Rusting air handler coils

[Cheryl]

Hello AHR folks, it's been a while since I've asked you helpful folks for help.

I have a heat pump with an indoor air handler, purchased in 2002. I found water standing on my basement floor and after drying it with the dehumidifier I attempted to find out the source. I then found more water coming from directly under the air handler, so called in for repair.

Guy opened the panel and the coils were rusted, and the water in the condensation drain pan and circulating pipe was orangeish and was clearly the reason why condensation wasn't draining and instead leaking onto the floor.

The unit (a 2 ton Bryant) was purchased in 2002. Why would coils rust so quickly and how can you prevent it after replacing the unit for many $$$? My heat pump uses R22 freon and apparently it is banned for new units but could be ordered for repairs, but to replace the coils would be nearly as expensive for the whole job as it would be to replace both the heat pump and the air handler. The replacement unit I'm looking at has stainless steel coils; is that going to last longer, and how to prevent this problem after replacement?

[Tony Hwang]

Hi, Have you done any PM on the unit since it was installed? Wonder if it is a case of penny wise and pound foolish. Pardon, had to say this.

[Cheryl]

I have, thank you for asking and replying! But apparently not 2x per year to drain and clean the coils as they tech I just got said you're supposed to do. I had no idea! I've had like every other year PM and no one told me 2x per year. So is this how to save the coils? 2x per year draining and cleaning? Does this mean draining the coolant, whatever replaced freon? Preon or whatever he told me is used now?

[Tony Hwang]

Hi, This is to make sure drain hose/pipe is not plugged up by algae growth or dirt so pan is always empty rather than water stays in there all the time. Moisture is cause for rust most of time. R22 is still available for sure. There are many ma y old systems still running on R22.

[dadiOH]

Stainless doesn't rust. Are they materially more costly?

One prevents the problem by assuring that the drip pan isn't holding water. It won't hold water if the drain line isn't plugged with debris or whatever. You can check either by looking at the drip pan or outboard end of the drain line (while unit is running) to see if water is dripping out.

In my opinion, PM every six months is primarily to enrich the company; ditto annual. We spring for it every 2-3 years.

[trader_4]

IDK how you're supposed to drain and clean the coils. Every system around here that I've seen, including brand new ones, just installed, have no provision for access to clean. Take a look at the cased coils sold by major HVAC manufacturers, and they are sealed. And draining makes no sense , there is nothing to drain unless it's plugged and overflows. Otherwise wat er drips into the pan from the coils and water runs out.

Are you sure you even need a new unit? IDK what kind of coils rust, typica lly they are made of aluminum. The pan under is typically plastic. Even if som e metal there is rusting, a you sure it's so bad that it needs to be replaced ? If it's so shot that there is a hole in it where the water is leaking ou t, then I can see it. But if the drain hole, drain line etc just got plugged up with some rust, crud, whatever, the unit could still have life left in it. There are a lot of companies out there that want to sell a new system, even when there is a minor problem, or no problem at all.

[Stormin Mormon]

CY: 14 years ago.

I

CY: Sounds like the right thing to do.

CY: The coils I've seen have often been copper tubes and aluminum fins. I can believe corrosion, but rust only in the steel drain pan.

and the water in the

CY: Sounds like a rusty pan.

and was

CY: If the pan is rusted though, it will leak. Or, you might have a clogged drain, and the water is overflowing the edge. Or, the pan might not be properly tilted towards the drain.

CY: 12 years of being wet is "rusted quickly?" Huh?

and how can you prevent it after replacing the unit for many

CY: Sloped drain pan, clear drain, and possibly run the air handler fan now and again to give it a chance to dry up.

My heat pump uses R22 freon

CY: Freon is a brand name. R22 is also available in Isotron brand, or Genetron brand, or Forane brand.

and apparently it is banned for new

CY: Might want to get a couple more quotes. I have a hard time believing that replacing an indoor air handler costs as much as replacing both.

The replacement unit I'm looking at

CY: Probably, yes.

and how to

CY: Slope, clear drain, run the fan occasionally, clean the area with coil cleaner.

. Christopher A. Young Learn about Jesus

.

[TimR]

This doesn't make sense. Coils are aluminum and won't rust. They have to be, they are wet all the time, that's how they work when cooling.

There should not be water in the condensate pan. It should be draining. B ut these clog all the time, partly because dust gets past the filters but m ostly because biological stuff grows in dark moist conditions.

When the condensate pan clogs, and they all do eventually, you have to snak e or blow the drain out - when it clogs, you still shouldn't get water on t he floor. There is supposed to be a secondary pan that catches it. Then t hat pan is supposed to have a float switch that shuts off the air handler s o you know you have to fix it.

There is no circulating pipe in this system, just a drain pipe. If there's water in the drain, it is clogged.

[Stormin Mormon]

CY: A good tech with experience in heat pumps can catch a lot of problems while they are small.

So is this how to save the coils? 2x per year

CY: In theory, the water that collects on the coils should run down into the pan and then down the drain, by gravity. Some times, things don't work as well. The coil might shift and be sloped the wrong way. Algae and dust builds up, and drains clog. A skilled tech would catch this kind of problem early.

Does this mean draining the coolant, whatever

CY: Unless you're doing major repairs like replacing a coil, you generally don't need to remove the refrigerant. The name Puron is a brand name for one brand of R410a. Just like Freon is one brand of refrigerants, which might include Freon 12, Freon 22, Freon 500, Freon 502.

[Stormin Mormon]

CY: Cleaning coils is something I've often done. Draining is when the drain tube is clogged, and needs to be cleared. I've done that now and again.

Every system around

CY: Every system I've seen around here (including the brand new ones I've helped install) has a cover that comes off for cleaning. Take a look at the cased coils sold by HVAC companies, they have a side that comes off.

And draining makes no sense,

overflows. Otherwise water drips into the pan from the coils and water runs out.

CY: Ideally, yes, it drains by gravity.

CY: Pan either plastic or some times steel.

Even if some

CY: Might be able to dry they system out, and plug the hole with (for example) epoxy cement.

CY: That's for sure!

[trader_4]

It's been a few years since I worked on mine, and I guess you're right that they have a panel that comes off, so I'm wrong about them being sealed. But even with the panel off, I don't see how you're going to clean much on a typical modern coil. Here's a pic of a typical Rheem, similar to what I have:

With the cover off, you aren't going to clean much of it. You have no access at all to the side of the coils that receive the incoming air. With no access from above, I guess you might get your arm in there, to try to clean two faces of the coils and you have very limited access to just a part of one other face. That means you can maybe clean 2 1/2 sides out of 6 sides of the coils. And you can't get to the sides that receive the incoming air at all, where presumably most of the dirt would be.

[trader_4]

o be, they are wet all the time, that's how they work when cooling.

But these clog all the time, partly because dust gets past the filters but mostly because biological stuff grows in dark moist conditions.

ake or blow the drain out - when it clogs, you still shouldn't get water on the floor. There is supposed to be a secondary pan that catches it. Then that pan is supposed to have a float switch that shuts off the air handler so you know you have to fix it.

's water in the drain, it is clogged.

+1

There are probably some metal parts in there that can rust, but not the coi ls themselves. The box for example that holds the coils, maybe some bracke ts, etc. And even if there is some rust, unless it's structurally compromised, I don 't see the compelling need to replace it. At least not for the customer.... These backup and leak water frequently, due to the drains getting clogged. Clean the drain, and keep on trucking.....

[Stormin Mormon]

Ideally, the system has a good air filter, and dust isn't an issue. But, in the real world people pull the filters out and let the system run unprotected. It's often necessary to pump out the refrigerant, and cut the coil out. Wet clean it with chemicals and put it back. Bit of work, for sure

Cheaper than replacing a thousand dollar coil.

With the cover off, it's possible to spray in some diluted Clorox bleach, and also to blow out the drain.

. Christopher A. Young Learn about Jesus

.

[trader_4]

Well, that's kind of where I was coming from. It may not be "sealed", but to get at it to really clean it, isn't typically possible by just removing a panel. I'll bet only a small percentage of the evap coils out there are ever cleaned.

I agree with the part about the filter. When I replaced mine after 28 years, the coils were still clean. And all I'd used in that one were the cheap 1" thick filters. Of course it also depends on the environment. If you have a dirty, dusty house, 3 dogs, etc, then the incoming air is probably a lot dirtier.

[TimR]

The purpose of the filter is to protect the coils from dust buildup, as wel l as the fan and anything else in there.

It is not to protect human health. A filter that could do that would have to trap much finer particles, therefore it would have much more air resista nce and would require a much more powerful fan, etc.

As the filter gets dirty, it probably gets more effective at trapping dust, but it also increases the resistance to air flow. Eventually it will prob ably tear and let air through untreated. We want to change filters at regu lar intervals but doing it more often is probably not better.

[RobertMacy]

YES IT DOES!!! Just not as readily as plain iron, though.

I have to continually wipe a sheen of red/brown off all our SS kitchen appliances!

We're talking high end crap, too.

[Tony Hwang]

Hi, I think the tech came was not really honest about the situation, may be trying to sell unnecessary high cost part(ie new coil) rather than repairing the issues and give the owner good run down on how to maintain it. Good honest techs are hard to ccome by but they are still out there. At least I can recognize it when I see one. One reason I turned DIY'er. I enrolled on a few night courses at local tech college to learn the basics.

[Tony Hwang]

Hi, My favorite filter is 16x25x5 Merv. 10 filter cartridge I replace twice a year. Every thing stays clean in the system. Only thing I clean at the start of the season is condenser coil out side.

[trader_4]

I think that depends on what kind of filter you have. Many typical HVAC filters will collect dust, pollen, etc that are detrimental to health. It doesn't have to be able to stop a virus to have a positive effect on health.

[dadiOH]

OK, it may get some light surface rust, depending on the alloy, but it doesn't get the scaley, deep rust.