Glycol questions

bergger

I agree with @ScottG.  Replacing old Rhomar with new you will not see a color change to know if the old has been replaced with the new.  Color is a good indicator if you are replacing the old Century with the Rhomar as one is yellow and the other is greenish.  As Scott mentioned I would just push in a bit more than your system requires and call it good.  Since the color change is not going to be noticeable I would also recommend using a shop vac to suck out the old fluid at the end of the line as you pump in the new.  It's the method I used on our 2021 400 and I think it just helps in removing the old and limiting the mixture of old and new glycol.  

manyman297

I agree on color change. Did a Rhomar exchange (just replacing original Rhomar with new) and noticed almost zero color change.

ScottG

Here's an image from Alde that shows the intended flow of glycol through the expansion tank. It sounds like nuCamp is now hooking these up in reverse. I'm curious to know if there is a reason for the change, or if it makes any practical difference in the operation of the system. Presumably it was designed this way for a reason, but it's not immediately obvious to me what that might be.

AnOldUR

@ScottG. My guess is that the system draws from the higher port to reduce sediment from being pumped through the plumbing.

ScottG

Greenhil said:

...

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. .

...

And, yes, if you were inclined to completely empty the system first, I think this would work much the same way as drawing the old glycol out through the expansion tank.

However--just in case this is what you were thinking--I wouldn't vac and pump at the same time. This might be how the Alde's proprietary bottom fill pump works, but if so that pump probably has a carefully balanced push-pull, and a recirculating feature. Try to duplicate this with a shop vac and I suspect your new glycol will get sucked out as fast as you pump it in!  :-0

Greenhil

ScottG said:

Greenhil said:

...

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. .

...

And, yes, if you were inclined to completely empty the system first, I think this would work much the same way as drawing the old glycol out through the expansion tank.

However--just in case this is what you were thinking--I wouldn't vac and pump at the same time. This might be how the Alde's proprietary bottom fill pump works, but if so that pump probably has a carefully balanced push-pull, and a recirculating feature. Try to duplicate this with a shop vac and I suspect your new glycol will get sucked out as fast as you pump it in!  :-0

Thanks - this makes sense. I can’t see why it would be necessary to use a vacuum. With nothing, apparently, between the tank and the drain, I hope pumping will be enough. 

qhumberd

ScottG said:

Here's an image from Alde that shows the intended flow of glycol through the expansion tank. It sounds like nuCamp is now hooking these up in reverse. I'm curious to know if there is a reason for the change, or if it makes any practical difference in the operation of the system. Presumably it was designed this way for a reason, but it's not immediately obvious to me what that might be.

Just for my clarification, I marked my 2019 400 expansion tank before doing my last flush. I have stayed with Century and not had any issues. When I did my flush and fill 2 years ago I used tap water (many gallons) followed by distilled water before refilling with fresh Century fluid. I believe my flow is like the diagram above so in my case the hookup has not changed. The small and large drains seem reversed in the diagram but NOT the direction of flow.

The hose from the port on R returns to the Alde and the hose attached to the larger port on L  receives fluid from the last convector in the loop.

So when starting the flush  with the 12 V pump in my 2019 the flush water is entering on the R hose  and pushing fluid thru the Alde and around the loop and out the L hose. In this picture the old glycol is just starting to come out from the L hose below, that hose being attached to the larger port on the reservoir. In the shop vac method the pull would be on the L hose below to drain the system, and the new fluid would be pumped in the R hose.

And as @AnOldUR said, the larger port coming from the convector loop would be a place for any debris in the system to settle and not return to the Alde boiler

ScottG

@qhumberd, I agree regarding the diagram. My expansion tank looks yours, with the offset port located to the right of the center port when looking at the front of the unit.

I also like @AnOldUR's hypothesis that the large recessed inlet provides a sediment trap to reduce the likelihood of debris being drawn out the tank and into the pump/boiler.

asfizer

 
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 @ pthomas745, or anyone with answers,
I'm new with all this glycol draining and replacing. I've scanned enough through this thread just to confuse me. I bought a new unused 2023 320 S BD in February of this year, 2024. I have only taken a couple short trips so far this year, but thinking I'll do the glyco replacement next spring. I'm unfamiliar with this heating system, but interested in in doing the flushing and refill myself if it's not that complicated. being retired, 78yrs old, on a fixed income I tire to do DIY as much as I can. One of my questions is how to pump the new glyco in and not be mixed with the old? How do I pump in the new using the correct drain plug underneath? The inter-most of the two is the one to pump the new in, correct? Can I use one of those small pumps that works by attaching it to a power drill? I have one is why ask. I'll get whatever is necessary. I guess by my scanning through all this I'ved missed on how exactly to do this.

pthomas745

@asfizer There are several approaches to the glycol changing.

Before any talk about how to do our own, and before there was even talk about the "Alde pump", owners did a simple "drain and replace."  Open the glycol drain under the trailer, drain as much as you could, add new glycol. 

Then, the long several year thread in this group came up with the DIY Glycol Exchange file, with the basic fluid exchange pump.  Not hard to do, very effective.

While researching the Alde (the group basically studied every nook and cranny of the glycol loop), it was discovered that a lot of the glycol could be forced out of the system by disconnecting one hose connector at a check valve, and simply forcing the glycol from the loop until it drained out of the trailer.  I did this method, and even though there was still some glycol in the Alde itself, it probably was more than 80 percent effective at removing the "old" glycol. 

Another method is using a shop vac to simply suck the glycol out of the glycol loop through the expansion tank.  Many owners have done the exchange this way. 

The discussions in this thread involving the drains are probably the next "method" that some one will work out for us. 

This link will take you to the DIY Glycol Exchange file.  The .pdf will show you the basic procedure, so some of the discussions will make more sense.

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

ScottG

@asfizer, what is described in the DIY document involves using the new fluid you are pumping in one hole to push the old fluid out another. Yes, there will be a bit of mixing, but this should not pose a problem unless you are changing glycol brands, or if your existing glycol is badly contaminated.

Older T@Bs only had a single drain, so using this pump-in/push-out method required adapters that were installed through the expansion tank. On newer T@Bs with the double drain, the process is basically the same except you are pumping and draining from the drain ports rather than through the expansion tank. This process does require the placement of a suitable clamp on the glycol hose between the two drains.

As @pthomas745 indicated, there are several ways to skin a cat. The method I describe in the DIY document was intended to mimic how Alde's proprietary "service pump" works. Other owners have figured out alternative ways to drain and refill the system. All seem to get the job done, and I'm not sure any one method is functionally superior to another.      

Jake_Elwood_and_us

edited

Citruscountytab400

I keep  the AC and heat on all year round.  I've never changed the antifreeze on my 2020 400, but check the ph every year.  I  also check the hoses and convectors every year.  besides for adding antifreeze to the refill/over fill tank twice a year during heating season, I've come to the conclusion (based on automotive technology,) the antifreeze ph goes acidic when used a few times a year, and then let to sit the rest of the year.  The same happens to cars with their cooling systems and oil, when driven short distances and never brought up to fully hot.  The Aldi is by far the worst system ever put in an rv, and a warm air furnace, like every other manufacturer uses, would be superior to this huge contraption of expensive parts.  I will be installing a mini split next year for heat and cooling, and approximately 1/2 the amp draw, but people are wasting their money with these two year antifreeze replacements, when it would be cheaper to keep the tab plugged in and running year round and never changing it.

gulfarea

I also will never have another Aldi system in an RV just to much maintaince! Art

jalars8

Having read everything in this thread, including the reply from Nucamp about change out of glycol, stating the dealer should do it, etc. -  my conclusion, with respect to my 2018 320s (which has the one glycol drain) is that it is relatively simple.  1.  I don't need to do a change over to the new blue/green stuff.  2.  Drain the old glycol through the one drain. I assume not every bit it will drain out of the system but enough to accomplish the job.  3.  Put in the new glycol by way of the expansion tank.  Don't need to use the Alde filling pump mentioned in the Alde manual (model 3020) because units sold in N America have an "automatic air vent" which bleeds the system automatically.  Fill to a half inch above the minimum level mark on the tank.   4.  During the first use of the system after putting in the new glycol, check the level in the expansion tank a few times and, if level is below where it should be, top it off.  I would appreciate any critique if there is something I am not understanding.  Hopefully, it is as simple as I think.  One question:  I saw in a thread here somewhere that the amount of the glycol solution necessary to fill the system is about 2 gallons.  Is that about right, or maybe is it different depending on the T@b model?  

pthomas745

@jalars8 This thread, by itself, is quite useful, but I wonder if you have opened and looked through the "Changing The Alde Glycol" thread that is linked on the first page, and the companion thread, "Corrosion of the Alde Convectors?"  There is a ton (I mean it!) of information and education in those threads from the very smart and talented owners who worked on these issues over the last 5 years or so.

Your thoughts are essentially correct.  You would be doing what is known generally as the "Drain and Replace" glycol "swap" idea.  Which many owners have done.

If you have not seen it, there is a "DIY Glycol Exchange" file that was the outcome of the "Changing The Alde Glycol" thread.  By studying and back engineering the Alde setup, and sorting out how easily the spendy Alde pump could be  duplicated with simple off the shelf hardware, a "complete" glycol swap is fairly easy. 

This is the link to the DIY Glycol Change .pdf file.  If you read through it, there will be some ideas on page 7 or so about how to fill the glycol, run the Alde glycol pump in the trailer to "burp" the system, and then get an appropriate glycol level in the Alde tank.

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

There are "alternate" ways of doing a glycol change, such as using a shop vac to simply draw glycol from the system, etc. 

In my 2017 320, I wound up using just about 2.5 gallons of the "Century" glycol.

Ask questions!

ScottG

As @pthomas745 noted, many owners have employed this exact approach for its relative simplicity. However, simply draining the glycol from the low point drain can leave as much as half of the old glycol trapped in the system. There are low point in the convector loops that prevent all the glycol from reaching the drain.

jalars8

I appreciate the responses and comments from you both, pthomas745 and ScottG.  I had, some time ago, read through the DIY thread on replacing the glycol solution and recently looked at the piece about making and using a DIY pump.  The zinger for me is ScottG's comment that draining the glycol from the low point drain can (will?) leave as much as half of the old glycol trapped in the system.  Based on a comment I had seen somewhere in the DIY thread, I had concluded (hoped, I guess) that the figure for old glycol left in the system would be around 20% - somebody's guess I think.  I understand the article on putting together a DIY pump but don't relish doing that in my 2018 320s, given the awkward location of the expansion tank, among other things.  I guess it can be done, but.... If I was to use a wet vac to try to remove more of the old glycol, where and how do you connect it?  

jalars8

Not sure that having a dealer do this is the solution given some of the comments I've read about dealers - do they know what they're doing - one comment said the dealer just did the gravity drain that I'm talking about doing.  Generally, can't say I've had great experiences generally with RV dealer service departments.  

jalars8

The more I look at the DIY pump instructions, the more I think it may not be as daunting as I first thought.  

Jake_Elwood_and_us

   I discussed changing the glycol with a retired mechanical engineer friend who has vast knowledge with heat transfer fluids. 

  His take on it is that it is heat which breaks down the glycol and since I don't use mine much he says I should be okay to wait 5 years. The oxygen in the reservoir tank would have minimal effect.

  Since I have already ordered the glycol and I'm at 3.5 years I figured I would go ahead with the change out anyway. 

  My friend also said that any old glycol left in the system is not a good thing and the exchange should be a total distilled water flush and new glycol added after as any old left in the system would infect the newer glycol.

  I decided I wanted to do all the drain and filling from outside the Tab. I contacted Truma and ordered the dual drain. Double Tee Bottom Fill & Drain fitting - Truma part # 35119-00876

  I have completed the replacement of the original single drain with the new double tee.

  It is a larger size than the original single drain, 7/8" ID vs 5/8" ID. I wonder if there is a smaller version of this, I never asked. I got the original part# from an earlier post from ChanW

https://tab-rv.vanillacommunity.com/discussion/2665/changing-out-the-alde-fluid/p12

  If you do this change out it is a bit of work to complete and will require draining the system first and using a hose clamp plier tool I got from Amazon. 

https://www.amazon.com/dp/B07CR6BN2Y?ref=ppx_yo2ov_dt_b_fed_asin_title

  I used a needle nose vice grip tool to pinch the center between the two drains. I used a vacuum to remove as much of the old glycol as possible. Next I used a hand pump to push the distilled water through the Alde system to the reservoir and let it gravity drain from there followed by the vacuum again. I was sure to keep an eye on the reservoir level which is why I used a hand pump.

https://www.amazon.com/Performance-Tool-W1156-Transfer-Siphon/dp/B00J8331U6

  Next I pumped the new glycol toward the Alde system and watched the return fluid until it was solidly the same color as the glycol I was injecting. 

https://www.amazon.com/dp/B0C7J6WBRP?psc=1&ref=ppx_yo2ov_dt_b_product_details 

  After the reservoir was midway full I pulled the bottom fill point and ran the glycol pump on high (5) for an hour and kept an eye on the reservoir level. I raised and lowered the tongue and rocked the Tab back and forth to release any air pockets which may have formed. Afterward I check all the bleed valves and lowered the pump setting to 2 and starting heating the cabin. I checked to make sure I was getting heat everywhere and called it good to go.

To be fair, this sounds simple but it was a bit of a learning curve and I'm not sure it was totally worth it to add the double drain. The time and effort to install it may be in excess to just doing the replacement through the reservoir as described by others in many other posts.

  That being said, I believe in two years when I need to do this again it will be fairly easy.

  This instruction is for my 2021 400 with the upgraded double drain. YMMV.

  1) Pinch close the middle part of the double drain with needle nose vice grips.

  2) Hook up the glycol fill line to the port which goes to the Alde pump and start pumping.

  3) Keep an eye on the reservior to make sure it does not overfill.

  4) Allow the return line to drain into a 5 gallon bucket until 3.5 gallons have been returned.

  5) Pinch off the fill port and cap off both ports.

  6) Run the glycol pump on high (5) for 20 minutes to allow mixing and air removal.

  7) Lower pump to 2 and start heating, check reservoir level and bleed as necessary.

  Done!