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  1. #1
    Join Date
    Jun 2011
    Location
    Oregon
    Posts
    11

    help me understand guts of outdoor unit

    I have a nearly-new Bryant heat pump (213BNA030-A ourdoor unit) installed at my house... works great so I'm not asking for fix-it help! I'm an engineer and I've been reading this site and just want to see if I understand what all these parts are in the outdoor unit.



    Can you tell me if I have this right?

    1- horizontal brass thing -- reversing valve (with orange wires leading to solenoid to actuate it)

    2- pink wires -- to thermistor for determining when to defrost?

    3- There seems to be 2 pressure switches -- one with blue wires (right on output of compressor) and one with yellow (right before liquid line exits unit) Why 2?

    4- The pipe with the label "336530701" on it -- is that the piston metering device for when running in heat mode? (indoor coil has TXV)

    5- black cylinder at bottom of pic (between reversing valve and compressor high-side I think). What is it? It looks like some sort of mini-accumulator but is much smaller than the thing I *know* is the accumulator on the top right of the pic.

    Thanks!

  2. #2
    Join Date
    Aug 2007
    Location
    Northern VA 38 degrees N by 76 degrees W
    Posts
    5,046
    Quote Originally Posted by willor View Post
    I have a nearly-new Bryant heat pump (213BNA030-A ourdoor unit) installed at my house... works great so I'm not asking for fix-it help! I'm an engineer and I've been reading this site and just want to see if I understand what all these parts are in the outdoor unit.



    Can you tell me if I have this right?

    1- horizontal brass thing -- reversing valve (with orange wires leading to solenoid to actuate it)

    2- pink wires -- to thermistor for determining when to defrost?

    3- There seems to be 2 pressure switches -- one with blue wires (right on output of compressor) and one with yellow (right before liquid line exits unit) Why 2?

    4- The pipe with the label "336530701" on it -- is that the piston metering device for when running in heat mode? (indoor coil has TXV)

    5- black cylinder at bottom of pic (between reversing valve and compressor high-side I think). What is it? It looks like some sort of mini-accumulator but is much smaller than the thing I *know* is the accumulator on the top right of the pic.

    Thanks!
    #3 blue low yellow high
    #4 Diverter header
    #5 muffler

  3. #3
    Join Date
    May 2011
    Location
    Ripley, WV
    Posts
    1,131
    Quote Originally Posted by willor View Post
    I have a nearly-new Bryant heat pump (213BNA030-A ourdoor unit) installed at my house... works great so I'm not asking for fix-it help! I'm an engineer and I've been reading this site and just want to see if I understand what all these parts are in the outdoor unit.



    Can you tell me if I have this right?

    1- horizontal brass thing -- reversing valve (with orange wires leading to solenoid to actuate it)

    2- pink wires -- to thermistor for determining when to defrost?

    3- There seems to be 2 pressure switches -- one with blue wires (right on output of compressor) and one with yellow (right before liquid line exits unit) Why 2?

    4- The pipe with the label "336530701" on it -- is that the piston metering device for when running in heat mode? (indoor coil has TXV)

    5- black cylinder at bottom of pic (between reversing valve and compressor high-side I think). What is it? It looks like some sort of mini-accumulator but is much smaller than the thing I *know* is the accumulator on the top right of the pic.

    Thanks!
    #1 yes thats the reversing valve

    #2 The pink wires go to the defrost switch/thermostat. (no thermistors on this make/model.)

    #3 There are two different switches one is a low pressure switch the other a high pressure.

    #4 Header leading into the outdoor coil.

    #5 As stated by previous poster that is the discharge muffler.

  4. #4
    Join Date
    Jun 2011
    Location
    Oregon
    Posts
    11
    Thanks so far... So is there no metering device on the outdoor unit? Indoor is a cased coil CNPHP3617 which says it has a TXV. What does the metering when in heat mode, the TXV on the inside coil still?

  5. #5
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    To help identify components, you'll find a copy of the electrical schematic on the back of the service panel cover. You can also do a google search and find a copy of the installation manual and data sheets using part of the model number.

  6. #6
    Join Date
    May 2011
    Location
    Ripley, WV
    Posts
    1,131
    If you look at the lines going into the outside unit you will see a small line and a bigger one. The smaller one brazes in just like the big one, but notice there is a nut at the end of the smaller line? Inside that area there is whats called a piston orifice, in cooling mode it moves very slightly in one direction and allows unrestricted refrigerant flow around it to your indoor TXV, in heating mode it goes the other direction and seats inside its holder and only allows refrigerant to flow through a hole in the center of it and that causes the pressure drop needed to operate in heat mode. I hope the Mods don't kill me for giving that much info.

  7. #7
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    24,946
    Quote Originally Posted by Rob_in_WV View Post
    If you look at the lines going into the outside unit you will see a small line and a bigger one. The smaller one brazes in just like the big one, but notice there is a nut at the end of the smaller line? Inside that area there is whats called a piston orifice, in cooling mode it moves very slightly in one direction and allows unrestricted refrigerant flow around it to your indoor TXV, in heating mode it goes the other direction and seats inside its holder and only allows refrigerant to flow through a hole in the center of it and that causes the pressure drop needed to operate in heat mode. I hope the Mods don't kill me for giving that much info.
    Rob,

    You give good information. Follow the link in my signature line and apply for your AOP (*) status.

  8. #8
    Join Date
    May 2011
    Location
    Ripley, WV
    Posts
    1,131
    Quote Originally Posted by jpsmith1cm View Post
    Rob,

    You give good information. Follow the link in my signature line and apply for your AOP (*) status.
    I applied a couple nights ago, I'm just waiting on approval or denial

  9. #9
    Join Date
    Jun 2011
    Location
    Oregon
    Posts
    11
    Quote Originally Posted by Rob_in_WV View Post
    If you look at the lines going into the outside unit you will see a small line and a bigger one. The smaller one brazes in just like the big one, but notice there is a nut at the end of the smaller line? Inside that area there is whats called a piston orifice, in cooling mode it moves very slightly in one direction and allows unrestricted refrigerant flow around it to your indoor TXV, in heating mode it goes the other direction and seats inside its holder and only allows refrigerant to flow through a hole in the center of it and that causes the pressure drop needed to operate in heat mode. I hope the Mods don't kill me for giving that much info.
    Aha, got it. Having read about a piston on this site over and over I just always imagined it to be bigger and easier to spot (like a TXV is pretty easy to find!) Makes sense, so it's in here right where the liquid line connects to the outdoor unit.



    Thanks for the details, I promise I'm not ripping this thing apart, just like to know how things work. Wish I'd studied more before buying it, but hey, it works.

    Is there some justification for using a TXV on the indoor coil and yet a piston on the outdoor on this heat pump? Obviously this is a lower-end 13 SEER setup and it's cheaper to only have 1 TXV, but how do they decide on which side to use which device? I'm in Oregon, this will probably be running in heating mode 90% of the time and cooling in 10%, and yet I have the fancy txv only in cooling...

  10. #10
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    33,392
    With the reliability of TXVs these days, be glad you only have 1!!!

    My Tappan is 14 SEER with variable speed and it is the same way, TXV in and piston out. Has an accumulator to protect the compressor. I'd rather have it that way than TXV and no accumulator.

  11. #11
    Join Date
    Nov 2006
    Location
    Southeastern Pa
    Posts
    16,998
    Quote Originally Posted by willor View Post
    Is there some justification for using a TXV on the indoor coil and yet a piston on the outdoor on this heat pump? Obviously this is a lower-end 13 SEER setup and it's cheaper to only have 1 TXV, but how do they decide on which side to use which device? I'm in Oregon, this will probably be running in heating mode 90% of the time and cooling in 10%, and yet I have the fancy txv only in cooling...
    This is what happens when manufacturers have to please the government.

    For example, the NEC (national electrical code) preamble reads (90.1 B)
    "...Compliance therewith and proper maintenance results in an installation that is essentially free from hazard but not necessarily efficient, convenient, or adequate for good service or future expansion of electrical use."

    This means that when a bureaucracy decides on a standard, it is the meeting of the standard ITSELF that is the point of interest, rather than the actual sensible construction or end result operation of the equipment.
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist

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