"holstein13"......Here is something I wrote on another forum, it's the basics of the Oasis system and explains how it works. It explains why sometimes the water is hotter than other times. It has to do with water supply and outside temp.....
This is our first coach with hydronic heating and everything was new to me. I like knowing how things work and have done my own repairs and servicing for the past 35 years. We live in California and rarely see really cold days while camping. For that reason, learning how the Oasis system works has been a process. I thought I would post what I’ve learned, in the past year, for those using a hydronic system for the first time. This may be too basic for some and I apologize in advance. If you see any obvious mistakes, please feel free to correct me so we can get the best info out there.
The Oasis "Heating Module", on my coach, is located on the driver’s side about mid coach. When you open the bay you’ll see the rubber push button to power the unit "Power On’. The Oasis system has a second unit, called the "Distribution Module" which is located close to the heating module. Mine is located directly behind the heating module and is accessed from the passenger’s side bay.
When the coach is not in use, the Oasis unit is turned off at the power switch on the front of the unit. Before a trip, I typically turn the unit on a day before so I don’t forget. Simply turning the unit on does not activate any heating.
Side note: The Oasis unit on Ventanas and Dutch Stars, when turned on, will allow the engine coolant to heat the unit while driving. This means that when you arrive at your destination, you’ll have hot water and the ability to turn the furnace on and immediately have heat. On models above the Dutch Star, the heating works in reverse and the Oasis system can be turned on to preheat the engine coolant before travel. This option can be added to the Dutch Star and Ventana (see QT’s by PDR John).
Once you arrive at your camping destination, you have a choice of methods for heating the unit. The Oasis unit can be heated electrically by two heating elements or by the diesel burner. The controls for the unit are located in the control panel above the windshield. The two heating elements can be turned on separately or together. Typically, if you’re on 30 amps, you would use one element. 50 amps would allow both to operate at the same time.
Side Note: When the electric elements are turned on, the indicator lights, adjacent to the electric element switch will light. Once the unit reaches temperature, the lights will shut off.
The diesel burner is also turned on at the control panel and can run in parallel with one or both electric elements.
The Oasis system has a "summer loop" and a "winter loop". The word loop refers to circulation of the boiler fluid. In the "summer loop", only water for the faucets and shower are being heated. In the "winter loop", boiler fluid is being circulated to the various heat exchangers (small radiators in the coach).
The "summer loop" is activated by turning on one or both of the heating sources (electric or diesel) while keeping the "Furnace" turned off at the thermostat. In this mode, you’ll have unlimited hot water.
The "winter loop" is activated by turning the "Furnace" on at the thermostat. You can leave the "Furnace" temp at a level below that of the coach and the system will continue to stay in "winter loop" and circulate boiler fluid to the various heat exchangers. When the thermostat temp is increased to something above room temperature, fans located behind each heat exchanger will come on and begin heating the coach.
There is a reason for a "summer loop" and a "winter loop". If you leave the coach in "winter loop" (Furnace on) during hot weather, boiler fluid will continue to be circulated to the heat exchangers. Even though the fans aren’t running, the exchangers will radiate heat, unnecessarily raising the interior coach temp .
The use of the Oasis system has been a learning experience for me. It takes some managing depending on how you like to use it. We recently did our first really cold weather trip and I learned several things, which is primarily why I’m writing this.
Depending on how you use the system, it requires some management. We arrived at a campground with an outside temp of 40 degrees. We had full hookups, so I turned on just the two electric elements. We like to sleep with a cool coach and I set the furnace to 60 degrees. In the morning, I turned up the furnace to 68 degrees and my wife jumped in the shower. The furnace was still running and trying to bring the coach to temp. My wife ended up with a lukewarm shower.
The furnace shut off at 68 degrees and I took my shower. It was hot. I thought the running of both electric elements would be the equivalent of running the diesel burner. Not so. Several factors came into play. The ground water was very cold and was being fed directly into the system when we showered. (Oasis technicians recommend using the onboard coach water in really cold weather and then replenishing it later.)
During our summer trips, we found two electric elements were plenty for a hot shower, especially since the system was not heating boiler fluid for the heat exchangers. Now in cold weather, with the heater running and showering at the same time, we needed the diesel burner and both electric elements. On this same trip, we boon docked for 5 days. The diesel burner is sufficient to heat everything by itself.
So here’s what we found. If we have 30 amp or 50 amp hookups during a summer trip, we’ll turn on one or both electric elements and have hot water. If we have 30 amp or 50 amp hookups during a cold winter stay, we’ll turn on both electric elements and the diesel burner. The electric burners will maintain temp and the diesel burner will supplement during high demand.
It’s apparent the diesel burner will provide all heating needs, but I don’t like to leave it on as the sole source of heat in a campground with hookups. Running the electric elements and the diesel burner will keep it from running unnecessarily.
Some other things.....When we first got the coach, I didn’t feel that the shower was getting as hot as it should. I called Oasis and they recommended that I turn up the flow valve. The valve is located inside the "Distribution Module" and requires removing the cover. This helped, but didn’t solve the issue. Another poster recommended that I remove the handle on the shower faucet and look for a restrictor. Sure enough, there was a red plastic ring used to restrict the travel of the handle. I removed the restrictor and have been very satisfied with the temp.
Oasis offers a service kit for $100.00. It includes tune up parts, filters and a large diesel fuel filter. The filter is similar to the engine filter and is located in the generator bay on my coach.
The unit also uses Century Transfer Fluid in the boiler system. The overflow canister for the system is at the rear of the coach in the engine compartment.
