Glycol questions

bergger · April 16

Yeah that's why I was wondering if there was a check valve between the two outlets. It would make sense that there was, the new fancy Alde pump the dealers are supposed to know how to use pumps new fluid into one of the ports and pulls the old out of the second port. With no check valve you would wonder if the new stuff going in so close to the where the old stuff comes out would just be sucked back out. But from the photo above it does not appear that there is a valve there. I also can not find the manual for the pump used for those with only one exterior port but not the new ones with two. My only thought is that the in-flow and out-flow portions of the pump extend all the way up into the ports to effectively block each other. So fluid going in won't mix with fluid coming out. But looking at the photo of the new pump it does not look like they go that far into the ports. So who knows??? Maybe a question to ask NuCamp.

bergger · April 16

I've actually sent an email off to NuCamp to try and get some clarification on how the new bottom fill/drain ports work. If we can figure it out it may make the whole process on the new trailers easier than on the old ones.

Robermcm · April 17

I’m going to Truma’s Elkhart office tomorrow morning for my dead boiler fix. I’ll ask about how the bottom fill method works.

Oh, and my reservoir is like Sunfellows in a ‘23 400 bd.

Sunfellow · April 17

Good point, ScottG.

Yoshi_TAB · April 17

Robermcm said:

I’m going to Truma’s Elkhart office tomorrow morning for my dead boiler fix. I’ll ask about how the bottom fill method works.

Hi, Maybe while you are there you can ask around and maybe get some intel on the corrosion issue;

-why do they think it's happening
-why did they change glycol brand (what is different about the two)
-does it seem just to be with TABs (i.e an assembly problem at hose connections)

ScottG · April 17

@bergger and @Robermcm, I'm looking forward to any information you can extract regarding the bottom fill protocol. (But I don't have much hope that answers regarding the corrosion issue will be forthcoming...)

Robermcm · April 17

i missed the corrosion question, sorry. Was camping in Elkhart!

I’ve got a treasure trove to share here on the forum though. Did the best I could to round out system knowledge as I got my boiler replaced (yep, wasn’t winterized and split the boiler halves in what was reported to be classic freeze damage).

Just got home, so I need to organize a little. Here’s a teaser.

Learning #1: Truma has a presence of Facebook. Small, like 500 members. If you ask a question, a tech from the Truma Elkhart u.s. home office will answer! Look up Truma North America and join. I’m sure we can easily double that membership. Eddie Green was the tech that replaced my boiler and who’s seen so many frozen damaged ones, it’s ridiculous. Jason Wright was the second guy helping out.

Learning #2: The head space thing is real. Both guys said to be sure to create head space in BOTH the boiler and the Flow tank. Especially in hotter climates. Simply open ONE of the yellow flapper valves, with water pressure off, for like 10 seconds. Then the other. If you do both at the same time, one can fill the other and reduce the effectiveness of you trying to dump a little water from each tank.

more later!

Robermcm · April 17

Learning #3: the ‘double Alde glycol drain flush’ uses a pull method on one side and no fluid is short cycled. I didn’t get great detail on this, except that it sounded a whole lot like the version of fluid change we talk about that uses the reservoir and a fluid pump. Pull old fluid out, let the new fluid siphon in. Unclear what connections they use to allow this. Edit update - see below in this thread for more detail on the double drain flush process. It’s an embarrassingly simple approach

Learning #4: Edit - this was a misunderstanding I fabricated out of a poorly worded question, I think. Ignore the italic text in this learning! End edit. the flow direction of water and glycol is the same, starting in the Flow tank, moving to the boiler, then heading first to the high point air bleed valve. That’s the bathroom in my 23 400. That’s the opposite of the flow as I understood for the glycol. A disassembled boiler in the waiting room gave me a change to experiment with the one way valves and it supported this learning. Both the boiler and the Flow have their own one-way valve.

Learning #5: They tested my breached boiler by pressurizing fixtures through the Nautilus city setting, heating circuit open (no bypass). When the reservoir started to fill up, that was proof. I know this has been discussed on the forum, but always good to hear it’s what the pros do. I told them that the hot water yellow flapper valve bled green Alde fluid, and this was their confirmation.

Learning #6: The Alde Flow tank is much more fragile than the boiler. Thin sheet steel holds the incoming cold water, and surrounds a ~3/4” diameter corrugated and coiled flexible tube (much like what you’d use to cool wort in beer making) for glycol to flow through. If the thin, rectangular tank freezes, it can leak big time, or leak a little around the cold water inlet, with small leaks initially hiding BEHIND the styrofoam cover that covers the services connection side of the Flow box.

Learning #7: The classic frozen water in Boiler damage is a horizontal crease that separates the top and bottom seams between glycol and water. This crease presses into the cavity that houses the electric heaters and, if displaced enough can cause the heater coils to touch the inner casing. This causes a ‘red’ over heat error, which often accompanies boiler breaches and this is why. I’m a little unclear on the overheat details here, so just relating what I heard about over temps as a symptom.

Overall - Great people, classy waiting area, fast and fair service. $1800 boiler, $580 Flow (quoted, but wasn’t needed). They gave me the old glycol pump and two circuit boards (main and propane fan) as spares. A tech and his supervisor(?) spent 3 wall clock hours on it and charged me for 2 total. I think that was a gift and I appreciated it. Hourly was ‘only’ $125 too.

Questions invited. I know this group has tons of expertise on these issues and how the system operates. Not trying to imply this is new or better info. Just regurgitating all I learned. Hopefully gives back to this group that’s helped me come up to speed so quickly!

Oh, bonus - they’re selling ‘scratch and dent Truma 12/24/120v coolers for cheap. A C30 for $328. Looked brand new to me. They had a shop floor area with a dozen or more of all sizes.

Pictures coming next.

Robermcm · April 17

My old, breached boiler. Pretty obvious cause.

Unrelated - Truma makes a ton of different water and cabin heaters. All displayed in their waiting room. All cool tech and likely in high end trailers. I know Bowlus uses them. (Alde flow inside pic included)

Robermcm · April 17

Oh, forgot one thing I learned - the yellow flapper valves. Was never quite clear to me why there were two valves. The cold water valve drains the Flow tank. The hot water valve drains the boiler. My p.o. apparently drained only the cold water valve, which is why the more delicate piece survived.

Binghi · April 18

Thanks for the detailed report, @Robermcm!

Robermcm · April 18

a few more recollections from my Truma visit…

The tech acknowledged Rhomar was the maker of their glycol, but he looked uncomfortable saying so. They must make a ton of $ off $50/gal of that stuff. Probably some corporate bulletin warning everyone. I didn’t get to the specific version, but this forum seems to be on track.

The 1cm above the MIN mark was totally ignored by the techs. ‘Anywhere between MIN and MAX is okay.’

The techs did respect the quality of the Nu_camp build. They see many brands and live in trailerville capitol of the world.

The techs said they fix a fair number of incorrect or less optimal Alde installs by manufacturers. No specifics. For me, that was extended to mean it was good to bypass the dealership for my replacement. Same day, 3 hour repair was an awesome bonus.

bergger · April 18

Except for the reason behind your trip to Truma I bet is was a cool trip. I'd geek out going there. I'm a fan of their products. Love the Alde, mostly! Just don't like the frequent glycol changes. I also have one of their Vario heaters with the CP control panel. It's mounted in my truck topper and is awesome. Heats up very nicely and is easy to operate. No maintenance either. I'd love for NuCamp to test out a Truma Combi unit in a T@b 400 to see how it does. I still think I'd investigate installing one in our 400 if our Alde ever completely crapped out.

Robermcm · April 18

bergger said:

Except for the reason behind your trip to Truma I bet is was a cool trip. I'd geek out going there. I'm a fan of their products. Love the Alde, mostly! Just don't like the frequent glycol changes. I also have one of their Vario heaters with the CP control panel. It's mounted in my truck topper and is awesome. Heats up very nicely and is easy to operate. No maintenance either. I'd love for NuCamp to test out a Truma Combi unit in a T@b 400 to see how it does. I still think I'd investigate installing one in our 400 if our Alde ever completely crapped out.

Yea, I really did geek out. The waiting room was clean and modern, with all their products on display (as photographed) on the perimeter. The combi looked cool but you’d need ductwork. Stealing from the cool cat in cold weather might work. Nu_camp could certainly design a way. From talking to the techs, a lot of inattentive people kill their Alde boilers. He pointed to a 20 foot stack of the units in shrink wrap awaiting their day.

ScottG · April 18

Great info and pics, @Robermcm. Those are probably the best photos of Alde innards I've seen, and they clearly show how freeze damage (or any overpressure situation in the Alde HW tank) can damage the boiler and result in domestic water infiltrating and overflowing the glycol side. Thank you for the detailed followup!

ScottG · April 18

I do have a comment/question about this statement:

Robermcm said:
...

Learning #4: the flow direction of water and glycol is the same, starting in the Flow tank, moving to the boiler, then heading first to the high point air bleed valve. That’s the bathroom in my 23 400. That’s the opposite of the flow as I understood for the glycol. A disassembled boiler in the waiting room gave me a change to experiment with the one way valves and it supported this learning. Both the boiler and the Flow have their own one-way valve.
...

Since glycol flows in a loop, the direction glycol flow is subject to semantics. Whereas the glycol has to first be heated in the Alde boiler, I share your interpretation that glycol first flows from the boiler to the Flow. Where it goes after that depends on whether the cabin heat is on. Of course, being in a loop, it eventually returns back to the boiler to be reheated (hence the ambiguity as to whether it flows from the Flow to the boiler, or the boiler to the Flow).

The following images diagram my understanding of how the glycol flows under different circumstances. This is based on the (unverified) assumption that only one of the two glycol pumps operates at any one time:

Image: https://us.v-cdn.net/5021717/uploads/editor/lg/9853al74dpqy.jpg

Robermcm · April 18

@ScottG, I’m still confused about this, I think. What you drew and shared above was my impression of glycol flow up until I asked the tech (twice) about it. Both times he said the glycol runs the same direction as the cold water. Flow to Boiler. After staring at your pictures, I may still be with them. When talking about heating the cabin, at least.

If tech was thinking hot water, then he’s right, as the flow pump runs the glycol back to the boiler. And, I guess, I’m right too, as it runs TO the flow from the boiler in a hot water only setting. There’s a one way valve in the flow too, and I think it’s permissive on the way out to the rear radiators.

What I saw in the waiting room was a used 3020, where the boiler glycol pipes were routing different directions than in a tab 400. Pic attached. The top pipe with the air bleed gold valve seemed to run 180 degrees opposite. It had a one way valve in it that let fluid flow away from the gold valve. And, there’s no glycol T-pipes coming out of the boiler for the hot water flow loop, so even harder to sort what’s going on. Must have been a stand alone boiler.

So, if I had the energy, I’d drain my stupid system and check both one way valves to see where they are permissive. That would settle it. The fact that I can’t draw how the glycol stays local when the Flow pump is running proves to me I have a ways to go to understand it. Can’t be hard. Just a test bed is unavailable.

Edit - I think your pictures are correct for the tab 400 boiler and flow set up and direction of fluid travel. I must have asked my question poorly. Will edit the earlier post too.

ScottG · April 19

I appreciate your confusion, @Robermcm. As I noted previously, the glycol runs in a continuous loop. As such, both of the following statements are correct, albeit a little misleading:

The glycol runs from the Flow to the Alde boiler.
The glycol runs from the Alde boiler to the flow.

In contrast the cold water does not run in a loop. It runs in a line, first from the supply to the Flow, then to the Alde boiler, then to the taps.

So the Alde tech wasn't wrong, per se, he was just comparing apples to oranges. :-)

Robermcm · April 19

ScottG said:

@bergger and @Robermcm, I'm looking forward to any information you can extract regarding the bottom fill protocol. (But I don't have much hope that answers regarding the corrosion issue will be forthcoming...)

Score! I wrote to Truma Elkhart about the bottom fill glycol replacement process and received the important (and oh so obviously easy) tip on how they do it…..

Good morning Rob,

For that double drain, they put a clamp in the top middle in between the two drains. One side is where the new glycol is run in and the other side is where it comes out. It is still a good idea to keep an eye on the reservoir while this process is being done to make sure that there is not a blockage and the reservoir is overflowing.

Hope this helps, have a wonderful day!

Best Regards,
Matalyn Prusinski
Sr. Customer Care Associate

ScottG · April 19

Thanks for that, @Robermcm! I've speculated for several years that this is how it work, but remained unconvinced as it seemed a little inelegant. However, the bottom fill process makes perfect sense if the two rains are not connected.

bergger · April 19

@Robermcm thanks and that explains how it is done without mixing the old and new or just sucking out the new as it enters the loop. But I agree with @ScottG that for such an advanced system, and yes elegant, putting what is in essence a clothespin between the too is a bit amusing! But I honestly wish I had the double port as it would make it much easier to access than going through the expansion tank and the very cramped space it is in. Using the shop vac method simply attach the shop vac to one side and my 12v pump the the other, turn the Alde pump on high and away we go! Cheap and easy to do.

ScottG · April 20

I don't even think you would need the shop vac, unless you were trying to completely drain the system before refilling. The new fluid being pumped in one hole would just push the old fluid out the other. (Providing, of course, you put that clothespin between the drains--haha.)

This is the same basic principle on which the original Alde service pump worked, with the big improvement of being able to work from outside the trailer rather than having to access and potentially remove the expansion tank.

When I was drafting the DIY glycol exchange process, I pondered similar modifications that involved adding a fill port (either inside or outside) near the existing single drain. I still think those were good ideas, but didn't pursue them as @gregndeb's modification-free tank adapters seemed at the time to be the simplest approach that would be accessible to the most owners.

@BrianZ ran with the fill-port approach, refined it, and ended up installing a very elegant flush-and-fill system using a multi-port valve similar to that used in the original Alde service pump.

Greenhil · May 8

Robermcm said:

ScottG said:

@bergger and @Robermcm, I'm looking forward to any information you can extract regarding the bottom fill protocol. (But I don't have much hope that answers regarding the corrosion issue will be forthcoming...)

Score! I wrote to Truma Elkhart about the bottom fill glycol replacement process and received the important (and oh so obviously easy) tip on how they do it…..

Good morning Rob,

For that double drain, they put a clamp in the top middle in between the two drains. One side is where the new glycol is run in and the other side is where it comes out. It is still a good idea to keep an eye on the reservoir while this process is being done to make sure that there is not a blockage and the reservoir is overflowing.

Hope this helps, have a wonderful day!

Best Regards,
Matalyn Prusinski
Sr. Customer Care Associate

As mentioned elsewhere, this seems a bit clumsy compared to a simple shutoff located between the two drains. I diagrammed my system and concluded the new glycol should be pumped into the innermost drain, while the old glycol comes out of the outermost one. There is only about 1 1/2” of space between the two drains, but I experimented with a pair of needle nose vice grips that seem to squeeze the tubing tight enough to keep the glycols from mixing.
As far as I can tell no one here or on the Airstream forum has tried a DIY glycol replacement using the two drain system. I imagine interest will grow as owners of newer models deal with this. I may give it a try following Scott’s DIY instructions, but using the hand pump attached to the drain and not the adaptors in the expansion tank. Just mulling over whether there might be problems I haven’t thought of.

ScottG · May 8

@Greenhil, I'm looking forward to your report if you try this. The only potential issue I can see is that once the fluid you are pumping in reaches the expansion tank, pressure will be lost and you will be relying on gravity to get the fluid the rest of the distance from the tank to the drain.

Whether this presents a problem could depend on the placement of the expansion tank relative to other system components. On my 2015 the tank is just above and upstream from the drain, so--if I had the dual drain--this bottom-fill approach would work just fine.

However, if there are other components (e.g., convectors, or the boiler itself) between the expansion tank and the drain, I can see where gravity might not be enough to maintain the flow and glycol just backs up into (and eventually overflows) the tank. This is alluded to in Alde's response to @Robermcm regarding the bottom-fill process.

Since I'm not certain exactly how the 400s and the newer 320s are configured, I can't specifically predict when and if this could be an issue.

Greenhil · May 8

That’s a good point, Scott. The caution from the Alde rep. about the tank overflowing did make me think.

Also, Robermcm wrote earlier that Truma told him, “the ‘double Alde glycol drain flush’ uses a pull method on one side…Pull old fluid out, let the new fluid siphon in.” The mention of pulling the old fluid out makes me wonder if there’s something I’m missing.

The bottom photo below shows the expansion tank located behind the toilet in my 2022 320 CSS. If I understand the system correctly the center line from the tank, which drops straight down under the bathroom floor, is the outflow.

The top photo is under the driver’s side bench just behind the bathroom. The red arrow points to the same outflow line. It comes from from under the bathroom floor, takes a 180 degree turn (above the arrow) and then passes over the drains, which are circled. This line continues along the length of the bench and enters the Alde unit at the back of the cabin. So as far as I can tell there is nothing but maybe 6’ of line between the tank and the drains on the outflow side of things. (The green arrow is pointing to the inflow line coming from the convectors and running under the bathroom floor to the expansion tank.)

I’m assuming that if I can pump the glycol as far as the expansion tank by pushing it from the drain closest to the Alde through the unit and then through the convectors to the tank it should come out of the drain closest to the tank by gravity without an overflow problem - unless I pump too fast or something plugs the tank drain or the outflow line. Does this make sense?

At this point I’m torn between trying this or just following the existing DIY method with the adaptors in the expansion tank. I guess my biggest worry is wasting a couple of gallons of expensive glycol in a failed effort!

ScottG · May 9

@Greenhil, if your system is configured like mine, I would expect the drain to be immediately downstream from the outflow of the expansion tank--just as you describe.

My only cause for pause is that you say the outflow of the tank is from the lower center opening. In my system this connection is the inlet to the tank; the outlet--which leads directly to the drain--is from the tank's higher offset opening. I suppose it's possible the hoses are reversed in your case, but presumably there is a reason Alde designed the tank as it did, and I'm pretty sure they specify that the lower center opening is the tank inlet.

If your assessment is correct, after the hose passes the double-drain it should enter the Alde via the circulator pump at the bottom of the unit, as that is the inlet to the boiler's glycol chamber. (In contrast, if the hose enters via the automatic air-bleeder at the top of the unit, the flow of glycol is the reverse of what you describe.)

You do raise a good point about Alde's bottom-fill method. Now I'm wondering if their proprietary pump applies a "pull" or suction to the outlet side of the double drain. This would certainly facilitate the flow of glycol through the system without relying on gravity.

Gkopan · May 10

I haven't read thru the myriad posts on glycol change, but is there a clear procedure for diy fluid change for my new-to-me 2021 400 that has never had it done and sat unused for at least a year before I bought it? Thank you!

pthomas745 · May 10

@Gkopan This link will take you to the section with the DIY Glycol Exchange .pdf.

https://tab-rv.vanillacommunity.com/discussion/comment/166510/#Comment_166510

That will have lots of info on the basic process. Have a look at your expansion tank and see how things might fit.

This is not the only "method". There is a "shop vac" method out there that works, and various modifications to the DIY method that other owners have successfully used.

If you look over the "Changing Out The Alde Fluid", that may be the best source for seeing how it is done. The entire 6 year 32 page thread is quite a slog, of course, but it is very educational. The link below goes to the last page of the thread. If you page backwards and check the photos, you should (maybe!) find an owner who has done it in a 2021 400 or a model close to it.

https://tab-rv.vanillacommunity.com/discussion/2665/changing-out-the-alde-fluid#latest

Ask questions....many owners have gotten through it with no issues and found the whole confusing thing pretty easy in the end.

Greenhil · May 10

ScottG said:

My only cause for pause is that you say the outflow of the tank is from the lower center opening. In my system this connection is the inlet to the tank; the outlet--which leads directly to the drain--is from the tank's higher offset opening. I suppose it's possible the hoses are reversed in your case, but presumably there is a reason Alde designed the tank as it did, and I'm pretty sure they specify that the lower center opening is the tank inlet.
If your assessment is correct, after the hose passes the double-drain it should enter the Alde via the circulator pump at the bottom of the unit…

After I read your post I sent Nucamp the photo of my expansion tank and asked which line goes to the double drain. Here’s their reply: “The larger line that is located in the center would be the drain line.”

As you suggest, I can follow the line with the double drain and it’s connected to the pump at the bottom of the Alde, so the glycol in that line must be moving in the direction of the unit.

As far as possibly needing to “pull” the old glycol from the other drain, I’m thinking I can use a wet vac if necessary.

Am I correct in recalling that the way to tell you’ve flushed the old glycol out is when what’s coming out of the drain changes to the color of the new glycol? In my model year, the old glycol is the same color as the new stuff. ls simply pumping three gallons into the system to insure the old glycol has been purged? Maybe another way is testing the pH of the old and the new glycol and comparing that to what I’ve pumped in.

Thanks for taking the time to respond, Scott, I really appreciate it!

ScottG · May 10

@Greenhil, I doubt you will bbe able to identify old vs new glycol by a change in color, or pH. If you are simply pushing the old glycol out with the new, I would go by the volume of new fluid pumped in. To do this, you would need to determine the approximate total capacity of your system. To be safe, I would probably pump in an additional 10-20% above that volume.

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