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renaldo
18-05-2008, 04:07 AM
Hello everybody.Fairly new to trade and new to this site.I am working for a Refrigeration company for the past year or so and dont have alot of service skills.I have been doing mostly installs.My friend asked me one day if i could look at his home a/c.I told him there was not much i could really do but "look at it".HAHA anyways he said its not blowing cold enough.What i saw was a piece of plywood coverong part of the fan discarge on the condenser on the liquid line was sweating like crazy.I asked him about the plywood and he said the guy who installed it (the a/c)said to leave it on to simulate summer conditions when he was charging it.My question is this..dont you take it off now that it is charged???and could that be the cause of the sweating?or is that something else? Pleasebe gentle on me. thanks.

Husky250
18-05-2008, 04:21 AM
Any kind of covering on the condenser will drive head pressure up. If Head pressure rises, so does temperature. In other words, restricted air flow = hot liquid line. That being said, some brands will meter refrigerant at the outdoor unit. If you have a system like that, its totally OK to see the the liquid line sweating. In that case think of the liquid line as a long cap tube. Must have insulation on the line set with that type of system.

Husky





Hello everybody.Fairly new to trade and new to this site.I am working for a Refrigeration company for the past year or so and dont have alot of service skills.I have been doing mostly installs.My friend asked me one day if i could look at his home a/c.I told him there was not much i could really do but "look at it".HAHA anyways he said its not blowing cold enough.What i saw was a piece of plywood coverong part of the fan discarge on the condenser on the liquid line was sweating like crazy.I asked him about the plywood and he said the guy who installed it (the a/c)said to leave it on to simulate summer conditions when he was charging it.My question is this..dont you take it off now that it is charged???and could that be the cause of the sweating?or is that something else? Pleasebe gentle on me. thanks.

hendry
18-05-2008, 05:22 AM
hi renaldo,

normally, i see liquid line freezing as signs of clogging upstream.

i suggest you check from comp discharge to evaporator to observe any abnormally. check & clean if found.

hope that helps.

hendry, on wesak day holiday.

powell
18-05-2008, 06:46 AM
hi renaldo,

Being that it has been serviced recently I would suspect that the liquid line drier is clogged. Pull the panel and check if the sweating starts at the LLD.

deu58
18-05-2008, 07:49 AM
Ask your friend if the unit has EVER put out any cold air, What is the temperature inside the house ? Does this guy want to have snow ball fights in his living room or is it really a legitimate complaint and the house is to hot? Take a temperature read right at the vent in the house also to determine what the air temp is actually being delivered to the room, Put your probe/thermometer directly into the air stream coming from the vent,

Do not assume the guy that did the work did not have a a hang over and simply made a simple mistake, Check that all the proper valves in the system are wide open and not throttled,

What is the out side air temp around the unit? Vancouver, This is May but you guys stay relatively cool even this time of year, Outside air temp may be bringing your head pressure/temperature down, Have you put your gauges on it? First with the board in place and then take that board away and look at your discharge pressure,

See if you can find the model on line, The manufacture may have some useful trouble shooting info and charts on their site,

What gas is the machine using? Look at your gauges and check pressure temperature relationship for both suction and discharge, The first thing you should do with any machine is put your gauges on it, Even if you do not know what you are doing it looks so professional to bosses and customers,:D

Can you access the sides of the condenser? Where the U bends for the tube rows are, starting at the bottom rows the first couple of rows should be slightly warm to the touch getting warmer as you go up the side of the condenser, The upper rows should be very warm to pretty hot,

Have you done a leak check? One of the easiest ways to do a preliminary leak check for any thing obvious is to run your hand over the lines, You are looking for any oil and/or line crimping, Pay close attention to any joints, Many times a leak of that nature is visible to the eye due to the oil, Nothing obvious then use a soap solution and/or electronic leak detector, I usually use both, Apply the soap with detector in hand, Out doors the wind can affect the efficiency of an electronic detector if the leak is really small, Is the compressor/condenser fan running continuous? Can you feel any heat in the air that is being discharged from the condenser coil?

Do you have access to the owners manual? If so find out what the running amps are for the compressor and then take amp reads for the compressor, This is to see if you have any load on the compressor

Is there a sight glass anywhere on the liquid line? If it has a sight glass this glass should be full, no level no bubbles just a solid glass, Some times it is hard tell if it is full or dry, For this pump down the unit, If the glass is full as it pumps down you should eventually see a level in the glass,

Feel the inlet and outlet of the filter dryer, If a dryer is getting dirty then there will be a pressure drop across the dryer, The out let will be colder than the inlet, If the dryer is really bad you will not have to feel it, It will be frosted or even iced, Take care though, A low charge can cause the same thing, If head pressure at the compressor is normal or high and the dryer is cold or iced then the dryer is acting as a metering device and is most likely bad, feel the liquid line from the filter dryer to as far as possible, it should stay warm up to the TXV if you can follow it that far, But if the line is colder than the outside air temp there is flashing in the liquid line

Considering that even in the north west where it stays relatively cool still most condensers do not require a board to be placed in front of them to raise the head pressure, I would say look at the simplest explanation first and see if the guy ever actually finished the job ,

My thing is containers but most trouble shooting procedures are the same,

deu58

The MG Pony
18-05-2008, 07:41 PM
All ways start with a quick visual! Is the unit clean, evap clean? Does it have a filter/dryer (F/D) attached?

Can you shine a light through the coils? (This is mostly a preliminary exam for general diagnostics)

With that said it seems we're past that stage or are we?

Attach gauges and do a P/T check, do we have the right gas in the system?

Ok lets fire it up, What is our out side ambient, whats our discharge, what is our delta T, any good? (This will give us an idea if we got air in the system, albeit the P/T check should all so make us aware of some thing is a-stray) We should expect to see a 30-35C (90f-95f) Condensing temp when charging or testing for correct charge (Hence the blocking of the condenser during charging as we want to tune the charge for optimum operation at peak summer temps)

If Head pressure is good but suction low, check the Delta T of the filter drier, we shouldn't have any delta, if over 2-3k difference it's toast and needs replacing.

Now lets go inside, Evap, air filters clean? Fan spinning good? Evap its self clean? Free flow of air in the duct work?
We should expect to see our coil around 4.4c-12.8c (40-55f)

What is our air entering temp? Leaving temp? Humidity level? Coil delta T?

Is it a captube system? What is our SuperHeat at 35c (95F) Condensing? Is it a TXV (TEV) System? What is our Subcooling & Superheat?

Once you correlate all the data draw a Log H diagram, this will give you an idea if it is under or over charged, or if some this is seriously wrong with it.

@DEU
Very nice clear concise explanation mate!

The Viking
18-05-2008, 08:18 PM
STEP BACK!

Are we talking about a standard "split" type A/C unit here?
(make and model would help in all original posts)

If so, are we talking about the smaller of the pipes going from the outdoor unit to the indoor unit?

If we are, that's not a liquid line...
That line is down stream of the expansion device in the outdoor unit.

(This is true for most modern split systems, so unless your mate has bought something obscure...)

renaldo
19-05-2008, 12:51 PM
It is a liquid line because I followed in to a drier and then into a tx valve.Looks like from all your tips ,I will be making a big service call.Thanks and i will get back to you what i find out.