Water heater heat exchange

[Dallasrules]

I have a 2011 Vista 36D. The water heater is leaking somewhere and I want to get started on repairing/replacing. It has heat exchange. I am not sure how this works, but, it seems that the water is heated by the engine system somehow.

My question is this. If I disconnect the water heater including removing this heat exchange hose, can I run and drive the motorhome?

I will not get the fix/replacement in before my next planned trip.

I know I can bypass the water heater through the normal plumbing, but what about this heat exchange hose. Also, I only see one hose going into the tank. I don't see anything coming back out.

In addition, does this also mean that my replacement would need to have the heat exchange?

[wahoonc]

I haven't dug into it however, you should be able to use a pipe nipple to bypass the exchanger. I don't believe there is a replacement unit available that has the heat exchanger in it. So you will lose that feature when you replace the water heater. Sometimes the unit can be repaired.

Aaron

[Dallasrules]

Originally Posted by wahoonc

I haven't dug into it however, you should be able to use a pipe nipple to bypass the exchanger. I don't believe there is a replacement unit available that has the heat exchanger in it. So you will lose that feature when you replace the water heater. Sometimes the unit can be repaired.

Aaron

Pipe nipple? So just join the input and output hoses together?

I was hoping it would be repairable, but someone has a new hopefully direct replacement for $400. Thinking I should just snatch that up.

[Morich]

My favorite part of this site is the interactive part catalog when I'm dealing with places I've not looked before!
Maybe a good time to get familiar with it to look at what the "motoraid" involves and what plumbing you might have?
There appears to have been some options on that RV water heater so it may be handy to look at parts involved before tearing in?
https://catalog3d.winnebagoind.com/menu/Parts.htm

From that and after choosing your specific RV, you can go to plumbing and choose water or the motoraid to look at the drawings!
Some hints on using the system may help speed things as it does take a bit to get the controls in mind if not used before?
Don in loser left of drawing , once you get there, is a plus (+?) sign? Before scrolling to zoom, etc, try clicking that plus then click on the part you want to keep centered. That helps to avoid losing track of the item you want to see.
Click on the drawing and hold to drag or swing the view around or scroll to zoom!
when clicking on a part it highlights on list at right or if you click on item in list it highlights on the drawing.

Handy way to get a look at an item if you don't know where or what it looks like but know the name or vice versa if you know the name but not what or where!

Link to go direct to one view of the motoraid:
https://catalog3d.winnebagoind.com/2011/176423.htm

Or for the two options of heater:
https://catalog3d.winnebagoind.com/2011/175973.htm

It doesn't always get the exact items on your RV, due to numerous options that may show up on different RV, but it does give lots of small detail that may help.
For the plumbing item, I like to look at the list for sizing like what size radiator hose, etc?
This older style plumbing info may also be handy?
https://www.winnebago.com/Files/File...m/Plumbing.htm

Good luck on the chase. We always loved having the hot water along the road as we drove, so I will hope you are able to find exact replacement. No ideas on that!

[Ray,IN]

Originally Posted by Dallasrules

Pipe nipple? So just join the input and output hoses together?

I was hoping it would be repairable, but someone has a new hopefully direct replacement for $400. Thinking I should just snatch that up.

If you plan on getting the leak repaired, yes use a short lengthof pipe to join the 2 hoses together. If you plan on buying a new WH, do as most others do; trace those hoses to holes in the engine block, remove the hoses and fittings, and put a metal plug in those threaded holes, so you never have to worry about one of those hoses leaking or bursting from age at some point in the future.
That WH feature is called "motor-aid"
A good HVAC mechanical shop could solder a heating coil onto the back of a new WH but for the expense, probably not worth the effort to obtain the results.
If you want hot water while driving, the new WH will run on propane anytime anywhere.

[Morich]

I may be late to ask the question or the OP may have more info but I wonder how certain they are it is a tank leak which makes it fatal versus a simple line/fitting leak?

Considering how strong and long lasting that tank versus how weak and funky the lines, if there is not something definite to say the tank is bad, I would first guess it to be far less problem and just a line leak!

Is there any good way to get a look behind the heater without pulling it out?

But that may just be happy wishful thinking and they may have already been on that trip!!

[Dallasrules]

Originally Posted by Morich

I may be late to ask the question or the OP may have more info but I wonder how certain they are it is a tank leak which makes it fatal versus a simple line/fitting leak?

Considering how strong and long lasting that tank versus how weak and funky the lines, if there is not something definite to say the tank is bad, I would first guess it to be far less problem and just a line leak!

Is there any good way to get a look behind the heater without pulling it out?

But that may just be happy wishful thinking and they may have already been on that trip!!

There is access behind the water heater from inside the MH. I have checked all the lines and I can't find any leak. The water just appears from under the water heater. It is only a couple of tablespoons. However, I think this has been leaking for some time because the floor in the hallway next to the access panel is soft. I just bought it last summer.

At any rate, I bought a direct replacement from someone off marketplace. They bought it and never had it installed. It is newer than mine, but the same model number. I paid $400.

[Morich]

A way too late idea?

I had heard the Motoraid was no longer available and never questioned it but I just looked in at the drawings for a 2019 Sunstar LX 30 footer and find it used a motoraid! Is it possible they are still used as late as that, making them possible to find if we look for a different model RV?
https://catalog3d.winnebagoind.com/2018/300509.htm

[tderonne]

Just for reference. Metal horizontal tube is the motoraid coolant "heat exchanger". I think that's what folks are saying you'd need to loop if you removed the water heater and needed to start or drive the motorhome.

[Morich]

Good picture there, Tim!
It looks like so little contact with the tank. Has anybody ever got far enough in to tear it down to see how much or how little contact there is between the 150-180 degree coolant water and the fresh water tank?
Is that the tank body we see peeking out as the vertical shine? Is the only actual metal to metal contact where the horizontal tube lays on the vertical?

I'm somewhat surprised if that is all there is as we were very happy with the motoraid when we had one but I had no reason to look too close at how or why it worked!

Letting my mind run around loose, it occured to me that there might be a somewhat simple way to make a standard tank without motoraid into a motoraid tank if we did find no way to replace it with new.

If we assume that we do have to do the trauma of pulling the tank, but we do have the lines from the engine back to the tank, would it not work to just retrofit the new tank?

Take a tank with foam insulation but no motoraid fitting, slice the foam to lay the metal motoraid tube on the metal of the tank? Maybe make it secure and add bulk to the heating by using a metal strap around the tank to hold the tubing tight?

With the little thought I had ever given to how it worked, I had assumed the heat exchange to be more like coils of coolant tubing wrapped all around the fresh water tank!
No idea it was this simple looking!
Does anybody have specs, ideas of when Winnebago stopped adding Motoraid as an option?

I had thought it was gone quite a long time back but still seeing it on drawings on new as 2020 Adventurer 30T! Maybe other small points on the tank keep it from being practical to cross breed?

[wahoonc]

Originally Posted by Morich

A way too late idea?

I had heard the Motoraid was no longer available and never questioned it but I just looked in at the drawings for a 2019 Sunstar LX 30 footer and find it used a motoraid! Is it possible they are still used as late as that, making them possible to find if we look for a different model RV?
https://catalog3d.winnebagoind.com/2018/300509.htm

They were discontinued sometime after Atwood was bought out by Dometic which occurred in 2014. All I know is that when people have looked for a replacement for the 10-gallon water heater with the motoraid it is no joy. That one picture doesn't look right. It has been quite a while since I have seen one out. From what I recall there is a coil that goes inside the water heater.

Aaron

[tderonne]

Another possible configuration of the "heat exchanger". Same idea, different tank.

[Morich]

I'm not at all sure they would allow placing the heat exchanger coils inside as that would let any leak in the coolant lines inside leak the antifreeze, etc. into the fresh water supply. So we might find antifreeze in the cooking water?

The two designs Tim has shown make a lot of sense for the safety of keeping the two far apart.
I'm just surprised that so little contact, metal to metal, did such a good job to transfer the heat.
Most likely just me underestimating how much the coolant at 150-200 degrees will transfer through the tank metal to heat the fresh!

When I've been most likely to appreciate the warmed water as we drove was places where I stopped to check the toad connections or tires, etc and got hands dirty. It was always something of a happy surprise to get in to wash up and find the water warm!
When your hands are frozen, even fifty degrees can feel warm!


Checking closer on when they got hard to find, it may be that any one specific size and style likely went out before the others!

[Ray,IN]

Originally Posted by wahoonc

They were discontinued sometime after Atwood was bought out by Dometic which occurred in 2014. All I know is that when people have looked for a replacement for the 10-gallon water heater with the motoraid it is no joy. That one picture doesn't look right. It has been quite a while since I have seen one out. From what I recall there is a coil that goes inside the water heater.

Aaron

The motoraid heating device was never inside the WH tank due to the danger of cross--contamination. That picture is the latest design. MIne is a 1999 Atwood W/motoraid and the piping is outside on the back of the tank.
This is a picture of a 2012 Reata MH Atwood water heater W/ motoraid:
post #6 - https://www.rvforum.net/threads/moto...-heater.59155/
The Winnebago service tip for this WH pdf is in post #5.



Please note the motoraid is the same as the picture in post #9 here.

[Morich]

Odd how many things we can find that just lead us further out into the bushes?
Found this in searching for Motor aid.
An ad which has a date of 2024 shows Wal-mart selling them through their third party sellers but none in stock.



Gone forever or just a new seller who has sold more than he has?
We may never know!

[wahoonc]

Originally Posted by Ray,IN

The motoraid heating device was never inside the WH tank due to the danger of cross--contamination. That picture is the latest design. MIne is a 1999 Atwood W/motoraid and the piping is outside on the back of the tank.
This is a picture of a 2012 Reata MH Atwood water heater W/ motoraid:
post #6 - https://www.rvforum.net/threads/moto...-heater.59155/
The Winnebago service tip for this WH pdf is in post #5.



Please note the motoraid is the same as the picture in post #9 here.

I stand corrected. The one I last worked on was an 80s Bluebird and it most definitely had a coil. It may have been in a separate section as a heat exchanger, I don't have pictures to refresh my memory.

Aaron

[Americanrascal]

Originally Posted by Dallasrules

My question is this. If I disconnect the water heater including removing this heat exchange hose, can I run and drive the motorhome?

I will not get the fix/replacement in before my next planned trip.

I know I can bypass the water heater through the normal plumbing, but what about this heat exchange hose. Also, I only see one hose going into the tank. I don't see anything coming back out.

In addition, does this also mean that my replacement would need to have the heat exchange?

Our rig came with the heat exchange feature on the water heater. Never liked it. We really got tired of constant very hot water while in travel. I'd rather use the electric heat when at the campgound to bring it up to usable temperature.

About a year ago I went through a preventive maintenace drill and changed all the hoses out on the motorhome. When I got to the water heater heat exchanger hose from the engine, I decided I didn't want that feature and sure didn't want buy or to run two 30 ft sections of heater hose from the engine back to the water heater. I cut the hoses as they came off the engine and looped them with new hose at the engine.

All has been well now for about a year. The water heater seems happy, the engine is very happy not having to send coolant 30' to the rear of the rig, and we are happy not having scalding 200 plus degree water coming from the hot water faucets while in travel.

[Bobn1957]

Originally Posted by wahoonc

I haven't dug into it however, you should be able to use a pipe nipple to bypass the exchanger. I don't believe there is a replacement unit available that has the heat exchanger in it. So you will lose that feature when you replace the water heater. Sometimes the unit can be repaired.

Aaron

My unit also has the heat exchanger and yes you could either join the two hoses together or plug them, my coach also has a heater in the back that is connected to the engine via the lines going past the water heater! Does your water heater have an aluminum tank or a steel one with a zinc anode? The aluminum would be repairable because it is likely cracked at a seam or joint while the steel one is likely corroded through.

[John Mo]

Originally Posted by Bobn1957

My unit also has the heat exchanger and yes you could either join the two hoses together or plug them, my coach also has a heater in the back that is connected to the engine via the lines going past the water heater!

Kept waiting for someone to point this out - my 2009 35J has a heater all the way in the back that's brought heat from the engine coolant. I've always suspected that the hot water tank is a stop on the way to the rear heater. The return line probably takes a different route.

FWIW, I love the motor aid feature. Hot water on the way. Hot water as soon as I park it and want to wash my hands after hooking up.