Charging by sight glass

[Peztoy]

When charging a refrigeration system by sight glass and its been off for hours, the case is warm. Do you clear the sight glass as soon as you can when you first restart the system, or let the case/product come down to its design temperature range and then finish charging to clear the sightglass.

[GT Jets]

When charging a refrigeration system by sight glass and its been off for hours, the case is warm. Do you clear the sight glass as soon as you can when you first restart the system, or let the case/product come down to its design temperature range and then finish charging to clear the sightglass.

Technically when the case is "warm" the system is overloaded, the sight glass is not there for charging, your thermometer is....

In all seriousness, it depends on much more than what you wrote. Receiver?, TXV?, Cap tube?, type of refrigerant?...

Not as cut and dried as you are trying to make it.

GT

[VTP99]

Is it a indoor or outdoor condensing unit ? This could make a big difference.

[Peztoy]

TXV, receiver, R22, reach in cooler.
I was thinking when you first start up the txv would be fully open because of the high load.
Later as the cooler comes down to temperature the txv would be more closed, the liquid line would have more refrigerant backing up in it, the sight glass would then clear when the system was running in its normal range.

[Peztoy]

Air cooled condensing unit in the ceilling.

[VTP99]

Is it a pump-down system ?

[GT Jets]

TXV, receiver, R22, reach in cooler.
I was thinking when you first start up the txv would be fully open because of the high load.
Later as the cooler comes down to temperature the txv would be more closed, the liquid line would have more refrigerant backing up in it, the sight glass would then clear when the system was running in its normal range.

This would be accurate.... Hence why I said the system would be overloaded.. So I guess to answer your question, the charge should be verified when the box is close to set point, which in essence is where it will be running most of the time.

GT

[2sac]

TXV, receiver, R22, reach in cooler.
I was thinking when you first start up the txv would be fully open because of the high load.
Later as the cooler comes down to temperature the txv would be more closed, the liquid line would have more refrigerant backing up in it, the sight glass would then clear when the system was running in its normal range.

Correct

[Chris_Worthington]

Thread relocated to the refer section

[johnpast]

Make sure that this system does not have a suction to liquid line sub-cooler. I once had trouble clearing a sight glass on an R-12 system in the same manner. I discovered that the sub-cooler had internally ruptured and hp liquid was short circuiting into the suction line.

[Tommy knocker]

Txv needs full column of liquid regardless of box temp. Full glass is not nessisarily full charge with receiver. Hot box and warm ambient charging to full glass will leave you grossly undercharged.

[heresjohnnyb]

I see everyone forgot the fact that its a reachin. It more than likely has a factory charge on the nameplate. If not then call the manufacturer. And dont say im just topping it off. thats like putting a bandaid on a compound fracture. If the unit is twenty years old with its second compressor in it then give a nice quote to fix it properly.Pull the charge and give it the factory charge. Dont rely on sight glasses. Especially when it was added in by the hack before you.

[ryan1088]

I see everyone forgot the fact that its a reachin. It more than likely has a factory charge on the nameplate. If not then call the manufacturer. And dont say im just topping it off. thats like putting a bandaid on a compound fracture. If the unit is twenty years old with its second compressor in it then give a nice quote to fix it properly.Pull the charge and give it the factory charge. Dont rely on sight glasses. Especially when it was added in by the hack before you.

That is not necessarily true. I have a freezer at a gas station that is a reach in display case with the condenser outside. It is most certainly not a factory charge situation.

[heresjohnnyb]

I didn't hear anything about remote condenser anywhere in this thread. But I know that's true I used to take care of a few gas stations with reaching cools and freezers. No fun but pretty cut and dry usually

[jpsmith1cm]

Txv needs full column of liquid regardless of box temp. Full glass is not nessisarily full charge with receiver. Hot box and warm ambient charging to full glass will leave you grossly undercharged.

I'll dispute that.

I've not seen a system with a receiver that won't clear the glass once the unit has settled down and come close to temp, in fact, part of the charging instructions include the step "clear the sight glass"

[Tommy knocker]

I'll dispute that.

I've not seen a system with a receiver that won't clear the glass once the unit has settled down and come close to temp, in fact, part of the charging instructions include the step "clear the sight glass"

I think you miss read. I said a full glass doesn't mean a full charge with a receiver. Do you dispute that?

[jpsmith1cm]

I think you miss read. I said a full glass doesn't mean a full charge with a receiver. Do you dispute that?

Maybe I did misread.

No, a full sight glass is just the beginning of charging a system properly.

I've repeated that advice hundreds of times.

[Tommy knocker]

Maybe I did misread.

No, a full sight glass is just the beginning of charging a system properly.

I've repeated that advice hundreds of times.

Thank goodness. I thought you took up the crack pipe.

[Peztoy]

Thanks for all your feed back.
Not a pumpdown system.
No suction to liquid line heat exhanger.
Remote condensing unit. Not a self contained case.
Got this quoted job from another guy. I replaced the compressor. 5 Lbs was reclaimed. I put 4 1/2 Lbs back in. Today I was later told the compressor was making noise before it quit. Now I'm glad I held back on the charge. If this wasn't quoted I'd want to go back to check a little deeper for compressor failure.

[Phase Loss]

I've seen a few larger Racks out there that won't clear the sight glass once settled down.

Typically on systems with over sized liquid lines. And low liquid velocities.

Laminar Flow...It's the Rivering Sight glass. You could fill the receiver to the max, and that glass wont clear.

However, this is absolutely not what you are experiencing.

charging a system with a receiver is all about receiver liquid level. You need enough liquid in the receiver to keep a level on your coldest day, there's calculations for this stuff.