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Old 08-22-2012, 06:20 PM   #43
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An expansion tank or "bubble" does not lower the pressure of the system. It just gives room for expansion of the water when it heats up. So if the purpose of an after market expansion tank is to lower pressure in the system I'm not sure that is a solution. Unless its quite large?

I don't know how Atwood decides what the pressure relief valve should be set at but obviously a low pressure would not hold the pressure needed when the water is heated. The one that's in there is not always enough when the water getting really hot, and "burps" a little out, as it's supposed to.

After six months using this thing I'm just having trouble seeing what all the fuss is about. If you must fuss about it, it's an Atwood design and they are all over the RV industry.

doug k
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Old 08-22-2012, 06:28 PM   #44
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Atwood's Contact Info is:
Marine Water Heaters - Atwood Mobile

To speak to technical support call:
1-800-546-8759
M-F 8am to 5pm EST
Atwood Water Heater Model #GE9-EXT
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Old 08-22-2012, 06:43 PM   #45
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An expansion tank or "bubble" does not lower the pressure of the system. It just gives room for expansion of the water when it heats up. So if the purpose of an after market expansion tank is to lower pressure in the system I'm not sure that is a solution. Unless its quite large?doug k
Your premise is totally wrong.

Thermal expansion in a hot water system refers to the increase in volume of water as it is heated. If the water system is closed as in the Airstream trailer design the result is an increase in water system pressure as well. In other words if we heat water in a closed container, pressure in the container will increase.

The exclusive purpose of the air cushion is to allow the water to expand as heated into the space occupied by the air cushion, compressing the air, instead of increasing the vessel’s pressure. In similar fashion the diaphragm type expansion tank allows the hot water to expand without increasing pressure.

If you look back at the excerpt taken directly from the Atwood manual I posted earlier you will see that Atwood states only approximately 15 ounces of displacement is needed.
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Old 08-22-2012, 06:55 PM   #46
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Totally wrong or somewhat wrong. I realize the expansion pressure will be relieved to some degree, but if the expansion space is not large enough the pressure may continue to build until it is relieved by the pressure relief valve. Not sure but I believe the new heaters get hot enough to boil and produce steam; this can quickly take up the space created by an expansion tank, depending on its size. I have briefly heard the "boil" in mine late at night just before it opens the pressure relief valve. That's why I shut the electric function off at night.

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Old 08-22-2012, 07:43 PM   #47
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Totally wrong or somewhat wrong. I realize the expansion pressure will be relieved to some degree, but if the expansion space is not large enough the pressure may continue to build until it is relieved by the pressure relief valve. Not sure but I believe the new heaters get hot enough to boil and produce steam; this can quickly take up the space created by an expansion tank, depending on its size. I have briefly heard the "boil" in mine late at night just before it opens the pressure relief valve. That's why I shut the electric function off at night.

doug k

Atwood is the company that engineers, manufactures and sells the hot water heater in our Airstream. I defer to their expertise documented below (left click on the image if you cannot read it):
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Old 08-22-2012, 07:47 PM   #48
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That's another choice if you need it.

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Old 08-22-2012, 08:00 PM   #49
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The response I got from the customer service representatives that I spoke with last week about the water leaks due to the hot water tank over pressurizing the lines and my putting in the RV-500 to fix it was “there is no problem as the Airstream water system is designed to handle the additional pressure and tested to 150psi”. If this is true why limit the incoming pressure to 65psi? Why have some of us had leaks?

From my discussion with AS, AS does not consider this an issue!

Brycom please let us know what Dan says about the problem.
Well... here goes, mind you some of the conclusions I have here are not really based off my discussion with AS more me digesting this issue a bit more in my own head.

---

I (finally) called Dan today (have been very busy at work so today was my first chance)... I reminded him we had talked a few weeks back, and he remembered.

I mentioned this issue, my concerns about it, here is what he said.

Regarding water getting to hot hurting someone:

"This really can not be a problem b/c the gas or electric share the same ECO (emergency cut off switch) and the system can never reach a temp where it would hurt someone"

Regarding water getting to hot damaging plumbing b/c of loss of bubble:

"The pop value will handle any over pressurization issue before it damages plumbing."

Regarding bubble maintenance or need of expansion installation:

"Maintaining your bubble is a maintenance item"

Collimare I concur AS does not consider this an issue.

I was kind of hoping Dan would be aware (at least) that there are people out there with questions in and around this system, but he was not. I was figuring based on the size and nature of AS there was a good chance of this but no, and for me that fine I guess, let me explain..

For me, AS still has my business. I have worked for large software companies (vmware, apple, emc), each of them had quality products, systems in place to ensure quality was gained from real world customer issues, but that system took a while to get moving for a specific issue. An example is I was assigned a P0 (highest there is) bug for an issue the US Navy was having, can you say big $$$ customer. I dropped everything, had it root caused and fixed in a week, but it still took a few months for the fix to make it into production code, and still a few more before the Navy got the fix. It was interesting to watch the *knowledge* of this issue make its way through the company (tech support, sales, other eng depts, managers, etc), it was a real issue, effected a large group of users beyond the Navy, and when it finally all came together I saw that knowledge of it was like many threads slowly merging, if that makes sense.

So, IMHO, it just has not been long enough, and I am sure there are some threads spawned at AS about this, sure there are AS people talking about it, but it has not come up company wide yet, the threads have not merged.

I would have hoped AS would have jumped on your issue to resolve it for YOU, once presented the facts. Sigh...

And finally I can see an angle where one could say this is a design flaw in the water system itself (more of my digesting I mentioned above), should not the system have a proper expansion tank? My on demand home boiler does.
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Old 08-22-2012, 08:49 PM   #50
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"....................And finally I can see an angle where one could say this is a design flaw in the water system itself (more of my digesting I mentioned above), should not the system have a proper expansion tank? My on demand home boiler does."

..............and so do most large motor homes!
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Old 08-22-2012, 08:55 PM   #51
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Bycrom,

Thanks for taking the lead and reporting back. It has been over a month since I presented the ATS switch issue to Dan and have not heard a thing back nor do I honestly expect to. If, and I say IF, Airstream was to actually do something about the ATS issue it will be phased in slowly sometime in the distant future without acknowledging that it was a problem. Unfortunately most companies would respond in the same manner.

Customer service are the first responders with set company policy statements/answers period. They are not the engineers and it would be hard for them to truly understanding the issue, I am not sure I do, though I know it has been permanently solved. Perhaps as you suggest it will eventually filter up.

I have never had any illusions that Airstream would address the problems, which is why I have made my own corrections to known deficiencies to my personal standards/desires. For those of you considering buying new I would suggest putting pressure on the dealers to include addressing issues that you deem personally important to you (tires, ATS switch replacement or removal, hot water expansion tank, dinette that makes into a bed easily, mattresses you can actually sleep on, air conditioning that actually cools the trailer when in direct sun over 85F (dual 13,500 units over 25' would be my minimum, this is the next and last major improvement item I hope to do) etc. etc… or at least be prepared to do them yourself. Cut the best deal and then start discounting for the cost of addressing “your” issues, if any, from there.

It is a WONDERUL trailer that can be made with care, to work or “does” work, as is, just fine per many comments and sentiment expressed on this forum. Both sides of the coin have been shown and it is you who hast to make the call.

I’ll continue my personal quest for the “bullet-proof” Airstream. May you be as happy with your results as I am with mine.
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Old 08-22-2012, 09:07 PM   #52
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I didn't read the lengthy thread. But to put it succinctly, install the large Shurflo expansion tank and be done with it.

I the same issues with mine, and they were completely solved.
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Old 08-22-2012, 09:39 PM   #53
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Quiet down TPI. We're framing this as a new trailer issue.

doug k
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Old 08-23-2012, 11:28 AM   #54
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It does seem to be a new trailer issue. It's the dual electric/gas heaters we are referring to.

Yesterday I installled a 2 gallon expansion tank and then put a pressure gauge with a spike needle on the kitchen sink faucet and opened the faucet to the full open position. I filled the hot water tank and let it reach temp three times and with the addition of the capacity of the expansion tank I held a steady 62 psi during the entire heating cycle. No spikes, no drop in pressure.

This addition will give me risk free operation that will be dependable for years. I don't even have to think about it.

I disagree strongly with Dan's (not me) assertion that no injuries are possible. A piing joint can blow apart at these pressures and anybody in the way can be drenched. 135 degree water will give you 2nd degree burns in 5 seconds.

Bycrom, I have also worked for large Software companies over the years mostly in clean room design and construction. A bad design on software and the resulting loss of consumer confidence are something these guys are very serious about. Lack of sales is a strong motivator. They jump on issues like this.

Back to AS hot water. Again, the hot water as it expands has very litttle piping area so the pressure builds rapidly. Installing a 75psi T&P valve is not a good idea. These devices while primarly are for limiting are not designed to discharge on a regular basis. The spring when flexed enough will weaken and eventually fail.

The 2 gal tank I installed gives me more capacity then I will ever need but I had it so I used it.

As I said before I will be glad to spec a system that will eliminate the "need for bubble maintenance".

Adios,
Dan
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Old 08-29-2012, 10:01 AM   #55
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Thanks for all of this information. My trailer happened to be in the shop currently getting some other warranty issues taken care of so I called him and explained what I've read from this thread and sent him a link to it. He talked to Atwood and has ordered and will install the expansion bladder that Atwood recommended. Glad to get this taken care of before I had a problem.
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Old 05-04-2013, 03:36 PM   #56
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Can someone give me a reference / contact for the necessary parts to install an expansion chamber? All I can find on the internet is a 2 gallon tank, seems oversized? Also interested in were best to locate the tank (30' FC).
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