures and saw 41suction / 175discharge. Everything within specs, superheat/subcool within bounds. What I DON'T see is a warm house. I am not getting enough boost in air and I am not getting enough drop from the water across coax.

    The 3rd stage electric strips are disabled and the unit is in stage2 almost all the time.
    ECM fan is set factory for 1500cfm. Loop pressures are a little low at 24/19 giving only about a 5psi drop across the coax, which would lead one to believe I have low water flow, yet BOTH of the pumps are working and, by themselves, give almost identical drops.

    Anyone? Any thoughts? I have basically run out of ideas
     
  2. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    What is in the water?

    Have you ever had the loop water tested? If there are no water quality specs for your machine in your I/O manual, download the latest and greatest from WF.

    Are you using antifreeze on the loop side if so what?

    How do you know both pumps are running? How do you know they are "working", (pumping the loop fluid)?

    I think you are not moving enough water or you are under charged. Looking at a pressure temperature chart for R-22 your system looks low on refrigerant to me, if you are moving enough water.

    Looking at your Data I would shut down the de-superheater and see if that helps the LAT.

    Mark
     
  3. geo_jon

    geo_jon New Member

    More Info

    The loop water is a methanol mix. Unit worked fine for probably 8 years (except for the
    repairs) Was never a problem with the loop water before. I have purged the system and did get a few bubbles out of it.

    I just had the txv and filter replaced and had 99oz weighed in as per specs on the unit. The subcool (in heat mode) should be 5-9 deg as stated further down my page. Last weekend I checked the head pressure and was seeing a steady 175psi, which would leave me a little over 7deg for a subcool. superheat is also within specs stated at bottom of webpage.

    The 2 Grundfos 26-99f pumps are very quiet but can be heard with a stethoscope. I have also temp. wired each one to run individually and see the same 3psi drop across the coax regardless of which pump is running. With both pumps running, I see approx 5psi drop across the coax. Spec on this unit is about 10.7psi drop at 12gpm. I would tend to agree with you that I am not getting enough flow of water through the coax, but I have no experience with pump failure modes. Would it be common for BOTH of those pumps to be equally weak? Seems too much of a coincidence Overall the static loop pressure is only around 15 (probably should be more like 40 in the winter) but I would not think having more pressure is going to increase the flow. My understanding is that it is just there to make sure the rotors stay "wet".

    I have tried shutting off the DeSuperheater. With it shutoff, my typical R22 temp, entering the air coil is around 110-115deg, my return air temp does not improve much;
    maybe a degree or 2 at best. I think the best air delta I have seen this year was 20.05
    degrees with 4.05 deg delta across the coax water, but was only briefly, most of the time, I am around 18.5 air delta, 3.8 loop delta.
     
  4. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    175 PSIG with R-22

    Will only get you a hot gas temp of 92.5*F entering the air coil.

    Are all the numbers in your linked page temperatures?

    How did you get the 175 psig number? Did you take a suction reading?

    Do you have an amp meter?

    Mark
     
  5. geo_jon

    geo_jon New Member

    additional info

    Mark, thanks for the followup.

    All of the numbers are temp (in F).

    175psi was the discharge pressure as read on gauge at service port, which is very close to compressor. Suction was a steady 41psi.

    I have checked amps before (although nor recently) and they were not out of bounds. From my notes, it was Feb 2010 and compressor was pulling 12.5A on high. This, from a tech with a clamp amp meter. At the time, he told me normal RLA on high was 17.6A.

    The temps are gathered by Maxim one-wire temp sensors mounted throughout the unit. They are suppose to be +/- 0.5C. Some are mounted with thermal grease to copper pipe and insulated on outside, some are not. They could be "less than" accurate, however the end result of the air delta should be correct as those sensors are just in the air path.
     
  6. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    The Simpsons

    for low refrigerant and low pumping are the same. I have never dissected a coaxial heat ex-changer of that age so I do not know how big the water passageways in a unit of your vintage would be.

    It is possible to clog the heat exchanger. Dirt, microbes, scaling could be anything.

    Although you can here the pumps running it is possible that they are not pumping. Bad or disconnected impeller is a possibility. If you can amp the pumps and compared the reading with the name plate you can "see" how much work they are doing.

    Since the laws of thermal dynamics have not changed I think you want to 3 GPM per ton.

    Mark
     
  7. WF_Inc

    WF_Inc Member

    geo_jon,

    We will be more than happy to look into your inquiryfurther. Please provide your modelnumber, serial number, and the name of the contractor you are workingwith. If you do not wish to post yourinformation publicly, please feel free to send us a private message.
     
  8. geo_jon

    geo_jon New Member

    WF Unit info

    WF_Inc

    This discussion is on the following unit:
    Model: ATV045D110CLT
    Serial: MD3868

    I am currently NOT working with a contractor as I have yet to find any that could actually offer anything that I do not already know about the unit.

    This unit was installed Summer 1995 so it has been around awhile. It did work fine, in the beginning. In it's lifetime, it has had the compressor, air coil, coaxial, txv, and filter replaced with real WF parts, bought from WF dealers.
     
  9. WF_Inc

    WF_Inc Member

    geo_jon,

    We have reviewed the numbers you provided. According to your information, there is an assumption of 12GPM; however, the pressure drop shows that the unit is getting approximately 7 ½GPM. We would need these numbers to be verified by an HVAC contractor to truly evaluate the operation of the unit.

    From the information you provided, it appears there may be an issue with the equipment. We would suggest contacting your local WaterFurnace dealer or HVAC contractor to discuss your concerns. If they are unable to provide a resolution, please have them contact our technical support staff for further assistance.
     
  10. geo_jon

    geo_jon New Member

    I would agree that the pressure drop across the coaxial exchanger would indicate 7.5gpm or less, and also that the "design" was for 12gpm (according to WF docs). For the sake of argument, lets say the water flow IS 7.5gpm when it should be 12gpm.

    According to the WF "Troubleshooting in Heat Mode" chart, LOW water flow would cause:
    Head Pressure: Low/Normal
    Suction Pressure: Low/Normal
    Compressor Amps: Low
    Superheat: Low
    Subcooling: High
    Air Temp Diff: Low
    Water Temp Diff: High

    I do not see a High Water Temp Diff, nor a High Subcool, the rest may be accurate.

    The LoopCenter is Dual Grundfos 26-99f pumps. Each pump, by itself, gives me a 3psi drop across the coaxial exchanger, and, if both pumps are running, I see a 5psi drop. This would indicate to me that if the pumps are at fault, they must be EQUALLY at fault (always a possibility).

    For the sake of argument, is there any "single" source of trouble that could cause the reduced flow? I only have 15psi (static) pressure on the loop and it is dead winter, with incoming water temps from the horizontal field of 32 deg. This pressure should be around 40psi (according to docs), but could the pressure really change things that much? Could there be bubbles in the loop causing the trouble? The loop is equipped with an expansion tank, however it's usefulness is questionable.

    This unit will most likely be replaced within the next year but I have put so much time and energy into diagnosing this unit that I would really like to know what it's problem is, even if I never pay to have it repaired.

    Any comments on causes of flow reduction would be helpful as I am not that familiar with failure modes of a closed loop.
     
  11. dgbair

    dgbair Just a hobby Forum Leader

    At 32 you could begin icing if you don't enough antifreeze in the loops. There have also been reports of stuff growing in the loop water if not properly treated.
     
  12. Blake Clark

    Blake Clark Member

    If your flow was low due to scaling or other buildup in the hx I could see the following data:

    Water Pressure drop across hx would not be an accurate way of determining flow due to more restriction. The pressure drop would be higher per given flow due to an effective smaller pipe diameter.

    So then the question is, if low flow, why not high water delta t? It makes sense to me that the scaling makes it more difficult to transfer heat from the water to the refrigerant - Thus low flow would not result in high delta T, though it would result in low suction pressure since the evaporation temperature would have to be lower to compensate for the increased thermal resistance in the coil.

    This then leads to a lower condenser pressure and lower delta t across the air coil.

    Maybe I missed something, but since you're "at wits end" I thought I throw my two cents in.
     
  13. geo_jon

    geo_jon New Member

    Thanks for comment Blake. Makes sense that, if the coax was scaled, then we have lower water flow (due to increased resistance), less heat transfer (causing the lower delta T), and, in turn, lower suction pressure, although I would have thought a scaled coax would lead to a HIGH pressure drop across coil.

    The coaxial exchanger was replaced by a WF tech in 2006, so it is not nearly as old as the unit itself. The first unit sprung a leak on the r22 side so it was not a water related problem. Having said that, my other thought was, what if they installed the WRONG Coaxial Exchanger (like one from a smaller unit). That would explain the low pressure drop (even if the water was 12gpm), would also explain the low Delta T. As the coax is all wrapped in insulation, I don't have any numbers for the part that is currently in there.

    Any hydronics experts out there? Is there any chance that air in the water loop could be causing this problem?
     
  14. Blake Clark

    Blake Clark Member

    Pressure drop is a factor of pipe resistance and flow rate. A high resistance with a lower flow rate would not necessarily result in a high pressure drop. How much flow is going through the higher pipe resistance would be determined by you pump curves. A Centrifugal pump will have a lower flow through a higher head. Too many factors for me to guess how your setup would respond to higher pipe friction, but it's at least theoretically possible for decreased flow without seeing a corresponding increase in observed pressure drop.
     
  15. geo_jon

    geo_jon New Member

    I would agree. Theoretically, scaling of the coax IS something that could cause all the problems.

    I guess the only way to know for sure if that was it would be to hook up a purge cart with a known flowrate and look at the pressure drop across the heat exchanger. I guess that would also answer the question "Is it the RIGHT Coax".

    If the coaxial exchanger turns out to be the culprit, I won't be replacing it, but, I would really like to know
     
  16. WF_Inc

    WF_Inc Member

    geo_jon,

    We understand your concerns and appreciate your position. Unfortunately, there are too many unknown variables. Can you please tell us if this has been an issue for the past 16 years, or has this just been an issue recently? Also, has the unit locked out on a fault? If so, could you please tell us what the fault condition was?
     
  17. geo_jon

    geo_jon New Member

    WF_Inc,

    This has not always been the case. First 3 years of operation were flawless until the compressor died. It was promptly replaced under warr. and unit went back to flawless operation. Operation was fine until round about 2005 when the unit became plagued with problems. R22 leak in the air coil, then the coax (can't remember which was first). Those pieces replaced with WF parts, mostly at my cost as I was out of warr. by that point. Once got things sealed again, the ECM blower fan locked up as a magnet came loose from the armature. I fixed the motor myself. Since 2005, the unit has really never been reliable. There were many "Lo Press" Faults and about 3 Techs that came to look at the unit, never resolving the problem.

    This prompted the creation of my monitoring site so that "I" could determine what the root of the problem is. Findings from a year of monitoring showed that the dryer consistently had too much delta T across it and so I contacted a WF dealer and purchased a new dryer and TXV and had them installed about a month ago. Since that installation, I have seen NO faults with the unit. In fact, from my monitoring data, I see no problems with the refrig. circuit at all. It just not produce the desired output.

    From WF tech docs, I see that the Liquid Line Temp, the Suction Temp, Suction Press, Discharge Press, water temp, subcool, and superheat are ALL within spec, yet the furnace does not produce a high enough LAT.

    At this point the unit runs in stage2 just about 24hrs / day. I have the electric backup heat disabled with the dip switch to hold down the electric bill. There have been no major changes to the house itself in these years, at least nothing that would cause it to need a bigger unit, yet, once the outdoor temp drops below 30deg, the temp in the house will begin to fall as the unit can not keep up.
     
  18. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    Yep!

    Air or air released from suspension will stop the flow like a closed ball valve. You mentioned reduced water pressure on the loop side. That could cause air pockets to form in the loop side of the system.

    Do you know why the pressure in the loop side is down?

    I do not install, one size fits all , push pull, flow centers. Why? Because I know how to size pumps to hydronic systems. I also know how to provide just enough pump to move the required heat transfer fluid. I only use pumps big enough to do the job and therefore reduce the amount of power wasted in the water to watts equation.

    I have hinted at, and now want you to amp the pumps and see if they are doing work. I also want to know where the pressure in the loop side went.

    Mark
     
  19. geo_jon

    geo_jon New Member

    Mark,

    Thanks for the explanation about air bubbles. The reduced loop pressure is probably my fault. About a year ago, I felt I was having trouble with air in the loop. I constructed a makeshift purge cart and purged the loop myself. I did get a very large "burp" out of the line, but, at the time, I still had a bad dryer in the system so it did not really help. Suspect that I shut the valves prematurely, not pressurizing the system as high as it should be.

    I will have to "setup" for an amp test on the circ pumps as I don't have a clamp amp. I do have a regular VOM that can handle 10A (should be good enough), but will have to wire it into the circuit.

    The pumps, both of them together, and each individually, HAVE to be moving water I would think. As stated earlier, I see a 3psi drop across the coax with either of the 2 pumps running, and a 5psi drop with both running. I also can confirm (using a mechanics stethoscope), that I can hear them start and continue running. None the less, I will amp them to find out.

    The system uses a bladder type expansion tank attached on the water in side, between the loop field and the first pump. I have had another tech tell me that he questioned the usefulness of the bladder tank, but has seen many installed that way.

    I also have a water injection ram that I could use to add water to the system, raising the pressure. I have just not done so because I was not convinced that it could make any difference, although in the presence of air bubbles, and your explaination, I can see that it could make a huge difference.
     
  20. Blake Clark

    Blake Clark Member

    I'm a DIY'er and don't have access to many of the tools of the trade. I've been thinking about how I would go about diagnosing this if it were my problem. Given all the unknowns, I'd try to eliminate the loop field and the coax first. I would disconnect the loop field and run tap water through the coax with a garden hose. Put a ball valve in-line to make flow adjustments. measure the flow with a bucket and measure the temps in and out. A temporary "open loop" for diagnostic purposes.

    Knowing the exact flow and temperature drop could give you a lot of information you don't currently have. In addition if this experiment brings your system back to life then you know problem is on the water side somehow. If this doesn't bring it back to life, the problem is more likely in the refrigerant circuit, but could still be a coax problem.
     

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