failed reversing valve

Discussion in 'HVAC' started by Lloyd E. Sponenburgh, Dec 28, 2007.

  1. I just replaced the reversing valve on an old Tempstar package unit.
    DAMN... the cost of the job would've half replaced the unit, but the
    owner sez no. So you do the work, and only warrant that part, no?

    It's a pilot-operated valve.

    Anyway, what I am curious is, what is the mode of failure on these
    valves? One assumption I could make is that one of the pilot lines -
    almost as small as capillary tubing - has become clogged. The armature
    in the pilot valve moves freely and hits both seats with authority.

    If there isn't a general consensus on why these fail, I'll probably
    dissect it on my own time to try and figure it out.

    And no, I don't want to fix it. I just want to understand why it failed.
    If they do fail from grod in the pilot lines, it seems to me it's just an
    invitation for a new valve to fail in the same way.

    Ideas?

    LLoyd
     
    Lloyd E. Sponenburgh, Dec 28, 2007
    #1
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  2. Bubba <> fired this volley in
    news::

    > Exactly why any refrigeration system needs to have someone follow
    > proper brazing practices, driers, charging, evacuation and servicing.
    > If it were that easy, everyone would be doing it.
    > Bubba


    I agree... sloppy, overheated, un-purged brazing seems to be the norm
    in this area, and I've had to do a lot of practice on scraps to get to
    the point where my joints are clean enough - inside and out - to pass
    muster.

    I gather you mean that chaff in the pilot lines IS the common failure
    mode?

    For what it's worth, though, this is a factory-sealed system - nothing
    but the service ports have ever been opened. So, if soldering practice
    caused the failure, it was from the factory. I guess dirt from a clumsy
    topping-off might have caused it, too.

    LLoyd
     
    Lloyd E. Sponenburgh, Dec 28, 2007
    #2
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  3. Lloyd E. Sponenburgh

    Mark Guest

    On Dec 28, 6:46 pm, Bubba <> wrote:
    > On Fri, 28 Dec 2007 14:20:32 -0800, "Roger" <>
    > wrote:
    >
    > >I doubt plugged pilot lines are the problem - at least I've never found any.

    >
    > Well maybe your eye are old and you need glasses? :)
    >
    > >The pilot lines see a pressure difference equal to the difference between
    > >suction an discharge, so its tough to plug em.  

    >
    > Never say never. It'll get you everytime
    >
    > >Given the age, I would
    > >suspect wear or debris on the main piston/slide/shuttle , gummed-up or
    > >damaged plastic or rubber on either the pilot or main or a plugged bleed
    > >hole on the pilot.

    >
    > Didnt you just say up top that pilots dont plug?
    > And the op did say the piston slid freely and with authority
    >
    > >  As to repeat failure - these things are installed in a
    > >position so they are damn tough to just replace using all the original
    > >fittings only without damaging the valve.  I typically play it safe andadd
    > >a couple (or sometimes more) couplings as needed in a place that's
    > >accessible and braze the valve with 50-60% silver with the valve completely
    > >out in the open, then do the couplings with the valve installed.  Also -
    > >doing this frees you from the need to use the OEM valve - the old monsters
    > >especially cost about the same as a compressor.

    >
    > Yup, same way I do them but I use the valve recommended. I also braze
    > (not solder) with the sticks, Dynaflow, Stay-silv 6 of 15 I believe
    > its called.
    > Bubba
    >
    >
    >
    >
    >
    > >"Bubba" <> wrote in message
    > >news:...
    > >> On Fri, 28 Dec 2007 19:20:58 -0000, "Lloyd E. Sponenburgh"
    > >> <lloydspinsidemindspring.com> wrote:

    >
    > >>>I just replaced the reversing valve on an old Tempstar package unit.
    > >>>DAMN... the cost of the job would've half replaced the unit, but the
    > >>>owner sez no. So you do the work, and only warrant that part, no?

    >
    > >>>It's a pilot-operated valve.

    >
    > >>>Anyway, what I am curious is, what is the mode of failure on these
    > >>>valves?  One assumption I could make is that one of the pilot lines -
    > >>>almost as small as capillary tubing - has become clogged.  The armature
    > >>>in the pilot valve moves freely and hits both seats with authority.

    >
    > >>>If there isn't a general consensus on why these fail, I'll probably
    > >>>dissect it on my own time to try and figure it out.

    >
    > >>>And no, I don't want to fix it.  I just want to understand why it failed.
    > >>>If they do fail from grod in the pilot lines, it seems to me it's just an
    > >>>invitation for a new valve to fail in the same way.

    >
    > >>>Ideas?

    >
    > >>>LLoyd

    >
    > >> Exactly why any refrigeration system needs to have someone follow
    > >> proper brazing practices, driers, charging, evacuation and servicing.
    > >> If it were that easy, everyone would be doing it.
    > >> Bubba- Hide quoted text -

    >
    > - Show quoted text -


    Most units make a loud noise I think they call "windmilling" when the
    reversing valve is changed during operation as when changing into and
    out of the defrost cycle. Do you think that switching under pressure
    could casue lots of wear to the reversing valve?? What exactly makes
    the noise?


    Mark
     
    Mark, Dec 29, 2007
    #3
  4. Lloyd E. Sponenburgh

    Mark Guest


    > I dont call it "windmilling" (...wtf?) I call it "the reversing valve
    > switching noise".
    > It doesnt change "into" and "out of" the defrost cycle. It does
    > however perform a defrost cycle when needed and terminates the defrost
    > cycle when needed.
    > I think any reversing valve movement causes wear. Same thing as when
    > your tires on your car roll on the pavement. When you can figure out
    > how to stop the wear, call me. I can make you famous.
    > Bubba- Hide quoted text -
    >
    > - Show quoted text -


    No I don't mean just the click sound...

    I hear mine and my neighbors make a 5 to 10 second very loud whoosh
    sound like the escape of pressure. I assume it is the refrigerant
    flow that happens when the reversing value changes position (for the
    defrost cycle) while the system is operating and there is a large
    pressure differential.
    Mark
     
    Mark, Dec 29, 2007
    #4
  5. Lloyd E. Sponenburgh

    Mark Guest

    On Dec 29, 7:40 pm, "Noon-Air" <> wrote:
    > "Mark" <> wrote in message
    >
    > news:...
    >
    >
    >
    >
    >
    >
    >
    > >> I dont call it "windmilling" (...wtf?) I call it "the reversing valve
    > >> switching noise".
    > >> It doesnt change "into" and "out of" the defrost cycle. It does
    > >> however perform a defrost cycle when needed and terminates the defrost
    > >> cycle when needed.
    > >> I think any reversing valve movement causes wear. Same thing as when
    > >> your tires on your car roll on the pavement. When you can figure out
    > >> how to stop the wear, call me. I can make you famous.
    > >> Bubba- Hide quoted text -

    >
    > >> - Show quoted text -

    >
    > > No I don't mean just the click sound...

    >
    > > I hear mine and my neighbors make a 5 to 10 second very loud whoosh
    > > sound like the escape of pressure.  I assume it is the refrigerant
    > > flow that happens when the reversing value changes position (for the
    > > defrost cycle) while the system is operating and there is a large
    > > pressure differential.
    > > Mark

    >
    > exactly-


    OK good.
    so my question now is, this large pressure flow seems like it might
    not be so good for the valve... In other words, does this wear out
    the valve?

    Mark
     
    Mark, Dec 30, 2007
    #5
  6. Lloyd E. Sponenburgh

    Richard Guest

    On Dec 28, 1:20 pm, "Lloyd E. Sponenburgh"
    <lloydspinsidemindspring.com> wrote:
    > I just replaced the reversing valve on an old Tempstar package unit.  
    > DAMN... the cost of the job would've half replaced the unit, but the
    > owner sez no. So you do the work, and only warrant that part, no?


    How you figure that? If you do the work then presumably you've
    diagnosed the problem. Labor should be covered for at least 30 days.

    >
    > It's a pilot-operated valve.


    They all are, AFAIK.

    >
    > Anyway, what I am curious is, what is the mode of failure on these
    > valves?  One assumption I could make is that one of the pilot lines -
    > almost as small as capillary tubing - has become clogged.  The armature
    > in the pilot valve moves freely and hits both seats with authority.
    >
    > If there isn't a general consensus on why these fail, I'll probably
    > dissect it on my own time to try and figure it out.
    >
    > And no, I don't want to fix it.  I just want to understand why it failed..
    > If they do fail from grod in the pilot lines, it seems to me it's just an
    > invitation for a new valve to fail in the same way.
    >
    > Ideas?


    Yep, forget about it. It'll work or it won't. Too late to worry about
    it now.

    We don't typically dissect parts to see what specifically happened to
    them, especially not reversing valves. Taking them apart would most
    likely obliterate all traces of the original defect.
     
    Richard, Dec 31, 2007
    #6
  7. Lloyd E. Sponenburgh

    Richard Guest

    On Dec 31, 12:01 am, "Jeffry Lebowski" <Nope@nono> wrote:
    > "Richard" <> wrote in message
    >
    > news:...
    >
    > > We don't typically dissect parts to see what specifically happened to

    >
    > them.
    >
    > The pistons have flouropolymer sealing surfaces that indeed can wear / flake
    > off.
    >
    > --


    And yet....so many have lasted 30 or more years. There is a fine line
    between "wearing", and "wearing out". If a reversing valve fails it's
    more than likely due to something other than ordinary wear, not that
    it can't happen.
     
    Richard, Dec 31, 2007
    #7
  8. Richard <> fired this volley in
    news::

    >> It's a pilot-operated valve.

    >
    > They all are, AFAIK.
    >


    Not all. That's why I specified the type. Some of the older low-
    capacity Tempstars (2-3 ton) have what I can only call a humongous
    changeover solenoid around a stainless steel valve body. No pilot lines
    at all (unless there are some internal pilot passages in the slide). But
    they don't change over under pressure, shutting down completely before
    switching.

    We have an inordinate number of package units around here, what with all
    the mobile homes. You see some strange ones, and some very, very old
    ones, too. I worked on one back in April that was a HUGE northern style
    gas-pack. It was big enough to be a 5-ton, but only good for 2.5. I'm
    not a gas guy, but this was only a condensor fan motor replacement.

    LLoyd
     
    Lloyd E. Sponenburgh, Jan 2, 2008
    #8
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