Corrosion of Alde Convectors

db_cooper

@fstop32 , my preferred option was what you describe, using a ball valve and running it out the door.  I carry a fair amount of junk under the passenger bench, and thought knowing my luck it would get hit by something and drain out. And being the low point, it would be the full 2 gallons.  Rather put a hole in the floor and seal it up.

 I also noticed our original drain has lost it's sealant and dirt and water have been getting in there.  I plan on filling that same time I install the new drain.  

Edited to add, I thought the Alde drain was one of the 3 hoses that go through the "grommet" together, but that's just the expansion tank overflow tube.  The Alde drain is hidden underneath the large hose as   a T fitting with a smaller hose running out through the floor.  I had not looked closely enough to understand that it was separate.  Picked up the hose and can see lots of daylight.

Denny16

db, I wouldn’t use a copper T in the Alde glycol lines, it may cause more issues.  Use a stainless steel or better yet, get an aluminum/galvanized steel one from Truma/Alde.  You do not want any copper in the system.
cheers

fstop32

@db_cooper, I noticed the same thing when I pulled the rubber drain T out of my floor, I'll be filling mine too.  All I saw in the Alde catalog I have was a galvanized steel T, however it was a 22mm x 22mm x 3/8" muff for drain and you can get a brass drain cock that will screw into it as well.  Or you can go with the same rubber drain like you've got now.

ScottG

Below is a typical chart that shows where galvanic corrosion between dissimilar metals is a problem.
Bottom line is that aluminum doesn't play very well with anything.

I pondered this issue quite a bit when I was originally thinking of installing a filling tee to facilitate glycol exchanges. Conceptually, this would have been the same as adding another drain.

Finding the right sized tee in aluminum was challenging. I did locate this place online that makes tees (and other fittings) in a range of sizes. I also considered plastic fittings, but those tend to be so heavy-walled that I was concerned about flow restriction in the glycol loop. I think the best bet would have been Alde's drain tee, which brought me to the problem of getting parts from Alde. Sigh...

Ultimately I abandoned the idea of a filling tee in favor of the gregndeb adapters which were simpler and required no modification of the system, so I haven't pursued this further.
 

ScottG

fstop32 said:

@ScottG, I meant to mention I'm going to replace the driver side convectors with an "in built" version that is recessed into the cabin panel which picks up cool air directly off the floor and lets it rise through the convector and then passes it out back into the cabin.  I thought that would help keep that compartment from being as warm.

@fstop32, if you were so inclined you could  just eliminate those driver's side convectors. Clearly nuCamp did so shortly after your T@B was built. I don't know if that decision was driven by economics or performance, but the heat works fine with just four convectors, the potential for a second low point is eliminated, and you gain back a little storage/mechanical space.

fstop32

@ScottG, when the estimate comes back I'll probably have to pair things down from my "wish list" and leaving out the driver side convectors will be my first move.

db_cooper

@Denny16
I agree that adding copper is a bad idea, but I may go through with it, but add a magnesium anode to the the expansion tank. 

I'm currently trying to get the parts from Alde, but I do not feel very confident that I'll be successful (much as @fstop32
 has found). 

If I do end up adding the copper tee,  I'll probably replace the fluid every year, which will be easy with the low point drain system.    And for sure will be watching those hoses for signs of corrosion.  Looks like those aluminum connections are the first thing to go in the system.

Denny16

@db_cooper, A galvanized fitting would be better (Aluminum better yet) as minimal corrosion issues, see Scott’s chart above, the closer together the metals are in the chart (orange squares) that do reach with each other, the quicker the reaction will occur.  Aluminum to galvanized (gray) shows reduced/limited reaction passivity, so this is your best choice, and cost should be less than copper.

This is a not the place to take a short cut my friend. The factory install used the galvanized fitting, I would follow this example.  Also, we do not know what the reaction (if any) will be between the Alde glycol and copper would be.  

As for parts, other TaB owners were able to get Alde parts (including the comp,etc Flo kit, fittings and all) fro, nüCamp.  I would contact them for the part number and place the order via yiur dealer.

Adding a magnesium anode to the the expansion tank (pkastic, non conducive material), will not protect the copper fitting, nor reduce corrosion issues in the Alde.
cheers

MarkAl

The sacrificial anode will work if you ground it to the Alde metal as the fluid acts as the current path.

Denny16

Mark, I agree, but connection it only to the reservoir bottle, will not do anything.
cheers

ScottG

MOD NOTE: I've consolidated the comments here about draining/blowing out old glycol with related comments  in Changing out the Alde fluid.

Topics were getting fragmented so I thought putting everything under one roof might make it easier to follow. 

db_cooper

Turns out all the connections have some buildup, even those that didn't appear to be bulging yet. While there's a little corrosion, even on the worst bulging connection at the rear convector there is not real damage, it's more of a buildup.  I consider that great news.

I had an email out to Alde/Truma about getting parts for a second drain, and got the usual response to bring my trailer to Elkhart or a NuCamp dealer.  Seeing as how I'm 2300 miles from Elkhart that probably won't happen.  I have responded and asked if Alde recommends sealant on these connections.  

Now that I know I can drain virtually all of the fluid using @ScottG method of blowing in the hose right past the check valve, I will be replacing the full 2 gallons every 2 years.  If I have to pull the connections and clean again in 4 or 6 years I can live with that.  By then the Alde will be 10-12 years old and probably dying of some other issue.  No idea what kind of lifespan to expect on these things.

Full disclosure:
2015 T@b purchased 2nd hand at 1 year old Jan. 2016
Partial fluid replaced 2016, 2017, 2019, 2020 with Sierra low tox, not Century

Alde gets ran quite a bit,  I run it on low during cold weather at home.

I don't think the difference in fluid has anything to do with this, since others have similar results, and based on usage I think it would look like @fstop32 Alde if I hadn't done the partial changes.  


Rear convector with bulging hose:









Rear bulging hose:




Inside rear convector hose



Side convector that showed no signs of bulging:

ScottG

Nice work, @db_cooper. Looks like you found pretty much the same thing I did.

fstop32

@db_cooper I feel your pain!  The response I got from Alde/Truma was the same initially.  I think the extent of the damage to mine might have perked their interest a bit but not sure what that will lead to as far as my finding parts to rebuild.  I think nuCamp & secondarily Alde/Truma are headed for a big hit if they don't at least come up with a way for owners to easily get their hands on the parts and info needed.
Let me know what they say about the sealant, I've asked the same question but no response yet...and a pvc cement sized can is around $26.

Maybe a bottle brush and a really good flush might clean that up sufficiently.  You might want to remove the check valve section so sediment doesn't get trapped there.

db_cooper

@fstop32  Good idea on the check valve.  As a homebrewer I have bottle brushes that will definitely clean the hoses out.    I respectfully laid out in my last email to Alde this morning that suggesting a trip to Elkhart for every problem was not the best customer service response, and that as much as I love the Alde compared to forced air,  that I find it hard to recommend a product that is difficult at best to get parts or service.

I'm going to a double flush with distilled water before I add the glycol,  I think I'll be good for a while after this.  

Between this and learning how to solder a new thermal fuse on the circuit board, I'm beginning to get a pretty good handle on this thing.

fstop32

A homebrewer!  If I can't get my T@b fixed I think I'll turn it into a brewhaus 8^ )

@db_cooper, speaking of that thermal fuse, is the photo below the fuse of which you speak?  I've also seen reference to a "glass fuse", would that be one in the same?

db_cooper

That would be the offender, @fstop32
  @ChanW figured it out around Jan 2017, and I remembered it when ours quit in April 2018.   I made a jumper with alligator clips and it fired right up.  I carry the jumper for emergency use when it happens again.  It's been 3 years since I replaced, so it will probably crap out before too long.  The glass fuse is the one on top of the Alde.  I'm going to jinx myself, but that fuse is usually the culprit, but ours has never gone out.  I think it blows more often with hookups and not turning the Alde off prior to plugging in.  I'm careful to turn off the Alde before plugging in at the house.

Here's the original thread:
https://tab-rv.vanillacommunity.com/discussion/4197/found-a-fix-for-no-alde-heat-when-all-fuses-are-good/p1

db_cooper

@fstop32
I was hoping to let this thread lie,  but alas it's not to be.

The corrosion is worse than I had feared,  especially at the connections on the rear convectors.  This was the spot with the biggest bulging, but it wasn't very noticeable.   It's so awkward to clean the connections back there, I decided to remove the convectors so I could clean them in comfort.  Unfortunately I found holes all the way through.

Not sure of next steps,  I forwarded these pictures to Alde as part of my current email conversation with them.  I'd be happy just to get a few connectors and 2 new long convectors.  The short ones under the passenger bench weren't bad.   We'll see.  I'm afraid we're going to see this a lot more over the next few years.  Just when I finally found a way to fully drain the system. Dang it.

I'm sure I could zip it all up and get a year or two without leaks.  My friend next door said he'd fix it if I buy him a Tig welder.     I told him JB Weld was cheaper.

Sigh......

fstop32

Sorry to hear that @db_cooper, I'd hoped that wouldn't be the case for you (or anyone else).  Funny (not haha) though, the worst corroded convector I had was in the rear and it was the one that came up from the boiler.  In my T@b the output of the boiler first goes through 2 short convectors under the driver side bench then up to the big convector in the rear.  The 2nd worst corrosion was the small convector under that driver bench...  Hmm, now that i think about it the further away from the boiler the less corrosion was found.
I hope somebody can get to the crux of this problem.  I agree with you that we are going to see more of this, not less.  I'd sure like to know an answer before I put mine back together.

db_cooper

Good day to be a homebrewer @fstop32!  There's a tear in my beer.

My two worst spots were where the top rear convector exited to the manual air bleeder, the air bleeder connection took the brunt. Then even worse was the same spot on the bottom convector at the fluid entrance.  There are patterns but I don't know what it means.

I may zip it up for the summer, we will mostly need hot water for showers. 

Does 2 make a club?   

ScottG

Sorry to hear that, @db_cooper. 

I think I found the most deposits (which presumably would be associated with the earliest corrosion) on the rearward connections to the two side convectors. (These were the ones I in the photos I posted.) I'm not really sure there is a predictable pattern among our findings. So far, a few other owners have reported bulges, but I'm not aware if they have dismantled for inspection.

Thinking it best to let sleeping dogs lie, I wasn't very aggressive in trying to remove the most stubborn deposits. I'm wishing now (well, maybe not...) I had done a more thorough inspection of the insides of all the fittings with a mirror and/or my fingers just to confirm that none of them had any corrosion breaking through. Now that I know what I am doing--and that it is relatively easy with my pump and adapter set-up---I'll probably revisit this issue next spring to inspect again. I expect by then we have a lot more insight into what is going on and hopefully have viable options for dealing with it.

Preliminary evidence does seem to suggest that system use is a factor in accelerating deposit formation and subsequent corrosion. We use the heat very infrequently--despite neglecting the glycol for so long that may have slowed the pace of deterioration. One second owner of a 2014 that had received almost no use at all (and no glycol change) reported draining discolored glycol from the boiler core, but did not note any bulges at the convectors.

The questions I'm pondering right now are:

• Is this issue related to whatever prompted the switch to the new glycol?
• Is there reason to think the corrosion extends to the boiler core and not just the convector fittings?
• If needed, how are we going to get parts (and possibly professional service) if a trip to Elkhart or Sugar Creek is not a realistic option?

To be continued. Thank goodness for homebrew!  ;-)   

RCB

This is getting very concerning. My comments and queries as follows, svp.
1. I was told years ago that glycol molecules are smaller than water molecules. I have no data to support this, but if there is any truth then it might explain why deposits exist between the inside of the hose and outside of the alum convector connection piece. My first Diesel engine was A UK built Petter. The maintenance instruction stated to retorque the head after “x” hours of running - well I thought I’d do it in the spring and went ahead to winterized the engine with automotive glycol - we did that in those days.  In the spring I found the cylinder full of glycol and was told that because of the smaller molecule, it was able to migrate between the head and head gasket.

2. At the least I think replacing the clip type clamps with double screw type clamps may well reduce future deposits. The outer clamp should placed as near to the end of the alum to minimize and fluid migration between the two surfaces.
3. At one time I had a cast iron hydronic heating system in an old house. The hydronic service person recommended flushing the system with a chemical solution to remove any contamination - the stuff that came out was gruesome. So, perhaps there is a solution that might dissolve and remove the deposits in the Alde.
4. When flushing the system, is there any reason not to flush extensively with tap water before flushing with distilled water ?
Thanks,

ScottG

Those are reasonable ideas, @RCB, but I don't have any definitive answers.

Regarding #4, my sense is that an extensive flush with tap water followed by a good rinse with distilled is better than half-hearted rinse with only distilled. Tap water is certainly easier to come by.  

fstop32

Good thoughts @RCB.  #1 would help explain why the point of corrosion appears to start at the confined rubber to hose contact.  Maybe the glycol seeps in and the corrosion inhibitors break down over time and they aren't being refreshed like they are on the inside of the pipes which constantly have glycol w/inhibitors flowing.  That's a WAG on my part but it might help explain why the corrosion appears to first start in those confined rubber to metal areas.
I'll be using the screw clamps in my rebuild and I'll be building better access to keep up with periodic examinations and tuneups.

I also think that introducing tap water to the system will, if not flushed out, introduce the chemicals and minerals present in the tap water which might mean we're trading one irritant for another one.  @ScottG, I like the idea of a thorough flush with the tap and then follow with a good albeit lower volume of "clean" water.  Hmm, this might give me a reason to set up the RO water filter we had before we knew what problems it was introducing into our "personal pipes" 

I seem to be full of WAG's today... 8^D

ScottG

In general, distilled water is probably more "pure" than RO water, particularly with regard to ions (which if I understand correctly are what you want to keep out of your Alde system). Now, if you run your RO water through an additional deionizer, that's another story--but I doubt you have one of those waiting around to be installed.  ;-)

Just geeking out a bit here. I have no idea if flushing with RO vs distilled water would make any practical difference. Either would certainly be a far better choice than tap water for a final rinse. 

fstop32

Yep, that RO thing was a lame attempt at a joke because I do have one sitting in a cardboard box in the garage 8^D  Besides it's way too much trouble when distilled water comes packaged by the gallon at the local DG.

db_cooper

I've decided, after sleeping on it, to do a temporary repair on the connections and convectors, which should last a year or two.  In the meantime, I will try to source new convectors if the cost is reasonable.  

I'm thinking that the boiler is probably compromised to some extent, so switching to the new fluid is not worth the trouble.  

Longer term, I may replace the entire system, as long as it's cheaper than a new trailer, and of course use the new fluid.

BridgerSunset

Great documentation of your issues, guys.  It's important.  Wish I had the answer. 

Pulled from this NACE (National Assoc of Corrosion Engineers) resource  Fontana's Eight Forms of Corrosion - NACE
is this clip below that I think could describe what we're seeing:

Crevice Corrosion

Intense localized corrosion frequently occurs within crevices and other shielded areas on metal surfaces exposed to corrosives. This type of attack is usually associated with small volumes of stagnant solution caused by holes, gasket surfaces, lap joints, surface deposits, and crevices under bolt and rivet heads. As a result, this form of corrosion is called crevice corrosion or, sometimes, deposit or gasket corrosion.

Thoughts:

Note that in the above, stagnant is the word, and we have deposits.

The system is under heat/cold cycles, so there's expansion/contraction of the rubber, which would invite fluid entry behind the connector.  That's a good way for fluids to get back there & never leave, leaving their deposits behind.  From what I've read from your findings, the corrosion is always & only found under the deposits?   What these deposits are comprised of seems key, since they are likely the "dance partner"  in the corrosion cell that's required to cause the aluminum preferentially to lose metal.

However, the deposits themselves could simply be a corrosion by-product, rather than a relic of the dried glycol.  This implies the fluid back there is corrosive in nature, by itself, since we have corrosion of aluminum.  Not sure if a high pH fluid after the corrosion inhibitor is gone is good or bad  - anyone know??  If it's bad, I'd expect corrosion throughout the entire system.

Besides frequent fluid changeout, I do think those ideas suggesting to supplement the factory clamp and externally coating the connector have merit.  

The system is not really a pressurized system, so there could be times when there's a negative pressure behind there. This might contribute, but not sure what.  Maybe oxygen gets pulled in, which itself can accelerate corrosion under deposits.

All else being equal, corrosion reactions are more pronounced in higher temperatures.  Would expect worse nearer the boiler outlet.

Sorry so long.  Keep up the good fight!

N7SHG_Ham

@db_cooper it is probably cheaper to replace the entire Alde system, but not inexpensive. I bet you would be into it $3k+

db_cooper

@N7SHG_Ham, that sounds about right, and I would do it as I like our 2015 better than the new ones.

@BridgerSunset, great post, good info.  My plan involves sealant and 2nd clamps, we'll know in a year or three of it works. 😛