Pelican Parts Forums - a/c problem

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Seriously? Air flow (fan speed) has everything to do with freeze up. Think about it.

Quote:

Originally Posted by fintstone (Post 7406440)

Seriously? Air flow (fan speed) has everything to do with freeze up. Think about it.

No, the evaporator core temperature must be "refrigerant" driven firmly to, or below, the freezing temperature of water. As a ratio, the number of BTUs required to reduce a specified volume of water from the liquid state to frozen is EXTRAORDINARY compard to getting a 1 degree movement otherwise, 34F to 33F, say.

On the other hand yes, provided the control system is faulty to the point of allowing evaporator freeze-up, but has "limited" refrigeration capacity, with a high(er) volume of airflow, airflow consistently ABOVE 32F, no freeze up will result.

But keep in mind that like your fridge's freezer section, your A/C is a closed system and will FREEZE unless you open the "freezer" door often enough.

where do you come up with this stuff?

what if the water is already 33 degees?

go pull the fuse to the indoor unit of you home AC and watch how fast the evap will freeze up.
why do you think one of the first things to check on a home AC unit is the air filter. a dirty air fitler reduces air flow and WILL cause the evap to freeze.

Quote:

Originally Posted by T77911S (Post 7408165)

where do you come up with this stuff?

what if the water is already 33 degees?

Please explain the context of this question.

go pull the fuse to the indoor unit of you home AC and watch how fast the evap will freeze up.

Home A/C is dual 5 ton GHP. Most home A/C system do not have control provisions to prevent freeze up if the thermostat is calling for cooling and the evaporator airflow rate is too low to keep the evaporator core above freezing temperatures. My ancient 911 has 2 control systems that should prevent freeze up even with ZERO airflow.

why do you think one of the first things to check on a home AC unit is the air filter. a dirty air fitler reduces air flow and WILL cause the evap to freeze.

You're right, but I haven't a clue as to why most home A/C systems lack this control. Maybe it has something to do with total lack of owner desire to produce system outlet much colder than 60F.

I don't know why home A/C systems typically do not have evaporator low temperature limiting.

I have 2 of those ~12,000 BTU portable air conditioner/heat pump (exhaust/intake air hoses through the window) units for heating the 2 garages on the property, and they both have active freeze up prevention controls.

Quote:

Originally Posted by T77911S (Post 7408165)

Yup, so true.
And amazing so many older home HVAC units don't utilize an evap freeze
out switch. So inexpensive to adapt. Most 'in the window' or 'in the wall'
don't have them either, I've seen many units just turn to a block of ice,
brand new, right out of the box.

So, we are fortunate the 911/930 have a simple and effective 'thermostat-freeze out' combo control
that if properly located in the evaporator coil... works!

Quote:

Originally Posted by kuehl (Post 7408292)

No, almost all "in the window" or "in the wall", or "on top of the RV" have the same simplistic capillary thermostatic control system as does "our" porsche.

Simplistic, now there is a word German engineers would like.