How To Replace a summer loop pump in a ITR OASIS Hydronic heater

[Rich W.]

We have not had a pump failure (knock on wood), but after some experience with the oasis, I wonder about the air pocket question.

A few times (2 or 3 years ago) I heard a surging sound. After some investigation found that the fluid level was a little low in the oasis unit. Added some fluid (pumping from the overflow container that was very full) and forced all pumps on until all air bubbles stopped appearing (took 5-10 min).

Had to repeat this a few times over the following months whenever I heard the surging sound.

Finally discovered the “straw” in the overflow container was drawing air. As a result the oasis heating would cause fluid to expand and go into the overflow but when cooling it would not draw fluid back into the main exchanger.
Once I fixed that straw issue we have not heard anymore surging and the fluid level never drops.
I wonder how many units with summer pump failures are due to air in the lines?

Great tip - I’ll have to check that - guess everyone should.

 

[turbopilot]

I believe this pump in particular never stops running as long as it has 12V power. And maybe that's part of the problem, which of these pumps run non stop until death?

Pump is rated at 20,000 hours which is 833 days. I seem to recall there is a way to turn it off with the coach is otherwise powered. I only ran my Summer loop only when the boiler was actually making hot water. Never had a failure.

 

[J&JD]

When not using the rv, stored , not in use etc, turn off the system with the switch on the front of the unit.

 

[Neal]

When not using the rv, stored , not in use etc, turn off the system with the switch on the front of the unit.

That is a good idea, however, there is the counter to that when things stop they gum up, corrode, who knows and don't come back on. It's like we hear....lightbulbs don't die when on, it's the turning on and off that kills them.

 

[turbopilot]

That is a good idea, however, there is the counter to that when things stop they gum up, corrode, who knows and don't come back on. It's like we hear....lightbulbs don't die when on, it's the turning on and off that kills them.

I think these pumps are magnetic drive. Here is a good source to understand these pumps. In motor homes they operate continuously to provide "always hot" water. I wonder if it would be a good idea to use a cabin motion sensing switch to turn on the pump anytime motion is sensed in the cabin? I suspect these pumps fail with simple bearing wear. @Neal save your old pump, tear it down and look at the bearing.

Bearing Wear: In mag-drive pumps, the bearings operate close to the magnets, which can cause increased friction and wear and result in increased maintenance requirements.

 

[Neal]

@Neal save your old pump, tear it down and look at the bearing.

A little late, that would be in the prior CG dumpster

 

[turbopilot]

A little late, that would be in the prior CG dumpster

Unfortunately someone will get one soon. Simple tear down should answer some questions.

 

[Rich W.]

I think these pumps are magnetic drive. Here is a good source to understand these pumps. In motor homes they operate continuously to provide "always hot" water. I wonder if it would be a good idea to use a cabin motion sensing switch to turn on the pump anytime motion is sensed in the cabin? I suspect these pumps fail with simple bearing wear. @Neal save your old pump, tear it down and look at the bearing.

They don’t have a bearing - the impeller just floats on the magnetic field. So as far as I can tell, when they fail its electrical - a sealed coil of some sort. You can see in the second pic what happened when I tried to bench test a failed pump “motor” with the impeller out.





Edit - correction (great article btw) There is a rotating shaft in the sealed motor which, according to this article, rides on a bearing or bushing. I can see how that could fail and once it does the motor seizes up and pops fuses, or in the case of applying current on the bench it lets the smoke out.


From the article: “Bearing Wear: In mag-drive pumps, the bearings operate close to the magnets, which can cause increased friction and wear and result in increased maintenance requirements.“

 

[turbopilot]

They don’t have a bearing - the impeller just floats on the magnetic field. So as far as I can tell, when they fail its electrical - a sealed coil of some sort. You can see in the second pic what happened when I tried to bench test a failed pump “motor” with the impeller out.

View attachment 21338

View attachment 21337

Or maybe not so sealed and that is the problem. Coolant intrusion into the coil?

 

[Rich W.]

then there is this:

Dry Run Protection

A principal reason for pump malfunction is operating without fluid, often resulting from human errors or system disturbances. In such situations, pumps may continue to function with no fluid, which leads to rapid deterioration or destruction of the pump in many instances. Nevertheless, specific mag-drive pump configurations can withstand dry operation. In industrial settings where pumps do not receive continuous monitoring, this capability to function without fluid can expressively reduce the likelihood of pump breakdowns and related expenses.

 

[J&JD]

when things stop they gum up, corrode, who knows and don't come back on. It's like we hear....lightbulbs don't die when on, it's the turning on and off that kills them.

I don’t know about that. I usually shut my Cummins engine down when I’m not using the coach. Why would you want the Oasis on if your coach is stored & plugged in. Makes no sense to me. I wonder what ITR suggests. I haven’t read anything on turning the unit on/off when not in use.

 

[MemoriesByTheMile]

We have had our coach for 3 years and it is now 10 years old.
Except when we have done maintenance, we have never turned the oasis off at the control box next to the main green unit. We have only turned it to “off” inside the coach on the panel.
I don’t recall if flipping the inside switch to off stops the oasis pumps from running. Would assume so, but don’t recall.
Interesting thread, continuing to follow as we want to learn to avoid unnecessary repairs.

 

[Neal]

I don't have the manual open but I believe ITR addresses "cavitation" in the pump replacement instructions. If for some reason fluid doesn't flow and the pump needs to prime, or whatever this is under, is documented somewhere by ITR.

 

[Joe Dutchstar]

Oasis Manual see page 49 for pump replacement procedure

https://itrheat.com/wp-content/uploads/2017/07/Oasis_Service_Manual1.pdf

 

[Kevin D Pem]

They don’t have a bearing - the impeller just floats on the magnetic field. So as far as I can tell, when they fail its electrical - a sealed coil of some sort. You can see in the second pic what happened when I tried to bench test a failed pump “motor” with the impeller out.

View attachment 21338

View attachment 21337

Edit - correction (great article btw) There is a rotating shaft in the sealed motor which, according to this article, rides on a bearing or bushing. I can see how that could fail and once it does the motor seizes up and pops fuses, or in the case of applying current on the bench it lets the smoke out.
View attachment 21339

From the article: “Bearing Wear: In mag-drive pumps, the bearings operate close to the magnets, which can cause increased friction and wear and result in increased maintenance requirements.“

So in the last 2 weeks, what have we learned?
1. The fluid in the system changes Ph! It appears to go acidic.

2. The pump runs all the time.

3. The expansion tank can, or is open to the environment (may lead to fluid contamination).

4. Bearings in motor fail.

We have also learned that many articles, and there drawings are not proofed.

What we or I don't know?

1. What kind of Bearing are used (ceramic would offer longest life)?

2. Is the motor brushless(if brushed no hope)?

3. How often is the fluid replaced?

To avoid misinformation, I would like to dispel, and get us back on track!!! The common refrigerator is constantly turned on and off, and many have seen lives well over 20 years. This is made possible using closed systems. An electric motor has one weak link, the Bearings. In the case of a sealed compressor there are no brushes, and the Bearings are not lubricated with grease. Ceramic Bearing when used require little lubricant.

So how can we increase the life of our system?
With the system as it sits. Check the Ph of the fluid on a schedule. Make sure there are no airlocks. Only run the system when aboard the vessel, or when required. I the pump has any of the above shortcomings, only two things you can do! Find a commercial pump, or reduce the hours you put on it!!! I agree with @Neemer or was that @J&JD there is no reason cycling should reduce it's life.