Recovering Refrigerant

[tek1]

What is the best way to recover refrigerant while a unit is running? I am heading out to a site, tomorrow, that is supposed to have six RTUs that are all overcharged. All TXVs, non adjustable. My plan is to monitor subcooling as I recover, the Service Manager won't let me recover and weigh it back in. I just found out about this on my way home, big surprise, right?

[hvac69]

I would just hook up to the liquid line and push the refrigerant directly into the bottles while weighing them. The only thing I would be concerned about is any oil that may leave the system, do have oil level sight glasses.

[2sac]

Send the tech back out who overcharged them in the first place.

If you don't know how overcharged they are, pull out more than you need, weigh what you need back in to hit your #'s. Pull it out and put it in thru a drier.
EDIT if the coils are dirty...good luck

[1tonn]

My first question is why is there an assumption that these units are over charged? Second , I believe it would be more accurate to pull the charge and weigh in the factory charge if information is available.
Do you really know how much it is overcharged or if it truly is. Checking the running unit and making adjustments on the current charge, superheat/subcooling/temps, would seem to me, to be more time consuming. At least once the correct charge is in you can fine tune it.

[carmon]

What is the best way to recover refrigerant while a unit is running? I am heading out to a site, tomorrow, that is supposed to have six RTUs that are all overcharged. All TXVs, non adjustable. My plan is to monitor subcooling as I recover, the Service Manager won't let me recover and weigh it back in. I just found out about this on my way home, big surprise, right?

how did roof tops become overcharged...

[hvac69]

My first question is why is there an assumption that these units are over charged? Second , I believe it would be more accurate to pull the charge and weigh in the factory charge if information is available.
Do you really know how much it is overcharged or if it truly is. Checking the running unit and making adjustments on the current charge, superheat/subcooling/temps, would seem to me, to be more time consuming. At least once the correct charge is in you can fine tune it.

Nothing like knowing a unit is overcharged and finding out it was 20 lbs over and knowing it would have been quicker if I just removed it all and spent that time inside opening all the balancing dampers that were closed because this person or that person was cold to find only one damper open. Low suctiion, HAH more refrigerant is the answer.

[tek1]

All good points. A little more background. Just keep in mind, I was thrown in the middle of all this a couple hours ago. I was told company "A" came out and for some reason, increased the fan speed by changing the blower pulleys. On all the RTUs. At that point they were not cooling very well, lots of complaints of high humidity. Company "B" comes out, and adds refrigerant to the the RTUs. Now we are called out. The complaint is high humidity. Another tech comes out, calls our in house mech engineer. They both determine that the airflow is too high, 800 CFM per ton. I am told i am going to change the pulleys, belts, and adjust the charges. There is documentation of all of the RTUs having refer added after the airflow was changed. Also, we are going to try to get 375 CFM/ ton. That's all I really know at this point, I'm sure I'll find out more soon enough.

I get that the best way, and probably the fastest, is to recover and weigh back in. I totally agree. However, the people that sign my paycheck don't see it that way. Looks like my hands are tied.

I am thinking that company "B" saw high SH, and just started adding refer...

[Toddbrewster]

Hey I used to do a lot of commercial service not far from you! I have had good luck just taking out the extra charge with a scale and recovery tank, hook onto the liquid line and slowly remove 8oz or so at a time till I have the correct readings, if they are grossly overcharged it would be faster to recover the entire charge and weigh the factory charge back in, if you have several units to remove charge from your tank will be warm and the pressure will be higher which will take longer to remove the extra charge. Is there any way you can take more than one recovery tank?? I know that is more you have to carry up on the roof but if you take 2 or 3 tanks with a vacuum on them it may speed things up a little. You said there is documentation of refrigerant being added, by chance does it say how much extra they added to which unit?? I always had the model, and serial number, and unit number or the area it serves on my report and which unit got how much refrigerant, also I would always leave a service card in each unit with a log of what I did to the unit for example if I added refrigerant I would record that or if I had to replace any parts, etc, was helpful for accounts with a lot of rtu's such as theaters/malls.
Good luck!

[tek1]

Not sure how much was put in each one. I have one cylinder with a vacuum on it, if I need more, I guess I need more... thanks for the input

[elvi]

Not sure how much was put in each one. I have one cylinder with a vacuum on it, if I need more, I guess I need more... thanks for the input

If you have access to it; does setting a tank in an ice bath speed things up?

[KnewYork]

If you have access to it; does setting a tank in an ice bath speed things up?

Yes, it does. Anything to lower the condensing temperature is going to help.

[just_opinion]

Unless it is a trane, you are screwed. Because this POS trane has not liquid port.
Advice - Put a recovery drum in the blower section and run the unit in cool mode of course. One unit at the time as you replacing the pulley

[elvi]

The only thing I would be concerned about is any oil that may leave the system, do have oil level sight glasses.

Once you recovered, could you not chill the tank, flip it over and allow the oil to flow back into the system? A sight glass on your gauges would help here?