liebert HVAC overcharge Q.

[T77911S]

we have a liebert AC system at one of our sites.
a guy I work with claims that an overcharged system will freeze the COMPRESSOR.
so he removed some refrigerant.

I don't agree that an over charge will cause the COMP to freeze and something else is really wrong.

cap tube system. so will an overcharge cause the COMP to freeze.

[billybek]

Had recently read an article on Cap Tube charging. They are not as common as they once were and I haven't worked with small HVAC systems for quite some time,

"If a cap tube system is overcharged, it will back up the excess liquid into the condenser, causing high head pressures. The pressure difference between the low and high sides of the system will now increase, increasing the refrigerant flow rate to the evaporator and overfeeding the evaporator, causing low superheats. It may even flood or slug the compressor.

Again, this is why a capillary tube system must be charged with a specified amount of refrigerant."

The link to the article: The Critical Nature Of Cap Tubes

Cap tubes when overcharged will raise the discharge pressure (less room to condense refrigerant) and increased refrigerant flow through the cap tube. Usually when discharge pressure goes up ( on a cap tube system) so does the evaporator pressure which makes them less likely to freeze but more likely to feed liquid refrigerant back to the compressor.
This will most likely sweep the oil out of the compressor and over long periods of time damage the compressor bearings.

Is it possible that you have a low airflow problem as well? Dirty filter/coil, blocked airflow, inefficient fan?

[DerkPerk]

Billy nailed it. More than likely low air flow or load will freeze up a system and possibly low on charge can freeze a coil too.

Maybe your co-workers terminology was wrong, by freeze he meant slug with liquid not necessarily turn it icy.

Must be a pretty small and old liebert to be a cap tube. I work on liebert units everyday.

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[T77911S]

He said he saw frost on the compressor so he removed refrigerant because it was overcharged. He claims that because liquid is getting to the comp it freezes the compressor.

Yes I agree with what Billy said. But would the comp freeze.
Mind you we run the ac 9n winter because of equipment it cools.
It's a 10ton+ system.

[DerkPerk]

10 ton cap tube system? The guy needs to be checking the superheat before removing charge if it is indeed a cap tube system. Just because it's frosty doesn't mean an overcharge condition.
If the pressures are dropping low enough to cause the evaporator to run below freezing, head pressure fan controls should be added. BUT, I'd get the charge right first.

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[nota]

working units never ever become ''overcharged''
unless somebody ''overcharged '' them

they do leak and lose charge
but freezes are mainly poor air flow
clean the coils and replace the filters

[T77911S]

yes, he charged it up, the compressor started to freeze so he said he removed some because it was overcharged. he said he checked the superheat and subcooling when charging.

what happened is Friday morning the system was frozen over. I DO NOT KNOW what was frozen. when I heard he removed some of the charge earlier (don't know how long ago) I assumed the evap froze due to low charge.
this is when the discussion of the compressor freezing due to an OVERCHARGE came up.
I told him I did not think that would happen with an overcharge and that it froze (today,friday) because he removed refrigerant and/or something else is wrong and that the compressor started to freeze because something else was wrong.