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Old 09-24-2006, 08:24 PM   #1
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AC freezing up

This is an old apartment building with a central AC unit in the walk in closet. It is a rheem and it is FILTHY......FILTHY FILTHY FILTHY.
I do not know if this sounds reasonable because I'm not well acquainted with AC units but as far as I can tell there is no outside features.
...and if that is indeed possible because I have personally never seen one then allow me to describe what it's doing. It will shut on an off adjusting the thermostat so I think it can cycle but perhaps is not doing so because it's hot and it just doesn't have enough ummph to keep it at 75 without running constant. The air slows down and there is frost on one of the...pipes? Something covered in black rubber.....anyway. I run it on fan and it starts blowing again and I cut the AC back on and it will work "okay" untill it freezes up again. It just started this today as far as I know, but I was told to keep the closet door open because obviously this isn't the first ttime this has happened. Before you ask questions about mainainance...know that this is owned by elderly people and there is not a whole lot of money around here. I just left the plumbing forum for a messed up toilet and I had has to clean handfuls of fly larvae out of the fridge so don't ask why I can't get somebody to fix it. It's complicated. If anythings repaired or replaced it will be this but OBVIOUSLY could use a good cleaning for starters before an AC tech is called. I have never seen such a layer of dirt and dust. It is disgusting and it smells....literally wreaks of cigarette smoke.
So's a rheem renb 1010 something else....I don't have the panel off right now but when I do I see this round thing and it says "washable" and "use a GT filter"...I'm thinking this is the original unit of 27 years and the whole place has seen some abuse. When I moved in there was a layer of dirt on the old filter...I say that because the filter wasn't merely incredibly dirty....I have never seen one so dirty. I changed it but it was a different kind of filter...perhaps not the right kind, maybe not thin enough?....but I took it off and no matter there because there is more dirt on the inside of the unit than there could possibly be on the outside so what difference does it make if there is no filter. If I can clean it I will replace it with one that was similar...if I can find one.
How do I wash it?
This thing is absolutely disgusting and if I can't get it almost all the way clean then what would be the point of knocking some dirt off.
How do I get it REALLY clean?.....and what are some things I should look for while I'm at it?
I don't see A coils...just this big round thing sitting with the round side to where you can't really see in it too well. I'm looking at the outside part of the round part...the side....when I look at it.


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Old 09-25-2006, 06:19 PM   #2
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ok...can someone tell me this?

There is some type of filter material on the inside walls of the unit.
They have to come out. Where can I get replacements? I've never seen that kind of filter. It has the regular type of filter too of course.


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Old 09-25-2006, 06:32 PM   #3
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That "filter material" on the inside of the unit is no filter at all. It's put there for sound attenuation. It's called "duct liner" and is available at an HVAC supply house. It is very different than "duct board" and "duct insulation wrap" in the unfortunate event that you get an unknowledgeable counter man.
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Old 09-25-2006, 09:29 PM   #4
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there seems to be 2 reasons that its not running right:

1. Its not getting a proper return air flow - that is dirty filters and most likely clogged up A coil - change filter and prior to this clean coil with a spray/foam you can get from HVAC supplier.

2. It also sounds like the Freon could be low. You will need HVAC man to top it up.

Both these things will make the unit freeze up and lock it out until it defrosts, GL
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Old 09-26-2006, 01:10 AM   #5
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First off, I know less about HVAC than any other system in a house, but the AC in the last apartment I lived would do exactly this every spring. I am unsure what you mean by “there are no outside features . . . if that is indeed possible,” but if you can’t find condensing/cooling unit, it is likely on the roof (there must be some part of the unit outside, as you are pumping heat from your apartment to the outside). This was always where the problem was in my old apartment (although we just called maintenance, so I can’t tell you any more). If utilities are included, then the cooling unit could be shared with other tenants, which would complicate a diy solution.
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Old 09-26-2006, 11:15 AM   #6
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If there is piping (refrigerant line) with insulation, as you say, then there is an outdoor condensing unit somewhere. But if you are freezing up, the most likely culprit is too low of airflow across your cooling coil. The faster the air flows over the coil (and "takes the cold away from it"), the less cold the coil and piping are, whereas, if you slow down the airflow, the outdoor unit is still treating the refrigerant the same and it just gets colder and colder until it can freeze up.

As mentioned above, check the filter and coil. If you have changed the filter, even if it's not the same type, a store-bought clean filter shouldn't be too thick to hamper airflow that much. From your description of the dirtiness of the unit, it's probably the coil. Clean it up - if the drain pan under the coil is working properly, you could even pour water over it and use an old toothbrush - and I bet you solve that problem.

As for the lining of the unit, the smoky smell will eventually lessen if you keep the unit filter fresh and new, but it will never completely go away - and even if you replace the lining of the unit (which is for both sound and thermal insulation), the walls of the building have the smoke in them.... and I bet all your ductwork is internally lined and has smoke in it too.


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