Hot Water Tank Coolant Routing

[mharner]

My 1997 Country Coach always had hot water generated from the engine. At some point I noticed it had stopped working, although electirc and propane modes still heat fine. I have had the engine rebuilt, and the timing suggests that this is when it probably stopped working. I have studied quite a bit of web info, and the general info doesn't seem to be panning out for me, maybe because my 1997 was an early implementation of over-the-road hot water. I can only find 1 pair of coolant lines going forward from the engine (send and return), the send line goes into a thick thermal wrap and disappears into the coach. The dash heat still works. Looking into the hot water compartment rear, I only see the fresh water routing and a brass line that must be the gas. The back of the Atwood unit does not have coolant lines going through it as I see in the Atwood docs on-line, nor does it have an "H" in the part number indicating Heat Exchange option! Here is a picture of the back of the tank. I hope someone has a clue how this should work.

http://www.michaelpagan.com/downloads/hot_water_heater.jpg

Mike
1997 Country Coach Allure
Cummins C8.3-RV325
Allison MD3060

[deandec]

Mike, on my rig, there is a coolant line running from below the driver side of the Cummins C8.3L to the front of the coach to tie into the dash heater.

(Note: I do not have the Hurricane Heater nor the Aqua Hot system.)

Then the line runs I think to the Atwood Water Heater and back to the radiator somehow.

Originally, there was a School Bus MP Pump P/N 28985 mounted to the frame rail near the engine through which the coolant was pumped to the dash heater. A similar pump is mounted on the passenger side behind the front "bumper" that assists the coolant to move to the water heater, I think.

Also at the rear was a gate valve that allowed the movement of the hot coolant to the front to be shut off in the Summer time.

Unfortunately, the coolant pumps are on whenever the ignition is on regardless of need. I have installed two new pumps at the rear position and finally removed the gate valve and the pump due to coolant leaks. These pumps are a common problem with this system.

I still get on the road heating at my water heater tank and heating at the dash heater.

My manuals discuss the above system in partial terms in several different chapters but nowhere is there a dedicated discussion of the flow patterns or plumbing for the entire system.

I will have my rig onsite on Wednesday and maybe I can get pictures of the Atwood plumbing that does seem to produce hot water from the engine coolant.

[LabRat]

Have you checked the back of the unit? We have a pair of EHP10's in our 2007 Rhapsody and despite everything on the Atwood website, our cooling lines come into the back of the units. Even our manuals talk about the coolant lines coming in from the front where the water enters and leaves.

Our over-the-road Webasto system is a loop from the engine to the house section, so it is as you describe with only one pair of hoses leaving the engine bay. The coolant is either heated by the engine or secondary Webasto heater.

[dons2346]

I would crawl under the coach and look for a gate valve somewhere. It sounds like the mechanics closed it to keep coolant from running out while they worked on the motor.

Now, where it might be is anyone's guess. I'd look for some coolant lines and follow them to see where they go.

[mharner]

Thanks for the responses. The main question right now is how could that tank have ever heated from the engine without coolant lines going to the back of it? I called the original owner and he verified that it always heated from the engine, or over-road. I called Atwood and they confirmed that the only heat exchange connections are on the back of the tank next to the fresh water connections, and my picture shows no coolant line connections there. I called and registered to pay Country Coach, but they have no info to offer. So, either Country Coach used some other method, or hot water tank fairies snuck in and changed my hot water tank and removed the coolant lines.

Dean, you offered to check your coach, and it sound like yours could be similar to my '97 Allure. If you have a chance would you look into the hot water compartment (mine's accessed from the side of the understorage bin) and verify if there are coolant lines routing into the back along next to the fresh water - there would be 4 water connections.

Thanks again,
Mike
1997 Country Coach Allure 32'
Cummins C8.3 RV-325

[LabRat]

I'll try to get pictures of mine, for I thought the same thing until I pulled my outer panels so I could get in and see why was going on. Now granted i have a slightly different set up, but i got similar responses from Atwood, in that the heat exchangers enter from the same side as the water. My heaters are mounted sideways and I can attest, despite everything Atwood said and manuals showed that my coolant lines come in from the opposite end of the heater.

My coach shows there are manual valves that can isolate the engine coolant lines from the house lines. I haven't found the valves, but understand why they would use them. As someone mentioned, look for the valves and see if open or not. Another way to do it and how I did it, is to just run the engine, find the house coolant lines and see if they get hot.

[mharner]

Wow, that is good info. Thanks!

[deandec]

Here is the picture of my 1995 Attwood Water Heater tank plumbing with engine coolant heating assist feature.

The coolant assist line enters the back of the water heater on the bottom left side and departs back to the Radiator (I assume) from the bottom right side.

My water heater is mounted just behind the driver side front tire.