T&T: AC problem

[Steve Sipe]

<snip>
> not really cooling. The cooling water
> is flowing fine through the exchanger. I'm thinking Freon leak?
>
> Keith
>   
<snip>

That is likely. Partial icing is a classic symptom of low charge.

The big question is, where's the leak?

I am experiencing a similar problem on my own system which is a 3 ton 
unit with 2 remote evaporator units. It can be a nightmare to find the 
leaks, especially on a remote system. A self-contained unit is bad 
enough, but at least the potential leak areas are a bit more contained.

Leak detection requires methodical troubleshooting, and at best it's 
labor intensive. The most effective method IMO involves injecting a 
UV-sensitive dye into the refrigerant circuit along with enough 
refrigerant to get the system running again. After running for a day to 
allow the dye to circulate, a UV light will reveal the presence of dye 
at any leak point. The leak can be anywhere, but a typical culprit is 
the evaporator coil. Mechanical connections (flare joints, expansion 
devices, etc.) are another. Once the leak is located, a course of action 
can determined for repair. Hope for a loose flare joint!

If the repair requires opening the system to replace a component in the 
refrigerant circuit, a protocol involving removal of the refrigerant by 
a reclaim machine (EPA requirement, but not always followed), purging 
with nitrogen while brazing to prevent oxidation or scaling of the 
copper tubing or fittings, then evacuating the nitrogen with a vacuum 
pump. This step is all-important, since it also confirms that the system 
is tight, since a leaking system will not hold a vacuum. It also removes 
any moisture from the system. Moisture is the enemy of refrigeration 
systems, combining with the heat of the compressor, the oil, and 
refrigerant to produce phosphoric acid which attacks the internal 
components of the system and the compressor motor windings, which in 
turn produce more acid as they break down, spewing acid through the 
system & eventually leading to catastrophic failure of multiple components.

In my own case, the PO neglected a small leak in the seawater connection 
at the condenser tube, allowing seawater to drip down over the remote 
condenser, with the end result of the accumulator rusting at the base. 
The accumulator must be replaced, not a horrible procedure, but 
certainly complicated by the nearly impossible access. I am fortunate 
(??) to possess the skills to make the repair, but it will not be a fun 
day! It is frustrating that the neglect of such a simple maintenance 
item resulted in such a miserable and complicated repair. Poor 
maintenance yields benefits in spades!

Good luck with correcting the problem, it's that time of year when an 
A/C problem suddenly becomes higher priority!

Steve Sipe
Solo 4303 "Maerin"
Middle River, MD