Learn TXV Troubleshooting & Repair for HVAC Technician

alright guys so we're here today to discuss the 
TXV and doing a teardown on it I did a live on   this a couple of months back on Instagram and 
I wasn't able to actually save it the way I   was hoping to and so what I'm going to do today 
is just a basic teardown and it's just a little   small spoiling valve it's actually eight it's got 
carriers name on it it's actually a spoiler design   carrier just put their logo on it anyway I want 
to show you the ins and outs of the actual valve   assembly how to disassemble it how to rebuild 
it and try to answer any questions I know that   I frequently get on so just from looking at it 
here this is going to be your liquid line coming   into the valve that's going to be a discharge line 
coming out on the bottom here not all valves have   these but a lot of especially supporting it 
so I'm a big fan of spawn as their valves are   usually extremely easy to repair and most of 
them are adjustable and so on the very bottom   here you take this little cap off sometimes these 
caps will be an actual hex this one's actually a   smooth round cap so you can do finger tight now 
you'll see a little adjustment head here this   particular one takes an Allen to adjust it and 
so what this is for is say you've got a system   that's running a super heat that's too high or 
too low you can take and adjust this valve to   increase or decrease that superheat and so if you 
want to decrease superheat you're going to rotate   counterclockwise and back that back that down like 
the nut out and it's going to look set it's going   to decrease your superheat if you want to increase 
superheat your just a clockwise and turn it in   as you do that's going to restrict the flow down 
internally in the valve and it's going to give you   more superheat going through your system okay a 
big critical thing that's very important when you   do that a lot of guys get tripped up on is you've 
got to be extremely patient when you're adjusting   TX fees especially if you've got a system if you 
work some heavy commercial where you may have to   TX fees or more in the same circuit that share 
the same liquid line it's extremely critical to   be very very patient you know you do not want to 
rush these adjustments because little happen to   use if you do you'll be constantly trying to 
adjust it to turn it in and you'll never get   it right and then you say you say you do think 
you have it right you'll leave and then you'll   give a call back later on saying you've got 
a compressor down and you get there and sure   enough the compressors fried because you flooded 
it back or you overheated it because you weren't   sending in enough refrigerant through either war 
another trick I wanna throw out there early on   is if you are having a valve you having to make 
a lot of adjustments to and you're seeing that   your pressures and superheat and subcooling is 
constantly erratic goes up and down up and I'm   not really stable at stabilizing very well what 
I would suggest to you at that point is go ahead   just stop shut that circuit down give it 10 15 
20 minutes to fully equalize let it settle out   and then try starting it back up because what 
can happen is every time you make an adjustment   on this valve that whole system has to rebalance 
in its refrigerant flow because like I said every   time other adjustment is made you're increasing 
and decreasing flow through this valve and so as   that happens you know those those flow changes 
take a minute to circulate through the system   and become normalized that's why you see some of 
the fluctuation that you do so if you become too   fast to react at times what you end up doing to 
yourself is the system has so many changes going   through it from from the adjustments that it could 
literally take a couple of hours for that thing to   balance itself back out so if you don't have that 
much time to spend to sit there and look at it if   you shut it down let it equalize and then bring 
it back online it'll kind of give it a restart and   you won't have to you can speed up the process and 
really see where that valve is that to make sure   you're not too high or too low and you're super 
heat at that point me personally well I shoot   for on super heat is ten to fifteen on just most 
applications there are some applications that I   work on to where I need a eight to twelve degrees 
of superheat and there's others that you know I   may want to adjust it to say a fifteen to twenty 
personally I do not use a super heat above twenty   degrees I hear a lot of guys talk to that think 
you know twenty thirty degrees of superheat is   is still okay I'm not saying that there's not 
applications where that's not used out there   but what I am saying is you're gonna put a lot of 
stress on your compressor that compressor is going   to run a lot hotter your discharge superheat on 
the compressor and that's any compressor that's   you know scroll reset you name it it's going to 
run a lot hotter and so you're just you're gonna   create a lot of extra stress on that compressor by 
running it that high and so then again the the if   you run too low that's kind of an obvious answer 
is you're gonna flood your compressor back so   that's what I do that's what I personally believe 
in I also want to make sure you understand that   these things do require a full liquid of column 
to come to them with some sub cooling to ensure   that they can actually function properly and so 
if you're say you've got a restriction somewhere   say you're just under charge to begin with and 
you're flashing before you actually hit the TXV   you're never gonna get a proper run all right 
let's get down to the breakdown so this is your   lower assembly here this is actual valve body and 
so you just take what I like to use I'll take two   big crescents click on there I've already broke 
this loose these tend to be pretty snug on there   just so you know so don't be afraid if you got 
little force on it there just a standard thread   so we'll just roll this out you want to be very 
very careful when you go to pull this apart if   you're gonna need to reuse any parts that you 
don't lose what's in there so the first thing   that's gonna come out this is your whole lower 
assembly right here it sits in there just like   so okay this is the the rod cap that sits on the 
bottom or sits up against the push rod that's in   there so a little cylinder rod in the middle so 
that push rod is what's actually controlling the   flow of refrigerant physically passing through so 
that rod sits down inside of here and this is a   little foot made to sit inside the spring okay 
this Springs pretty dark in my opinion I think   that this system probably has some heat issues 
there's a lot of things you can determine just   by looking at the internal components there's 
been numerous TXV I was having trouble with   couldn't get it to to properly control superheat 
whatsoever I got to open it up and sure enough   everything inside is completely black and you get 
to looking at it and you realize what somebody   overheated the valve so it'll it'll cause a lot 
of damage so take the spring out it's also got   another bottom adjustment plate if you look down 
the side there see it's got a kind of a cone shape   that is the actual adjustment screw that's on the 
bottle night that's exposed here inside here is a   rubber grommet some valves you can actually remove 
that grommet and pull this whole stem out this one   I was going to have to kind of break it up to 
try to do that so I just didn't didn't bother   but anyway which so you're adjusting that actual 
needle they're coming up which is pushing up   against this base here this indented cone shape 
sits on top of that and then your spring sits   in a seat right here and so if you ever happen to 
put one of these together that's how it's an easy   way to always know which way it's supposed to go 
if you lose track the screen goes on top of that   and in this top see it's just like so and I see 
your rods gonna go in there so what you're doing   when you were just this bottom part is you're 
actually adjusting that spring tension and so   when you turn it in clockwise to increase 
superheat what you're physically doing is   you are actually turning up the pressure this 
spring is applying to the piston all right to   the rod the push rod and so as you apply that 
pressure it forces it to close down and reduce   flow by reducing flow you're increasing superheat 
well the vice versa works the other way around so   that whenever you turn it counterclockwise and 
you back it out you're decreasing pressure and   so by decreasing pressure you're allowing the 
the push rod to open up more and allow more   flow through decreasing superheat so forth so 
that's your basic lower assembly then we will   take and take the power head off a lot of times 
these power heads themselves you can buy separate   at the supply house and so this is what actually 
has your thermal control portion so this top head   the power head is as we refer to it as charged 
with a similar gas – whatever refrigerant it   is controlling it is important that you make sure 
that this head matches your refrigerant so if you   get r22 you need to have an r22 compatible power 
head and so as the suction pipe coming out of the   evaporator heats or cools it heats and cools 
the refrigerant inside of this bulb which then   in turn affects the pressure of the bulb and so 
as the bulb increases or decreases pressure it's   increasing and decreasing pressure on this plate 
here and that plate is pushing down on the top of   your rod there so that push rod goes all the way 
through the body of the valve that's the top side   right there and so that's how it's applying its 
downward pressure so as temperature increases on   the bulb meaning the pipe you superheat is going 
up what it does is it pushes harder down on that   on that diaphragm in there and it forces the push 
rod further down which again that increases flow   decreasing superheat and so as this bulb starts 
getting cold the refrigerant in there restricts   reduces pressure reduces pressure on the diaphragm 
the spring pushes the rod closed because the back   pressure against the the rod and the diaphragm 
and it allows it to choke back on the refrigerant   increasing the superheat that's really all it 
is there's no more complicated than that if you   ever pull a power head off it should be firm it 
shouldn't be mushy to where you can kind of feel   it playing around in there if you ever do pull 
one off and you feel that that's how you know   that power head has lost its charge something has 
happened that charge you know even when you take   it apart should never release and this is all this 
both of these use just a like to like metal seal   right so this is all brass most of your valves 
like this are gonna be a brass tile so there's   no special sills or anything but what you have 
to be very careful of as all this brass has to   be very clean when you go to put it together 
because that's how it's actually making its   seal is is a like metal to like metal seal so and 
you have your push rod which we can actually just   push right out the bottom there and that's what 
it's doing so this pushrod he sits in there just   like so you can see all the way through that 
valve and so if you don't you can kind of see   it in there you can see where the liquid line is 
coming in up inside there yeah there it is let's   get shot that's where the liquid line comes in 
and pressure hits so what it does is as it needs   to reduce flow the diaphragm relieves pressure 
the spring pushes up and it pushes this bottom   section up against the bottom plate there of the 
body and that's helping choke off the refrigerant   and in this skinnier section here in the middle as 
it needs to increase flow that's along the liquid   refrigerant to go by it and so the diaphragm 
pushes down against the spring opens up the   rod and it allows refrigerant to start flowing 
past the pass the push rod increasing the flow   no more complicated than that be very very careful 
these rods though they're extremely easy to lose   they this particular one only goes one way some 
of the larger valve designs you'll see there'll   be two little rods in there one on each side of 
the head be extremely careful not to lose these   guys especially if you need to reuse them I know 
a very common question I get all the time is okay   well if I need to if I want to rebuild a valve you 
know where can I do that most of the time what I   found is they do technically sell rebuild kits for 
TX fees but those kits come and they're usually   like a two to three piece set that you have to buy 
individually there's not just one master kit that   I have seen that the manufacturers produce so what 
I found is on jeepers but much easier is I get an   exact replacement to the valve that I have and 
it's very critical it has to be an exact and I   just use all the components out of that new valve 
and put it into my my old valve body that's saying   the old valve body doesn't have anything wrong 
with it which in my experience 98 percent of the   time is the case rarely does the body actually 
fail or get an issue it's almost always the   components of the body and so that's what I end 
up end up changing out if I have to replace the   TXV what I end up doing most of the time is I pull 
the power head the lower simple I pull everything   out of it so we're all it is it's strictly the 
body and then I'll put the body in place sweat   it in and that way I don't have to worry about 
any any overheating or anything else happening to   that valve giving me trouble down the road another 
thing that's really handy is put a little oil or   nylon me personally I like to use my log on the 
push rods and you reassemble and that helps get   some smooth action as it moves up and down help 
it give it a little bit longer life okay sometimes   these push rods can't actually stick inside that 
bore and then you know that's when you'll start   seeing some issues with it controlling a lot of 
guys I'd like to do the ice bath test on the bulb   nothing wrong with that which are really really 
when I was first taught that test I was told you   know you just watch your pressure to see what your 
pressure does you know see your suction pressure   fluctuate slightly the issue I ran into that is 
it became very unreliable what I've seen is the   best test is yes you can do the ice bath but if 
you do don't want your pressure watch your actual   superheat because you're gonna see your superheat 
dramatically swing as soon as you go to do the ice   bath because it's gonna think that it's flooding 
back and it's gonna try to open up that valve   and you're gonna see that the superheat spike up 
dramatically so just a little extra piece in there so a lot of guys get confused on how the TXV is 
actually what I'll act what all pressures are   acting on it so again you got your liquid 
line your discharge you've got three main   pressure or I guess you can make a case for four 
pressures acting on this TXV okay so you've got   your diaphragm pressure on the powerhead 
pushing down on the push rod alright you've   also got your spring pressure pushing up back 
against the push rod so you've got your spring   and diaphragm pressures you've also got your 
equalizing pressure right so the equalizing   line goes back to the suction line you want 
it sometimes somewhere after the bulb so you   want your bulb prior to up you want it upstream 
from the equalizing line just in case any liquid   does get back through this equalizing line which 
can sometimes happen it doesn't affect your your   you're sensing bulb temperature reading anyway so 
this is applying pressure right here through the   port which is helping give pressure back against 
the diaphragm okay and then the so recap we got   an afferent pressure spring pressure equalizing 
pressure which is also up here on the diaphragm   and then finally the the last one you can make a 
case for is you have the liquid line pressure that   is forcing itself down against the bottom of the 
actual push rod and then technically you have the   suction pressure also pushing or pulling against 
the push rod as well from the from the discharge   side of it which is right there that really 
large opening so you those are kind of just   extra pressures but those aren't the official 
pressures that we really consider when we start   talking about TX fees so yeah that's your basic 
breakdown it doesn't really matter what size of   t –xv you have some of these if they don't have 
the edge Cement stem on them like this one does   then a lot of times you know those are gonna be 
a fixed t –xv and you're not going to be able to   adjust them now it's not that you can't rebuild 
them but I would suggest against it those are   set by the factory and they they'll they'll still 
have an adjustment in there if you ever take one   apart it just has a cap on the bottom it doesn't 
actually have an adjustment assembly you'll still   see that you can still make adjustments it'll have 
the same exact dissemble you see here it'll have   a spring and the rods and everything but what 
it will be doing is the bottom plate that's in   there will be set to a certain point on these 
inner threads and so that's that you you'd have   to count exactly how many threads it took to come 
out with it and then whenever you want to put it   back together count exactly how many turns to 
go back in so it would be a very very precise   thing I do suggest if you are doing one of those 
just go ahead and replace the whole valve don't   worry about taking it apart if you want to take 
the power head off and that's it if you can't   dam Foss is one that they almost always have the 
power heads molded into the valve or sweated into   them tore they're not actually removable and so 
that's just something unique to Danfoss not that   the other manufacturers don't do it at all but 
they don't do it near as frequently another big   critical thing that I see a lot and I have to 
fix a lot behind people is you're sensing bulb   here always needs to be on a horizontal if you 
ever read the manufacturer's literature on how   to do sensing bulbs properly they will tell you 
that they want that bulb on a horizontal and they   want it in a 10 o'clock or 2 o'clock position 
on the pipe so just imagine if you had a pipe   there and you imagine a clock on that pipe or the 
bottom of the pipe of six the top of the pipe is   12 well you want 10 o'clock or 2 o'clock on that 
pipe and that's really what the what they that's   the most preferred mining location on a TXV bulb 
and I do I do know that then I'll acknowledge that   when you start to work with some very large 
pipe like say two inches and above you may   have to move that bulb down a little bit lower 
on that pipe at ten ten or two maybe still a   little high because it's such a large pipe but I 
personally have never mounted below I say three   o'clock or nine o'clock so I know that there are 
some some theories out there you can research if   you like they kind of read up more about those 
now in the event that mining it horizontal is   not possible and you have to do a vertical mount 
on a TXV bulb you always want to make sure that   you mount it with the equal over the would 
the pressure tube the pitot tube coming up   you never want to mount it with that tube facing 
down that the there is this refrigerant that's in   there can condense into a liquid and if it does 
and it gets and it gets in this tube but in the   actual diaphragm it can either cause a failure 
or it can it can cause some some weird readings   where it's not controlling right down the road 
so it is important that you just mount that bulb   in a upward position to protect the the diaphragm 
in the powerhead okay it's like so that's a very   common thing it's also very important that these 
get insulated and they're very very tight to that   pipe if that bulb is not tight on there or if it's 
not insulated it's going to throw off your reading   I personally I do not like using zip ties I will 
use either a actual bulb mounting kit or if I   don't have one I'll get some pipe clamps and even 
a bulb this size I'll put a pot clamp on either   side of it not one just right in the middle you 
can see where this one had one just right in the   middle like I said it may be a little overkill 
but I don't have issues and my TX fees either the another critical thing is if you've got an 
old piece of pipe you want that pipe to be nice   clean brass and you want your bulb doing a nice 
and clean metal so if you get any corrosion or   buildup on either the bulb or the pipe what it can 
end up doing is it can act as a barrier between   you and the or between the pipe and the bulb and 
you're not actually reading the pipe properly at   that point another critical thing is you cannot 
mount this on any joints you want this to be even   if you say you say you have some soft copper and 
you've got a little bit of waviness in it you want   this to be a straight of piece of pipe as possible 
no joints no nothing in the way to cause it to   not sit perfectly on top of that pipe okay I've 
seen that several times you take and peel back   the insulation on TXV and sure enough is sitting 
right on top of a joint and it's no wonder your   super heat is acting crazy and so because then at 
that point it's having a sense through two layers   of of coppers that are just one it does make a 
dramatic impact on your sensing ability I know   that I get into a debate a lot a lot of guys think 
that wolf the sensing bulb was in the Airstream   he doesn't need to be insulated personally I 
say that is false I'd completely disagree with   that line of thinking because what the Airstream 
is and what this what the the line temp coming   off of that evaporator is may be considerably 
different at times and so and that becomes the   case any difference at that air around it has to 
the pipe it's going to impact the the ability for   the valve to sense what that pipe is actually 
doing so you really really want this bulb to   be able to sense as close as possible to whatever 
that pipe temperature is so I suggest to everybody   matter what the application I know manufacturers 
are terrible about sending these pre-mounted with   no installation on them at all I highly suggest 
you go ahead and insulate that bulb at all times   anyway guys that's your basics on doing a TXV 
tear down and rebuild and the basic operation   of how they actually function like I said I've 
I've been using these practices for a number of   years they've always done extremely well by me I 
have extremely few issues with my TX fees and when   I do you know understanding that's the big thing 
I try to get guys to understand is understanding   how these valves truly work and their in-depth 
processes of what they do makes all the world   of difference and being easier to diagnose when 
you have to and when you need to and so I highly   suggest that if you're not that familiar with 
TX fees pay attention to this video and then do   some reading they do have some very good material 
out there oh I will also mention that most of the   TXV that work on they have a 4-point adjustment on 
the on the adjustment assembly they don't use an   allen wrench like say this one does have an Allen 
the vast majority you'll run into you will need   your service ranch or you can put your service 
wrench on it and I do usually what I like to   do full rotations is how I count mine so say I'm 
running a 30 degree superheat 50-ton system okay   if I'm running 30 degrees I'll probably go 3 to 
4 full revolutions counterclockwise to decrease   that superheat I want to get it down to about 15 
right and so I'll do that and I'll give it some   time and I'll let it sit and see what it does if 
that's enough then I will I'll leave it alone but   if I say after making those four revolutions I 
go from thirty to twenty all right then I may go   another two probably two revolutions maybe three 
you know depending on how the system responded and   then seeing where I land there if I land at the 
fifteen where I want to be and then I'm perfect   if not again I'll just make some more adjustments 
if I overshoot then no big deal then I'll just go   clockwise in one turn or half a turn you know but 
I do it in revolutions when you start reading the   literature that's how they describe it as well a 
lot of guys are get kind of spooked on how much to   adjust it and they'll just barely make all these 
little tiny turns they don't really do a whole   lot of actual adjusting to the pressures in there 
anyway guys that's my two cents it's how I do it's   how I suggest it I'm always here for questions 
if you have any spend time with your family guys

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