Questions About Internal AC Coils

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I have a Conquest 90 Max gas furnace with central air.
I also have a bunch of questions:
1 - The internal coils have not been clean since it was installed 5 years ago, so I decided to take a look and see if they needed cleaning. Problem is, I'm not sure how to access them.
I removed the screws from the panel where the condensate and refrigerant pipes are, but as you can see from this picture, I can't remove the panel because of the vent pipe.
http://imageshack.us/photo/my-images/62/furnacef.jpg/
If I could tilt the top or bottom of the panel outwards, I could remove it, but the vent pipe prevents any significant tilting.
There is no other panel that I can remove. The other 3 sides that surround the coils are a single piece which has the duct work on top of it. The duct work would have to go up in order for the 3-sided surround to come off.
How do I get to the coils?
2 - Through the limited opening, I can see into the coil area with a flashlight. I see 2 tee-pee sets of coils and as far as I can tell they are perfectly clean, at least on the surfaces that I can see with the panel open as shown. Should I just close it up and forget about it or are there areas I should check - assuming I can gain better access?
3 - When I removed the panel I saw 2 stickers, both of which raised questions in my mind:
3.1 - One sticker has a picture of a "condensate drain trap" made from a piece of flexible tubing attached to the drain output pipe. As you can see from the picture, I don't have a trap. At the bottom of the PVC pipe seen behind the gas line is the condensate pump.
The pump sends the condensate up a flexible tube and across the ceiling to the utility sink.
I don't need a trap with that set up, do I?
3.2 - The other sticker says: "Coil is shipped with a low pressure (5 -10 psi) charge of dry nitrogen. Evacuate system before charging with refrigerant."
Would the unit work (i.e. cool) if the system was not evacuated/ charged when it was installed?
I'm not saying that it wasn't evacuated/charged because I don't remember if the installer did it or not, so I'm just curious.
Thanks!
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That is a typical A-coil set-up on top of your furnace. I have the same set-up. Yes it is a pain getting to the A-coil. Bottom line is if you change you filter regularly, and if the unit is cooling fine, there is no need to get in there. Its not worth the trouble. I had my unit 8 years already and no problems so far.
You don't really need a trap on the drain line. It drips slowly, its not like a steady stream of water like a sink.
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The only time a trap would be required would be if it drained directly into a sewer line. You could cut the plastic pipe and then use a coupling to rejoin it. But if you can't see any dirt and if it seems to be cooling ok, leave well enough alone!
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wrote:

That's 2 answers that say "if it seems to be cooling ok"
How do I know? I never had central air before this unit so I have nothing to compare it to.
It doesn't seem to be any different than the first year, but how do I know if it was right the first year.
Is there some standard measurement such as cooling degrees per hour at a given temperature or percent of humidity removed per hour?
How do you check the performance of a central air system?
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DerbyDad03 wrote:

The cheap way: Stick a thermometer in an air outlet. The standard is twenty degrees of cooling. That is, if the ambient room temperature is 80 degrees, the AC should be pumping out 60-degree air.
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wrote:

@Bob:
You would want a trap in the small PVC drain line for the condensate line if it drained directly outside -- to keep bugs out of your HVAC duct...
I have never seen such a vent directly connected into a drain or sewer line, that would provide a direct pathway for black water to back up into your HVAC duct if your main drain line ever clogged...
The air gap provided by letting the condensate drain line drip into a floor drain or utility sink ensures that sewage will never back up into the duct work...
~~ Evan
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On 5/28/2011 8:17 PM, DerbyDad03 wrote:

Are you sure you can't get the PVC vent loose and swing it aside? Me and my bud I do AC work with never install a 3/4 PVC drain without a union so we can service the drain if it clogs up. You can cut the 3/4 drain line and install a coupling without glue so you can get it loose. I always use unions anyway. With the 3/4 drain out of the way, you could easily remove the cover. Big box stores have the unions.
http://www.grainger.com/Grainger/Union-1WKD7
TDD
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wrote:

@TDD:
That vent pipe is for the flue gasses from the burner in that high efficiency direct vent furnace... I wouldn't cut into that for any reason EVER, as if you don't glue it up perfectly when you put it back you will have issues with carbon monoxide leaking into your home from the exhaust products during heating season...
The better solution here is to have the OP cut the sheet metal panel which can not clear the obstacles and obtain a piece of flat stock which he could install so he could screw it back into one piece when he is closing the coil compartment on the main trunk duct back up again... The joint the OP cuts in the cover panel and the screw heads can be sealed up with foil duct sealing tape...
~~ Evan
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On 5/29/2011 1:25 AM, Evan wrote:

Perhaps I confused you, I only cut the 3/4" PVC "drain" line not the vent stack which is usually in the 3 to 4 inch diameter range. :-)
TDD
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While I would not cut the vent pipe unless it was really necessary, the notion that you can't do it "EVER" because it's dangerous is pure nonsense. It's just glued together using regular PVC cement and if you can glue a piece of PVC, it's no big deal. IF you think that is high risk, explain how all the furnaces, hot water heaters, etc, prior to high efficiency used simple galvanized sheet metal pipe that just got shoved together and secured with sheet metal screws. The seal there was far worse than what you get today with PVC pipe.

I'd like to know how he's going to cut that piece of sheet metal when the access is so limited. For sure I'd cut the exhaust pipe before I did that. I'd also check to see what the exhaust is or isn't connected to inside the furnace. There is a small chance it could be disconnected from inside.
But, if the coils appear clean, I'd just put it back together and save a lot of trouble. The real problem here is that the eqpt manufacturers typically don't provide a means to clean the coils. Nor do installers take that into account when doing the install. On the other hand, if you have a decent filter, I've seen systems that went 25 years and the coils were still fine.
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On 5/29/2011 9:01 AM, snipped-for-privacy@optonline.net wrote:

The older systems that you could simply slap together as you described were natural draft. High efficiency designs use induced draft and the flue is pressurized because of it.

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Yes, that and you can have a slightly imperfect glue joint on a length of PVC drain pipe and never find out about it until the line clogs and the entire pipe fills up with water...
With a high efficiency condensing boiler exhaust pipe, there is an induced draft in the flue pipe and it is under pressure, any imperfection in the PVC glue joints in a flue pipe on such a boiler would allow dangerous carbon monoxide gas to leak into the house...
~~ Evan
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What exactly do you think the typical HVAC guy does with regard to that PVC exhaust pipe that is so different from what a guy like DerbyCad could do? Do they use some secret solvent or glue? No Do they use some special skills, different from gluing ordinary PVC pipe? No Do they presssure test it for leaks? No
You jump into things you don't understand and issue all kinds of nonsensical advice. Some recent examples:
Code says metal eletrical conduit can't touch metal HVAC ducts or any other metal
Nitrogen is recovered from an HVAC system
I would not cut that PVC exhaust pipe to clean the coils, because he's looked at them and said they are clean. But if Derby wants to cut it, for whatever reason it can be put back in place with a simple PVC coupling.
Also, there is no dangerous amount of CO to leak back into the building unless the furnace is operating improperly. And even then, it would have to a significant, leak, not a small pinhole leak.. Yeah, there is slight pressure in that PVC exhaust pipe, but it's minimal. It's not a 50PSI pipe.
This is a homerepair newgroup, isn't it? Explain how gluing a simple PVC coupling into a furnace exhaust is any more dangerous than a homeowner replacing a gas stove or dryer. Or wiring up their own hot tub or dozens of other things that they do every day.
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wrote:

Trader4:
Are you implying that I shouldn't take Evan's advice to grab a pair of shears and cut the access panel in half (while it's still stuck behind the vent) and then fabricate my own panel to cover the gap ceated by the cut?
That seems so much easier than altering a PVC pipe. ;-)
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wrote:

You are right, there are dozens of things that homeowners do every day that they absolutely shouldn't be doing because they are not properly trained in how to do them...
Because they are lucky and manage to get the thing done without injuring themselves or burning their house down today doesn't mean that the repair or improvement will stand the test of time...
As far as a PVC vent pipe for a high efficiency burner being involved in some repair -- no way, not unless the homeowner in question has experience gluing PVC and can create consistent air-tight joints...
The problem that _this_ OP has is a sheet metal problem, not a vent pipe, drain line or refrigeration line issue...
The sheet metal panel is too large to manipulate it around the obstructions near its installation -- so either someone would have to remove the obstructions EVERY TIME they wished to access the main trunk ducting panel OR make the panel so that it can be removed around the barriers by cutting it into smaller pieces which are attached to eachother in the same way the outer edge of the panel is affixed to a gasket...
For all the "common sense" you offer, I haven't seen too many threads where you have offered your wisdom where no less than 5 other people hadn't offered it first...
I came up with the answer in this thread that seems to be something the OP might actually consider doing if he actually wants to open up the duct work and inspect/clean his coils...
~~ Evan
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As it turns out I was able to remove the panel without cutting anything.
It's hard to tell from the picture, but the PVC vent pipe has putty around it where it enter the exhaust port on the furnace.
http://imageshack.us/photo/my-images/62/furnacef.jpg/
Once I removed the putty I was able to lift the vent out of the port and move it (with some effort) to the side just enough to be able to swing the bottom of the panel out enough to rotate it around the other obstructions and out.
Unfortunately, I think it was all for naught. I don't have much more access to the coils than I did before.
Behind the exterior panel there was another panel whose purpose is to keep the condensate from soaking into the insulation on the back side of the exterior panel. Once that was panel was removed I found this:
http://imageshack.us/photo/my-images/703/acoils.jpg/
I can't get to the coils anyway. There's barely a 1 1/2" opening at the largest point along the top near the bar code label. Unless I'm missing something, the only thing I can do is inspect the coils because there's no room for a coil brush to reach anymore than a very, very limited area of the coils.
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It looks like you have a double A-coil, not a single A-coil.
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On 5/30/2011 3:12 PM, DerbyDad03 wrote:

Oh cool! You have a W coil. No joke, that's what it's called. If you remove the 3/4" PVC drain and put it back with a union you may actually be able to (with some help) slide the W coil out of the housing with the refrigerant lines still connected. You can set it on top of a large trash barrel next to the furnace and with great care, get some evaporator cleaner and a water hose (hot water works best) and clean it up to like new condition. Of course a shop vac is another useful tool to bring to the party. I slide coils out all the time to clean them but if I can't set it to one side with the lines still connected, I have the knowledge, tools and equipment to pump the system down and remove the evaporator coil for an outdoor cleanup. The first picture you posted looks like there would be enough room to slide the W coil out with the lines attached for a good cleaning. :-)
TDD
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wrote:

Feel free to stop over when you're in the area 'cuz this DIY'er ain't sliding nothing out of any housing! :-)
If it gets to a point where I think it needs cleaning, I drop the big bucks and have a professional do it.
In the immortal words of Dirty Harry, "A man's got to know his limitations."
Thanks anyway!
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On 5/30/2011 7:30 PM, DerbyDad03 wrote:

Well, it's an advanced DIY project but you may still be able to lift it up to inspect it by looking underneath. :-)
TDD
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