Open Loop EWT and LWT delta is very small

Discussion in 'General Discussions' started by llaforest, Nov 11, 2013.

  1. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    "Conversely, none of the gymnastics such as preheating the house or shutting returns seems feasible nor should be necessary."
    Most every geo system has auxilialry heat in heating dominated climates. This is one of the reasons why. Where Electric auxiliary is not an option, a propane furnace and a split system make sense it one wants automatic back-up. Where manual aux/emergency heat is designed in, so to are "gymnastics".

    An ecobee will alert if temperature drops after 3 hours and a call for heat. So once house is warmed up, no reason to get in this situation again.
  2. geoxne

    geoxne Active Member Forum Leader

    50F EAT is at minimum of Building Operating Limits per IOManual page 37, table 9a. Also, read paragraph above table that explains that operation at a limit requires other parameters to be normal.
  3. llaforest

    llaforest Member

    I know it is the minimum according to the specs, I went through this manual hundred of times. It's just that having my own readings, I think this is not an optmized value and I am wondering if CM is just playing safe or if they ran extensive tests to maximize these limits. I'm sorry but when I see my water leave at 43F, I cannot understand why it would go in lockout.

    Until I speak to an engineer that explains to me why this probe is before the refrigerant went through the water, I will not be satisfied because it makes no sense for me.

    Anyways, my certified installe ris supposed to pass over my question to his contact at CM. We will see if there is a solid reason for that or if it's there because it's wokring and no question's asked...
  4. geoxne

    geoxne Active Member Forum Leader

    Do not disregard what "engineer" suggested on the first page of this thread. Operation at limits brings everything into play. Bring everything up to normal temps if possible and calculate HE, then compare the specs with correction factors applied. Calculations should be within 10% of spec. Also, verify sensor readings with independent source.

    LT1 is your only coax coil freeze protection. Consider the following-
    Ave water coil temp- 44.9F
    DeltaT to Freezing- 12.9F
    Coil water vol(assumed)- 1.5 gal
    BTUs away from freezing at no flow condition- 161.1855 BTUs

    Even if HE plummets to 24,000 btu/hr the coil will freeze in about 24 seconds in a no flow condition with no freeze protection.
  5. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    again when your refrigerant is cold enough to freeze water, you don't want it to contact your water. I thought Curt explained this very well.
    You know your entering air is cold and your entering water is cold. Warm up the air, speed up the water and don't be suprised by a low DT.
  6. mtrentw

    mtrentw Active Member Industry Professional Forum Leader

    While there is much consideration from many on this thread that he still may be looking at a bad thermistor, charge, or clogged dryer; the thread raises a question in my mind on whether some programming tweaks can open the application for geo without aux heat. It would seem with low enough air flow, a geo unit with adequate water temp and supply could provide heat and be much less restricted to ambient temps. If the heat removal is predicated on air flow, then an absolute minimum airflow allows for extraction of available BTUs from the water source without a freeze risk. The question then devolves to finding an ECM that performs well as you get significantly slower and a manufacturer developing a unit with programming to account for it. Many have implemented solutions that vary water flow based on delta T. Why not vary airflow based on delta T?

    Or heresy of heresies, what about a thermostatically controlled bypass damper that short circuits a majority of supply back to return until it can come up to temp. It could allow for geo use in an environment where aux heat is not an option yet could avoid the gymnastics of manual or haphazard work arounds.
    Last edited: Nov 18, 2013
  7. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    or just use a crankcase heater :rolleyes:.

    But then residential units are really designed for "residential" conditions.

    Outside one's house - heat pumps of all types are designed for all different conditions.
  8. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    Taking another shot at this...

    I'm not able to convince myself that greatly reducing airflow on the load side would do much other than depress COP. Refrigerant will leave condenser and enter TXV as a high pressure tepid-to-warm subcooled liquid. The only pressure / temperature that matters for freeze protection is the refrigerant condition immediately after the TXV...if that is much below freezing, icing will follow. The compressor needs some refrigerant superheat to guarantee a liquid-free inlet. If the superheat is set higher than necessary and the source water temperature is marginal, the TXV will back off enough to cause icing conditions immediately downstream, and then pop goes the LT1 weasel.

    In summary, I don't envision airflow or other load side schemes as the solution to this problem. The TXV is designed to adjust to high side pressure changes in order to maintain low side superheat. Varying airflow would simply exercise the TXV.

    I reiterate my advice to check thermistor, charge, TXV setting, superheat. In other words, look to the basics before embarking on esoteric schemes.

    An earlier suggestion I made to manually lock out Y2 during unoccupied periods might also serve to stave of LT1 trips by reducing refrigerant flowrate and thus increasing low side pressure, lifting Tsat above LT1 trippoint.

    I hope the foregoing is helpful.
  9. llaforest

    llaforest Member

    OK, during the weekend, I ran some tests and they were not very conclusive. When I attach a probe under the same tie-rap as LT1, I get 1 degree colder than the LT1 probe. I could also see that LT1 probe is very slow to change. My probe went to 28 very fast, then climb back up and stabilized at 31. During the same time, LT1 probe had only the time to get down to 32. But I can say that LT1 probe seems to be working...

    I wanted to get readings at other locations on the refrigerant circuit but the readings were absolutely not precise. I will need a tie-rap and some heat conducting grease to have precise readings. So I didn't move anything of course and I won't until my measurements are accurate and in a range I find valid. I want to measure after the dryer, to see if refrigerant is colder than before dryer, and the most important is to know the temperature of refrigerant after the water coil. I want to know the delta between the leaving water and the leaving refrigerant.

    One odd thing is that LT1 is just after the TXV, not after the filter/dryer as shown on diagram. I am wondering if the refrigerant looses some more degrees in the filter/dryer. My readings a re inconclusive.

    To comment the above, I think that reducing air flow would have the same effect as warmer air by reducing the pressure drop in the the air coil which is the main problem here. It could work but then, with slow air flow, yes the COP would drop, but more important, would you be able to heat the house to get out of this loop and slowly increase air flow? Not sure...

    I just also understood why the modulating valve is acting weird. It's not checking LT1 temp, but only the water temperature drop. It is set to 4F delta and it is the max delta I can have without going under 30F. This is why I get LT1 lockout so easily, I'm really on the edge on every side. So at startup, when the valve tries to adjust to get a good delta, the system is not yet stable and it is very easy that by playing with the water, I get bellow 30F and hit a wall.

    I am also wondering why they do not check the water pressure drop between in and out. No flow is the most serious cause of failure and it is an external factor not controlled by the machine. There is external ports to take pressure readings but no sensor. It would be easy to block the machine when no pressure drop is detected in the water circuit. I am thinking of installing a pressure differential switch to avoid heat pump running when no water is circulating. It would be a low flow protection and it would react way before LT1 drops bellow 30F. Then maybe I could move it.

    This is exactly what I need to know, and yes it might prevent me from moving LT1 probe.
    Can I simulate a water pump failure without risks of breaking the water coil?
    This can very much happen and I need to know I'm not at risk

    By the way, I really appreciate all the inputs you give me, it's an accelerated refrigeration course and it's very appreciated. Maybe I sound stubborn sometime but I take everything that's on here very seriously and will not try anything stupid. Since the country house is two hour drive from Montreal were my installer is, I cannot afford having him around to perform these tests and I want to have a certain autonomy in case of failure. Which leads me to the next point, the system as to be dumb proof, we will be two couples in that big house separated in two and the other three are just intimidated by the complexity of the system and since it is my baby, I need to make sure it is stable and easy to use...
  10. ChrisJ

    ChrisJ Active Member Forum Leader

    "Which leads me to the next point, the system as to be dumb proof, we will be two couples in that big house separated in two and the other three are just intimidated by the complexity of the system and since it is my baby, I need to make sure it is stable and easy to use..."

    What about only setting temp back 5*F instead of 20* when your not there? We hear from pro's a lot set it and forget it. I understand you have a "country" house but you installed the most efficient technology possible. Let it run while your not there it's still using less energy then what ever you were using before with deep set backs and heavy energy use when you want to warm it up.

  11. llaforest

    llaforest Member

    Hello Chris, oh yes I will let it run all the time with a little set back when we're absent. It's just that in case a 1 day power failure, if the house cool down, it will be hard to start it back. And since I'm operating on the limits like that, I'm scared that at some point, it will start and get an LT1 lockout and then again the house would cool down and make it harder to start it back up.

    Our auxiliary heat is wood stoves, so they are operated manually and their heat is not spreaded evenly in the house so it is very long before the heat pump can start without crashing.
  12. ChrisJ

    ChrisJ Active Member Forum Leader

    I remember reading some where you didn't have the capacity for 20KW of aux heat, what about 5KW? My 4 ton unit has just a 5KW toaster in it.
  13. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    this would have been the perfect application for a split with propane furnace. you could still get electric baseboard or propane fireplaces.
    The designer should have explored options i.e. aux not full emergency heat etc. It is still possible to install a 10 K on amperage available and have an either or setting.
    If you put in 10 k in baseboard and set them to 10F less than geo, they will likely only come on if geo isn't running and keep your home from freezing.
    Who designed this system that wishes a refrigeration system to operate in circumstances injurious to it's well being?
  14. llaforest

    llaforest Member

    This is how it will be installed yes. There will be baseboards around the house because I didn't want auxilary to be on the same machine. They are not installed yet though and they won't be everywhere. So the problem is that all the bedrooms will stay cold and there is a lot of returns coming from all these rooms. So it keeps incoming air too low and it won't start. Plus if I'm not there and the hvac gets an error, I'm not scared the house will freeze because of baseboards, but the hvac will never try again automatically... So I want to avoid lockouts.
  15. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    Yes but you can remotely do a soft reset with an ecobee stat
  16. llaforest

    llaforest Member

    In the future yes, but still only modem 56kb connection! :rolleyes:
  17. llaforest

    llaforest Member

    Another brick just fell on me during the last weekend. Since the beginning, we are running the machine in manual mode because it is more stable. I was doing tests in auto mode and I got a lockout for a stupid reason.

    Started in Stage 1, flow at 80%, which is 10-11 gpm and delta T between EWT and LWT was programmed at 4F, which is the smallest possible value we can specify.
    Since it had been off for 30 minutes, the water was one degree lower than steady state temperature in the 400ft pipes, so delta T between entering and leaving was 3F. The valve started to shut down to get back to a 4F delta. Guess what, lowering the flow with colder water temperature ended up in immediate lockout. They have everything they need with all these sensors, but it seems their algorithms are very simple and do not take much into account!

    Another question: In manual mode, every 30 minute or hour, I'm not sure exactly, the compressor shuts down. Everything else continues to work and then it start back again probably 5 minutes later. It does that on regular basis... No error, nothing, just like it't taking a break! :)

    Another point, why are they not using the pressure sensors on the water lines to determine if there is a flow or not. No flow is by far the most serious condition given the delays the sensors take to react. They could have done a differential of both sensors to make sure there is a drop in pressure. Now I will install a flow sensor myself and use it has a part of an E-Stop loop to make sure compressor cannot be energized when there is no flow. This is a no brainer in my opinion.

    Is there an engineering contact I can have with Climate Master to speak with someone that is aware of the firmware in the machine, there is a lot of small improvements that would be dead easy to make but it seems that no one from CM is listening this forum...
  18. hardchines

    hardchines Member Forum Leader

    We have a Climate Master TZ22EER Digital installed 1 month ago.

    Is it normal that the delta between EWT and LWT is only 4 degrees?
    EWT is 46.9
    LWT is 42.9
    LT1 is 31.9
    GPM is 10

    Since LT1 is already near 30, I cannot lower the flow or I get LT1 lockout. I hate to see the LWT at 42.9 because there is still a lot of heat I could have taken from that water.

    I am also surprised to see that the delta between LT1 and LWT is more than 10 degrees. In a perfect world, LWT should be close to LT1. This indicates to me that the heat transfer between the water and refrigerant is not very efficient.

    Are these numbers sound normal to experienced people?

    I agree with most all of these expert opinions and I recommend you listen to them( not tongue in cheek) .

    I have a CM that had the same issue, my unit is a split setup and I have EWT from 48-50F, I am open loop, when I ran at 1.5 to 2gpm I would get theLT1 fail, I spoke to the tech at CM and he recommended to raise the water flow to a min 3 GPM as recommended, my installation docs. say 1.5 on one page and 2GPM on the other page, I pump my water from a well and that cost money so keeping the flow down was important to me. I did try 3GPM but would still get the fail, I talked to the same people you are working with here and did what they recommended but to no avail.

    Only one tiny spot on the heat exchange coil gets to the trip temp and that is where they mount the sensor, so I reasoned that it would be virtually impossible for the coil to freeze with 50 degree water flowing through it and if it did the gas pressures would go up and trip their respective limit switches thus protecting the system. This is what I did ," I cut the jumper" for closed loop allowing the temp to drop at the sensor to a lower temp prior to fail, I run 1.5 GPM per ton, I have a delta of 11-12 degree 's, I have two units running with this flow rate and temp deltas, one is a CM split and one a CM package, my test has been running for 5 years non stop air and heat, I use NO supplemental heat and my house is more comfortable then it was on oil heat, I love my GEO's ! I live in northern NY not a warm place in the winter or cool in the summer.
    Last edited: Dec 13, 2013
  19. llaforest

    llaforest Member

    Anything else to say hardhines?
  20. hardchines

    hardchines Member Forum Leader

    You have but to ask the question, as "EVERYONE IS ENTITLED TO MY OPINION" !


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