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Posted by John Gilmer on June 13, 2005, 12:20 am
> Is there anything at all that can make the A/C coils be less cool than
> they would be at "full tilt"? One reason I want to know is that I see
> many cases of central A/C units freeze up; the coils are obviously very
> cold and apparently there is too much water and/or not enough air.
The "usual suspect" is insufficient air flow to keep the coil temperature
about freezing. When you can independently vary the speed of the "inside"
and "outside" fans, then it's possible to control the humidity by running
the fan at a lower speed until the humidity is reduce to a preset level.
Any particular coil is limited in the amount of moisture it can remove
(rather than the moisture condensing an then blowing back into the living
space.)
Under certain circumstances, low refrigerant can cause the problem. When
happens is that the pressure in the "low" side (the inside coil" get's so
low that the little refrigerant that's left creates a small area in the coil
that"s well below the freezing point of water. That part of the coil
"freezes up" and insulates the coil there. The point where the refrigerant
vaporizes in the coil continues along the junction between the ice and just
liquid water. Usually, however, low refrigerant will cause "no cooling."
This doens't happen often because the "cooling" capacity of a unit that's
very low on refrigerant isn't much and ice does conduct a little heat.
>
>
> |> or get a unit that's too small some of the time and be downright
> |> miserable. I will gladly sacrifice a few "perfect" days to avoid a
> |> single
> |> "miserable" day
> |
> | I said properly sized. If it is too small, it is not properly sized is
it?
> | You will still get reduced humidity in any case.
>
> Having more capacity could, perhaps, reach desired temperature faster.
> But would an over capacity A/C tend to freeze up more?
Nope! It's thermostat will just shut off the compressor when the return
air temperature falls below the set point. As others have notes, it will
tend to short cycle.
>
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