I mentioned awhile back that I was bidding on an RV-500 Precision Temp tankless hot water heater on EBay. I eventually won the bid and got the unit for $600 + $10 S&H. It arrived here several weeks ago in a box that was distressed. I worried about the shape of the unit before even opening the box.
It turns out that they had packed it with some Styrofoam blocks and the only visible damage appeared to be that it was packed on its back and that is where the hot and cold water lines fittings protrude. The fittings stick out about 3” each and 1 looked to have been pushed in pretty hard. Hard enough to bend it to the side and slightly buckle the copper housing for the heater chimney where it is soldered around it before exiting the back.
I have been fighting a bug for 3 weeks and the weather has not been helping so it has taken me until now to get on with this installation.
Though I had seen forum comments about swapping out a Suburban 10 Gal DSI HWH to a precision temp that made it seem very easy, I am not one to take off with that shining assumption… As I have said before, my middle name is Murphy and if it can go wrong it usually does.
To get started, I did not want to just go and do the full conversion and then find that there was something wrong with the tankless unit and now could not easily swap back to my old Suburban until they could be worked out. I decided that I should do some basic tests of the tankless, like water pressure test, gas leak test, electronics test and then heating test.
Since I am not equipped to do these all on a bench in my shop I figured that the most damaging failure was probably water leakage so I made some adapters and hooked up the water hose on the bench and flushed it then let it hold pressure… No Leaks! Good.
Next test (electronics) required water and gas hookups so I decided to make some adapters to the existing water and gas lines rather than go heavily modifying what is in there. This really was just a matter of picking up some 3/8” copper tubing, A flaring tool (I had one that got away from me sometime ago), Some flare nuts for the gas line adapter (and a shutoff) and some PEX to FIP connectors for the 1/2 water lines to be attached to the new HWH.
The RV500 Documentation recommends removing any HWH bypass kits as they are not needed. This step will greatly simplify the water supply and routing. Plus, in my case, it makes it much easier to put the water filter for the sink where it really should be located.
The most difficult issue I faced was that the unit I got came with a flush mount kit and door and this required some significant modifications to the existing opening that the Suburban had been removed from. I wanted to not make that mounting position unfriendly to put the suburban back into should the tankless not work out satisfactorily for us. These were not cosmetic changes to mount this guy flush. However, Precision Temp makes a surface mount kit that should work perfectly for what I have to mount and where.
I put a 2x2 across the bottom of the opening. The entire opening is exactly outlined with 2x2 aluminum square tubing welded in place. I was not interested in tangling with that structure so the 2x2 wood spacer across the bottom raised the tankless up 2” and centered it pretty well in the opening. I then put in a 3/4” spacer over the top of the unit to give the top facing screws something to bite into . I made it T shaped so that the ends of the Ts extended beyond the side vertical supports to keep the strain off of the screws holding it in place. It cannot pull out through that wall without taking the whole welded aluminum wall out, too.
Finally, I put a stop cock on the end of the existing gas line so it can be shut off if needs be. Also, the difficulty of getting a line into and connected to the gas controller in the tankless water heater was not going to be made with the existing copper gas supply so this was an easy way to pre plumb the inside gas connection and bring it out to where it can easily be connected to the gas shutoff valve (you can see it in the middle of the picture with a blue shutoff handle.
Finally, I was running out of time for the day and figured I could just hook the two twist on connections that had fed the other HWH directly to the replacement, but….. The tankless has the hot and cold water connection reversed from normal tank type HWH. Hot is at the bottom and cold is at the top of the back of the unit so the lines I needed to test with were about 6” too short …. grrrrrrrr.
A quick trip to Home Depot with a stop for dinner at Char Grill and then home again to make patch tubes to hook up the water lines to the rest of the trailer. They put such a combination of Tees, valves, elbows and more Tees in there to feed the kitchen, and the icemaker that trying to use it was another 1/2 day job and I still did not want to wreck that piece of plumbing incase the tankless did not work. This would get water to everything in house but the kitchen sink, the water filter and the ice maker. We can live with that overnight.
Once it was all made and installed and pressure tested for leaks (gas and water) I was ready to take a shower….er… not quite.
I had used the water pump to provide the cold water supply to the tankless because the outside shore water supply was still connected to that rube Goldberg bypass tree of piping and there just was not any way to quickly connect shore water into this new hookup without a lot of surgery.
So, the problem was to get shore water either into the water tank to fill it enough to shower or hook it into the cold line somewhere other than cutting a Tee into what I had just finished up. A little thought reminded me that there is a drain valve for the cold water line and when I checked the end fitting that the protective screen screws onto, I realized that I already had something that could screw onto that fitting and just put shore water straight up the regular drain line to pressurize the system and make it work until I can rework the Christmas tree of plumbing on the bypass setup.
And it worked perfectly so I could have my shower tonight.
AND BOY WAS IT WORTH THE WAIT AND THE TROUBLE!!! That is the first full body, full time, full function shower I have had since moving into DakotR 19 months ago.
The hot water it produces is definitely hotter than anything I ever got out of the suburban HWH even when using both electric heat and gas heat simultaneously. I did notice that when I pinched down the water flow with the “pause” valve on my new shower head, it did shut off the heating. But that was just a way to stretch out the hot water from the old tank HWH, anyway. I will give a little more info on my new shower head that I really like, somewhere else. But for now, its a great combination… a 1.5gpm showerhead handheld that delivers all the water you want to shower, wash hair, shave, etc. with the tankless HWH.
This first experience with the RV-500 has me cussing the years of “tiny” showers, with no water soaping sessions and ice water to rinse out my hair. This is a no brainer. Some folks can argue the fine points of conservation of water, gas, electricity,etc. but people have priorities based on real life personal experiences and its no sin to be able to enjoy a good shower, occasionally, rather than NEVER.
Tomorrow, I will unhook all of this and remake the replacement plumbing tree that feeds the sink, water filter and ice maker. I will also mount in the backing plate that must be slipped over the entire tankless unit from the back before it is pushed into the mounting hole in the wall … (a little step I missed when I was putting it in this afternoon while fighting 3 squadrons of anopheles mosquitoes intent on sinking my spirits before I could finish this job enough to take a shower.)