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  1. #14
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    Feb 2007
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    Ref cycle

    Ryan. www.howstuffworks.com has a simple explaination for this and almost anything else

  2. #15
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    Jan 2004
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    The small line is always a high pressure liquid line.
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    How many times must one fix something before it is fixed?

  3. #16
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    May 2007
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    DC Metro Area (MD)
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    Quote Originally Posted by beenthere View Post
    The small line is always a high pressure liquid line.
    This answers my question--thank you.

  4. #17
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    Apr 2002
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    Quote Originally Posted by rponson View Post
    Ryan. www.howstuffworks.com has a simple explaination for this and almost anything else
    Here's "Howstuffworks" drawing of a typical outside H/P unit connected to a typical inside unit. Notice in heating mode, both lines that come out of the outside unit and go inside -the small liquid line in reverse flow, and the vapor line - are part of the high side (high pressure) and are warm.

    http://www.howstuffworks.com/how-to-...-heat-pump.htm

  5. #18
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    May 2007
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    DC Metro Area (MD)
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    Thanks! But then what is the "low side" in heating mode? I've got cooling mode down, but I thought only the liquid line was the high side in heating mode, not the vapor line. Can someone please clarify? I found some good info online but it doesn't pinpoint my question.

  6. #19
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    Apr 2002
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    Omaha, NE
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    Quote Originally Posted by RyanHughes View Post
    Thanks! But then what is the "low side" in heating mode? I've got cooling mode down, but I thought only the liquid line was the high side in heating mode, not the vapor line. Can someone please clarify? I found some good info online but it doesn't pinpoint my question.
    I'm not very eloquent at explaining but I'll try:
    In heating mode the "low pressure side" of the system is contained within the outside unit.
    It's comprised of the suction inlet of the compressor (the true suction line), the outside coil,one side of the reversing valve, and the outside coil metering device (a piston, or TXV). If you wanted to measure the low side pressure (in heat mode), you would have to connect a gauge to the "true suction" gauge port (contained somewhere inside the unit). Some manufacturers provide one and some don't (I'm told). You couldn't measure it outside by connecting a gauge to the gauge port on the vapor line outside because (in heat mode) it contains hot , high pressure vapor coming from the compressor discharge .

    With heat pumps, that big line outside is always the vapor line and the small line is always the liquid line. But depending on the mode of operation, they reverse the flow of direction. In A/C mode, cold vapor is exiting the house thru the large line, and warm liquid refrigerant is entering the house thru the small line. In heat mode, hot vapor is entering the house thru the large line, and warm liquid is exiting the house thru the small line.

    Think of it this way: liquid, HIGH pressure refrigerant is coming outside thru the small (liquid) line into the outside unit. It then flows thru the metering device (the beginning of the low side) and sprays into the outside coil (which is acting as an evaporator) , turns from a liquid into a LOW pressure vapor (and absorbs heat energy), flows out of the coil, thru one side of the reversing valve, thru the (true) suction line ,into the compressor suction inlet, gets compressed (beginning of high side) into a HIGH pressure vapor, comes out the compressor discharge outlet thru the other side of the reversing valve, into the HIGH pressure vapor line which comes back out of the outside unit and goes back inside the house, where the HIGH pressure vapor goes thru the Inside coil (acting as a condenser), releases heat , cools down and condenses into a High PRESSURE liquid, and goes back outside to repeat the cycle.
    Does this make it any clearer? Remember, with heat pumps, the only true "suction line" is the short section of the vapor line between the compressor suction inlet and the reversing valve, which is all contained within the outside unit.
    (It's late.....if I've made any glaring errors I'm sure somebody will correct me)

  7. #20
    Join Date
    May 2007
    Location
    DC Metro Area (MD)
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    Snewmen24, thanks a lot for your thorough explanation. It makes perfect sense. Now I know what that port sticking out of the side of the unit is for. Great explanation.

  8. #21
    Join Date
    Feb 2006
    Location
    Tn.
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    1,344
    you think you will ever get into the hvac field Ryan.I think you should try the work or try sales .

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