Questions About Internal AC Coils

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.

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!

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?

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

@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

@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

1. 5 years ? They need to be cleaned, even if you changed your filter religiously stuff will still build up on the coils... Even if you think they look clean...
2. You can't see in there very well and probably wouldn't see the tiny stuff which builds up in the coils anyway... Once people can be able to "see" dust on the coils the have been wasting energy in their cooling system for quite a long time... Dust insulates the coils making the system work harder to provide the same amount of cooling capacity and provides a nice convenient medium where any excess moisture in your home from humidity can condense and freeze, icing up the coils... (which is *not* a good thing)
3. Irrelevant questions, your condensate drain clearly does not directly connect to a sewer line or it would have a trap in its drain line -- nor does it drain directly outside...

As far as the coil being shipped charged with Nitrogen that is how the coils are protected from damage during shipping and installation... All of that gas would have been recovered and evacuated from the system before it was charged prior to the pressure testing which is done before any refrigerant is added, without refrigerant your AC wouldn't cool your house at all...

To answer your question about how to get at the coil, here is your answer:

You need to obtain a proper pair of steel metal shears to cut the cover panel down in a straight line from where the refrigerant lines exit the duct box to where the condensate line is located... You would then need a piece of heavy gauge flat stock and some gasket material... One side of the flat stock gets attached to the larger piece of the cover panel permanently... With the additional joint you create you can remove the cover from both sides of flue vent pipe without disturbing it's integrity which would cause a hazard, and if you properly gasket and seal the new joint line you create in the cover plate with real foil duct tape you will not impact or change the level of static pressure in your duct work...

Want to keep your AC working at peak performance for years ? Clean your inside coils with proper coil cleaner every year before cooling season starts -- don't forget to do the same with the coils in the outside heat pump unit, all sorts of things can obstruct the cooling fins in the coil outside from dirt to things left by bugs, plants or animals... If the cooling fins in the outside unit are dirty or have lots of stuff clogging them, then the fan can't induce a proper draft to transfer the heat into the outside air and the system won't run very efficiently wasting energy...

That looks like a very nice and neat install on your furnace and AC coils, the only thing your installer overlooked was how on earth the next guy was ever going to be able to open the cover up to service or clean the coils without having to cut out and remove the vent pipe and repair the same every time someone needed to open that cover plate...

~~ Evan

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

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.

How would cutting the PVC drain pipe help?

If I cut (or even removed) the drain, I still couldn't pull the bottom of the panel away from the furnace.

I'd have to rotate the panel along the same plane it's on now, but there's 4 1/2" of panel between the cut out for the drain and the edge of the panel. In other words, way too much material to be able to rotate the panel enough to remove it.

re: "Are you sure you can't get the PVC vent loose and swing it aside?"

The vent stack is sealed with putty around the inlet and then again where it exits the house. Are you suggesting that I remove the putty then pull the vent stack up and out?

I removed the lower panel and it looks like I'd have to lift the vent about an inch to clear the black inlet tube on the furnace.

I'm not sure if that's doable, but if that's what you're suggesting, I investigate further.

I understand all that work is needed to get at the coils to clean them, but to me its not worth the trouble, plus you risk damaging your coil trying to make some kind of access to get to it. If you ae going to go through that trouble, wait until the A-coil craps out and replace with a new one.

I agree with the other poster. If there is at least 17-20 degree or more difference in the return plenum and supply register, the system is fine. And if the return line of the refrigerent line is cold and sweaty, thats a good sign too. If your house gets to the proper temp with the compressor regularly cycling on and off throughout the day ( about 2- 3 times/hour), I would leave well enough alone.

Thanks for the info.

Seeing that the exhaust port on the furnace and the cutouts on the panel came that way from the manufacturer, how could the AC unit been installed differently such that "the next guy" (me!) was going to be able to remove the panel?

The only way I could it happening would be to have reversed the AC unit (if that is even possible) so that the panel was opposite the vent. That of course would have meant a vent pipe coming out of one side and the drain and refrigerant pipes pipes coming out of the other. That would have ended up being a very ugly installation.

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.

Please. I'd bet that 95% of the coils in central AC systems have never been cleaned, ever.

Some manufacturers call for a trap to be installed without regard to where the drain terminates. Not sure of the reason for this. One could be to reduce air loss through it or keep bugs out.

You don't recover nitrogen.

It would be interesting to hear from Derby if he thinks that's feasible.

I'd like to see a manufacturer that recommends doing this. And if it's so important, why don't the manufacturer's have a design where you don't have the huge problems Derby is having?

I'd say it wasn't the installer that overlooked anything. It was the manufacturer. That install looks exactly like the typical install instructions from the manufactuer. Every one of them I've seen shows the exhaust glued to the stub, and glue joints the rest of the way to the outside. The manufacturer designed the furnace and the cased coil. So, if they wanted access, they could have planned for it. I agree it would be a good idea to have access, but you have to deal with the hand you're given. And what I see here is the typical situation.

You unscrew the drain pipe which will allow you to rotate the cover out and remove it. If the A coil is really dirty, I pump the system down, disconnect the line-set and everything in the way, slide the A coil out of the housing and take it outside to give it a good cleaning. I wish I had some pictures of the systems me and my friend GB install so I could give you an idea of how we install a system so it can be easily serviced. It amazes me how many AC installers won't spend a few extra dollars and take a little more time to insure a system can be accessed for service later on. ^_^

TDD

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.

Looks like the installer was lazy......The vent pipe should connect with an elbow so the pipe is out of the way or should be removeable if that is not practical.

Jimmie

I believe the trap prevents blowing the slightly higher pressure discharge air out the condensate drain pipe.

The nitrogen definitely should have been removed so there is only refrigerant in the system. The whole system is pumped down - evaporator coil, lines, outside unit.