Aqua-Hot Filter Change

[Birddog Pilot]

This has probably been addressed before, but I can’t locate the information. I’m in the process of servicing the Aqua-Hot and was wondering if there is a secret shutoff valve somewhere between the fuel tank and the Aqua-Hot filter? Or do you just work real fast and have a big bucket to catch the overflow? I would imagine the system is gravity fed through the filter to the burner unit. I thought before I created a big puddle of Diesel #2 on the hangar floor I’d ask those of you who have been through this process.

[MRL]

Check out Mark Quasius website: RVcruzer.com - Home Page Look under "Hydro-Hot System Mods"

[Birddog Pilot]

Raymond -
Thanks for the information on the RVcruzer.com site; what a wealth of information. Mark has an excellent web site with excellent pictures and commentary.

I figured I'd probably have to add some shutoff valves to the Aqua-Hot filter. WRV apparently wanted to make the annual service program just a wee bit more challenging; and that's why they omitted a means to shut off the fuel while changing the filter.

[Roger Berke]

Dick

Normally you do not need to shut off fuel before changing the filter. If the filter is above the fuel level in the coach fuel tank, there are only a few teaspoons of diesel that come out when you remove the filter. If the filter is below the level of the fuel in your tank, then the fuel will siphon out. I use fuel pinch off pliers if I have any question. You will see on Cruzers web site that he added fuel shut off valves on his filter assembly. A great tip to help with filter removal is to put a zip lock bag around the filter before you remove it. Unscrew it and drop it into the bag.

Much more information on Yahoo Group listed below.

- Roger Berke -
Moderator - http://autos.groups.yahoo.com/group/HydronicRVHeating/

[Birddog Pilot]

Hello Roger,
Thanks for the Yahoo Group site for Hydro-Hot. My fuel pick-up point must be well above the filter or there was a siphon action because I had a bunch of fuel come out when the filter came off. The next time around I'm planning on installing a shutoff valve. Diesel fuel down both arms while the new filter goes on is not something I would look forward to every year.

[Old Rv'er]

The other thing you can do is plan on doing the filter change when the fuel tank is at or below 3/8 left. Take it down to 1/4 left on the gauge, and you should not have a fuel pour issue. The AH/HH system is supposed to shut off if the level in the tank is at or below 3/8 remaining. Now on mine, I know this is in fact true, because we did not fill up one time in Montana and it was just at half, by the time the real cold weather got there, it was not working any longer, first time out in the coach, and even though I read the manual, it never clicked into my brain, to check the fuel level of the coach. Normally, I never let the fuel level go below 1/2 left, but when doing my service, I am going to let it get down to 1/4 left as above. Then while you have it apart, you can add those valves we all want to add.

[EngineerMike]

If you run the generator slide out you can see the end of the fuel tank. Gauge its height vs. the frame. Then locate the AH/HH fuel filter & gauge its height vs the frame. Should be easy to figure where the fuel tank level will be (% full) to be below the rim of the filter. Then if you have calibrated your fuel gauge during fill ups so you know what the quarter marks really mean, its simple to know when fuel is below the filter. Once you crack the filter w/fuel below that level, the siphon will drain back to the tank, no muss no fuss. If the filter rim is below the 1/4 level of the tank then you're not good till less than 1/4.

[Birddog Pilot]

Monty & Mike -
Thanks for the excellent suggestions; I'll definitely try them out when it comes time to install a shutoff valve/s. "I love the smell of diesel in the morning," except when it's running off both elbows.

[Old Rv'er]

As a word of suggestion, everyone knows to NOT use any galvanized plumbing in the diesel subsystems. There (if memory serves) is a large amount of zinc in galvanized plumbing parts, diesel causes that zinc to leave the galvanized coating and accumulate in the fuel, which will ruin any fuel injection system or burner assembly. I don't know for sure, but I think copper is ok, someone with a better metal knowledge please chime in here and tell us what we need.

The Cummins manual does not address it I don't believe. Zinc is bad in Diesel systems.

The AH/HH modification example everyone uses to do this project is on this forum, but I cannot remember the gentleman’s name, but he has pictures, etc, so it's a great job. Up until last Monday week, I was still working, now I’m retired and so some of those projects are something I could do, provided the fuel level is at the right place to start. WRV should have thought of it when the coach was built, in fact it should be required as part of the AH/HH manual for an approved installation.