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I have the correct Manifold Gauges for checking the low and high side of the heat pump. How do I read the gauges to ensure that my system has the right charge? Outside ambient temperature is 85.4.

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  • Robert May 27, 2011

    Is this a r410a unit or r-22? And does it have a txv or fixed orifiice metering device

  • David Motcheck II May 27, 2011

    It is a R-22 system and it has a TXV valve in the system

  • David Motcheck II Jul 27, 2011

    After all your help previously, I had to rip into my system to do some repairs and discovered that I have a fixed piston installed into my coil. Not a TXV. How much does this change what you mentioned earlier?

  • David Motcheck II Jul 27, 2011

    Now it is all coming back to me. Wish I still had my tools. I got rid of my wet bulb meter a while ago thinking that I would never need it again. Thanks for your help.

  • David Motcheck II Jul 27, 2011

    I just replaced my run capicitor on my heat pump so the inside air temperature is 83 degrees, not wet bulb. I have my gauges hooked up to monitor the pressures. The Low side piping is somewhat cool but not as cold as it has been in the past. It use to have condensation on it. I will forward you the pressure readings that I get soon.

  • David Motcheck II Jul 27, 2011

    Okay, here is the latest on my system. Inside temperature at the return is 79 degrees. Outside ambient temperature is 90 degrees. Low side pressure is reading 61 psi and the high side is reading is 230 psi. What do you think?

  • David Motcheck II Jul 27, 2011

    Here is the latest. Temperature at my return is 79 degrees, not wet bulb. Outside temperature is 90 degrees. Low side pressure is 61 psi and high side is 230 psi. What do you think?

  • David Motcheck II Jul 27, 2011

    Do you think that it would hurt the system if I added a little freon? I inspected all the lines with no kinks visable. I evacuated the system and drew a vacuum then added the freon. If I have to evacuate the system again, so be it but I would rather wait until a couple months from now when the temperature outside is cooler.

  • David Motcheck II Jul 27, 2011

    I am slowly adding and monitoring the system. Originally the low side was at 61 psi, now it is at 65 psi and the high side is holding out at 230 psi. I can really see the difference in the air output.

  • David Motcheck II Jul 27, 2011

    I have some R-22 into the system. The low side reads 65 psi and the high side is maintaining 230 psi. What do you think?

  • David Motcheck II Jul 27, 2011

    It has been about an hour. Low side is at 65 with a high side at 240 with an ambient temperature of 87 degrees. It is getting there. I am starting to see condensation on the low side piping.

  • David Motcheck II Jul 27, 2011

    Here is the current update. Outside ambient temperature is at 87 degrees. The low side is reading 65 psi and the high side is reading 240 psi. The low side piping is finally starting to sweat.

  • David Motcheck II Jul 27, 2011

    The outside temperature is now at 86 degrees. The low side is holding at 65 psi and the high side is at 240 psi.

  • David Motcheck II Jul 27, 2011

    The outside temperature is at 86 degrees. The low side is at 65 psi and the high side is at 240 psi.

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In order to know if you have the correct charge you must measure the subcooling since it is a txv unit. The outside unit will have the proper subooling you need printed on the data plate. Hook up you gauges and let thebunit run for 10 minutes, after 10 minutes check the high side pressure, that high side pressure will correspond to a saturation temp, write that number down then measure the temp of the liquid line and subtract the saturation temp from the liquid line temp, it should be the same as printed on tjhe data plate if it is higher than that add refrigerant untill you get whtas printed on tne data plate. Is there is no data plate use 12 degrees of subcooling.

Posted on May 27, 2011

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  • David Motcheck II May 27, 2011

    My suction pressure was 65 and my pressure side or high side was at 113 psi. Does this make sense to you?

  • Robert May 27, 2011

    Those pressures seem way too low, is the unit cooling?

  • Robert May 27, 2011

    Measure the subooling and we can figurenout whats going on with your unit.

  • David Motcheck II Jun 10, 2011

    Here is the latest on my Rheem system. The outside ambient temperature was 95 degrees F. The high side gauge read 120 psi which corresponded to a saturation temp of 106 degrees F. The temperature of the liquid line was 112.1. Subtracting the two will give me a 6.1 degree subcooling. My back panel has a chart that has outside temperature in a column on the left and I assume pressures going across the top. Not sure how to read it.

  • Robert Jun 10, 2011

    Does the panel chart tell you what the subcooling should be, usually it will be eithet 10 degrees, 12 degrees or 15 degrees of subcooling. Based on the info you gave me it sounds like your unit is undercharged. With a 95 degree ambiant your head pressure should be around 250 psig not 120. The way you read that chart is take your pressure and your temp and where they intersect it will give you subcooling. However, most manufactures will have subcooling as 10, 12, or 15 degrees. But if it has the chart use it to find proper subcooling

  • Robert Jun 10, 2011

    Have you tried to add refrigerant to tne system?

  • David Motcheck II Jun 10, 2011

    It has been nearly 21 years since I worked on R22 systems. The service ports where I have my gauges connected to have brass caps and a set screw or valve that can be adjusted with a standard flat tip screwdriver. I always remembered that these should be open unless you are isolating the heat pump, then they should be closed. This is correct right?

  • Robert Jun 10, 2011

    That is correct, anytime you isolate the outdooor unit from the indoor unit the valves should be closed, or when you pump the refrigerant down into the condenser. Other than that they must be open.

  • Robert Jun 10, 2011

    So you have 6 degrees of subcooling and your high side pressure is 120 psi, what is your low side pressure?

  • David Motcheck II Jun 10, 2011

    Here is the latest. I am using the Yellow Jacket Manifold that can check R22, R12, R412 and R506. When I read the high side pressure at the top of the gauge, it says 240 psi but when I go down to where it says R22, it says 117. The low side says 63 on the gauge but reads 34 when you look at the R22 wheel. The outside ambient temperature is 92 and the vapor line temperature is 71 degrees F.

  • Robert Jun 10, 2011

    Ok the high side pressure is where it should be, the low side pressure is too low, with a normal high side pressure and a low suction pressure with low subcooling it looks like you may hav noncondensables in the system such as air or a liquid line restriction.. I would recover the refrigerant, pull a vacuum on the unit, and then weigh in the refrigerant charge to what the unit holds

  • David Motcheck II Jun 10, 2011

    Thanks for the information. I hope that i have enough R22 to charge the system. All I have left is about 20 lbs of refrigerant. I was having a hard time reading these new gauges as they are not the same type I used years ago. We use to use just the gauge line for the refrigerant that we used. Apparently not the cause now days.

  • Robert Jun 10, 2011

    Yeah i hear you, things keep changing in the hvac industry. Now r410a will be the new refrigerant instead of r-22.

  • Robert Jul 27, 2011

    It does not change it very much, with a fixed orifice metering device you need to know the indooR wet bulb temp, outdoor dry bulb temp to find the proper pressure.

  • Robert Jul 27, 2011

    No problem, do you need anymore help?

  • Robert Jul 27, 2011

    That low side pressure is too low for tne conditions, i would suspect a low charge

  • Robert Jul 27, 2011

    But since the high side pressure apperars normal, this would indicate a restriction in the system to me

  • Robert Jul 27, 2011

    Add some freon and see if the low side comes up a little but watch the high side pressuresomit does not get too high. Let me know

  • Robert Jul 27, 2011

    Try to get it to about 70 and then see if it holds for about a half an hour

  • Robert Jul 27, 2011

    See if it will hold for a half an hour.

  • Robert Jul 27, 2011

    That low side should be aout 70, is it not taking any more freon in?

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  1. you can find this Manifold Gauges

Posted on May 27, 2011

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