Frost on suction line? - Page 3

Calculating Sub-cooling.
1. Take the high side pressure and convert it to temperature using the p/t chart. That will give you the "saturated condensing temperature".
2. Measure the "liquid line temp" at the outlet of the condenser
3. Sub-cooling = saturated condensing temperature - liquid line temp
4. Ideal range 9-15F

Calculating Superheat.
1. Take the lowside pressure and convert to temperature using the p/t chart. this will give you the "saturated suction temperature"
2. Measure the "suction line temperature".. 6" from the compressor... right above the accumulator on a rotary.
3. Superheat = suction line temperature - saturated suction temperature
4. Ideal range 8-12F

You will need some way of measuring temperature . you can use a infra red head gun or a digital temp reader with K probes . If you go the probe route them you will need to put some artic ceramique thermal compound on the K probe tips and then Gorilla tape them to there proper places and put some insulation tape around them as well per above instructions . You will also need a pressure / temperature chart for your refrigerant. Google is your friend ! These instructions are for a rotary compressor but a recip compressor works real close to the same principal. You really don't need to calc sub cooling with a cap tube system but it's go to know and can tell you a lot about the condition of the charge .

BTW ... I got those measuring instructions from Drewmeister over at Extreme Overclocking .com . I printed them out and keep them in my notes . Thanks Drew !!

good luck O.P. and LUK how it goes

Edit .... http://www.thermoworks.com/products/probe/tc_wire.html In case you want to purchase the probes.Get model # 113-362. The only issue is the digital temp readers can be a bit pricy . UEI makes good readers and some better digital volt meters come with at least one K probe port on them . Then you can switch the plugs around one at a time to take your readings. You need to let the compressor run for at least 15 minutes from a cold start up before you take readings . This way the refrigerant will be in it's "true" state.

-Flock
Edited by flocko - 8/13/11 at 2:35pm

Here is what I would do :

Start the system with gauge set installed and tepm reading devices in place .
Let the system run for 15 minutes NO load . Personally , I would run all the tests with no heat load of any kind to start with .
After the system has run for 15 minutes then take the following readings and report back :

high side reading
low side reading
compressor amps
compressor volts
voltage at your power source (the wall outlet)

Take temperatures at the following areas :

1) Ambient air temperature in the room you are in . Try and duplicate the worst temps( hottest room will ever get) the unit will ever see . This will help when adjusting the charge , if in fact it needs adjusting .
2) condenser out put line
3) compressor shell
4 ) suction line . On a rotary compressor this would be about 2" above the accumulator . On a recip compressor I'm not sure . Just measure it at the end of the suction line closest to the compressor.
5) In coming condenser air temperature. I do this with a digital meat thermometer . Just stick it in front of the condenser .

All the above testing is why I can't tell you what to do with the super heat . We just don't know any info . There are many causes of super heat and sub cooling issues . I'm not going to go into them until we get your results . You are also stretching my knowledge base here quite a bit . I have one unit under my belt and a SWEET piece of work under way right now.

Once we get the no heat load charge under control we can start all over except this time you can do it under load . The charge adjustment at this point will be most likely minimal.

REMEMBER : always let the system balance from a cold start before taking any readings for 15 minutes . Any adding of or reduction of refrigerant will need to be be done VERY slowly . I mean real SLOW. You don't want to flood the compressor .

A couple bits of advice :

1) Take some pics (detailed ) of the unit .
2) We need detailed specs of the unit not just compressor model . What is the metering device ? What is the make of the condenser . What are you using for fans ? What type of refrigerant is in the system
3) Get some refrigeration tools !
4) Get a pressure temp chart for your refrigerant .

Lastly ..... Running the unit on the high end of the superheat will give you the best cooling

Yes , Drew is a .... well , GENIUS and very adept at this art . He has been a trooper for me and has the patience of a Saint . Many folks on this forum share that knowledge as well (not me , mind you) and will be more than willing to help !!

EDIT : You posted while I was typing ..... sorry !!!

-Flocko
Edited by flocko - 7/11/11 at 3:35pm

Nah ... no stud hear for sure

The cap tube IS the metering device . So ... we now know how the refrigerant is being metered ! Cool

Yes ... your super heat at idle will be a bit lower than at full load . Full load is what matters the most. .

I have no clue about anything to do with oil cooling . Just being honest !!!

Bye your last reporting it sounds like your already on the the high end of super heat. DO NOT go out of the high end of that range . I would love to know what your compressor temps are ? As well as the other requested info .

Sounds like your getting VERY close !!

Please luk how it goes and GOOD Luck