Thanks for the video I enjoyed it. I started in the HVAC field in 1978 at 18 years old and am still doing it although I am now a service manager in an office. I conclude that the 57 piston was indeed too small as proven by the 65 piston being listed in the Goodman piston chart as the correct one for the 3 ton condensing unit. That one was easy. I conclude that the system was overcharged because the 57 piston would not allow for enough refrigerant flow for proper cooling and overcharging will force more refrigerant into the evap. coil and "get more cooling" even to the point of flooding back to the compressor. Note that the superheat was zero which indicates flooding in this case. The high subcooling and high head pressure readings are both indicative overcharge in this case. As for the restriction talk, although high subcooling may indicate a restriction in some cases, you will also have high superheat and not low superheat as long as the refrigerant charge was correct and of course proper airflow through the evap. coil. Also, a restriction in itself with proper charge and proper airflow through the condenser coil will not significantly raise the head pressure and in this case the high head pressure was another clue of the overcharge.

Looking at some of the other comments and noticed the same thing as what they noticed. First, a .065 is larger than .057, so either you read the number wrong or the new one should have been even larger. Second, if there was a restriction, the evap would be starved and you would be at freezing or below and superheat would be high. You had a flooded evap so it was overcharged or piston too large, which if true means like the other guy said, may have been .087.

I watched this video because i thought I had the same problem. It all started with a hissing (rushing) sound near the piston that would come and go as the unit ran. I'm an auto mechanic so the first thing I thought was low refrigerant charge because that is what some car systems do when low. I checked every inch of the system and no leak. The unit had ran fine since it was installed 10 years prior. A couple of years ago during a storm we lost one leg of our power and the condensing unit was making a horrible growl so I turned it off until power was restored. This was the clue I needed. One morning the condensing unit started the growl, no storm or power outage. I turned it off. Hooked up some gauges and they were fluctuating just like in this video. So I thought clogged piston. The piston size was written on the case with the bag taped to the unit as well. An it matched the Goodman chart. I checked power across the contactor and had 112v on one side, 83v on the other and 120v and 120v coming in. I removed the contactor and sure enough the contacts were cooked. Luckily there is an AC supplier close by and I bought a new contactor and capacitor. Pressures are now stable and no more hissing sound. I was surprised,

I had the same problem this week with a R 22 system good man air handler the installer left the 09 piston in I removed the 0.9 Piston and replaced it with a 65 and it’s working great, thank you for the great videos keep them coming

A restriction would cause low pressures unless it was restricted and overcharged. Which they often are previous tech saw low pressures from restriction and added refrigerant. Also with a restriction superheat and sub cooling will be high. The symptoms your unit is showing is overfeeding metering device.

Make more videos! One of the few worth watching

Great video and great content, very educational and insightful of real world. Big Thanks...

HOLY CHIT...couldn't figure out why my high pressure line kept tripping when above 95 degrees outside! Thank you! Mismatched piston.

Thanks for sharing this. Not something I really consider, so it's good to have this in my back pocket.

New to your channel. First time seeing an oversized piston so this was very helpful. Not sure where you are at but those houses looked like the ones near me in Canton Ga. Thanks again. Brian

Awesome video for sure

Very nice video!!!

I’d of cleaned the outdoor coil, checked airflow inside and recovered some refrigerant… even if it is the wrong size piston, it’s definitely overcharged

Man that vacuum pump jumper thing would be a life saver for me and so will the rest of the video

That jumper cord u use for the vacuum pump we call them suicide cords or power thieves

Great video Buena suerte para el nuevo año…

Thanks for this video, you did a great job! However, to me those readings you're getting aren't symptomatic of too large of a metering piston. If you had too large of a piston the superheat would be too low like it is, but your sub-cooling would also be too low; the liquid refrigerant would be flowing too fast out of the liquid line and never have a chance to sit and cool long enough to give you the proper amount of sub-cooling. I think what you have here is too small of a metering piston installed AND a gross overcharge of refrigerant or a very dirty evaporator, or secondary heat exchanger or air filter.

Your video helped me fix my problem. I installed a Goodman 2 ton condenser onto a Rheem 2 ton n-coil with a txv. My low side pressure was really high and it was not cooling. I removed the txv and installed a .57 piston. The low side pressure came down and after adding refrigerant. It’s cooling better.

The video is good but as far as I know the super heat within a normal working range should be between 8 and 16 degrees Fahrengeith. and the Coollin sub from 8 to 12 degrees. Other than that, the video is very good. It has very good tools to diagnose AC equipment. Blessings .

What do you match the piston to? The air handler or the condenser unit?

Great video thank you

Great video thanks

I had this problem today. I replaced a leaking coil with a cap tube replaced it with a coil with a piston instead. Installed a 0.068 piston for a 2.5 ton outdoor unit r22. And it was doing this sorta. its working decently had a 19/20 ish TD across the coil target superheat was 16 but It was maintaining 8 to 5 degrees of system superheat also added in a filter drier because system originally did not have one but I can't seem to get the super heat up. I suspect low airflow but its a super old system with old wood box style duct work. Even went through the house and made sure all the registers were open for proper airflow it really has me scratching my head.

Good video boss

I have a question. Based on my research, a 4 ton r410a unit typically calls for a .080 or .082. I installed a .082 and my pressures are a little high. According to Mr Cool, it calls for a .085 which again, based on my research would be too large. If I increase to a .085 I fear I will be flooding the compressor. I actually intended to install a .080 but nobody in town had one. What would you recommend?

Good video thank profesor

good stuff thank you

What’s the name of that alligator 120 v connector and how to connect vacuum pump?Thanks!

So with the coil flooding, would it be icing up? Or running hot?

Would the wrong piston cause the evaporator to freeze up?

Does the piston go in only one way? Because I’ve seen other videos where they put it inside the other way around. The side that has the washer went in first. Thank you!

That .057 orifice is the size for a 2 ton R410A system. Why would a 3 ton ADP coil come with a .057 in it? They messed up at the factory, or someone changed it. Should have been the pretty close piston right from the factory in the ADP coil.

Good video ty

Is this R-22?

Ok that orface looks odd the .065 should be larger than a .05~ correct? Thats very odd. Im dealing with a frank system It has a 2.5ton outdoor 2ton indoor and a .071 piston, what im seeing is it shoukd have. A .065 piston. The low side line freezes at the unit within two minutes as if there is hardly enough of a piston restricting, but it restrics enouge to cause a small difference between the high and low side 50psi difference. Low side well over 200psi, installer likely overcharged as it would not pump down the refrigerant all the way before the compressor tripped. So i will be weighing in a charge and dropping a .065 in its place to see how it does and adjust accordingly. But tell me a bit about that damn orface whats is up with that? I wouldnt think the orface would be smaller. For a larger unit, as the numbers apear to go up as the capacity goes up while the piston size also i creases, but you are saying it is smaller, very odd

I hate to tell you this, but you're wrong, a .057 metering piston is SMALLER than a .065 metering piston. As the number moves closer to .100 the bigger the orifice. As I've already said, what was wrong with this unit was that a too small piston was installed and it was grossly overcharged with refrigerant. I bet you recovered at least 2 pounds over nameplate. Also, in the TXV video you referenced the nameplate charge to determine the amount of charge to put in, which was 201 ozs and you said you'd added 16 ozs for the lineset. Goodman explicitly states that the charge that comes with the unit is for 15' of each line, so, theoretically, if you had a longer lineset you'd add refrigerant, if you had a shorter lineset you'd remove refrigerant, but you can't go by that. Factors such as the install crew didn't thoroughly read the, guess what, installation instructions might have led them to install the wrong size suction line. Many installers think that they should install a suction line that matches the size of the condenser suction line fitting. But, if they would have read the 'Recommended Interconnecting Tubing' Chart that comes with the condenser installation instructions(for Goodman condensers, which is the brand I sold) they would have, most of the time, installed the correctly sized suction line. You can't just use a rule of thumb to determine the charge of the unit. The correct way to do it is to measure the ACTUAL length of the suction line to determine if it's longer than 15'(or eye it if your good at that) and if it is, then you can use the nameplate charge as a starting point and then charge by superheat and sub-cooling whether iit's a fixed metering device(metering piston or cap tubes) or a TXV(you don't know if they installed the correct TXV or if something is wrong with the TXV like it's stuck in a fixed position or if its got a dead sensing bulb) always check both when checking the charge or re-charging. I'm sorry to say I learned this the hard way and it costed me time and money, OUCH! There are three metering piston installation issues I found that caused these systems to not properly cool: 1) as you found, they didn't install the correct metering piston, good find! 2) they installed it backwards 3) they didn't install one at all, or a combination of these. For example,, I did sometimes find that they had installed the wrong metering piston AND installed it backwards. I discovered that there was an Lennox company in my area that had been in business since 1964 that had a service manager that taught his crews and techs to install the metering piston backwards since he didn't read the instructions on the plastic bag that the metering piston came in. He also didn't tell them that they needed to install the metering piston that came with the condenser and not the one that came with the evaporator. So I knew when I got a call from someone that had a Lennox AC installed by them and they told me the issue was that, in really hot weather(above 93 degrees) it ran all the time and it never reached the temperature they set the thermostat at(most of the time it was a reasonable setting from 70-77, but sometimes they'd have it set to, say, 65, which was ridiculous) that it was a distinct possibility that it was a metering piston issue. Of course I checked the more common things first; well, I serviced the unit first to eliminate any of the common issues like a dirty air filter or coil or blower wheel or secondary heat exchanger fins, or a dirty condenser. Then, I checked the charge and about 85% of the time on these Lennox units that they installed it was a metering piston issue. Whew!! That was a long-winded comment. I hope I wasn't too critical and that it helps. Have a great weekend! if you have any ?s, comments or concerns, please let me know.

Why only 14 split?

so, it had an undersized piston and was way overcharged trying to make it work. go figure, they were probably too lazy to go in the attic and change it, so they just cobbled it and left.

I got that jokee😂🤣

👍

You talk about it definitely giving signs of a restriction. Then discovering it was an oversized piston and it was definitely flooding. It can flood and restrict at the same time?!

Why did you have to recover the refrigerant instead of just pumping the system down? Thanks for the video

14 split with correct orifice?

Does this cause inside coil to freeze up after 1 hour?

What piston size should I use in 4 ton 410 unit

You need to be educated more. A restriction would be low suction high superheat high subcooling low head. The head pressure low because the key factor is the outdoor fan. The refrigerant spends more time in the condensor in subcools and the liquid stacks. Liquid is more compact then expanded vapor so it takes up less space that's where the decrease In Head pressure. This system severely over charged.

Could have been overcharged?

Bro it is overcharge high sub cool low superheat most likely they charge it by beer can cold method

Almost seems like noncondensibles

Please go back and edit video and focus on piston stamp. It appears to read 057 but is clearly much larger orifice than the one you mention is 065. Most commenters are hung up on what you said rather than what their eyes are seeing. Most likely an incorrectly stamped piston. Uncommon but not super rare.

#57 piston or .057 piston is SMALLER than the one you trying to put in #65 or .065. You read the number on the old piston wrong. It's probably a .087 piston. Trying to get a glass or go see an eye doctor.

Not a good idea to pump through manifold

The lower the piston size the smaller the hole......u read wrong!!!