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View Full Version : Whath to do with a logged coil evaporator / condenser?







AlexLPD
23-02-2017, 04:23 AM
Hi to you all.

This is a new problem to me.

I will describe the system;
20TR condensr unit, two scroll compresor York brand.
20TR evaporator unit York.
220V , R22.
The condenser and evaporator are no far apart, a 10-25feet as much,in the same floor level.

Im the third tech, on the site, the past two, changue both compressors and they burned dow again.

So, long story short...they calll me to put to service two units describe as above... I didnt like much the scroll option, because this AC are in heavy loads and they usually work more than 18Hr at day (not on a single row)

We changue the tandem compressor othe the unit 3... for a mesa piston compresor of 20TR for R22... we changue the TXV for a brand new danfoss... It work like a champ...

We do the same thing on the number 2 unit... changue the tandem scroll compressor for a single coppeland discuss compressor.
So.. changue the TXV same model as before, alll welding as made with N2 purgue I personally inspect all the weldings to make sure they are clean.

We changue the old filter for a replaceable core of danfoss rated for 20TR, a core, a sigth glass (wasnt before).
High pressure N2 to make sure we didnt have any loss
I personally like to make a triple evacuattion process on this systems, so we did it, and the next day, add some refrigerant and ohhhh boy... things was awful ...

High pressure side 315 PSI
Low Pressure Side 95 PSI
Superheating -F (Did not take sorry)
Subcooling -F
Compressor amps (51.6A /52)

The sigth glass at this point it show not bubbles, but like foam fluid passing... So We leave it for the day..
The nex day... we remove some refrigerant the systems dont perform well... And for half of day we were seeking anything.
Until the sigthglass of the compressor got my attention...i cant see nothing, so a litte pinch to the contactor compressor show me, in deed the compresor carter was at the top of is capacity.

We remove the refrigerant, put a service hose and a ball valve at the end of the gear oil pum, and we pinch the contactor, at the first time we remove about 1.5L of oil (quite dirty, so I only assume this oil was in the system long before)

So, I think, we can back on duty... evac the system, add the refrigerant slowlly and this time, seems quite better:

High pressure side 290 PSI
Low Pressure Side 86 PSI
Superheating 28F
Subcooling 20F
Compressor amps (47.9A /52)
Ambient temp: 89.6F - 32C
Condenser Air temp: 114.8 - 46C

Still one big problem remains... and this is; the unit is not cooling properly;

Evap Air Intake; 86F 30C
Evap Air Dischargue; 71.6F 22C

So... we leave run for a while and after the compressor sigth glass was full again, stop the unit, recall the refrigerant, and remove some more oil...

It began to improve;

High pressure side 250 PSI
Low Pressure Side 70 PSI
Superheating 39F
Subcooling 13F
Compressor amps (42.9A /52)
Ambient temp: 91.4F - 33C
Condenser Air temp: 111.2 - 44C

I get the next figures out the evaporator coil;

Evap Air Intake; 82.4F 28C
Evap Air Dischargue; 69.8 F 21C

So even when we finally remove 3Lt of oil of the systems lines. The system dont give us more than 7C of split between the inteake and the air send to the room.

Its important to me to solve this issue, because they are at least two more units in the same weird problem.

A weird thing happend to the end of the day today as yesterday, before we remove any oil; the pressures once the compressor is of, didnt equilibrate even at the 10min, for example if low is at 85, will move slow to 90 but not beyond, and high pressure will fall from 350Psi to 340 but not more...

Today has we removed some of the oil, the system balance whithin 3 or 4 minutes at the same static pressure (don have solenoid or anything else but the TXV)

But in the last test, the system dont balance...is like the TXV was clogged.

Due the fact the system was overfilled with oil, I think is safe to assume the condenser and the evaporator migth as well.

What is the proper thing to do? .. Leave the system recycle the oil ... Open the system and flush the oil ? This would do something ? as the system mixes up, oil and refrigerant?

Thanks for any insigth, sorry for any ortografic horror.
Have a nice day.

mbc
23-02-2017, 06:37 PM
Hi
A lot of thing happened
1) look for oil type they used before and compare with your oil . See can you mix those oils?
2) your system was broned ..So your system and oil inside of that be come acidity and you need antiacide core
3) your evaporators should have U traps and your piping
slope should be to compressor side( avaporatore to compressor)

AlexLPD
24-02-2017, 08:25 PM
Thanks for the response, you have a lot on reason to point it up the filter issue.

But even so... How to manage to improvee the system?
Whath should I do know... clean the interior of the evaporator from the oil and install a trap for the oil at the exit of the compressor?

Thanks.
-Alex.

mbc
25-02-2017, 03:49 PM
Hi
To clean it it is two ways
Run compressor with high room temperature (OIL COMES FASTER TO COMPRESSOR ) you do not need to run your system for long time
15 minutes for each time OK
Do it and repeat it until all oil comes off

2nd one
Took all refrigernt from system ( recover it )
And put hole on butom of suction pipe in evaporator and with high pressure N2 wash it .

AlexLPD
27-02-2017, 02:53 AM
Thanks for the response, I will do the second because the room is already climatized by other 2 units, and will be difficult to achive high room temperatures.

I think the system will be full of oil, we already remove 3lt from it, but will do this, for maximun cleaning.

Thanks a Lot.

-Alex.

AlexLPD
28-02-2017, 09:37 PM
Well In deed we do the cleaning of the system, removes like one more L of oil, check for leaks, vacuum and recharge the refrigerant, the pressures improve and the numbers in general are more less better, but
Why on earth I have a split in the vaporator of only 5-7C???

These are the numbers if some one have more Ideas, today Im in the site and I will, cut the lines of the TXV valve, to see if there is a clogged TXV (Think so and hope so, Im tired of this stuff)

14639

14640

14641

Yesterday the second test, it was prone to a refrigerant low charge, but today's after add some more, I think this is gravitating more to the "obstructed TVX scenario".

14642

AlexLPD
02-03-2017, 10:41 PM
Well... In this case, I have been Here for 3 days in a row, and the litte S... dont works stills... yesterday we flush the evporator, use air and after N2, then we seal the system and make a triple evac, we break it wit N2... Chargue the refrigerant, and the oil was brand new, after this, we start the system...

The oil on the sigth glass was new, and after some minutes become dark as the oil we pumped down the first time... I dont Know how many oil this thing was clogged with...
We remove from the carter 3 or so L, the evaporator comes with 1 or so L, and yesterday one of the recovery thanks was carrying about another L of oil. Today we have to clean the god damm thing all over ... To see how this thing comes around.

-Alex.

cadwaladr
03-03-2017, 02:16 AM
Is there an oil separator on this system?

mbc
03-03-2017, 04:24 AM
Hi
Donot forget to put antacid core on system it is very important
Don't worry about color main thing is acidity you have in system
By the way
Please send you system drawing with pipeline size and all information might piping size in suction line is wrong
Also slopes of pipes in soction line

AlexLPD
07-03-2017, 02:40 PM
No there is not an oil separaton, one of my main tougths, but in this case scenario, I have the same unit, the same evap, and the same set up, 10ft apart, even a semi-hermetic compressor, R22... and works like a champ... 15C of split between the air inlet and the air outlet.
Maybe the one difference is the compressor, this unit who are not cooling at a rigth split (I have a constant 6C split) is a coppleand discuss compressor, the other one (the one who is working like a champ) is a nice split of 15C and is a Mesa Carlie compressor of 20Hp... both.


Thanks, for the reply.
-Alex.

This other unit, dont have a oil separator either.
Thanks for the reply.

AlexLPD
07-03-2017, 02:44 PM
Hi, and thanks for the income... well In deed this is the thirth stone core we changue in this system, the firts was fillet with some dark matter, the second affter the coil cleaning its in much better shape, but the soft seals (white stuff that go in the metal holder of the stone) was very dark.

And this third one, an acid core removal.

The condenser unit is located about 10Ft from the evap, the suction and liquid line travel along, just have a 24cm (about 10inches) up slop in the system.

AlexLPD
07-03-2017, 02:57 PM
After this, we open the system again, and changue the oil, three times, with a low chargue of N2 to flush anything was left on the system (condenser coils)... final stuff... the system retrivies clear nice oil...

We remove the N2, add a acid core stone, make a triple evac procedure, close the system. And here becomes very interesting;

Make a fresh chargue of HY222 ( a No clorated reemplace for R22)

I have all the subcooling and superheat data will post in a moment. But was calling for a mayor refrigerant chargue so we did...

Now the system performs "Very well in paper at least"

I have a normal suction, high discharge (maybe the new refrigerant) , normal superheat and normal subcooling, whith normal Amp compressor amp, I even got some cold back to the compressor (this was not happening before) so, it can work 24/7, I have a steady temperature across the evaporator coil (15-16C in the bottom, or in the left or in the rigth) This wasnt happenign either, the system was low on chargue and the evap present a lots of different evap temperatures.

THE ONLY PROBLEM:
Low delta split on AC Unit... the same 6C came in...

So... The unit delivers 21C at the room...

I know the duct work o this unit is crappy... Each outlet has 20-30ft for dischargue,
and the main duct legth is about 50M (150-180Ft)

I was reading high static pressure can affect system performance... but can explain the low delta T on the evap?

Main difference with the working Evap ... that has 2 or 3ft ducts for each exit.

Any tougths?

Thanks.
-Alex.

AlexLPD
07-03-2017, 10:11 PM
Im on the site, we remove the duct work, Still the steady 6C od difference in the inlet or outlet air.

I got this parameters on the evap lines and gauges:

HP 330PSI PT(53C) RT(47.5C) 9.5C SUBCOOLING
LP 85 PSI RT(15C) PT(9C ) 10.7C SUPERHEAT.

On of the may things bothers me right know is;
1.- The systems is operating between the range of sub-cooling and superheat. 8-12f or 11-13C

2.- High side is high of this refrigerant... I meant the PT char for R22 at this temperature is 57C, the saturation point of YH222 is 53C

3.- Even when the suction line says I must be expanding gas approximate at 9C, the real temperature of the evaporator reads 15C at the biggining of the liquid line enter to evap, and about 18-20C in the same row at a 80Cm apart, so ...

4.- Compressor amps are normal to low, even in high load high ambient temperatures.


So, after I ennumerate this reasons I start to think either the TXV is stuck or deffective, or even clogged with something (Even when we already clean it twice) ...

I dont have this problem in any other Danfoss TXV, But the system was so clogged and dirty internally It migth not surprice me something else is wrong.

Will come with an uptdate.

-Alex.