How Does an RV Oasis Hot Water System Work? – RV-N-Style

How Does an RV Oasis Hot Water System Work?

Shower spraying

I have a Newmar Mountain Aire Class A RV that uses an Oasis Hydronic System for heating water and heating the coach. A friend who had just gotten a similar coach asked me about the operation of the heating system. He was in Montana and the weather had turned cold. I realized that I did not fully understand the workings of the system myself. Since I do a lot of my own maintenance, I thought it would be beneficial to do some research to try and understand the system better. Here is what I found.

How does an RV Oasis Hot Water System work?

The Oasis Heating system uses a diesel burner controlled by a multi-function controller as a primary source to heat a coolant fluid (anti-freeze and water). It also uses two 1500-watt AC immersion elements as secondary heat sources. The system heats the fluid which can then be circulated to meet all heating needs. This includes hot water demand as well as coach heating.

The Oasis System accomplishes this in multiple ways depending on the specific demands to the system. This includes:

  • Being in a campground in Summer with full hookups
  • Boondocking at a site in the Summer without hookups
  • Being at a campground in Winter with full hookups
  • Boondocking at a site in the Winter without hookups

The system explained

As I stated, the Oasis system heats a coolant that is circulated to meet all hydronic heating needs. It accomplishes this with the use of a heating module and a distribution module.

The Heating Module

The heating Module contains an 8.2-gallon stainless steel coolant tank that is insulated to minimize heat loss. It is this coolant in the tank that is the source of heated fluid. When combined with the Distribution Module and its integrated pumps, the Heating Module is able to circulate the coolant fluid to all spaces that heating is needed. Using the integrated heat exchanger in the Distribution Module, the Heating Module can also provide a supply of hot water for showers and sinks.

The Distribution Module

The Distribution Module, as the name suggests, handles the distribution of the coolant fluid to where it is needed. It does this with three distribution pumps, a heat exchanger for heating multiple zones, engine heat function and domestic hot water.

Operation of the system

Operation of the system depends upon the heat source selected and the demands required.

Different RV’s will have different remote control panels, but they will all have the ability to:

  • Select the burner
  • Select one AC Element
  • Select both AC Elements
  • Turn on optional Engine Pre-Heat (if equipped)

While the Burner is considered the Primary source for heat, it is perfectly acceptable to use one or both of the AC elements instead.

Operation in Summer with Full Hookup

Operating the system in the Summer months with full hookup available offers a few choices. Since heat demands will probably be limited to hot water requirements, the choice of heat source can be minimal. As long as there is any heat source active, the Distribution Module will respond to a call for hot water. You could select the burner, or one AC element or two AC elements or all three.

Note: Use of the Burner requires the use of the coach’s fuel supply. Remember to watch the fuel levels.

Note: The use of the Burner will provide continuous hot water, where use of the AC elements may provide limited hot water. (I have never had an issue with running out of hot water using just the AC elements.)

Operation in Summer while Boondocking without Hookups

Operating the system in the Summer months while boondocking can limit your choices. If you are going to be running your generator the whole time, you can operate the same as above. If you plan to stay on the batteries as much as possible, you would need to use the burner.  Since the AC immersion elements require 110 volts, you would not be able to use them. The load demands on the immersion elements would be too high for an inverter in most RV’s.

Note: Use of the Burner requires the use of the coach’s fuel supply. Remember to watch the fuel levels.

Operation in Winter with full hookup

The Oasis system makes use of a Summer loop and a Winter loop. In the Summer loop only the water for the showers and sinks is being heated. In the Winter loop, coolant is being circulated to the various heat exchangers in the coach’s cabin zones that require heating.

This “Winter loop” is activated by turning on the Heat at the thermostats. This will allow for the coolant to start circulating through the heat exchangers for the different cabin zones. Raising the setpoint temperature for a specific zone causes the fan for that zone to start blowing air across the heat exchanger.  There is an aquastat that will prevent the fan from blowing cold air into the cabin. Once the temperature in the cabin zone has reached the called for temperature, the fan will stop.

However, even if the setpoint temperature is lower than the outside air, the coolant will still circulate through the heat exchangers, which will allow for heat to build up in the coach. Make sure to turn off the Heat when not needed. This will place the system back in the “Summer loop”.

Determining which heat source to use will depend on different factors:

  • Outside temperature
  • Wind conditions
  • Ground water temperature
  • Personal comfort level

You may be able to satisfy your requirements with one of the sources, or you may need to use all three sources. Either way is acceptable to the system.

Note: Use of the Burner requires the use of the coach’s fuel supply. Remember to watch the fuel levels.

Operation in Winter while Boondocking with no Hookups

Operation of the system is basically the same as above with the exception of power requirements. Again, if you plan to run the generator the majority of the time, then your options are the same. If you plan on being on the batteries as much as possible, then you are limited to burner operation. Depending on the factors I mentioned above, this will take some management. For example, you would probably not want to try and shower at the same time you are trying to get the coach warmed up. Or you may need to find a happy medium for generator on and off times.

Note: Use of the Burner requires the use of the coach’s fuel supply. Remember to watch the fuel levels.

Oasis System Problems

Some common problems with the systems as outlined in the operating manual are as follows.

  • Burner does not start
    • Make sure DC power is available to Heating Module
    • Make sure Power Button is on (green LED should be lit)
    • Is the Burner selected on the remote control panel?
    • Main fuse or circuit breaker blown or tripped?
  • AC immersion Elements don’t come on
    • Make sure you have AC power
    • Make sure that the element or elements are selected at the remote control panel
  • Burner Starts but Flame Faults
    • Check Fuel Supply
    • Make sure intake or exhaust not blocked
    • Check Fuel Filter
    • Air in Fuel line?
  • Burner starts but Zone Faults
    • Make sure Power LED for Distribution Module is green
    • Make sure component matched LED pairings are all green

Oasis Hydronic System Maintenance

Owner maintenance on the system is pretty basic. It consists of:

  •  Checking the coolant hoses and fittings for leaks
  • Checking coolant levels in the overflow bottle (3/4 when hot)
  • Checking for obstructions to the intake and exhaust
  • System fuel filter for clogging
  • Fuel lines and fittings for leakage

Related Questions

Is the Oasis Heating System problematic?

Like any mechanical system, the Oasis System can have problems. I have read most about pumps failing from time to time. I read of one coach owner that had a bad weld on the coolant tank. Most say that the Oasis tends to be better than others on the market.

When should you use the burner?

The use of the burner is considered the primary heat source according to the manufacturer. Many coach owners do not use the burner when the weather is mild and there is full hookup available. It is perfectly acceptable to use any of the heat sources in the system separately or together.

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