Help read these numbers...

Timco

I am just breaking into AC as we type. Got a call today about a frozen condenser and found a pound of dog hair welded to the inside of the coil. I cleaned the coil, cleaned the condenser and took these numbers



Outside air 93* 26%rh

Register reading after being on for 15 min 58.2* 56%rh

Suction temp 60.4*

system charge 60# even suction, 215# liquid side.



The house was getting cold when I left but I would like to learn what these numbers really tell me about the system's health. Of course I changed filter and left 5 behind.



Thanks in advance, Tim

Techman

WELCOME BROTHER

Hi Tim,Can't talk now ,over the weekend is looking good . I predict you will be back there again.What was the indoor temp &R.H.? Upon arrival & after running for 15 min.Is there a sight glass ?What was/is the EVAPORATOR coil [ you had a typeo there,bro, darn computers ]superheat? What is the condenser coil subcooling? How did you clean the EVAP coil?Did you clean the outdoor condenser coil also? I find they usually go hand in hand if the evap is dirty.The suction/head pressurers are low!What SEER equipment and type of metering device ?Is the indoor blower wheel clean? Gotta know! Gotta go!

Bob Bona_4

Hi Tim

I agree with Tech. You will probably be back.

Without knowing the condition of all the components I will still say the discharge temp is high, and the pressures are low. If I'm seeing more than 55 degrees at register, there is most likely more problems. 

The good news is that the high/low readings are proportionally acceptable. IF all other areas of the system check out, it is undercharged.

Timco

Sheeeeeeesh...

Where to start. Indoor temp was well into the 80's. Did not take readings since it was a hot kinda humid day had ac had been off for a day. Did not check superheat or supercool, need to know how. Do some systems need over 60# suction pressure? Used coil cleaner on both evap coil and condenser. Evap had a layer of dog hair that peeled off then I used coil cleaner followed by rinse, evap and condenser. Both were very dirty. Lots of books on how to install but I need to get into service and reading these numbers. Another tester for super heat / cool? Took register readings maybe 10 min after firing up after cleaning. Thanks a lot for the advise and info guys. I really want to dive into this and learn what the numbers actually mean. Metering devise is fixed not txv. Early 90's. Did not check seer. Blower wheel dusty, rinsed it well now clean. R22. Call was frozen condenser but they had it off and I did not see it. No leaks at visible braise joints found.

Timco

Discharge

System was on for 10-15 min when reg checked. Attributed high discharge temp to high 80's temp in the house. More info in reply above. EPA test next week but need to dive into this and learn what the numbers mean. Thank you.

Techman

On my mark,get ready,get set ,get go!!!

42 years of learning,studying,practicing,reparing,re-engineering and so forth, I have!Now ,just because the CUSTOMER called and said the condenser was frozen doesn't meen you have to tell us that the cond was frozen,since we all know it was the evap that was frozen over,and possibly/probabily the suction line out to and into the cond unit was frozen also.Go to the book store [heatinghelp] and check out the ACR heatpump books , Our very own Professor Silberstein has  some really good books[what a coincidence] ,! I have every one of them! IF IF IF all systems were installed properly then us service guys/gals would be meerly "parts changers" but that is not reality.So now enters you, me ,and many others who have to figure out what is really wrong by doing the right thing,WE HAVE TO KNOW HOW ALL OF THOSE MANY,MANY,MANY UNIT'S OUT THERE ARE SUPPOSED TO WORK PROPERLY IN THE FIRST PLACE,then we compare what is right to what is wrong and sometimes/most times we get it right.But,to me ,I get my professional rocks off by figuringout/straighting out many problems that were installed along with the equipment, and also by the uninformed repair/parts changers after the fact. Oh you had a question? Ho Ho Ho..The gauges are a Pressure/Temperature chart .Get yourself several  different P/T charts from several different supply houses by several different mfrgs.Now what I'm going to say next is Kinda/Sorta, Kinda/Sorta what Dan H. means by "it depends".Older units head pressurers ran from 95*f [181.8psig]condensing temp/on a 70-72*f day/with stabilized conditions and 125*f[277.9psig] condensing temp on a 95*f day also w/ stabilized conditions.The low side ran around 32*-36*f[58-63psig]on a 70-72 *day & on a 95*day it was 35-40*f [62- 68psig].Kinda/Sorta.Also,the  air temp at the supply register temp should be K/S 52-55*f on a 70-72* day & 55-60*f on a 95*f day. Kinda/Sorta.Get a pad just for #'s, pressurers,temps and test and record for yourself .

Timco

Thanks

I bought HVACR 1&2 and Modern refrigeration and ac from this site already, but reading only takes one soo far. Many, many subtleties come from watching learning and asking questions. In this case, customer is happy to have ac on and working but if charge is low I'd like go be able to properly diagnose that and charge for the fix. Same with any other deficiency. Since I never actually worked as or with any ac guys this is something I will need to learn the hard way by reading and asking.

Techman

Timco

o.k. hi 80's indoor,93 outdoor, startup pressurers should Kinda/Sorta be 75-85 psig low side /hi side 260-300 psig,yours were low . so probibily low on refrigerant.your low side was 60 psig =34* et,[evaporator temp].as the house temp drops so does the regrigerant temp.32*f is freezing,so a 5*f drop in indoor air temp and the e.t. will be k/s 28*f -30*f and the evap coil frosts over all over again

Timco

Thanks again

So where does the RH come into play with these numbers? Indoor, register, and outdoor. Is there a chart for startup vs running pressures or does the temp/press chart tell you everything? Is there a standard basic proceedure for starting and checking a system after it has thawed? What does the suction temp at the condenser tell you in relation to system charge?



Thanks, Tim

Techman

Tim

Kinda/Sorta there is no chart  for startup readings,there are plenty of charts for running conditions in various O.A. /I.A.temp /R.H.So does this normal system you're working on  have a moisture indicator/sightglass ?Or do you have an electronic sightglass? During "pulldown conditions" charge the system to 7/8 of a full sightglass for a few hours,then,when indoor temps are more stable top off the charge.K/S the R.H.is what it is;2/3-3/4of the system BTU's first goes for dehumidification during "pulldown" ,1/3-1/4 drops the temp , then @ "stableized conditions" the opposite ratio is true .Again ,the R.H. is what it is.Re-engineer the ENTIRE system and you can guesstimate the proper temp/R.H.Now if the room/section/house is uncomfortable start at the begining.After a freezeup your 1st and foremost check/test is the Pressure/Temp of the system compressor for damage,due to slugging liquid back to the comp and damageing the comp , and/or damage due to low/lack of comp oil due to frosting/due to dogs/due to low air flow/due to duct work/due to wrong grills and or registers.No damage,the customer is lucky! This time!Superheat at the comp DEPENDS on a lot of factors,Across the evap coil10-12*f, back at the comp 12 1/2 -20 -30* f Kinda/Sorta 

Timco

Making sense

This really is starting to make sense. How does a freeze up affect compressor oil? Can this be replaced? Check this by noise of compressor or temp? No sight glass on this system or any other system I have looked at. The sight glass will show what's happening? You say they make an electronic or clamp on version? Seems to be an important tool but if not required no one wants to spend the extra $15 to buy one. I can't tell you how much this is helping all the reading I've been doing come together. Very hard to learn from a book. I would love to return the favor you have been doing here. Very interesting info. Learning my vac pump and gauges and tank protocol is next! I really want to do this. My mom lives in CA and has had no AC for more than 20 years. It will be great to fix this for her as well as offer AC service. I am mostly steam and hot water but get enough calls every season to make this well worth the effort.

Techman

Let the fun begin!

Tim,check out.R.S.E.S. -its all educational,monthly magizine,.S.A.M. -dozens,dozens &dozens of articles on every subject /part in the system's H.V.A.C.R. ice, hyronics,steam.too Check out Copeland Comp.Co.for thier 3-day C.O.S.S. school & get their books and the "Application Engineer Builliten" binders.FABULOUS reading/studying.Check out N.A.T.E.& A.C.C.A. Supply houses around here[L.I. N.Y.] are the best for sponsoring all sorts of classes.                                                                                                                                                                                                                            

      Frosted evap .          Oil gets  left behind ,because  all  the liquid droplets ,from ,atomization  by the metering device [like an oil nozzle],donot boil off into a vapor . Therefore ,not as much vapor mass  as there should be. Once past the metering device,the oil get dragged back to the comp by the mass of the  vapor and  the speed of that mass.     

  Sight glass/Moisture indicator.You can see the fullness of the liquid line refrigerant charge  . AND the moisture indicator part is very important.                                                                                                                                                           

Bob Bona_4

Takes time

You will see over time and get a feel for where pressures should be weighed against typical system deficiencies. That's what Techman means by kinda sorta. You have to know when to fold 'em and call it the best it can be sometimes. 

Sight glasses are rare in residential. Just another tool to help steer the way. 

I was looking at UEI's latest superheat/subcool meter the other day and thinking how much simpler it has become to check that stuff than, say, only 15 years ago.

I've found because of some crazy system installations out there that sometimes you have to try to dial in the best average of high/low pressures and SH/SC sometimes has to take a back seat.

One of the handiest tools I have is Yellow Jacket's valve core changer that lets you change those cores "on the fly". The valve cores at the service ports are prone to leakage more than any other spot.

13 SEER and up, TXV's, 410A, is forcing guys to step up the game. Think modcon vs. dry base!

If you come across a freeze up, all you can do at the time is check filters and airflow. It can take HOURS to thaw, even when it looks like the exterior of the evap is clean, the innards can still be iced. You will never see accurate pressures until total thaw. Only thing you can do is tell client to keep ac off (pull disconnect to make sure), leave fan on, and prep them that they may see water on the floor. Give it at least 4 hrs, or return the next day... 

 

Timco

Electronic sight glass

Asked about this today at the supply house and they looked like I asked about a snipe. Any further details on this? Other terms for it?

Bob Bona_4

just the wording

"sight glass" would be a brazed in fitting for the liquid line. Typically commercial.

"electronic sight glass" is a strange term for me, possible a generic term for a digital sh/sc analyzer? 

Techman

Oh yes there is,

or used to be. My "Electronic Sight Glass" by TIF mn#4000A is two screw-on probes that puts out an ultrasonic signal  between the probes. The noise and/or lights indicate a full or not full liquid line,and it can detect suction line floodback.The 1st use I got out of the thing was on a  #2 fuel oil  line 20-25' above ground. Yup,there was oil vapor pockets up there .There aren't more than a hand full of units [res/comm]  that DO NOT have a Moisture Indicator/Sight Glass and a replaced filter/drier,that we work on. The M.I./S.G. help's me help them.The F/D helps them.We have replaced hundred's of F/D 's a second time because the M.I. was still wet/caution.And more than a handfull a 3rd time.Golf,anyone? Four!!!!!!!!!.Oh YES!!!!!!We use flare M.I./S.G. and F/D's on 5/8 liquid lines and smaller.We can change out the F/D easily,when needed.A little bit of labor,a little bit more of labor,a couple of flare nuts ,F/D/ &M.I./S.G.,maybe some copper,wrot coupling. There you go! And we sold a few minor parts.And I get to hone my flaring skills!