Icing up due to overcharge?

[Poodle Head Mikey]

It would never frost and all would be well. Like a flower case.

PHM
---------

Why does refrigeration keep coming into this?

under, over, correctly charged, a 40deg boxes coil is going to ice up no matter what. Which is why it must have at the least a off cycle defrost.

oh never mind this is 4 years old and someone already pointed this out

[fixitman]

I'm not going to read the 12 pages of previous posts to confirm this. But, as I remember, someone in the thread kept bringing up a medium temp refrigeration example to "prove" that everyone discussing the original example that started the thread thread was wrong. So some of us tried to help him see the error in his ways ... at least in part so that we could get back to the original question. By that time, the thread was already derailed.

It's a tactic that works sometimes ... but as this example shows, not all the time. In this case some very insistent ignorance took over the thread ... because one person refused to re-examine his incorrect assumptions. It's the way of the internet ... even this little corner of it.

[coolguy4u]

i just ran across a refrigerated dryer that was freezing up , system hold 135lbs of r-22 , has a txv , desuperheating valve and a hot gas bypass
this thing has had many hands on it and was told by customer that they have been having a company gas it up every 6 months , when i sniffed around with leak detector no leaks were found , then decided to recover refrigerant and weigh back in to know were to go from there , when all said and done i recovered 228lbs out of a system that should have 135lbs

and with being said YES freezing up can occur if overcharged

[fixitman]

So, just to be sure ...
You're saying that you recovered the unit, weighed in a new charge, and **with no other system correction** the freeze-up problem went away?

(Sounds like this thing must've had a helluva big receiver and/or accumulator on it.)
[This is funny - the spell checker doesn't like "must've" but accepts "helluva". I'd have thought both of those words would be in the Official Tradesman's Dictionary.]

[prorefco]

I haven't read all 11 previous pages but I'd like to weigh in on this discussion. An overcharge of an A/C system will not cause an ice-up in and of itself. If the system is overcharged and yet ices up, the ice-up is caused by something else other than charge. What I have usually found is low air-flow (caused by dirty evap, restricted duct or other airway, loose belt, etc) and a previous tech saw low suction pressure and added more gas to bring up the suction. In lots of systems, this will provide a temporary fix until the original problem gets worse. Then, a "good" tech comes to the rescue and corrects the airflow only to find an overcharge condition.

Now on walk-in COOLERS, an overcharge CAN cause an ice-up NOT because of low evap temp, but because the unit is marginally sized for the load and the increase in head pressure reduces compressor capacity which in turn causes longer running times. This in turn doesn't give enough defrost time between cycles. This can happen even though the unit has a defrost clock. I must admit that it is a little rare to find this condition but on days of above normal loading with marginally sized equipment, the overcharge can result in icing.

comments??

[fixitman]

I haven't read all 11 previous pages ....

Now on walk-in COOLERS, an overcharge CAN cause an ice-up NOT because of low evap temp, but because the unit is marginally sized for the load and the increase in head pressure reduces compressor capacity which in turn causes longer running times. This in turn doesn't give enough defrost time between cycles. This can happen even though the unit has a defrost clock. I must admit that it is a little rare to find this condition but on days of above normal loading with marginally sized equipment, the overcharge can result in icing.

comments??

Right - this was egg-zackly the scenario I proposed. Running warm due to overcharge, but still far enough below freezing to frost the coil. Not enough time between cycles to defrost completely before the next compressor cycle. All it would take would be an unusually humid day - or an unusually large amout of traffic in and out - and it could ice up. Reduce the charge, lower the evap temp, shorter on time & longer off time, allowing for complete defrosting between on cycles.

You don't wanna read all 11 pages. They were largely wasted by someone acting insistently stupid.

[Hvacn3d]

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[jpsmith1cm]

Closed old thread.