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View Full Version : American standard needing more refer then the factory charge.



samgevas
07-14-2016, 04:41 PM
I recently moved from the north San Francisco Bay Area to Phoenix. The temps are a lot higher and so are the SEER ratings of most of the systems I'm seeing. Keep this in mind.

I have noticed lately that newer (0-4 year old) 16 SEER+ trane/AS split system are taking 2-2.5 lbs over their factory charge to satisfy the required subcool, regardless of lineset length.

Is this a thing with newer high efficiency tranes or is the new climate playing tricks on me? It's common for me to be charging with an indoor DB/WB of 90+/65 and outdoor temps well over 105.

I'm just used to the factory charge being good as long as the line set is under 40'.




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BNME8EZ
07-14-2016, 06:35 PM
Trane/AmStd are charged for 15' line sets, it use to be longer. i don't think that would be enough for 2+ lb though. I assume these are 410 systems. I have noticed that you have to take your time charging these especially on hot startups. If there is an EEV involved it is really important as they react slower.

hedrash
07-14-2016, 07:13 PM
Read the installation instructions. A LOT of 410A units are shipped low of charge due to its ability to get to hi pressures while shipping. I had the exact opposite issue with McQuay ( now Daikin) water sourced heat pumps. They'd come over charged & routinely go off on hi head lockout. Needed to remove 12oz (average) to get them running right. Called their tech support & they issued a service bulletin after having to do this on 20+ units in one building.

We can control fire & ice.....

beenthere
07-14-2016, 10:14 PM
At 95 indoor and 105 outdoor. You won't get factory listed SC on a 15' line set with factory charge, until the indoor temp drops.

hedrash
07-14-2016, 10:43 PM
I recently moved from the north San Francisco Bay Area to Phoenix. The temps are a lot higher and so are the SEER ratings of most of the systems I'm seeing. Keep this in mind.

I have noticed lately that newer (0-4 year old) 16 SEER+ trane/AS split system are taking 2-2.5 lbs over their factory charge to satisfy the required subcool, regardless of lineset length.

Is this a thing with newer high efficiency tranes or is the new climate playing tricks on me? It's common for me to be charging with an indoor DB/WB of 90+/65 and outdoor temps well over 105.

I'm just used to the factory charge being good as long as the line set is under 40'.




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Keep in mind, the higher the Seer unit, the lower the Subcooling will be. The head pressure will be significantly lower on higher SEER units, so less subcooling. The 8 seer units needed like 30 subcooling, 10 SEER units needed like 15, 12 SEER 10-12 & 13 SEER need 8-10 cooling. Now when we get up into 16+ seer, 4 Subcooling suffices. A lot of this has to do with the pressure through the line set. Increased pressure increased friction & friction means PSIG loss which could result in flashing prematurely. If you notice, 18000 btu & 24000 btu a/c unit's have 3/8" liquid line sets & 3/4" or 7/8" suction lines to decrease friction and pressure drop. Ideally you should get the system running until the inside DB & WB is within the charging chart that comes with most new equipment. Yes, it's a bummer, but be glad you're in Phoenix & not Florida with 89% indoor RH, waiting for the house to dehumidify before it starts to cools off. Also, confirm your air distribution, most techs ignore this & it drives me nuts. Air Distribution is THE MOST IMPORTANT ASPECT of HVAC. In residential you do not want more than 700-900fpm of supply Air in the main trunk, reducing the plenum as needed (ALWAYS BEFORE YOU SUBTRACT 50% OF YOUR TOTAL AIRFLOW. I.E. If you have 2000 cfm & remove 1000cfm for branch ducts, you must reduce your main Supply plenum. If you take 500 cfm off of 2000, it's perfectly ok to rescue the plenum, just don't exceed 50% of total air volume) to maintain proper velocity and volume. Velocity is significantly more important than static when it comes to duct sizing. 300FPM for filter grilles, MAX, 150 FPM for electronic Air cleaners, etc. You've got to know you're moving the correct airflow otherwise you might as well just start flipping burgers at In & Out. If you ever need any advice of help regarding Air Distribution, please contact me, I'm more than happy to help.


We can control fire & ice.....

TechmanTerry
07-15-2016, 06:48 PM
I LOVE THE LEARNING PART!

hedrash, got a Q here.! A 14SEER,r 410,3t, evap 30' up there,50' lineset, has a minimum REQUIRED SC ? So now I upgrade the system to that 4* SC systems and all is good? IDK!

hedrash
07-15-2016, 06:52 PM
I LOVE THE LEARNING PART!

hedrash, got a Q here.! A 14SEER,r 410,3t, evap 30' up there,50' lineset, has a minimum REQUIRED SC ? So now I upgrade the system to that 4* SC systems and all is good? IDK!
Just go by what the manufacturer specifies in their charging tables. Most of the higher seer units have variable or staging compressors, so if you slow the compressor down the refrigerant "backs up" in the condenser, which is fine because the TXV or EEV regulates the refrigerant. At full load the unit only needs the 4 Subcooling. Also linesets are important. I see a lot of guys used the existing 7/8" line when the unit has a 1-1/8" suction valve. Gotta upgrade the lineset as well

We can control fire & ice.....

beenthere
07-15-2016, 08:09 PM
A line set that rises 30' to the evap, will lose a min of 3 of SC. If the attic is real hot, you can lose another 2. You could be flashing before the TXV and losing capacity.

hedrash
07-15-2016, 08:15 PM
A line set that rises 30' to the evap, will lose a min of 3 of SC. If the attic is real hot, you can lose another 2. You could be flashing before the TXV and losing capacity.
True, absolutely correct beenthere, which is why you need to read the manuals. A lot of these higher seer units also are starting to insulate the liquid lines as well. Supposedly it's a .556psig/ft rise, so in 30 ft you lose 16.7psig (just over 3 loss in saturation temp) which I think would be enough to cause flashing in only 4 subcooled R-410A. That's where you go back to the installation manual. That's not even accounting for the friction loss of elbows, line length frictional loss, valves, filter driers, etc. If I'm not mistaken (and I have been more times than I can remember) the 4 Subcooling should be at the TXV.

We can control fire & ice.....

samgevas
07-15-2016, 08:28 PM
Some of the system I'm referring to have EEVs but most have normal TXVs.
The manufacture charging charts on these all say indoor temps between 70-95 and outdoor of 80-120, so I assume that the required subcool is still relevant, but I'm not 100%.

I think I'm pretty good at letting the system stabilize as I charge. Most of these systems have tranes charge assist port/control and when they do I use it. I would never rely on it, but it's a free second pressure/temp reading to back up my own so I figure why not.

Air flow in residential is always a crapshoot. If I can get 350-400 cfm per ton I'm happy. I don't see a lot of systems where the problem is too much airflow.


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hedrash
07-15-2016, 08:43 PM
Some of the system I'm referring to have EEVs but most have normal TXVs.
The manufacture charging charts on these all say indoor temps between 70-95 and outdoor of 80-120, so I assume that the required subcool is still relevant, but I'm not 100%.

I think I'm pretty good at letting the system stabilize as I charge. Most of these systems have tranes charge assist port/control and when they do I use it. I would never rely on it, but it's a free second pressure/temp reading to back up my own so I figure why not.

Air flow in residential is always a crapshoot. If I can get 350-400 cfm per ton I'm happy. I don't see a lot of systems where the problem is too much airflow.


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Yeah, the airflow changes with higher SEER units I forget the numbers offhand.

We can control fire & ice.....

hedrash
07-15-2016, 08:52 PM
Some of the system I'm referring to have EEVs but most have normal TXVs.
The manufacture charging charts on these all say indoor temps between 70-95 and outdoor of 80-120, so I assume that the required subcool is still relevant, but I'm not 100%.

I think I'm pretty good at letting the system stabilize as I charge. Most of these systems have tranes charge assist port/control and when they do I use it. I would never rely on it, but it's a free second pressure/temp reading to back up my own so I figure why not.

Air flow in residential is always a crapshoot. If I can get 350-400 cfm per ton I'm happy. I don't see a lot of systems where the problem is too much airflow.


Sent from my iPhone using Tapatalk
Air distribution is becoming more and more important than ever and most techs or installers usually aim for .08 static or .1 static on their ductulator instead of relying on what should be used, fpm or velocity. Just because your unit's fan assembly may be rated for .5"wc static, doesn't mean that's a good thing. Techs & Installers really need to go by the guidelines setup by velocity. 600fpm in return trunks, 700-900fpm in Supply trunks & 600fpm in branch ducts. Proper Air distribution is PARAMOUNT to properly charging a system. People will throw an electronic Air cleaner rated for 150-200fpm in a stream of air running at 650fpm, the cleaner becomes relatively useless. Same goes for filter grilles, etc. A filter grill should have 200-300fpm max going through it. Otherwise the filters and obstruction & drops airflow. I tell everyone I know to go on the NATE website & download the air distribution study guide for $60. You can split it between ten of your fellow techs & it's going to open your eyes big time.

We can control fire & ice.....

BBeerme
07-15-2016, 09:05 PM
Even though I'm pretty darn good at what I do, that sounds like a great idea.

And since I'm a dinosaur, wouldn't hurt to get a bit more edumacation.



Air distribution is becoming more and more important than ever and most techs or installers usually aim for .08 static or .1 static on their ductulator instead of relying on what should be used, fpm or velocity. Just because your unit's fan assembly may be rated for .5"wc static, doesn't mean that's a good thing. Techs & Installers really need to go by the guidelines setup by velocity. 600fpm in return trunks, 700-900fpm in Supply trunks & 600fpm in branch ducts. Proper Air distribution is PARAMOUNT to properly charging a system. People will throw an electronic Air cleaner rated for 150-200fpm in a stream of air running at 650fpm, the cleaner becomes relatively useless. Same goes for filter grilles, etc. A filter grill should have 200-300fpm max going through it. Otherwise the filters and obstruction & drops airflow. I tell everyone I know to go on the NATE website & download the air distribution study guide for $60. You can split it between ten of your fellow techs & it's going to open your eyes big time.

We can control fire & ice.....

hedrash
07-15-2016, 09:22 PM
Even though I'm pretty darn good at what I do, that sounds like a great idea.

And since I'm a dinosaur, wouldn't hurt to get a bit more edumacation.
It's a .pdf file so it's easily shared & just print it out & put into a binder. All of their study guides are like $60, they contain a lot of information

We can control fire & ice.....

BBeerme
07-15-2016, 09:24 PM
You got a link?



It's a .pdf file so it's easily shared & just print it out & put into a binder. All of their study guides are like $60, they contain a lot of information

We can control fire & ice.....

hedrash
07-15-2016, 09:42 PM
You got a link?
Actually I do & the guides are $40 not $60. https://store.natex.org/training

We can control fire & ice.....

catmanacman
07-16-2016, 11:40 AM
The outdoor units have enough refrigerant for 15 ft line set and the smallest matched coil
when you add a big ass coil to the mix it takes more refrigerant

TechmanTerry
07-16-2016, 10:05 PM
If and when I get involved in an install,I will do the math/numbers your way and have a looksee.

I've been Ductwork trained by Carrier, Fedders,RSES.And by a few others! I have NEVER done an Upfront Load Estimate,I have NEVER WON a bid/estimate based on BidSpec. BUT, BUT ,I have NEVER been slow since 79'(except by choice,by taking the phone off the hook) because I un-jumble the mistakes left by others,so I use ALL of the Ductwork parameters and using the"velocity only" just doesn't fit into my Service/Repair/StraightenOut/Do/Done/Smile back at smiling customer/Get paid kinda Business.. Now, in a Wonderful Neighborhood World,I will have to go crunch some numbers. But it is good thinking!