Charging walk in coolers and freezers

[270wsm]

Ya but when the boss bids wrong, its us who take the heat. I get a phone call telling me to hurry. You are correct Jp, sporlan method is the best, I should be using it more often.

[270wsm]

When using the sporlan method, how long should you let the system run, after clearing the sight glass, to make sure its going to stay clear before adding the flooding charge? If the box temp is high should I let it drop to near design temp frist?
After doing a compressor change out today, I pulled a vacuum and charged system to a full sight glass and let it run for 30 minutes. After 30 min it was still clear so I added the flooding charge. After adding the extra 2 pounds my sight glass started flashing again. WTF? So I cleared it again and added the extra 2 pounds again. It stayed clear that time.

One of our oldtimer techs told me that when the box temp is real high the TXV will be wide open and glass wont clear until the TXV starts throttling. Any truth to this?

[jpsmith1cm]

When using the sporlan method, how long should you let the system run, after clearing the sight glass, to make sure its going to stay clear before adding the flooding charge? If the box temp is high should I let it drop to near design temp frist?
After doing a compressor change out today, I pulled a vacuum and charged system to a full sight glass and let it run for 30 minutes. After 30 min it was still clear so I added the flooding charge. After adding the extra 2 pounds my sight glass started flashing again. WTF? So I cleared it again and added the extra 2 pounds again. It stayed clear that time.

One of our oldtimer techs told me that when the box temp is real high the TXV will be wide open and glass wont clear until the TXV starts throttling. Any truth to this?

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.

[jpsmith1cm]

http://hvac-talk.com/vbb/showthread.php?t=233832

In case you are interested.

[270wsm]

Thanks JP.

[TXTech1]

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.

[jpsmith1cm]

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.

Just do the math unless you're dealing with a micro-channel type condenser, in which case, follow the manufacturer's suggested flooding charge.

[VTP99]

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.

[Bobbycold]

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.

[cthegreat1]

Hi,

Another thing say you are charging an R22 refrigeration system (large pan cooler) which requires 34 pounds of R-22. I had a heck of a time getting that much charged in. I ran warm water over the container many times to get the pressure back up to charge in the vapor.


Thanks

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?

[cthegreat1]

http://sporlan.jandrewschoen.com/90-30-1.pdf

There is the link for charging with headmaster valves.

Raising the head pressure while charging is a waste of time, really. Yes, it will clear the sightglass, but it won't speed charging in any way.

Follow 90-30-1 and walk away.

What is the 90-30-1 ???

[Poodle Head Mikey]

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
-------

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?

[jpsmith1cm]

What is the 90-30-1 ???

Follow the link in the post you quoted