Charging by weight

[tudorice]

Hi ive come across some machines that specify that the refrigerant charge gets weighed in. Now the question remains which im just verifying the answer i was given, does it have to be charged in with liquid or vapor?

[Tayters]

Ah the old refrigeration conundrum - What weighs more, 1lb of vapour or 1lb of liquid?

What answer were you given and what's your thinking behind it mate?

[monkey spanners]

Hi ive come across some machines that specify that the refrigerant charge gets weighed in. Now the question remains which im just verifying the answer i was given, does it have to be charged in with liquid or vapor?


It depends on the refrigerant, if its a blend then yes it needs to leave the bottle as a liquid.
It depends on a lot of things such as system size, ambient temperatures, type of refrigerant, if you need to get the whole charge in before running the system, as to which method is best at the time.

What type of system are you working on?

[tudorice]

the systems vary, but mostly R22, R134a and R404a, sometimes R410a. I normally would charge 134a 404a and 410a as liquid, the reason i ask. I recently worked on a scotsman ice machine that spec was 1.5kg of R22. Now i replaced the compressor tecumseh FH5522e originally had AH5522E. but when i charged 1.5kg in it was way overcharged.

[monkey spanners]

R134a and R22 can be charged as either a vapour or liquid as they are single component refrigerants.
R404A ,and R410A less so, need to leave the bottle as a liquid to ensure the propper blend is maintained.

[tudorice]

thought as much, but in the case of the R22 ice maker. 1.5kg of vapor or 1.5kg of liquid? I normally just charge until the superheat is right

[monkey spanners]

1.5Kg is 1.5kg. If its over charged with 1.5KG of liquid it will be overcharged with 1.5KG of vapour too. Its the same volume once its in the system.
The main thing with liquid charging is that it is easy to slug the compressor, dilute the oil or overcharge the system as the refrigerant is entering the system relatively quickly.

[lawrence1]

My electronic scales know when it's weighing liquid or vapour and that makes it easy to use as well.
Lawrie

[nevgee]

thought as much, but in the case of the R22 ice maker. 1.5kg of vapor or 1.5kg of liquid? I normally just charge until the superheat is right

Tayters got it right .......What is the difference? 1kg of feathers or 1 kg or lead?

[nevgee]

My electronic scales know when it's weighing liquid or vapour and that makes it easy to use as well.
Lawrie


I would be interested in knowing how do they know?

[Gingerair]

I may get shot down in flames here, but as a general rule charge any refrigerant that begins with a no.4 only in it's liquid phase...

[nevgee]

1.5Kg is 1.5kg. If
Its the same volume once its in the system.

.


I'm sure you meant mass ;)

[nevgee]

everyone hold up their hands that don't charge with liquid .... be truthfull now :D

[lawrence1]

nevgee,
when i place an empty cylinder on my scales it reads that weight,,,,when i place a full cylinder on my scales it reads that weight too.

[nevgee]

My electronic scales know when it's weighing liquid or vapour and that makes it easy to use as well.
Lawrie

Ok? ...... you say your scales know the difference between vapour and liquid? I was curious how they did this?

[Tayters]

I may get shot down in flames here, but as a general rule charge any refrigerant that begins with a no.4 only in it's liquid phase...

R400 gases are zeotropes and as Monkey says they need to be charged as a liquid (unless I suppose you are going to use the whole bottle up).
R500 are azeotropes which can (along with the other remaining refrigerants) be charged as vapour or liquid.

If not, I'm next to you in the firing line.:eek:

Happy New Year!

Andy.

[monkey spanners]

I'm sure you meant mass ;)

I'd like to think thats what i meant too :D



I have an idea that, though we weigh in refrigerant, what the system 'sees' is volume, so we might put a kilo of R22 but only need 600 grams of R290 to do the same work, what the system needs is a litre of liquid.

Jon :)

[Tayters]

the systems vary, but mostly R22, R134a and R404a, sometimes R410a. I normally would charge 134a 404a and 410a as liquid, the reason i ask. I recently worked on a scotsman ice machine that spec was 1.5kg of R22. Now i replaced the compressor tecumseh FH5522e originally had AH5522E. but when i charged 1.5kg in it was way overcharged.

Assuming the rest of the system was functioning correctly and the compressor was the correct replacement then I'd have charged by the data plate as well. I've been caught out though taking the plate as gospel I now make sure the charge is correct by measurements afterwards. This particular unit had head pressure through the roof, I recovered roughly twice as much as the data plate, discovered the defrost heater wired permanently on, recharged to the specified weight after rewiring controller. Went back the next day with my tail between my legs to find the system short of charge. Only then did it click that the charge was right all along:o
Still, got another free lunch out of it!

Cheers,

Andy.

[tudorice]

thats what i thought monkey spanners. Bloody so - called senior technicians poking holes in my brains. He claimed that i must only charge with liquid no matter the refrigerant, that if i charge with vapor that not enough liquid will be in the system. LOL

[tonyelian]

hi
you mention that you have replaced the compressor&refrigerant r 404 has different structure and it has different molecule so that is the reason of over charged scotsman ice machine you can charge it by throttle way thats mean thru suction open and close suction must be at 55 psi at the begenning of the refrigeration cycle&32 psi at harvest