http://hvac-talk.com/vbb/showthread.php?t=233832
In case you are interested.
There was an interesting thread, to me at least, on here about a year or so ago. I'll see if I can dig it up.
An evaporator holds more refrigerant when it is cold than it does when it is warm, so, logically, you need to wait until the system is close to temp before adding the floding charge.
http://hvac-talk.com/vbb/showthread.php?t=233832
In case you are interested.
Thanks JP.
Just finished reading this thread mainly because I dont work on walk ins often (mostly stick with the easy residential HVAC) and needed to figure out how to properly charge a walk in. I realize that this thread is a few years old and was wondering if Sporlans method is still the best way to calculate the correct charge or if there has been an update/new method since this thread closed.
But I need to know how much to put in the receiver as well as the condenser......
sorry I could not help myself after reading all of that.
After reading the first page, I would like to ask if you are sure it is the condensor fan that your tech shut off, and not the evap fan? I usually start putting a weighed charge to the liquid side with the unit off, then to the suction side with the unit running. Sometimes while charging that last few ounces, I can sometimes get it in a little quicker by shutting off the evap fan, but not the condensor fan. I would only have it off a very short amount of time, and only for getting those last very slow ounces into the system. To be honest, it is a rare time that I need to do this, maybe once last year.
I always charge as a liquid that goes through a meter which changes the liquid to a saturated mixture... 404A MUST be done this way, r-22 is either way. The key question is if the compressor is running or not.
If the compressor is not running, I'd turn the evap fan on and charge as much through the high pressure side as a straight liquid. This saves time. the main point is to get the LLS open so the ref can go the the evap and to ensure that the compressor is not getting any liquid.
Comments?
One of the best kept secrets in the HVAC/R business must be that all refrigerant gets charged as a liquid. <g>
Who the hell has the time to warm the cylinder repeatedly and then wait for pounds and pounds of refrigerant to boil off? Don't your service managers scream over all the time you are taking?
There are little vaporizing widgets you can charge through but why not just crack the suction side gauge handle and let it boil/vaporize in through the crack? If you are very curious (as I was <g>) use two 1/4" flare MxF sight glasses. Put one before the suction hose - screw it onto the left bottom side of your gauge set - and put the other one onto the suction access flare on the unit. Then crack the suction gauge manifold handle a little and see what the refrigerant looks like in the sight glasses.
With the manifold gauge cracked - tell me what you see.
And also note the suction pressure increase on your gauge (valve open versus valve cracked) initially 'set' it for 5-10 lbs over running suction pressure. Use an analog gauge and watch the needle flutter. If the needle is steady the gauge valve is either open too far or closed too much. <g>
PHM
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PHM
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When faced with the choice between changing one's mind, and proving that there is no need to do so, most tend to get busy on the proof.
I gotta say I'm impressed with your patience and restraint JP.
From reading this thread from start to finish I was sure that someone was pulling your chain but when I got to the point where they both stated that they were drinking I almost fell off my chair I was laughing so hard.
Plus this thread is almost four years old.
I have a Bailey walk-in freezer.... How would I calculate the amount of refrigerant needed for this system?
the link http://sporlan.jandrewschoen.com has expired....
You could measure all the tubing in the system piping and both coils and calculate the internal volume. Then work out where there would be various vapor volumes at the various pressures. And so forth.
Or you could look up the total receiver volume for the system refrigerant and then use 75% of that as the charge. If you have to bid the job - use 100%. <g>
I have worked on systems which could not be pumped down - but not very many.
PHM
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PHM
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When faced with the choice between changing one's mind, and proving that there is no need to do so, most tend to get busy on the proof.
PHM
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When faced with the choice between changing one's mind, and proving that there is no need to do so, most tend to get busy on the proof.
http://sporlanonline.com/90-30-1_072012.pdf
Try that one.