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Originally Posted by MicahWes

I use 5 foot hoses on most systems. A ball valve on high-side hose is all you need to isolate high side and remove all but vapor from the hoses back through suction. The vapor left in the hoses is negligible.

This is one of those things that I picked up in the service where several units expect the suction pressure checked montly on some of the smallest units for PM's. It was surprising how few months it took somethings to lose enough refrigerant to effect operation.

I use 5 foot hoses on most systems. A ball valve on high-side hose is all you need to isolate high side and remove all but vapor from the hoses back through suction. The vapor left in the hoses is negligible.

And Bobbycold, thanks for the advice. Never thought of the shorter hoses on smaller systems. Makes total sense

So, what you're saying is that it's possible to check super heat at evaporator, obviously. But, checking it after the accumulator is not gonna give you a necessarily accurate reading. It will vary based on the amount that boils off. So, lets say you hoped to achieve a super heat of 20 or so without an accumulator, then you would expect a lower number with one? I'm beginning to think that I'm over thinking some of this stuff, haha. Trying to get too technical

Originally Posted by EricDMKAJ

Well, if its there in case of liquid making it back to compressor, I would think that the liquid boiling off could throw things off. I could be way off with this, I never deal with them on centrals

Not really.

Think about it.

If liquid is coming back the suction line, you already have 0 degrees superheat.

The accumulator catches it and allows it to boil off slowly.

How would this raise or lower the superheat?

Originally Posted by EricDMKAJ

Excellent. Ok, now I see what you're saying. Sorry for all the confusion, I'm just so used to refrigerators (critical charge) and central air, which I just charge by sub cool for Txv, and superheat for fixed orifice.

So, as far as charging on a cold day, how is that done differently?

As far as the lowest possible ambient, should I assume based on the area that I work, or is that stated on the condensing unit.

And lastly, I was taught that if a unit has a receiver, I can't check sub cooling. And if it has an accumulator, I can't check total superheat at the compressor. True? Or not true.

Thank you so very much for helping me through this. Going to the new job, they know my knowledge level is residential, and are training me accordingly. I just want to be prepared with the basics before I get knees deep in it

Ice machines and small critically charged systems have only one method of assuring a proper charge. Sure walk ins and large reach ins can often be charged using the variety of methods, but those smaller critical charged units are so tight, that I have found recovering all refrigerant and charging the system by weight is the only way to assure a proper charge. I'll also say that before putting a gage on anything like that, I will make sure I don't have an electrical problem, which is far more common than a refrigerant charge issue. Unless you already got some, may I recommend that you get a couple short hoses with a valve and put a suction gage on one and a discharge gage on another? You'll want to use gages that retard on very high pressure, as nothing frustrates me more than an ice machine going into harvest while I have a suction gage attached to it that can't handle the high pressure. The long hoses on our regular gage and hose set remove enough refrigerant to make a difference if you apply the gages a few times. The shorter hoses with a gage really come in handy for me, if I do need to check the suction or discharge pressures. Good luck, however with your new career line. Personally, I prefer refrigeration and ice machines than AC's, though I still have to work on AC's.

Well, if its there in case of liquid making it back to compressor, I would think that the liquid boiling off could throw things off. I could be way off with this, I never deal with them on centrals

Originally Posted by EricDMKAJ

Excellent. Ok, I'm going to try to soak this document in as much as possible. I'll get it to stick, haha. Thanks again.

Going back to the accumulator, your evap superheat shouldn't change, but total superheat should, is how I understand it. I would assume accumulators used on cap tube or orifice split AC?

Why would an accumulator change superheat?

Does it add heat? Remove it?

Excellent. Ok, I'm going to try to soak this document in as much as possible. I'll get it to stick, haha. Thanks again.

Going back to the accumulator, your evap superheat shouldn't change, but total superheat should, is how I understand it. I would assume accumulators used on cap tube or orifice split AC?

Originally Posted by EricDMKAJ

Excellent. Ok, now I see what you're saying. Sorry for all the confusion, I'm just so used to refrigerators (critical charge) and central air, which I just charge by sub cool for Txv, and superheat for fixed orifice.

So, as far as charging on a cold day, how is that done differently?

As far as the lowest possible ambient, should I assume based on the area that I work, or is that stated on the condensing unit.

And lastly, I was taught that if a unit has a receiver, I can't check sub cooling. And if it has an accumulator, I can't check total superheat at the compressor. True? Or not true.

Thank you so very much for helping me through this. Going to the new job, they know my knowledge level is residential, and are training me accordingly. I just want to be prepared with the basics before I get knees deep in it

How is it charged differently? READ the document. It is rather difficult to explain, but the authors at Sporlan did a good job.

Basically, you calculate the total flooding charge for a warm day, THEN calculate how much the condenser is ALREADY flooded due to the lower ambient, then add the difference.

The minimum ambient is for the area that you work. I use -20 around here because, well, it happens every few years.

You CAN check subcooling on a receiver system, it just isn't a good charging metric. Just as you CAN check superheat on a system with an accumulator.


No problem on the assist. We all have to start learning somewhere.

Excellent. Ok, now I see what you're saying. Sorry for all the confusion, I'm just so used to refrigerators (critical charge) and central air, which I just charge by sub cool for Txv, and superheat for fixed orifice.

So, as far as charging on a cold day, how is that done differently?

As far as the lowest possible ambient, should I assume based on the area that I work, or is that stated on the condensing unit.

And lastly, I was taught that if a unit has a receiver, I can't check sub cooling. And if it has an accumulator, I can't check total superheat at the compressor. True? Or not true.

Thank you so very much for helping me through this. Going to the new job, they know my knowledge level is residential, and are training me accordingly. I just want to be prepared with the basics before I get knees deep in it

Originally Posted by EricDMKAJ

And, one other thing that you said. Just to make sure I understood you correctly. On fan cycle control units, you still charge using the 90-30-1 chart?

Most fan cycle units that I work on also have a headmaster.

On those very few that don't, I'll add the computed flooding charge and go, too.

Keep reading, Eric.


Let me try to sum it up for you.

Let's assume an 80 degree ambient (for simplicity sake)

Come up on a unit that is low on charge. Sightglass flashing hard.

So, we find and fix the leak and start adding gas.

Step one is to clear the sightglass. It doesn't matter how much or how little gas is in the unit to do this. Just add enough to clear the glass.

Now, run Sporlan's numbers and reach your computed flooding charge and weight that charge into the unit.

You're done.


It gets more complicated charging them on a colder day, but let's get you straight on this, first.

Originally Posted by EricDMKAJ

You know, I've read this sporland document all day, and it finally clicked. You have to evacuate system completely of refrigerant before starting this process. Then, you figure out the volume of condenser. Then, you weigh in refrigerant until glass clears. You subract the number you just added from your total, and that's the additional you have to add in. Correct? Thank you so much, I am a tech that fully believes in the science side of the trade, and hate charging based on WAG. Thank you. You're a life saver

You do not have to remove all the refrigerant to charge to the sporlan chart. Clear the sight glass first. Then add the refrigerant per the caculations from the chart to add refrigerant needed to operate in lowest expected ambiant.

And, one other thing that you said. Just to make sure I understood you correctly. On fan cycle control units, you still charge using the 90-30-1 chart?

You know, I've read this sporland document all day, and it finally clicked. You have to evacuate system completely of refrigerant before starting this process. Then, you figure out the volume of condenser. Then, you weigh in refrigerant until glass clears. You subract the number you just added from your total, and that's the additional you have to add in. Correct? Thank you so much, I am a tech that fully believes in the science side of the trade, and hate charging based on WAG. Thank you. You're a life saver

I understand everything you're saying, I just have one issue. The only way to charge by sporlans way is to first evacuate the system. Then, weigh in charge to sight glass. Then, depending on how much you weighed in (changing based on ambient), you take difference of that and what is supposed to be in condensing unit. So, just to be clear, there is no way to charge these correctly without first evacuating entire system? Sorry to be a pain...

Originally Posted by EricDMKAJ

Wow, small world. Poor Youngstown has gotten do depressed, hoping it turns around eventually. Another question....as far as fan cycle controls, im assuming to charge these properly, you have to keep the condenser fans running to know your high side (ambient + 30, converted to pressure). how would those be charged in the winter/summer? do you have to add the additonal winter charge for those like you would for a head master? i dont believe i would have to, im assuming i could charge it the same year round

Most units that I see have a means of head pressure control like a Headmaster or ORI/ORD valving setup.

Make sure the condenser fan is running, charge per the 90-30-1 that I posted and you will be fine.

If if DOESN'T have a low ambient control valve, you're stuck on "best guess" charging methods.

What I'll typically do is just follow the chart anyway. It has worked for me so far.


The "ambient +30 doesn't always hold true, BTW. It's a fair "guess" particularly at high ambients but it is really only a guess. Once your ambient drops, that number flies off the roof.

Wow, small world. Poor Youngstown has gotten do depressed, hoping it turns around eventually. Another question....as far as fan cycle controls, im assuming to charge these properly, you have to keep the condenser fans running to know your high side (ambient + 30, converted to pressure). how would those be charged in the winter/summer? do you have to add the additonal winter charge for those like you would for a head master? i dont believe i would have to, im assuming i could charge it the same year round

Originally Posted by EricDMKAJ

Wow, i can't believe i've never seen this information before. thank you thank you! And as far as the packaged AC, and split system AC, that is charged the same way as done in a residential setting i assume. gather ambient temperature, wet bulb, and follow chart just like you would normally, correct?

Yep.





Just noticed that you're fairly close to me. I work the greater Y-town area into PA and WV