No Cooling - Very Low Suction !
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- Опубликовано: 14 окт 2024
- In this call I found multiple problems. But, I was called out for no cooling. I had a very low suction, 5.3 degrees subcooling and 70 degrees superheat. I tried to show why I think the problem is the TXV. #hvac #hvactech #hvactechnician #hvacguy #hvaclife #txv #ruud #nocooling
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I suspected charge after I heard the compressor on the initial start (1:45). The 5 sub is way too low and needs to be around 10-18 or whatever the panel say's. The quick and best way to check a txv is to pull the condenser fan wire outside and watch the suction pressure. The increase of head pressure is normal after motor stops but the txv should maintain the suction pressure with little to no change. If the pressure stays about the same then the txv has proven itself to be working and if the suction pressure increases as the head pressure increases, we know the txv is bad. This test takes 60 seconds and can actually be used on PM's to test them before cooling season. Try it a few times and get the swing of it. This is a quick accurate way and keeps techs from having to remove the sensing bulbs. Extremely accurate. Thanks for the clip.
I agree on raising the head pressure. That’s the only way I will charge a micro channel with a TXV. I know this is not a micro channel but bagging the condenser will sill work.
Good tip thanks. I’ll try this going forward
thanks for the tip
How do I pull condenser fan wires to check pressures when system is running? Do I shut it down, remove fan wires then switch it back on?
@@olurotimiadepitan5087 remove one of the high voltage fan wires
Did anyone else not notice his black lead on his meter was off when he was checking for call on cooling at the condenser?
Wow!
Yes, at 2:40, he attempts to test for 24V coming from the thermostat, but his black negative lead fell out just before doing so!
I bet after he saw your post, he was like, 🤦♂. 😆
Yep. And he wasted probably 15 minutes of his time going back in to see if he had a call at the board, subsequently killing power and had to wait for the 5 minute delay. Lmao.
Mark the yellow wire then pull the wire you want either direction and see it move,easy 😊
Probably the txv. Frosting up at the txv. If its stuck open I could see the low temp on the liquid line. High superheat and low subcooling, I might of tried adding a little freon to see if it changed the subcooling any. If it was working fine before and you didn't find any leaks, I would say txv. Did it have a low TD? Good video. Love the tough ones. Love this channel. Truly one of the best.
Txt didn’t move when you warned it. Problem found. Nice
one of my co-workers gets mad at me bc I find a lot of bad TXVs, I get the running joke, but yo sometimes these TXVs suck, and it's like almost scary to say it's a bad TXV bc people will assume you're wrong. I've seen a low on charge unit w/ a bad TXV, how I figured was when I added gas, my suction pressure did not change at all, tis one of my tests if I'm really doubting myself. Great video
I know you know what you are doing; there's no telling how many decades of experience you have in our field. But I have a question...
Why didn't you check air flow and static pressure before checking the charge? You didn't even check the air filter.
The reason I ask is because that's what we're taught in school, is
E.A.R. - Electrical, Airflow, Refrigerant.
Just asking!
Love your videos, big guy; keep 'em coming!
I had several situations similar to that, had to pull a pump down and remove the strainer just before the txv and on most cases the strainer in there was clogged, clean and reinstalled and issue solved
Thanks! I did not know there is a strainer under the TXV. I am having the same issue.
I've learned something new . i didn't know you could jump the contactor to got it running.
Yes you can do that all need is 24v to jump 24v side of the contactor
You tested the low voltage at condenser with less unplugged from your meter 😂 done that a few times myself, the first time you tested it
I didn’t notice. But, you’re right.
whoops, good catch!
Good job Curtis.
Excellent job.
Diagnosis of a Txv is the hardest I think. Especially since it's too expensive to dump in a couple of pounds to see if there's a difference. Warming the bulb won't do anything since it's already maxed out in temperature at 75 degrees super heat. I had to pull out the gas and weigh it just the make the call on one system, however I had to remove the gas anyway. It was the heat side expansion valve.
I think the low ambient is throwing you off. You should have more liquid stacked in the condenser since it's so much cooler outside than inside. My money is on low charge. I'd stop the condenser fan to get the head pressure up to see how subcooling and superheat react.
I found that a small magnetic screw holding bowl works way better than that tool. Plus it doubles as your screw holder. I love to add a little 410a to watch if the low side drops, which confirms a restricting TXV. Of course that's a more expensive approach.
Always when in doubt shoot it with a little fridegrant..
@@georgesummerlin1602 it's doubled in price over the past year or so.
The price is insane
I have been in those cases and I weigh out the freon. If freon doesn't meet factory charge it's low. Weigh in proper charge and then see if it's still doing it.
With the price of r410a being so high, I've been doing that lately
Pretty cut and dry from what I seen. No need to over think it. Good job.👍
Mechanical contractor here 40 years in the business. Bad TXV and water heater vent is just fine like that.
Listen to years of experience. Will save you headaches at the end
If the temperature was above 65 degrees. I would say your diagnostic is correct. Seeing how the outdoor ambient is 54 degrees. I find it hard to believe the txv has failed. Ac should not be running below 65 degree ambient both indoor and outdoor. This is due to low vapor refrigerant in the coil with low temperature airflow blowing across the coil. There is no load on the system. Causing the txv to meter down the amount of refrigerant in the coil. Causing a high superheat.
Also tried to restrict the outdoor unit fan to drive up your head pressure, while rasing your subcool to verify. When low ambient conditions apply.
This past week I had a tane ac that wasn't cooling right when it got 80° last weekend. 38° superheat and 9° subcooling (rated 8+/- 3) at 45° outside. I was pretty sure it was the txv but I decided we needed to double check when it was warmer. I'm not gonna be "that guy" who always blames the txv
I use a spring clamp and a short piece of a paint stirring stick to hold in door switches.
The pressures didn't rise on the bulb test. Bad txv. The system may still have a leak and low charge that caused the valve to stick.
I noticed 410a on the unit tag. If it's 410a, the unit is under charged. Need to add more refrigerant.
I was sold on the TXV once you grabbed the bulb in your had and no change happened. I'm totally on board on this one.
I've replaced 20 txv this summer that's a very common repair but sometimes the txv oil will unstick them and trane will warranty their txv oil for the repair I've used it several times and it worked I wouldn't try it on an old unit but a newer unit yes it's alot easier than replacing the txv
I think you're right on the TXV. It could be slighly low on refrigerant too, but the fact that the valve pinched and stopped the suction pressure at 77 while compressor was off says something is going on. I'd say a partial loss of bulb charge. If the valve were working correctly and the charge was just low, the pressure should have done more equalization before the valve started to close.
Hey, what ever came about of that HP that was tripping off on high head that you suspected indoor valve?
Not sure. I don’t know which video you are speaking of
I'm sitting here debating with myself. Did the bulb lose its charge? Is the txv piston stuck? Is it low on refrigerant or a combination of a couple of things?
Usually bulb loses charge. Rubbed hole in the tiny tube or diaphragm is leaking. That's why the more expensive txv like sporlan have replaceable heads. But diagnosis of a Txv is the hardest thing to me.
I question it because typically, the low side pulls all the way into a vacuum or real near and will "stack" liquid and give a pretty normal subcooling. Maybe this one stuck open just enough to feed to keep that from happening from a lost charge in the bulb. I guess we will find out.
@@TheWilber09 the diaphragm is most likely leaking. Which causes the valve to restrict the freon.
TXV;'s are the bane of my career... so much brazing in tight quarters!
What is it Rheem city down there? It's all I've seen in the like 5 videos I've watched of yours.
Rheem dealer
pump it down,remove valve check for debris,if not install piston and test.but if you carry a valve change it.good video.
I would check and resolve two things first. Address the return and check blower wheel that thing was shaking pretty good is it packed with dust and hair or am I just seeing things. I’ve fixed two units in the last year that were both txv’s. One I was able to swap the power head and as soon as I did you could hear the refrigerant flow from one side to the other side of the unit. It sounded like a reversing valve.
After you stopped it did the two sides try to equalize? It didn’t appear to in the video.
@@moonlightacmaintenance3232 no, not at all
Where did you get your tool bag ?
I see you didnt noticed that the black lead on your meter was not plugged in when you first checked the voltage at AC.
May have missed it, but any chance the filter drier could be your restriction?
I believe he said 64 on both sides
14:39
Sensing bulb lost its charge, not sure what’s been going on at quality control, but they need to start taking thickness of their coils and TXV bulbs. I’ve seen some coils leak because the metal was too thin, it just gave way through the seasons. Expanding and contracting, will make any coil or bulb leak if it’s too thin. There are thickness gauges for paint coating, wouldn’t hurt to test thickness at common places where leaks happen before shipping it out to the customer
Great video thanks again always
Maybe they forgot a Schrader in the bypass port, I've seen that a couple of times
Hmmm? Is thats at th3 condenser right? The inside txv it shouldnt have a shreder valve?
Was high low pressure balanced out before start up or if you turn unit off does take for ever to balance out pressure txv are tricky like reversing valves
I use tape for the door switch and why aren’t the pressures equal the units not on I think we’re on to something
I don't know if there is a follow up video. But because the clothes dryer is not venting properly could the coil be clogged from the under side?
Hey guys! I think that the evaporate coil was installed wrong. It should be upside down and shaped "A" corn. Am i wrong?
Most likely you did not need to make that jumper.
The power was most likely at the wire nut on the yellow wires and if not you could determine which switch it was by continuity or low voltage.
The first time you checked for voltage outside your meter lead was not in the meter.
12:22 lol wtf man. That’s how you get a backwards running compressor and a chared up contactor
Nothing wrong with the system. Outdoor temperature is 57 degrees, thermostat won’t able to turn it on for cooling call. Even we could force units to work, you will see high superheat because of very low heat load. Also we need to figure out sub cooling for TVX , he said it’s moderately low, but not extremely low , considering the outdoor temperature 57 , so Txv is good. Nothing wrong with whole system.
what do you mean that the txv is locking down
Great
It's always the txv 😂
In the car world specially hondas the distributor 😂 or fuel pump for everything else
What was your delta T?
With a 5 degree subcooling there's no way your suction pressure would be that low. TXV it is
It can be. Depends how hot it is outside though
Check the screen,before the TXV.most likely obstructed.
its never the TXV, unless when it is.
1 txv for the ac. 1 txv for the water heater lol
Trouble shooting 101 also use a cup of ice and water.
Thanks again for the videos!
🥃🥃🍺🍺🍺⛳🎳
Stay safe.
Retired (werk'n)keyboard super tech. Wear your safety glasses!
To me it looks like the valve's power head lost it's charge.
Wondering if anyone noticed. When at first checking for a call outside on the control wiring. The negative test lead wasn’t in the meter until afterwards he was putting the meter away. Oops
Does anyone else use a long flat head and put their ear on the txv to hear if it opens and closes?
When is it NOT the txv 😂☠️
👍
Txv was not responding, faulted out.
low on gas and txv problem. lol
😵💫😄😄😄
Cooling call in the winter smh
Txv. All day
Bad txv
AC renew
Taylor Carol Hernandez Mary Hall Ronald
Txv is bad
Txv for sure. Good thing it's a mechanical one easy to change.