View Full Version : Rheem TXV/coil do not match handler
08-16-2006, 04:36 PM
We have a Rheem split A/C system of unknown age, model number RBHA-14A00N0AA. It recently froze once, then recovered but cooled not as well. Our freon was "topped off" and unit worked find for a while, then the fan started cutting out and not coming back on. Our techs have diagnosed high pressure cut-off due to a stuck TXV valve leading to the coil. The problem is, the coil numbers do not correspond to the model of our air handler. The coil was attached to the end of the air handler, with a special box built around this. First, why would someone do this? And can anyone tell how old our unit is based on the model number?
Our techs have been unable to find the proper TXV valve -- this is the biggest problem. Our system has been down for days, and Rheem cannot help; techs are now dealing with Alco to find the part. Any thoughts on this problem? Is this going to signal an impending replacement of the entire system just because of an old TXV valve?
P.S. We have a steel drain pan if that helps at all with the age.
User in Maryland
08-16-2006, 05:05 PM
-If the Freon was topped off then it's likely you have a Freon leak. Freon does not get used up. It's in a closed loop.
-But I wonder if you actually have a leak because now that you have been topped off, your high pressure safety is tripping. Think about it, more Freon means higher pressure.
-Now here's the weirrd part that you'll just have to trust me on. A stuck TXV usually sticks closed. A closed TXV means lower pressures, not higher.
-It's almost always the case that if you already have a TXV then it can be replaced with a universal type. It may be a bit harder to install a universal (piping may require slight alteration). But it's nothing out of the skill set of a good tradesman.
-The coil and air handler thing is nothing to worry about. They may or may not be an officially sanctioned match, but it's quite likely that they work fine together.
Here's my WAG:
You were never actually low on Freon. You got a restriction at the metering device, which impeded the flow of Freon to the cooling coil. A restriction means low Freon pressure. And it will also cause ice to form. The first tech misdiagnosed low pressure as low Freon (NOT the same thing) and added Freon till the pressures came up. The added pressure forced enough Freon through the restriction to make it act normal for a while. But with all that extra Freon the compressor couldn't handle it on very hot days. The super high pressure caused the safety to trip. So the next time out they decide that the problem was actually the TXV (closer, but not necessarily right - see next paragraph). Of course, they owe you a refund for the botched first try. But you'll never hear that. Anyway, now they'd rather find the OEM TXV so they can replace it easily but they're having a hard time finding it. Being that's it's real busy right now, it's easier to make you wait for their parts guy to find the OEM part than it is to have a tech just install a universal TXV sized to your coil.
I use the term restriction instead of failed TXV because while both are possibilities, in my experience a restriction is much more common. A lot of "techs" don't bother looking for a restriction. They just condemn the TXV. But most TXVs have a screen in front of them. The actual restriction is usually (but definitely not always) at the screen. Cut the screen out; install a filter/drier in it's place; and you're good to go.
Like I say, it's a WAG. I could be wrong. :)
08-16-2006, 05:21 PM
You are certain a stuck valve equals lower pressure? This directly contradicts what we were told. They diagnosed high pressure in the system, then went looking for the obstruction. Said the TXV was stuck closed. How big is this screen device? The valve piece was pretty small; no apparent screens visible unless it is inside the valve itself. Can a layman find this?
We will call another company for installation of a universal valve if they keep stringing us along.
User in Maryland
08-16-2006, 06:37 PM
A restriction will cause low pressure in the entire system. If you have a restriction you cannot get ref. to the compreesor, therefore nothing to compress to make higher pressure.
If the TXV was stuck closed the suction pressure would be in a vacuum.
The screen that Ira is talking about is inside the copper tubing.
I suggest you call another contractor, this seems to be taking you for a ride, or don't know what the hell they are doing.
08-16-2006, 06:56 PM
Originally posted by citypaws8
You are certain a stuck valve equals lower pressure?It's refer 101. It's doesn't make sense to the lay person because you're dealing with a substance that exists as both vapor and liquid in the system. When Freon flow is cut off, it just pools as a liquid in the condenser and does nothing but drop in pressure. You could have ten or twenty percent too much Freon in a lot of systems and yet the pressure will drop low if there's a restriction. You generally have to put a LOT of Freon in the system to make the pressure go too high because of a restriction. So as I say, they botched the first try by putting too much Freon in. That in and of itself is not a capital offense. On very rare occasion I make that mistake when I'm in a hurry. But when they discovered their mistake they should have copped to it and made things right. The low pressure they found on the first visit and the high pressure on the second may seem unconnected, but they are directly connected. The connection is the restriction and the contractor.
As kar says, time to find a real contractor. Good luck.
08-16-2006, 07:05 PM
Incidentally, IF you do have a restriction and not a bad TXV then the seeds of that restriction may have been planted the day it was installed. Look here (http://www.hphaa.com/services/installation/anatomy.htm) at point 16. I worked on a system that was at least 5 years old before enough scale accumulated in the screen for their to be a service call.
08-17-2006, 09:28 AM
Many, many thanks for all the responses here! This is a big help. We found another contractor recommended by a friend who is coming to rediagnose the issue, and we will be taking the first service company to task.
User in Maryland
08-17-2006, 04:50 PM
Please cross your fingers for us. We are permitting the original service company to redeem itself. Using the info here, we wrote a very detailed complaint letter and their service manager called to make things right.
He said that as a general rule, his company does not install universal-fit TXV valves, that this has gotten them into trouble in the past, but they did locate through Alco (and already have on their truck) the replacement valve we need. We will pay for the part, but they have capped the labor hours (at 3). We are somewhat resigned to accepting the part given the age of our system, which we believe may be as old as 14, and believe that a new valve can't hurt. Also, they have offered a partial refund of previous appts and will provide a full indoor and outdoor chemical cleaning for free, which hasn't been done in a few years. And they can do it all before the weekend.
If this fails, our back-up service company is scheduled to come later in the day, though we'd be back at square one with them on diagnostics. Hopefully this route will work.
Again, many thanks.
User in Maryland
08-17-2006, 06:08 PM
It sounds like the first company is making a reasonable effort to make things right. But unless the second company knows that their appointment will likely be cancelled, it's wrong to keep that appointment. You cost them money when you knowingly keep an appointment that you'll likely cancel at the last minute. Time is money and personally I get a little miffed when people treat my time like it's worthless. I'd cancel the second company ASAP and then call them again only if you need to.
08-18-2006, 08:18 AM
No worries. We had the same thought and cancelled the back-up service folks first thing in the morning, figuring it's better to call them back next week if we end up needing them. I'm sure somebody else can use their services today.
Thanks for all the feedback.
User in Maryland
08-18-2006, 09:33 AM
first of all none of this would happend if the techs use the superheat and subcooling method of charging. Right alway they would see that there was something wrong. with the txv
That is why I never charge a system by pressure. I always take the extra time to hook up the temp clamp on the pipes and subcool and superheat.Also I agree with putting a universal txv I put many of them and some of them work better than the original ones. I remember I had a cust call that had a Rhemm air handler with a Tempstar condeser the installers change the outdoor unit but they never change the line set and left the 1\4 in. liquit line on it and they didnt change the metering device to txv. I change the line set and put a universal txv on it and the unit works like a champ. Goes to tell you that universal txvs work very well.
08-19-2006, 05:46 PM
Now, we're really frustrated!
Company replaced the TXV valve. Installation went well, no surprises. They completely cleaned our outside unit afterwards. Before they left, they checked our pressure. It was 200-250, with temps inside about 81 and temps outside about 84, but they said the valve seemed to be regulating well and preventing the pressure from hitting the cut-off point. They chose not to recover any of the 2 lbs of freon they initially added.
We reached 73 inside that night, which is our target. Temps outside were about that, so we were even. Early Sat morning, as soon as temps outside started to rize to high 70's, our unit froze and stopped cooling! It's now 80 inside, 84 outside. It's ridiculous. We've never had these cooling problems. It's running, but we are freezing at least half-way up the distribution line that runs from our outside compressor, up the side of the house, and in to the attic, where the air handler is. I keep thawing it with the hose, then raising the thermostat, but it freezes no matter what. What is this about? We have always been told that the biggest reasons for freezing are poor air circulation - i.e., a blocked return or debris around the fan - or low refrigerant. We know these are not problems. We have an electrostatic filter, it is perfectly clean after our very first call for this problem!
This is exactly the problem we initially called service about! They chose to add freon, then our valve went bad. Is this related? Though they cut us a break yesterday, we are afraid that their actions caused the valve to go bad in the first place, and now we have no relief from the initial problem, just a big bill to fix their error.
The only thing they said about our unit is, outside on the compressor unit, there is a low pressure cut off that is not connected. It can carry a charge, they checked it, but the two wires are cut and go nowhere. Is this at all related? It has always been like this, though, and we do not understand why now, our 3rd summer in the house, there are issues.
Please advise re: the cooling issue and whether the high pressure from the freon could have damaged the valve. We kept the old one in case it needs checked. Obviously, we have to call a new company now, but I would like to know what to have them look at.
User in Maryland
08-19-2006, 06:15 PM
P.S. There are only trace amounts of air coming from our vents, though what we can feel is cold. Also, as soon as we thaw the lines outside, they freeze instantly!!!
User in Maryland
Call another service company before your current one damages the compressor. They obviously don't know what they're doing.
08-19-2006, 07:16 PM
"they said the valve seemed to be regulating well and preventing the pressure from hitting the cut-off point"
That sentence makes no sense at all. What the TXV does has relatively little to do with whether or not you have too high a head pressure. Pressure that's too high is caused by a dirty condenser, too much Freon or other such things - NOT the metering device. These guys either don't know their trade or they're talking stupid because they can't talk straight.
You're wasting time by thawing the ice you can see. The ice you can't see inside the cooling coil box is what matters. That ice is blocking airflow. Turn the system off and let that ice thaw. It can take hours for that to thaw on its own. And the water that results from the thawing may go places you don't want it to. If your furnace is in an attic then you may get damage to your ceiling unless you have a secondary drain pan.
FYI: I can't tell by your post if this is what you're doing, but running an air conditioner overnight can cause ice to form on an otherwise properly operating system. If, for example, you had a two story home with a single thermostat upstairs set to 73 then ice could form if the unit ran overnight.
The additional Freon is not likely to have caused the valve to go bad. But then anything is possible. Personally I still think you probably had a restriction, not a bad valve.
The low pressure switch that's not connected is not really related to your problem. It would cut the system off if the unit was very low on Freon. But it's not going to prevent ice formation.
If running the unit overnight isnít your issue, then you need a real technician out there. Good luck on that one. Iím of the opinion that 80% of contractors are incompetent, crooked or both. :)
[Edited by Irascible on 08-19-2006 at 07:20 PM]
08-19-2006, 07:41 PM
Cannot check the air conditioner with it froze. Need to turn off system and turn fan to "ON" (if thermostat has this option). When air flow is strong from registers you could turn system back on, but beware if overcharged or low airflow it is not good for compressor. I wonder if you could have low airflow and the refrigerant added instead of checking air flow. HVAC tech should be able to verify airflow.
08-19-2006, 09:28 PM
Thanks. Some of this makes sense to us, but not all of it. What is bad air flow? We have vents in every 1st and 2nd floor room except one, and the large return is in the ceiling at the top of the stairs.
Yes, we are a/c hogs, pretty much running the system from April to October, but in a brick house it is necessary. We always do this, and don't understand why this temperate spell (in the 80's) is causing problems. We were fine all summer, then had a few weeks of 100 degree temps, then back to the 80s in the day, 70s at night. We keep the thermostat at 73 always. On the hottest days, our system has never kept up, usually topping around 76 inside. When the hot spell broke a few weeks ago, the temp inside started topping at 78 and we found freezing -- that's when we placed the first call. The thermo is on the 1st floor in the warmest room, where there are no vents. The 2nd floor is actually cooler, presumably because the air handler is right above in the attic and so vents are very close. It's always been that way. We have a basement, too, but no air vents there.
We definitely have to call someone else next week, but just wish we could troubleshoot something on our own in advance of rising temps and to try to forego more time off work! We did find earlier this evening that the metal mesh filter in front of the electrostatic was quite dirty. We hosed it and will reinstall when it dries.
We have already spent $500 in repairs, and had we known in advance, we would've just put a downpayment on a new unit given our 14 year age, and been thankful for the included service plan. At what point do we just call it quits with this one? I guess at least one more diagnostic call is in order. They told us the coil was old but good, and definitely not dirty.
User in Maryland
08-19-2006, 09:51 PM
Unfortunately, you have likely been hacked. There is no easy way to put it. I am not sure how else to handle it but to make the company make it right. You may just consider having another company look at it and get it done correctly.
08-19-2006, 11:37 PM
$500 in repairs and they left a dirty filter? Too bad you don't have pictures and documentation. I'd take them to small claims in a heartbeat.
Bad airflow means a lack of volume. The lower the air volume through that coil, the colder the coil will get. A very dirty filter by itself could be the cause of your problems. Dirty filter equals less airflow equals colder coil equals increased odds of ice formation.
08-19-2006, 11:50 PM
Originally posted by citypaws8
He said that as a general rule, his company does not install universal-fit TXV valves, that this has gotten them into trouble in the past,
I have never in my life installed a TXV on an extisting coil and had to go back, spend the extra bucks buy the best valves "Sporlan" is all I will buy and 99% of the time you should be good to go.
Now I will also say that I know the valve company's are probably working 24/7 to get valves out to the distributors and mfg. in a big hurry today so you might come by a few bad ones, but maybe when they get caught up we won't even have to be concerned.
08-20-2006, 02:56 AM
Has anybody tested the static press on this unit? The least they can do is a temp. rise method. It works well. Have another company perform this test.
08-21-2006, 09:57 AM
Many thanks. Given all the time off work already, we have to wait a little later in the week for a follow-up appt with a new company.
Our handler does have a draining pan, so we have no worries about the thawing. We thawed the unit with just the fan, restarted without the mesh filter in place (it's still drying), and it ran a full 24 hours ok except for it really didn't keep the house very cool. With thermo on 73 and temps outside in the high 80's, we were 77 inside since the early morning. That is really the cooling issue we want to get to the heart of. Normally unless we're mid-90's or above outside, we keep 73-75 inside easily.
This morning the unit froze again. Don't know what happened between Sat night and Sun night, but we had the same temps, same thermo setting. Mesh filter is still not in, so this time it was not a clogged filter issue.
We're a little concerned still about the high freon since they added 2 pounds and didn't recover any of it after replacing the valve. This is what the original co. was speaking of when they said the TXV valve was working -- i.e., with the extra freon, the system wasn't cutting off with the new valve in place.
We have the old valve. Anyone know where we can send it for testing? We would love to know if it needed replaced in the first place.
We're understanding the air flow issue, but don't understand what would have caused a new issue to come up. If the system worked fine early in the season, what causes air flow issues to arise later?
User in Maryland
08-22-2006, 05:01 PM
Our new air folks are coming tomorrow to re-diagnose our mess, and just so we know, we have asked a sales person to come also and prepare a quote for replacement of this 14 year old Rheem system.
This particular company sells Trane, Rheem, and Carrier. Any big differences between the brands? And where can we go for detailed consumer-driven feedback about these brands?
User in Maryland
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