Okay, more questions partaining to A/C evaporator coils and condensation drip lines...


Have just installed a piece into the drip line of my home's central A/C evaporator unit that will allow me to connect a garden hose and wash out the line downstream from the evaporator, as well as adding bleach water to the same part of the system. Thing is, the 3/4" PVC pipe was almost completely blocked by whatever is growing in there, and now I am wondering if my evaporator coil is in similar condition. It's been at least ten years since this unit was installed, and it is a sealed unit, with no access to the drip pan for placement of tablets or chemicles to prevent the growth of what now nearly blocks my drip line. Am I going to have to pay someone to take this damn thing apart and clean it, or is it possible that I could do that? I am fairly handy with tools, but have never (yet) attempted anything like this. What say those who know about such things? I am willing to tackle it, I would just hate to screw it up.
Just for informational purposes, the evaporator sits above the blower unit (in a closet at the center of the house) and the rest of the system is up in the attic (ductwork) and outside (compressor, I believe it is called.) I guess I need to get some estimates, and talk with someone who does this professionally. In the meantime I am all ears for those who care to share their opinions on what I describe.
Thanks,
Dave
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Dave wrote:

Definitely not a sealed unit. There should be a cover or covers that are easily removable with two or four screws to access and inspect the "A" coil and blower. It's unlikely that there is any gunk growing on the "A" coil, but it could be grungy if the filters have not been properly maintained. The condensate pan(s) below the "A" coil could have some growing gunk potentially.
Also, be careful with any garden hose flushing since depending on how things are setup, it could backflow, overflow the condensate pan(s) and run down onto the blower and blower motor.
You should snake the drain line to clear most of the gunk before trying to flush anything.
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Hey Pete,
Thanks for the quick reply. I have looked for removable panels, but all I see looks like sheet metal wrapped around and taped. And I installed a ball valve "upstream" of the bit that the hose hooks to, so it can be turned off to prevent water from flowing back into the drip pan.
And I have already found someone with whom I have a working relationship to come out and look at the beast, for a reasonable price. So I will probably not be tackling this one. And *if* I hook a hose up to it, I will have the wife inside watching for any cataclysmic events while we talk on the wireless phone, so I can shut the water back off post haste. I may just add more bleach water, and call that good. It is flowing, just very slowly.
BTW, I really don't know that a snake will do this job, as there are several ninety-degree corners in the drain line before it makes its way outside. And it is only 3/4" PVC. I don't know if anyone makes a snake that small, although I have one close to it. I think it's only 25 feet though, and this would likely require at least thirty-five feet I believe.
'Preciate it...
Dave
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Lol, on a properly installed and sealed section of ductwork you might have to remove some of the foil tape and mastic sealing the edges to do a major servicing of the coil by taking the duct apart... Which is why you would call a service company in to do that work if you don't know how to do it yourself...
Did you expect a small square access panel that had a label on it "coil inside" ?
~~ Evan
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Behind that tape, there should be a removable panel to access the A- coil. Or it may just be a single-shaped coil placed in the duct at an angle. But it had to get there somehow and so there is a removable piece of sheet metal that will allow you to get at the cooling coil. A shut-off upstream of your flush point is an excellent idea, good thinking.
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Dave wrote:

While mine has removable panels, it seemed a lot of trouble to remove eight screws.
I drilled a 3/4" hole in the sheet metal for adding the bleach (with a funnel), closed the hole with a cork, and called it done.
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Looking at the thing again this AM, I see that there are four screws in addition to the tape. But there are also hoses coming out of that panel, which is the only panel I have access to. And those hoses would seriously interfere with an attempts to get the panel out of the way. Your idea of just drilling a hole sounds like a wonderful one, so long as I don't hit anything on the other side. Will have to consider this, and find a way to make it work. Thanks for the input...
Dave
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I've seen A coils installed in ducting that has no access panel that is removable. In that case, you would need to cut an opening. Obviously you need to know what you are doing and use a saw that will only penetrate 1/4" or so beyond the metal. If you use a long saw blade you run the risk of destroying the coil. If you need a big opening, extending near the bottom, then I'd start from the top. Cut that open, down the sides part way, then you can see inside and know how much clearance you have at the bottom where the A coil will be closer. Then cover the cut-out up with a new piece of sheet metal and tape as needed.
Another consideration would be if you plan to ever install a humidifier. Now would be a good time to do that if you want one.
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I've seen A coils installed in ducting that has no access panel that is removable. In that case, you would need to cut an opening. Obviously you need to know what you are doing and use a saw that will only penetrate 1/4" or so beyond the metal. If you use a long saw blade you run the risk of destroying the coil. If you need a big opening, extending near the bottom, then I'd start from the top. Cut that open, down the sides part way, then you can see inside and know how much clearance you have at the bottom where the A coil will be closer. Then cover the cut-out up with a new piece of sheet metal and tape as needed.
Another consideration would be if you plan to ever install a humidifier. Now would be a good time to do that if you want one.
YES YES YES! This is what I think I have, which is why I am looking for an expert who works in the field. Thank you, now I don't feel so much like the Lone Ranger. So tell me, how often do you think such an A coil would need to be cleaned? It's been at least ten years since this one was installed...
Dave
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On 7/1/2010 8:24 AM, snipped-for-privacy@optonline.net wrote:

It's not unusual for me to pump a system down storing the freon in the condenser, closing the service valves, disconnecting the line set from the evaporator, sliding it out of its housing and taking the dirty clogged up thing outside for a proper cleaning. Sometimes it's the only way to get a system with an A coil back into good operating condition. It can be time consuming but you may have no other choice if you want an AC that works like it should. Sometimes I have to add an expansion valve to a system to make it work right.
TDD
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I was just looking at my evaporator unit with the thought of where to drill, and realized I don't need to drill. There is an extra fitting next to the drip line, like it was set up for two drip lines but they only used one. And the cap on the second fitting is not cemented in place- it turns with the help of a pair of pliers. Now waiting for the HVAC guy to confirm for me that I can use this fitting to add bleach to the system. Damn. Oh, and the bleach I put in the drip line list night worked at clearing it out while we slept. I poured some water into the pipe earlier to see how much it took to fill it up, and it never got full. Checked outside and the hose had spit out all the goo that I saw inside the pipe yesterday. It now runs clean and clear. Only the 18 or so inches above the ball valve now need to be cleared. I love it.
Thanks, all.
Best
Dave
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