Questions About Internal AC Coils

[trader4]

What do you think the reason for this is? I know Rheem at least says you should always have one in the drain line. But then they don't say anything about putting one in the aux, ie overflow line for the coils. And even if you did put one in there because it's only for an overflow, the trap would soon dry out. Hence, if you have one drain line that is open, why not two? Also, some installs I've seen they put a trap in, others none. More common is none from what I've seen.

My thought would be they would be most concerned if the drain line was routed to a sewer drain, which makes sense. Other than that, the trap would prevent the loss of some conditioned air.

[trader4]

I don;t see that the installer has any choice. The typical exhaust fitting is PVC female glue type at the top of the furnace. Putting an elbow in doesn't solve a thing, you then just have the elbow in the way. Also, manufacturers spec out the max number of elbows allowed, and less is better.

And short of not gluing it, I don't see a way to make it removeable. To make it removeable, which would be a good idea, would require the manufacturer to do so.

[DerbyDad03]

How would an elbow help? The panel goes all the down to the top of furnace housing.

If an elbow had been used, the elbow would be in the way.

The only way the vent will not be in the way is if it is removed from the exhaust port completely.

[trader4]

That was my thought too. But then you still have the overflow drain outlet that even if it had a trap, the trap would soon dry out and be useless. I guess having 1/2 as much air loss is better though.

Most of the nitrogen just escape to the atmosphere when the factory plugs are removed. Then you're supposed to flow nitrogen through the tubing while brazing. Then that nitrogen gets vacuumed out. The outside unit, ie condenser, is usually shipped pre-charged with R410A so that does not need to be pumped down.

[Evan]

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

[HeyBub]

A p-trap on the condensate line serves the same purpose as a p-trap on a sink: it blocks sewer gas from infiltrating your A/C system.

Your question can be answered with another question: Does your house sometimes smell like a privy?

[Ed Pawlowski]

"HeyBub" wrote

He's dumping the condensate into a sink.

If he was going into a drain, he'd need a trap for the reason you stated. If he wad going outside to the ground, he'd want a trap to keep bugs from crawling in. I don't see any need for a trap in this case.

[DerbyDad03]

..

Your answer can be questioned with another question:

How are sewer gases going to get into a piece of flexible tubing that hangs over a utility sink?

[trader4]

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.

[bud--]

Here (and probably everywhere else) condensate drains are an "indirect waste" and go through an air break to a sink or floor drain. They can't connect directly into a sewer system.

[DerbyDad03]

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. ;-)

[HeyBub]

My bad. I thought his condensate drain went to the sink's vent pipe (mine does).

[Evan]

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

[Evan]

To address point number 1:

Yes, that is code in the four states in New England that I have done repair work in...

To address point number 2:

Nothing may be vented to the atmosphere when doing any sort of HVAC work in Massachusetts or Rhode Island... Nothing... So if Nitrogen is charged in a coil during shipment to prevent damage, it must be recovered prior to the pressure test and the refrigerant being charged into the system...

Next fallacy ?

Maybe that explains a lot of the NY attitude -- too many pollutants in the air...

~~ Evan

[DerbyDad03]

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.

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:

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.

[hrhofmann]

e:

It looks like you have a double A-coil, not a single A-coil.

[The Daring Dufas]

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

[DerbyDad03]

te:

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!

[The Daring Dufas]

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

TDD

[bud--]

Not in the NEC. Doubtful 4 New England states are insane.

Good point. Nitrogen is one of the serious air pollutants and nothing is being done about it. Your capturing it is a step in the right direction.

You NYers need to listen to Evan. Capture the nitrogen before it is too late!!!!