Quebec Disconnect a pump?

Discussion in 'General Discussions' started by Lyra, Dec 9, 2018.

  1. Deuce

    Deuce Member

    I do understand this, I asked a very simple question. To put it simply just speaking of gpm is there an ideal flow rate and can too much flow hurt performance?
     
  2. Eric Kurtz

    Eric Kurtz Member

    No, too much flow does not hurt performance. But neither does it help it noticeably. It is akin to running an extra 100 watt light bulb 1' away from another one. Recommendations are usually 3 gpm per ton because that is the calculated most efficient for the energy used.
     
  3. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    I would argue that statement. Monitoring shows that pumping lesser gpm saves you significant energy overall without costing you much more on the compressor side.

    The problem is that the current rating assumes a given pumping penalty (namely the pumping energy needed through the heat pump only, not the loopfield). Thus manufacturers "over pump" to save a few watts on the compressor, even if it costs them many more watts for pumping. The additional pumping watts are not accounted for in the AHRI rating system. Same for the blower.
     
  4. Deuce

    Deuce Member

    Thanks Doc!
     
  5. Eric Kurtz

    Eric Kurtz Member

    Thanks for the clarification, Doc. How much can you drop below that 3 gpm recommendation before performance is noticeably affected?

    In my case, the difference between 7 gpm and 9 gpm is only 20 watts. Takes a long time to add much savings at that rate.

    But maybe there is something I'm missing
     
  6. nc73

    nc73 Member Forum Leader

    I run mine at 7 but 2nd stage requires 7.5. I'm in 1st stage the majority of the time so technically I'm over pumping by 1 gpm since 1st requires less than 6 gpm. I say as long as you're close enough to 3gpm per ton, all is good.
     
  7. Eric Kurtz

    Eric Kurtz Member

    Are you implying that it is acceptable to slow the blower down and increase LAT without noticeably hurting performance? If so, how much in your experience is ok?
     
  8. Eric Kurtz

    Eric Kurtz Member

    From what I have learned about refrigeration in my job (agricultural and commercial coolers), increasing head pressure is not good for compressor life.
     
  9. nc73

    nc73 Member Forum Leader

    You should really only decrease blower speed if you get noise in your registers or your ductwork is inadequate and you won't reach the cfm anyway.
     
  10. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    How much does the heat pressure increase? What is the average EWT?

    Head pressure is influenced by average source and load temp, influencing the refrigerant temperature. The heat pump has no clue how much air goes over the coil and how much water flows through the source coax.

    As a rule of thumb, you keep the EWT above 30 and the delta T on the air side below 25F, and the heat pump is very happy long term. Optimizing blower and fan speed can usually increases average performance by 15%, without sacrificing life expectancy.
     

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