Rusty AC Drain Pan – Deeper Look Inside

[Alex F]

For the past couple of weeks I’ve been bugged by a very unpleasant (to say the least) smell coming from somewhere in the sleeping quarters. It was noticeable when I ran FWD AC, however when I try to sniff the area by the AC the smell wasn’t that obvious. With fan circulating it all over the place it’s really not easy to find the source, but I kept going back to the rusty AC.

After taking a closer look I said to myself that whether this is a source or not I have to do something with this horrible looking thing. So, I called Dometic got the part # for new SS drain pan and placed the ordered through local distributor. Last week we had a heat wave and AC being in HU mode didn’t do much in regards to cooling. When we opened the salon door we received a “shock doze” of the stinky smell. We opened the FWD hatch and started ventilating the area while searching for the source….

To make long story short, our cruising was cut short and we decided not to postpone until new drain pan arrives and pull the AC out.

Here’s what this mess looks like:





This mass of gross stuff you see is no possible way to clean as it's under the evaporator. So, unless you break it all apart you'll never get to it.






As you can see the issue is NOT just the rusty pan, but every metal component (compressor, evaporator, etc.). Anything that sits in that pan lower than about ½” is all affected. To make the situation worse, all the scum and rusty mess that you see is all getting in to the AC evaporator intake and gets distributed throughout the ducts right in to your lungs.

Upon further investigation I drew the conclusion for the cause of the smell:

1. It’s obvious that no matter how well I try cleaning the pan before storage there are small pockets where I just can’t get every single drop of water out and if any is left it only gets spoiled.
2. Looking back at the possible scenarios I don’t see how it’s possibly for the water remain in the pan from last fall, b/c we run the heat for couple of months and usually the pan looks dry way before the boat get stored. So, IMO it has to be new condensation deposits that just didn’t get flushed.
3. The drain tube. When I pulled the unit out, ironically I could still feel the sticky smell in that area. So, I realized that with so much rust flaking off the tube must be clogged not completely but enough to have poor water refresh rate contributing to the smell. When I took the hose to flush the tube my theory was proven very quickly.
4. Even though we can't blame SR for this horrible design their contribution was made by installing the drain tube incorrectly restricting adequate drain to poorly designed self contained system.

I used the wire brush on a drill to clean everything I could reach and the rest hat to be treated with some chemical. I had EZ ON/OFF on the shelf so I decided to give it a shot. Oh boy, is that stuff strong or what…..but it did a great job to get rid of everything I couldn’t reach by hand.

I flushed it all thoroughly with fresh water, then used air compressor to dry as much as I could from the pockets.

The next step was to apply break cleaner. At that point I thought that the unit was ready to be painted. So, I applied two coats of Rustolium spray paint. I have no idea how well it’ll hold up, but I thought that this was my best approach to save $2.5K-$3K for new unit.

BTW, before installing everything back in the new SS drain pan I will shim everything about 1/2" off the bottom.

The main point of this thread is to remind folks (I was one of them) who see the rusty stain on the hull and think that it’s not a big deal the detailers will clean it easily. Remember that all this stuff you and your crew BREATH IN.

 

[JimFromMD]

Would it be worth coating the pan with something before reinstalling it so that it wont rust again (solving only one of the rusty issues I recognize). I had thought about taking mine out and coating it in that informercial spray sealant that they spray on a screen door which is used as the bottom of a boat. Cant think of the name for the life of me, but you get the idea.

 

[Alex F]

I'm hoping that new stainless steal pan will hold up for few years. By then, I'll replace the whole unit. Over the years the vendor started to realize the issue and completely went away from metal pans. The newer models are using some special plastic material.

I'm still scratching my head about the salon unit. It's a nightmare to go to it. Working on FWD unit is like a walk in the park compare to the salon unit, which is located under the entertainment center. I only hope I don't have to take it all apart.

 

[carterchapman]

Would it be worth coating the pan with something before reinstalling it so that it wont rust again (solving only one of the rusty issues I recognize). I had thought about taking mine out and coating it in that informercial spray sealant that they spray on a screen door which is used as the bottom of a boat. Cant think of the name for the life of me, but you get the idea.

Jim,

When I replaced the pan on my 340, the new SS one came coated with a "bedliner" type of material...

 

[Alex F]

Jim,

When I replaced the pan on my 340, the new SS one came coated with a "bedliner" type of material...

Carter, that gives me some hope that my new one might have some extra protective coating. It better as it costs around $200.

 

[fwebster]

Alex,

I can't get everything in perspective from the few photos you posted, but looking at the water level on the components, it sees to me that your drip pan might be too level. When you put all t his back together, you might think about shimming up the ends away from the drain with some rubber shock bushings......they will raise the level to facilitate draining rather than containing water, and dampen noise.

 

[Alex F]

Frank,

The pan is a simple one level thing. I was planning to shim the pan as you suggested, but I also will change the drain outlet (as you know those pans have several in different locations) so it will follow natural gravity toward the stern. So, if we're looking at the pan facing the bow the port stern (or bottom left) corner will be the lowest point with the drain tube there and the other three corners (mostly the stud stern or bottom right) will be shimmed.

I hope it makes sense what I tried to describe.

 

[gerryb]

Alex. my salon air system and pan was much worse than what you showed above! Never thought to take pictures but it was a layer of crud across the bottom of the pan 1/4 thick...And the boat always had that same weird smell. I've upgraded to the new TURBO model and am refurbishing the old unit. I soda blasted the existing pan which cleaned it all up very nicely. Then sprayed the inside with the rubberized spray paint you see around nowadays - 2 coats - got it from Costco and looks like it will work great. I'm also blasting the rust off the bottom of the compressor and evaporator and will paint the compressor to match. Will be adding some compressor lubricant and checking the refrigerant pressures as well. I decided to upgrade to the newer unit even though it did cost a couple of thousand. I wanted the quieter compressor and much better design as I intend to keep this boat for quite some time. Plus I figure I'll be able to get some money for the refurb'd unit once I sell it. Take a look at the TURBo unit's pan - much much better design...

Edit: I also decided to install a better filter and UV light to help with keeping air a bit fresher around the unit. I'll post some pictures when I'm back on the boat.

 

[Rocket]

Alex, be careful if you Shim the evapoator coil up 1/2 inch. You will create a gap and air will be sucked underneath the coil and not Through the coil. Bypassing the coil with reduce performance and possible freeze the coil due to loss of air across the coil.

 

[Alex F]

Alex. my salon air system and pan was much worse than what you showed above! Never thought to take pictures but it was a layer of crud across the bottom of the pan 1/4 thick...And the boat always had that same weird smell. I've upgraded to the new TURBO model and am refurbishing the old unit. I soda blasted the existing pan which cleaned it all up very nicely. Then sprayed the inside with the rubberized spray paint you see around nowadays - 2 coats - got it from Costco and looks like it will work great. I'm also blasting the rust off the bottom of the compressor and evaporator and will paint the compressor to match. Will be adding some compressor lubricant and checking the refrigerant pressures as well. I decided to upgrade to the newer unit even though it did cost a couple of thousand. I wanted the quieter compressor and much better design as I intend to keep this boat for quite some time. Plus I figure I'll be able to get some money for the refurb'd unit once I sell it. Take a look at the TURBo unit's pan - much much better design...

Edit: I also decided to install a better filter and UV light to help with keeping air a bit fresher around the unit. I'll post some pictures when I'm back on the boat.

Gerry,

I know what you mean about the new units. I've researched them when doing my bridge A/C project and was going to buy the 16K BTU Turbo if I didn't find the 22K BTU unit.

Selling the old one in working order is a good idea.

 

[Alex F]

Alex, be careful if you Shim the evapoator coil up 1/2 inch. You will create a gap and air will be sucked underneath the coil and not Through the coil. Bypassing the coil with reduce performance and possible freeze the coil due to loss of air across the coil.

That's a great point. I wasn't aware of this. Let me understand this correctly. As long as I shim the components in the way that evaporator has direct contact at the bottom and the whole bottom is closed off (kind of like sitting on a "shelf") it should be fine?

 

[gerryb]

When you reassemble the old unit, make sure the evaporator base is lying flush on the pan. You want the fan motor to only suck air through the evap coil. If you need to shim anything, shim some small pieces of rubber under the pan.

I bet most people wouldn't immediately think the AC pan could be the source of foul smell in a cabin. The smell is hard to describe .. kind of like vinegar mixed in with mild degreasing chemicals...?

 

[Rocket]

Sort off, if you lift the evaporator you will need to seal of the bottom so you draw all of the air through the coil. however you will need to also create some weep holes in order for the condensate to drain. To be honest, it sounds like it is more work and trouble than it is worth. If you are getting the stainless steel pan you are essentially starting with a clean unit. I would put it back together as per factory and use Algea and deoderent tablets. I use them and the pan stays clean. If you drop the tabs in every few week, keep your filter clean i think you will be happy. try grainger http://www.grainger.com/Grainger/COMSTAR-Condensate-Pan-Treatment-4PDC4. Also clean your evap coil with simple green and some water.

 

[Dave S]

Alex

I don't have the smell problem but I have the rust problem with my unit as well and need to address it shortly. But I also wanted to mention another issue that occurred on my boat as a result of the rust. The drain box for the condensate line on my boat is also full of rust and the other day I could hear the sump pump in that box running and running and not turning off. When I took the lid off the box, I found the float was stuck from all the rust in the box. I was able to fix it temporarily but I still have to take the box out and take things apart to clean everything properly.

Dave

 

[gerryb]

Alex

I don't have the smell problem but I have the rust problem with my unit as well and need to address it shortly. But I also wanted to mention another issue that occurred on my boat as a result of the rust. The drain box for the condensate line on my boat is also full of rust and the other day I could hear the sump pump in that box running and running and not turning off. When I took the lid off the box, I found the float was stuck from all the rust in the box. I was able to fix it temporarily but I still have to take the box out and take things apart to clean everything properly.

Dave

Good point... The Third issue is the rust stains you get on the hull when the sump pumps out that water/rust dilution overboard.

 

[JimFromMD]

Sort off, if you lift the evaporator you will need to seal of the bottom so you draw all of the air through the coil. however you will need to also create some weep holes in order for the condensate to drain. To be honest, it sounds like it is more work and trouble than it is worth. If you are getting the stainless steel pan you are essentially starting with a clean unit. I would put it back together as per factory and use Algea and deoderent tablets. I use them and the pan stays clean. If you drop the tabs in every few week, keep your filter clean i think you will be happy. try grainger http://www.grainger.com/Grainger/COMSTAR-Condensate-Pan-Treatment-4PDC4. Also clean your evap coil with simple green and some water.

Hey Rocket,
Would those tabs work in the shower sump box to keep gunk / funk from forming too? I've seen where people put hot tub chlorine/boron tabs in their shower box and also in the sea strainers to keep growth down... but have also seen the debate about whether the harsh chemicals do more damage than good. What's in this product (if you know).

James

 

[Alex F]

New SS pan arrived yesterday, so I proceeded to put things back together. BTW, the pan had special coating, which was sticky and also comes off easy. Oh well, it is what it is. I thought about shimming the components inside the pan, but then decided against it for few reasons. It's not easy to secure the shimming material (whatever would be used). As we all know these units vibrate a lot when they run, so I thought for a moment that in case if I'll have a loose end somewhere and the shimming part will create extra noise from the vibration it'll drive me nuts and I'll have to take the whole thing apart to start from scratch. So, I said to myself that it's not worth it. If this POS "lived" since 2005 it'll survive another few years after my rebuild. The main idea is to shim the whole unit such way that the water runs to the drain and stays in a small section.

Went to the boat to install everything back and when I walked in the master state room I've noticed minor smell that was still present. It was day and night difference, but the more I worked in the area the more it bugged me that something is still not 100% cleaned. That's when my phase 2 of the "fun" project began. More on this later as I have a lot to share, but have to run right now.

 

[HUMPH]

Hey Rocket,
Would those tabs work in the shower sump box to keep gunk / funk from forming too? I've seen where people put hot tub chlorine/boron tabs in their shower box and also in the sea strainers to keep growth down... but have also seen the debate about whether the harsh chemicals do more damage than good. What's in this product (if you know).

James

Noflex Digestor keeps the sump pretty good too. Breaks down any crud and helps with hair balls.

 

[Escapade]

I too am plagued w/ this rusty pan syndrome. After Reading this I thought about two options, What is your opinion if I were to bead
blast the pan and put a layer of glass down. Or send it out for Powder coating Hi Gloss white? Thanks, Mike

 

[carterchapman]

I too am plagued w/ this rusty pan syndrome. After Reading this I thought about two options, What is your opinion if I were to bead
blast the pan and put a layer of glass down. Or send it out for Powder coating Hi Gloss white? Thanks, Mike

Mike,

That's a good question. I saved mine for three years after I replaced it with a SS model, thinking that I could do that and have it as a spare. Finally threw it out last week in a "garage cleaning" fit!

It's interesting - in my '05, it's just a painted steel pan prone to rusting (as we all know). In my '03, it has some kind of a coating on the steel and then it is painted - no rust on either one there...some bean counter decided to save a nickel. I wonder how many free SS ones they had to give out?