Finding TXV problems?

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I haven't done a lot of 410a stuff but the fact that I've already seen a bad TXV on a new unit makes me very suspicious of them. An intermittent problem is always hard to diagnose if it doesn't show up while you're there but at least you know that the compressor IR valve opened so that limits the possibilities. You could disconnect the fan & see if your high pressure switch trips instead of the compressor IR valve. If it does that would point more to the TXV, if not then the motor cutting out intermittently. I haven't had to pump down a 410 system yet but with 22 its not uncommon for the IR valve to open & not the HP switch because the head pressure doesn't get that high on a pump down. The IR valve has more of a tendency to open on longer lineset installations. Anyways I would still suspect the TXV. Sometimes an educated guess is all you can do to try & solve a problem rather than doing nothing.
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The pressure has to be high in order for the IRV to open.
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I understand that but things don't always work exactly to specs & still have no effect on normal operation. Say the IRV was designed to open at 600 psi & the HPS to 550. It would not seem unreasonable for the IRV to trip first. It would only have to be 10 % off between the two of them. The other thing is with an IRV the back pressure may have a role in its opening to a small degree. A valve might open at 500 with 25 on the low side but not till 600 with 200 on the low side. I only guess this because like I said before I've had a lot of IRV's open on pump down before the HPS. The amount of refrigerant has something to do with it also because if I recover about three lbs. the same unit that trips the IRV will usually pump down with no problem.
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Make sense(?), no. Why(?), Here we go... If in fact, you were to close the LL service valve to pump the unit down. This would eliminate the complete lineset and evaporator from the condensing unit, leaving the refrigerant to be pumped into the condenser coil. If in fact, there wasn't a long lineset (or overcharge situation), the unit would pump down just fine.
Now, since you think it's the TXV closing... This would leave you the above condition, but you're adding the LL to the condenser coil loop. Basically leaving you with a larger condenser coil. This wouldn't create a problem for the compressor, unless, the unit is excessively charged. Which shouldn't be the case, since you measured the subcooling and its fine. Unless, you added refrigerant to the system to cover another unknown problem. Did you happen to check the superheat? And since you installed this unit new, do you remember adding any refrigerant? Another thing that goes along with this, is if you limit the gas to the compressor, the head would drop off. Another factor to this equation, is that this unit has a LPS. If it was pumping down far enough, the system would shut down on LP.
As I see it, the only way for a TXV to cause the compressor to open its IRV is for it to be stuck open. Leaving you with high suction pressure and allowing excessive refrigerant flowing to the compressor. However, why isn't the HPS shutting the unit down before the IRV opens? I could only see this, if the compressor was recieving liquid refrigerant.
Do we have enough air-flow for this 5-ton unit? Does this Aspen evaporator have a hard shut-off TXV? Is there anything odd to this install?
If it was me, I would recover the refrigerant and weigh it. Evacuate the system and charge it with virgin R-410a to specifications. Just to make sure there's not a problem with non-condensibles or a refrigerant overcharge condition. I'm not second guessing your technical abilities, but I would make damn sure there wasn't something missed at the factory.
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wrote:

Agreed. I havent pumped it down yet.

Slightly larger yes, but remember.......Tempstar uses 7mm tubing instead of the normal 8 or whatever. This allows for a 40 something percent smaller amount of actual volume in the lines (straight from Tempstar info).

It isnt. Its charged correctly. Remember the smaller tubing though, above.

I didnt check superheat and I did add refrigerant to the system when it was installed because the lineset was longer than 15 ft. Somewhere around 35 if I remember correctly. I did measure it at the time so I could get an accurate number to add to the system.

See above

I have to check again but I dont believe this unit has a LP switch and I know for certain it does not have a HP switch.

?? Im just going to have to agree to disagree with you on that one.

Again, it has no HP switch.

We did the ductwork and HVAC on this home when it was new (about 18 yrs ago) and did a Manual J and manual D on it.

Yes it does. Externally equalized too.

Nope, just the problem it is exhibiting now.

I know you arent second guessing me and I appreciate the info. You did forget though that if Im going to dump the charge and add new that I would of course replace the filter drier. :-) I get no bouncing of the gauge pressures while the unit is running so I dont suspect any non condensables and as I always preach, this one got an evacuation to below 500 microns with my JB pump and digital vac gauge.
It still has only done this twice in about 3 wks now. Very intermittent and correcting it temporarily is as simple as turning it off and back on. I suspect the TXV or a weak IPS in the compressor but since I cant isolate it Id replace both at the same time and hope I dont receive another bad compressor or TXV. Im still waiting for some answers from Tech support at ICP since they seem to be acknowledging that they are having some sort of small isolated instances of this problem. Hopefully I will get an answer soon before this customer "fries my arse". :-) Bubba
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Wouldn't make any difference, as the refrigerant charge is less because of the smaller tubing. It's a ratio that isn't really going to change.

No biggie... .6 oz times 20 feet = 12 oz extra.

The N4A360 should definately have a high and low pressure switches. page 17 numbers 17 & 19 http://icpindexing.mqgroup.com/documents/086477/42104510001.pdf

It should have both a hi and lo pressure switch.

Why, you're not opening the system to atmospheric pressure. There's really no need to replace it unless you just want to. Now, if you are going to open the system up for repair... yes change it, no questions asked.

I don't think you'll have a problem with the client... she already requests you because she trusts you. It's just simply something that's odd and you're going to make it right for her when you locate the problem. It's not like you're not trying. :-)
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wrote:

hehe. Somebody forgot to read the fine print. If you will look on page 3 of the link you sent you will see LPS DTS HPS, LLS switches ALL have an asterisk by them. Then look at the bottom of the Legend on that same page and you will see " * MAY BE FACTORY INSTALLED" Obviously that means "May Not Be Installed to because I dont have any of them that I know of but I will take a pic of it when I go back and post it for you. :-) Bubba

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Yeah, I saw that too... They list that on almost everyone of their tech sheets... like the H2A3, H2H3, H4A3 and H4H3. However, *all* of these come with both switches... this is the Premium line as you probably already know. The ad sheets say the H includes both, while the N says nothing. EPMS shows them, go figure. I don't mess with the N series... just don't care for them. I didn't think ICP manufactured a R-410a unit without a HPS... guess they must have found a way to save money. <rolleyes>
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The joke around here is anyone who knocks Goodman has never installed ICP. They come up with problems that defy the laws of refrigeration. I've installed some of their units that have lasted twenty years but also some that have gone where no unit has gone before. My favorite is the "Green Slime". For those who never heard of it, it's some chemical reaction in the oil that formed green slime & clogged up the entire system. The unit not pumping down doesn't surprise me at all. If you told me pumping down the unit made the garage door open with an ICP unit it wouldn't be a big surprise. So if there was a faulty TXV in another manufacturers coil be happy your truck is still running.<g>
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On Wed, 25 Jun 2008 12:46:30 +0200 (CEST), Gary

Yep, I remember the green slime. Do you remember the 90% furnaces that got clogged with the white oil/grease that was used in the manufacturing process of the secondary heat exchanger tubes? Those were a fun mess to clean up. Oh and the one where the furnaces needed one of the condensate lines held down lower to keep water from trapping and sjhutting down........ Oh and the one where..............................(and on and on) :-) Bubba
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Yup, problem is, it's all junk anymore. I dont care what brand it is. So are the parts. Did a No A/C call yesterday. Trane 90% TUX100. Somewhere around 8 yrs old. Maiin circuit board was fried. Didnt see any water marks that did it. It just burnt up the fan relay on the board, thus, no fan on a call for cool. Drove to pickup the new board from R.E. Michel. Installed it, connected the wiring, turned it on and immediately got the red constant on LED meaning "Internal control failure. Replace board". That kinda sucked beings thats what I just did. Thought is was my futz up somehow so I double checked the idiot proof wiring and polarity. Nope. All is well. Called RE Michel. Counter dunce gave me a number to call their service tech guy. Called and left a message. One day later and I still havent received a call back. Went to get a second new board hooked it all up the same way and GEE, this board works just fine. Nothing like White-Rogers quality control checks. Fuquers. Bubba
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wrote:

Next time pickup two and take one back on the next trip to the distributor. :-)
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I agree its all high efficiency junk. I'll bet I've had a dozen blown transformers this year on units under warranty. The problem: GE contactor, bad coil. Rare failures years ago have become common place today.
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There's very little gas in my area so I only work on one or two gas units a year so I've been lucky not to run into any of their furnace problems. I usually have to take a class just to know what's happening because I don't get enough on the job experience with gas.
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wrote:

Well, after this and one other N series, I think we are done with them too. The noise level alone is very big compared to the Premium line. I do remember a diff in price of about $400 from the builder grade to the premium line but sometimes the money just aint worth it. Bubba
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:-P I already changed the stat. That didnt work so I changed it again. Then someone told me it takes up to 4 stat changes before you get one that works so I changed it 4 times. It still doesnt work. Should I change it again? :-)

Nope. Not true. This came from the TSA at my local distributor. Im very good friends with him and get a lot of info Im probably not supposed to have sometimes. Like, I know exactly how many units have exhibited this same problem within about a 100 mile radius of here. The most recent being another one yesterday. Anyways........ With shorter line sets these Tempstars will NOT hold the entire charge and will allow the internal relief to open. I dont know if I can get that for you in writing but I will if someone wants it.

Bingo
If ONLY I could catch it in the actual act. :-)
There is NO high pressure switch factory installed or field installed on this unit. I have to look at the unit again to tell you whether or not it has a LP switch installed.

That might be ok on larger commercial stuff by soooooo not worth the effort on resi crap.

Thats a thought but right now Im pretty confident its not the bypass.

Not to worry though. I will figure out the problem and I'll be happy to report back with my findings. Bubba
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Interesting! I'd have thought the condenser would hold the entire charge and pump down easily. I guess the IPR would be easy enough to check. Disconnect the fan motor or block the condenser and see when it opens. One more question-- does that unit have a 2 speed fan motor? We have had problems with Amana and Goodman (ain't that a shock). The thermostat that switches the motor speeds acts up somehow. The only one I have had personally was DOA on a brand new unit I installed. I just bypassed the POS and hooked the motor to high speed. If the motor was cutting off on overload it would stay off long enough for the compressor to overheat and cut out of IOL also, but if that thermostat is erratic, maybe the fan can cut out just long enough to cause the IPR to open. Remember-- it is usually the thermostat. Larry
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The N series (which Bubba is dealing with) is a single speed motor, while the premium H series has the two speed motor.
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On Tue, 24 Jun 2008 21:19:44 -0500, snipped-for-privacy@webtv.net (lp13-30) wrote:

Just a single speed on this unit. Bubba
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wrote:

Yeah, I'm just the kinda of guy that would like to see just that, if you can get it.
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