High and low pressures

Discussion in 'Maintenance and Troubleshooting' started by dogspower1, Jan 15, 2011.

  1. dogspower1

    dogspower1 New Member

    I have a fhp gt036 i bought from my heat & air guy it was installed in a new home and took right back out because they did not have water to run 3 unit its 3 ton i hooked it up in my shop to try it before installing in my home with my gauges hooked the low side runs 67-70 high side is 150psi book show low side at 68-71 high side at 215-230psi i am running 5 gpm with ewt 65 did not check out going but was much colder by hand, temp. in shop about 50f are the pressures right looks to me high side is low ,thanks scott
  2. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    High side pressure is directly affected by temperature of airflow across coil.

    Your shop at 50*F is radically different from a home at 70*

    Google a PT chart for R22 to better understand the thermodynamics.
  3. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    I'd keep the gauges off of there unless something is wrong and you've ruled out all else (i.e. air and water flow issues).
  4. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    Curt and Joe are right

    R-22 or a way low R-410A system. Get the PT charts and do the guage work with thermistors or a good analoge super heat thermometer.
  5. dogspower1

    dogspower1 New Member

    yes its r22 also how does the chart work
  6. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    Not going there

    I'm not trying to be unkind, but if you don't understand the significance of gauge readings...how to interpret them, maybe you oughtn't be fooling with them.

    We are helpful folks, but we can't run HVACR 101 one thread at a time.

    Either bone up online or consider a class at a community college VoTech program.
    makemice1976 likes this.
  7. dogspower1

    dogspower1 New Member

    I am so thankful that ever one on this forum is as kind as you are !
  8. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    Think boiling water

    in a pasta pan. We are taught that water boils at 212* F or 100*C at sea level and O# PSIG. What is boiling? It is the change of state from a liquid to a vapor. What is tough to see is the amount of heat needed to make that change. We can have both 212* liquid and 212* vapor in our pasta pan. So why does all the liquid not vaporize all at once? It does not do that because of "Magic" and the magic is called "Latent Heat", (google that one).

    Latent heat is absorbed by the liquid as it changes state to a vapor. Latent heat is released by the vapor as it changes back to a liquid. I do not think we need to deal with solids as they are to difficult to move around to do us much good heating a home.

    So how does a woodchuck pump heat or a heat pump chuck wood? They do so by using magic. Water is not a good refrigrant as it boiles to hot. R-22 is a good refrigerant as it boils at -41*F or so. What we are doing with a heat pump is boiling the refrigerant using the heat from the earth loop(s). The pumping part comes into play when we compress the boiled refrigerant and force the latant heat out as the vapor returns to a liquid.

    The above numers are for sea level and no pressure, if we add pressure to the mix then the numbers all change. Think about a pressure cooker and why every one has one in Denver. So rather than putting a set of refrigeration manifold guages on a system, which allows some refrigerant to excape our closed system. If you have a PT chart for the refrigerant in your system and a good thermometer you can see what is going on pressure wise in a closed system. The last tool I reach for are my guage sets and I own five sets as I deal with multiple differant refrigerants and they all have their own PT curves.

    We could go really wild and get into dew points and their pressures and bubble points. Then there is super saturated vapor and lots of other cool things you can see if you know how to look.
    Last edited: Jan 19, 2011
  9. dogspower1

    dogspower1 New Member

    Thanks for the reply that make good sense. That what i was asking for ,also my gauge set is not for r22 so checking it with the pt chart works best,thanks agine

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