Luxaire A/C Charging

Matt Undy

I have been doing some research on refrigeration systems and have been troubleshooting a problem with my mom’s central air conditioning. I just want to make sure my thinking that it is a low charge is correct. Here is what I have observed. Unfortunately it is about 50 miles away so I can’t just check any info I do not have tonight. I would appreciate a more experienced opinion on if my reasoning is correct.

The system provides marginal cooling and it always has. I don’t have a heat loss calculation as of yet, but ballpark estimates seem to show the sizing is correct.

The return air to the furnace is 68 degrees.

The bottom inch or 2 of the evaporator was icing and measured 33 degrees. The top of the evaporator measured 68 degrees. The evaporator is an “A” type coil installed in an upflow furnace.

The ambient temperature is 73 degrees outdoor.

The liquid line temperature was 80 degrees soon after I started the condenser. It quickly climbed first to 87 degrees then settled around 89 degrees.

Evaporator and condenser look very clean, no dirt came out of condenser when flushed with hose. The condenser fan appears to be working correctly. There is a lot of airflow out of the furnace plenum. I got access to it through a collar for a bypass humidifier.

About 10 years ago the outlet temperature was around 60 degrees and the plenum was sweating so it is likely the evaporator was also icing back then.

Label inside condenser has table of paired evaporators and charge to add if any. System was pre-charged self piercing flare fitting lineset type. Table says when paired with installed evaporator to add 10 oz. of refrigerant. The installer never attached a gauge manifold to the schrader service valves much less added 10 oz. of Freon-22. I suppose the evaporator could have been charged with 10 oz. but there may be a combination where that would result in an overcharge so it probably wasn’t. See below about identifying the system, if anyone knows how York was doing this back in the 80’s I would appreciate the information.

There are no traces of oil anywhere on the system including inside the plenum and condenser.

The lineset used is 25’ and self piercing as stated above. Were these sets pre charged with the needed charge for their length?

(notice how the trademark Freon disappeared when they implemented the sales restriction? Does DuPont even manufacture r-22 anymore? Seems like it would be too much of a potential liability for that large a corporation. But I really need an answer to my charging question.).

The system: It is a luxaire installed about 1986. The rating palte on the condenser has completely bleached out in the sun. It has a capacity of 2.5 tons and has a Copeland SR06-0225-PFV compressor. Its rating plate indicated an EER of about 6 when rating plate capacity was divided by rating plate volts x amps. It is probably higher since it is rated 208/240V. It has a dark brown cabinet and the fan is mounted in a sloping hinged cover with the condenser being flat and comprising the back of the sloped front box. Since it is in Michigan it doesn’t get all the much use and even though it is nearly 20 years old it should still have a lot of life left in it. It is paired with evaporator GHUA37AA. I e-mailed York with basically this information and they replied asking for what city I was in then never got back to me. Seems to me if they made a rating plate that can’t stand up to being outside its their problem to identify the equipment…

Can anyone identify this unit? Does anyone have the specific charging instructions for it or will I have to just use the superheat method and take a guess on the ranges in superheat charts? I am strongly considering weighing in 10oz. and seeing where that gets me. It must be somewhere around ¼ the total charge.

Thanks for any advice you can give me. I suspect that I would really have to search for a technician that would give the problem as much thought as I already have. I won’t say anything about the otherwise fairly competent technician who filled his leaking truck tire from the r-22 cylinder or who used the temperature / gauge chart instead of the approach method when the temp/pressure chart clearly says that it is not to be used for charging…

Matt

Dale

do mom a favor

The cost of a brand new 10 seer ac is pretty low. Especially a janitol or whatever is the value brand at the local supply house. Just put in a new one, the old one is almost 20 years old and the electricity cost makes the change worthwhile. If you really want someone to spend labor hours on this, With ice ( not frost) on the evap I would guess an indoor air flow problem, maybe a summer/winter bypass in the winter setting. I guess I would check the air flow first. Then, since you don't know what the status is I would recover, evac and weigh in a charge and trim with superheat. I would also cut out the threaded lineset when I had the charge out, replace or add a filter dryer and solder everything. The treaded linesets leak in cold weather. Too me the labor isn't worth it on a unit this old.

Steve Minnich_1

WOAH Matt

Thats a whole lot of questions and information there.

I trust you're EPA certified to be working with refrigerants. The problem is probably easily solved with a service call.

Its most likely a restriction in air flow or perhaps as you suggested, a freon problem.

You should be getting roughly a 20 deg. delta T across your evaporator coil if properly charged, and everything else is CLEAN and working as it should. "Weighing in" the charge now would be useless, unless you started from scratch without any freon in the system. It should be charged according to superheat, the manufacturer's rec., or some other reliable method based on the unit, outdoor temp., and indoor temp.

Steve

Steve Minnich_1

But,

I also agree with Dale. If the unit is twenty years old, it is probably inefficient and not worth sinking any more money, time, etc. into it.

I'd go at least 12 SEER though.

Steve

Matt Undy

Leaking fittings

Thanks for the information. I have some more information and questions which somone on the clock with a guage set and tank of freon handy might not ponder to the length I have.

The next paragraph is long and winding but basically i just want to know if it can leak in the winter without leaving oil.

Ahh, I see about the fittings (I also see about the system but the payback in Michigan's climate would be somewhere in the decade range.) If the fitting leaks in the winter when the system is not runing, would there be no oil in the refigerant to leave a trace? Do tracer dyes mix with the gasceous refrigerant to leave a trace? It seems this would be very hard to actualy see leaking. I've seen systems with this type of lineset were 20 or so years old 15 or so years ago which didn't seem to leak refigerant.(I can believe it could be leaking, i'm just not convinced that it is leaking. I'd be inclined to charge it, see how much it takes, then see if its low next year for the $5 or so before condeming it since it is clearly a system under 50# and isn't at all clear that it is leaking vs improper installation.)

The SEER of the system is probably near 10, the EER is much lower. Without specs weighing in a charge isn't an option since the printing washed off the ratings plate years ago.

I suppose you could call the frozen water on the bottom inch of the surface of the evaporator frost. It melts in a few minutes if you pul the disconnect on the condenser. There seems to be quite a lot of indoor airflow and the top of the evaporator never gets cold, just the bottom inch or so which is where the refigerant enters from the liquid line and orfice. When i've seen window units ice from clogged filters the whole evaproator iced, not just the section where the refigerant entered. If its an airflow problem it would be from an undersized return. I'm very inclined to think that there is not an airflow problem, the ac airflow is noticabley much higher than the heating flow. I'm not questioning your advice, I'm just trying to give some more information as to why I think its a charge issue VS airflow.

I forgot to mention the gugrling noise near the orfice which has always been there, lliek a stream of liquid and gas is flowing through it. It is a broken type of noise, it isn't the constant fluid flowing noise of most systems.

If I were to recover the charge and open the system, I would repalce the orfice with a TXV, replace the filter/dryer, install service valves so the charge can be pumped down if the system needs to be opened again and I guess now replace the flare(are they flare or are they something proprietery to the industry) fittings on the outdoor side with brazed fitings and tubing. I would also remove the 4' or so of etxra lineset coiled up on the ceiling in the basement.

The most labor intensive part of either replacement or repair is recovering the charge.

Thanks

Matt

p.s. I can see I talk too much, sorry about the convolution.

Steve Minnich_1

Matt

Yes, you can have a refrigerant leak without an oil trace.

Testing air flow by "feel" doesn't prove anything. You should at least use a digital thermometer with the system running to see what the temp. drop across coil is.

Gurgling noise is not unusual, especially after shutting system down.

I live in the NW suburbs of Chicago. Like most of the guys here I "mess around" with both my heating and cooling systems every now and then. I've changed my AC system 4 times in the last twenty years. I can show you all kinds of payback formulas with which I'm sure you're familiar, but nothing beats first hand experience. Years ago, when I took out the 8 SEER system and installed a 12 SEER unit, our summer electrical bills were cut by more than 50%. That was enough payback for me.

I would suggest calling a reputable contractor in your mom's area, ask that they diagnose the problem, and then make recommendations on what to do next. You're then free to get a couple of quotes on the repair or replacement.

Also, for what its worth, recovering freon is not that big a deal. Replacing a line set (freon line) on an older home can be an absolute bear sometimes, and the sheetmetal revisions to replace an A-coil can also be very involved-if done properly.

Good Luck Buddy,

Steve Minnich, Radiant Comfort Systems

Kevinj

Does this have a black rubber covered suction line ????

Tony_8

suction pressure ?

It's relevant and important to know. Temp of liquid line is meaningless w/o knowing the pressure also.

Don't judge all the local AC contractors by what a "hurrier" did or did not do 20 years ago. Call the BBB for names. Do it right, do it once.

Dale

Thread connectors

The o rings in the connectors do leak out over the winter and leave no oil, there's pressure on the system since the evap is at heating outlet temp so all the refirgerant is driven outside. The cheap fix try is to cut out the threaded fittings and solder pipe in, I would only pay for a filter dryer. When ever I have lost charge over winter and no findable leaks with a sensor and then 150psi of dry nitrogen I just cut out the threaded fittings, has always worked so far. The system is designed for a fixed orifice, I would check it for blockage after recovering and leave it unless you have a lot of TXV's free to mess with. I would weigh in liquid about 3 pounds, after pulling a vacuum, then use a chart for fixed orifices to adjust the charge ( Carrier makes a nice slide rule one that works with any other brand I've tried it on ) and look for about 10 degrees superheat when it 85 outside.

Matt Undy

What do you mean by balck rubber? Its not rubber per se but it is convered in black foam of probbaly some sort of plastic.

Matt

Jeff Lawrence_24

Thinking.

If the bottom of the coil is frosted and the top is considerably warmer, that makes me think about a metering device problem.

On your next trip out, can you get the superheat reading, subcooling reading, and delta T across the evap and condenser? That will hepl with further diagnosis.

Jeff


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don_38

Im

> It's relevant and important to know. Temp of

> liquid line is meaningless w/o knowing the

> pressure also.

>

> Don't judge all the local AC

> contractors by what a "hurrier" did or did not do

> 20 years ago. Call the BBB for names. Do it

> right, do it once.

don_38

I

> It's relevant and important to know. Temp of

> liquid line is meaningless w/o knowing the

> pressure also.

>

> Don't judge all the local AC

> contractors by what a "hurrier" did or did not do

> 20 years ago. Call the BBB for names. Do it

> right, do it once.

don_38

I

agree with jeff need to know what the refrigerent is doing inside the coils.with the subcool temp you gave it sure sound like you got a good colum of liquid headed to the evaporator.

If this is a orfice system,you need to check the superheat
this will tell you what the refrigerent is doing inside the evaporator coil.If you are flooding or starving coil.

Coil made look clean,but if mom has not had them clean in awhile,I'll bet they are dirty and poor airflow is the reason for it freezing up.

We need more info as mention above.

Jeff Lawrence_24

DAVID!!!

Long time, no hear!

How've you been?

Jeff

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jim lockard

I am with the group

Plus /minus 20 degrees across the coil, 10 to 15 degrees super heat and let it work. As for the wrench on line sets no thank you done too many they leak. You can not prove them tight til you get a call 2 weeks after you have done the job and the house is warm. Then you pump the system up find the leak,fix the leak, pump down and recharge.
Those A/C techs that scale in R-22 are few and far between.
For my money I would replace the system. Best Wishes J. Lockard

Mark Hunt

Tony hits a point here


also, have you checked to make sure that the outdoor unit is clean?

I've seen this happen when the coil on the OD unit gets blocked.

Or it might just be time to retire the unit.

Mark H

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Mitch_4

carrier slide rule

I would ignore that 10° of superheat thing. Using the Carrier slide rule means measuring the wet bulb inside. I have had superheat requirements of 24° depending on the humidity and it can get very humid where I am at.

That being said. The slide rule works great, and I use it all the time. It is the most accurate method. It is also a simple way to check your charge.

The quick connect you have will leak and not show oil. I cut em out and replace them all the time if I find a leaker. Otherwise leave well enough alone.

Did you see the bottom of the coil? most humidifiers are connected above the 'A' coil. you need to see the bottom.

What are your running temps and pressures? high and low side are needed to properly diagnose your problem.

If you thin you have a 10 SEER at almost 20 years old (1986 you said) then I would be amazed. More likely 6-7 if your are lucky. you are correct about the EER though.

a 12 SEER replacement would be the way to go. Be smart and do it right. That unit owes you nothing.

MHO

Mike

Matt Undy

Update

Ok, i went up ther on saturday with a gauge set, tehrmometer and superheat chart. Here were the initial conditions:

Ambient outdoor: 75 degrees
Supply air: 64 degrees
Return air: 68 degrees
Suction: 37 PSIG, 94 degrees
Discharge: 130 PSIG

This seemd to be an obvious undercharge so I added refrigerant to get these conditions:

Ambient outdoor: 78-82 degrees
Suction: 51 degrees, 65 PSIG
Liquid: 89 degrees, 215 PSIG
Air supply: 51 degrees
Air return: 66 degrees

I added around a pound of refrigerant though my scale wasn't precise enough to measure closely.

Unfortunately the superheat chart I had at the time was for 80 degrees and I didn't yet understand that the wet bulb tempurature of the indoor air was the important part. I first charged to about 20 degrees of superheat but the subcooling was only 10 degrees. I added a bit more to brign the subcooling up to about 15 degrees. I have since found the carrier chart and I believe I am in the ballpark. The conditions of the day were a boundary condtion and the return air temp was so low because it is a retrofit of forced air heat with all supply and return on the floor. The house was at about 73 degrees indoor. It wasn't a particularly humid day for Michigan so my guess is that the RH is near 70-80% and this brings me in a slight undercharge on the carrier chart, the superheat is just a littel higher than the chart but it gives +-5 degress and I'm in that tollerence.

We'll have to see how it performs when its 90 out and my mom's baking and if its low again next spring.

Thanks for all the help.

Matt

jim lockard

Looks like

You are getting there Matt. Delta T at 15 degrees could be a little higher I like to see 17 to 20. May want to add just a tad more R-22 to bring that suction temp down or pressure up 50 degree pipe over 70 psi suction should put you close. A quick check on you high side gauge is to be about 30 degrees above return air or in your case about 95 degrees +/- 225 psi red gauge. Keep fine tuning it your getting close. Mom will be chillin soon. Best Wishes J.Lockard

Matt Undy

Charging Chart

Here is carrier's chart for r-22:

http://www.blueguitar.org/new/misc/hvac/bdp_sh.pdf

Could the low delta T be because of the low return temp? More heat will move from 80 degree air to a 40 degree coil than from 66 degree air correct? I had a superheat chart for 80 dry/67 wet indoor air and I had to guess based on similar indoor outdoor differnatial on that chart.


I forgot to mention, the gurgling in the liquid line is intermitent now, not constant. I was considering adding a bit more charge to get rid of that but I didn't want to overdo it since I don't have recovery equipment (I suppose a section of large diameter steel pipe with a cap and a few fitings would work for my needs, or make a pipe bomb...).

I'll make a wick and print out the Carrier chart and fine tune it sometime soon. I think it is already colder than it ever was, I think the liquid line had always gurgled and the label in the condenser was quite clear about the installed combination needing more charge which was never added...

BTW, I could be convinced it has an SEER of around 8. The point is that she keeps the house quite warm, its about a 1000 ft^2 house and halving the cooling bill woudl still take a long time to pay back. A more cost effective method would be to put the A/C on an interruptible service. She has electric stove and dryer and a lot of lights on most of the time. The electricity used by the a/c is all in the utilitie's higher rate band so she'd save about 1/3 by spending the $50 or so for the seperate service equipment, permit, and loop of thermostat wire.

Thanks

Matt

Matt Undy

See Mad Dog's post of about a month ago about trades people. I think the only trades person I have ever hired that has really done better than I could have given some time and research was the guy that cleaned my sewer(and kept telling me how hot the previous owner's daugters were, which i didn't particularly care to hear about but he really knew what he was doing with the sewer).

I feel that unless special expensive tools are involved I can resarech it and do it correctly myself easier than researching somone that knows what they are doing and cares enough to do it right on your job. Think about what this would ential for charging an a/c system? You would need to convince them to let you talk to the tech, have them call back, know how it should be done, and ask them questions about superheat calculations and weight methods. Given that its only hot about 3 months out of the year up here there are ging to be very few hvac techs with a thorough understanding of refrigeration. I'd probably be better off with somone that works on commercial and industrial process and food storage refrigeration.

Most people will only complain if there is grossly inadeqaute cooling, in fact my mom wasn't even complaining. If the charge is just off a bit and its jsut using more elecricicty most people wouldn't get it fixed or ever link it to an incompetent tech.

I've already told you about the guy who installed my mom's system not adding the charge per the label...not that he owned a charging scale anyhow. The guy who isntalled my system filled the tire on his truck with r-22 becuase it was low but both of them did excellent sheetmetal work. There's the tire shop doing suspension work that didn't even own a torque wrench who also screwed up part of the spindle becuase the caliper pins were frozen and they tried to wedge new brake pads in anyhow. The Builders Square contractor that attempted to install a water heater in my mom's house that bent the hot and cold water and gas piping such that it was all crossing over eachother instead of ofsetting the risers to meet up. I'm sure the 2 HVAC contractors mentioned were in good standing with the BBB.

Even references usually aren't that good, usually the person givng the reference doesn't know enough to know if the job was done such that it will last.

Matt

Tony_8

So why are you here ?

You obviously think quite highly of your abilities to do everything as well or better than anyone else. If you don't have a recovery machine and are not EPA certified, you're breaking the law adjusting the charge on Mom's AC. Did you ever stop to think that maybe a competent tradesman won't tolerate your BS of telling him his job ? Or quizzing him about how he's going to do it before he even comes out ? Competent tradesmen in ANY field can spot a PITA a mile away and usually defer the work to someone else. I used to enjoy quietly proving my capabilities to know-it-alls, now I enjoy watching them suffer incompetence.

Matt Undy

Mainly to see if anyone has the Luxaire factory charging procedure for that particular model(though i'm now convinced that superheat is at least as accurate).

Matt

jim lockard

He is here

Tony because he will not get off his wallet.

Kal Row

i hate to rain on your party...but

EPA types are cooks - AL..OF..THEM!!! - it's government gone astray

they can hit you with a 27000$ fine for what you have already admimited to doing - so be carefull

having said that, if you replace the system - make sure to get a scroll compressor on the new condenesing unit - go for the 12+seer - (my personal favorite is RHEEM) make sure to retrofit your a-coil with an expansion vlave

Ken D.

Luxaire

In my experience,superheat and subcooling are the best ways to go in general. Different manufacturers may have specific procedures, but in the end it all comes down to superheat and subcool. The general test procedure is, but not limited to the following; Test to determine weather you have the proper CFM across the ID and OD coils, check ALL pressures and temperatures, amp out motors and compressor, check all air handling parts for cleanliness, check to determine if the system was designed properly in the first place. A problem in any of these areas can affect performance in a big way. Using and acting on this basic information, any system can be troubleshot. How much it entails and costs is the problem each owner of the equipment must weigh for themselves. As far as the competency of various technicians, in every profession the are hacks and professionals. Unfortunately there are a lot more of the former than the latter. It mostly comes down to cost. People will always go the way of the cheapest price and wonder why they did not get a first class job when the never intended to pay for a first class job. A top mechanic, just as a top engineer or doctor or lawyer commands a price. I have heard so many times "Joe is the best mechanic, but he charges more that I will pay". So Mr.Home or Business owner gets Harry to do it when Harry can't carry Joe's toolbox. Harry leaves with what little money he made, and Mr Owner wonders why the system does not work. The Top guys don't make what they do to rip off the customers. The Top guys have countless amounts of their own money and time attending schools and seminars as well as reading and researching the entire spectrum of their trade. They purchase the majority of their own tools. Tools must be replaced when they become obsolete, lost stolen or broken. It is never ending. The companies that employ top men generally have the latest trucks, spcialized equipment, factory training, certifications, licenses and support personnel, not to mention liability insurance. The US has bcome a third world nation in it's thinking of quality,price and value.
So next time you call a tradesman that charges the least, think of the hidden costs of aggravation, lack of abilities lack of professionalism, lack of liability insurance, lack of training, lack of a truck that can make it down the street, Etc., etc. There is no such thing as a free lunch. Ask Frank Blau

Tony_8

I figured as much

Look at his e-mail address. Looks like maybe he's an engineer, or even an engineering professor. That's why he wants the chart on paper, no test equipment required (or experience, training, etc.) Some of my best friends are engineers, none of them are like this. The engineers I know who are like this have Rube Goldberg houses

jim lockard

School teacher with nothing to do this summer

Matt charging up an A/C unit is not as hard as you are making it. Perhaps mom should just call someone to fix her A/C and thats it. Best Wishes J.Lockard

Tony_8

never said it was hard

I took exception to his statements about tradesmen and having never hired a competent one, as if there aren't any. He paints with a broad brush, and if you're in the northern part of the country, he got some on you too.

Matt Undy

It isn't that hard perhaps it looks hard when described in a bit too much detail. Thanks for you help. 2n'd attempt for somone who has never doneit before isn't bad. You have to remeber this was designed at a time when a can tapper and a hose were common and the very lucky had a $.50 guage on the low side in that hose. Energey efficency also wasn't a concern in the design. I've mostly seen this unit in subdivisions built in the 70's. I'm sure I'm already clsoer than the manufacturere had hoped.

Matt

Matt Undy

I'm sorry if I offended the people here, I wasn't refering to you, I was refering to what seems to be the other 90% of the trades that for whatever reasons don't know or don't care about the quality of thier work. I said that one i've worked with was competent though I never said (or intended to say) that was the only one. I'll leave it at that because every sentence I write opens up the opportunity for a paragraph of flaming and my intent was to say that I didn't mean everyone.

Matt

Tony_8

accepted

More than just wetheads here as you can see. I do a lot of air-side work also, and am well North of "the line". Being the perfectionist that I am, I sometimes am too sensitive and take offense at "broad strokes". In the future, when describing situations, try to leave out anecdotes of incompetence experienced. Little, if any, chance of offending anyone that way.
Enjoy the AC when you visit Mom this Summer, and I bet her electric bill for cooling will now drop as well.

Tony

jim lockard

Sorry Tony and Matt

Proud to be south of the line. Best Wishes J.Lockard