Hydro-Hot, developed in 1998, was the result of consumer demands for a streamlined heating system that doesn’t take up excessive space in the RV. Based on the principle of heating with liquid, known as hydronics, Hydro-Hot offers unlimited domestic hot water and zoned interior coach heating.
A heat storage tank built within a galvanized cabinet is the heart of the Hydro-Hot system. The mechanics involve thermo-plastic self-bleeding circulation pumps, rubber hose internal plumbing connections, 4 psi coolant system pressure, auto reset fuses, solid state electronics and up to five heating zones. Weighing less than two hundred pounds, Hydro-Hot combines the furnace and hot water into one efficient unit.
Some model coaches built in the late 1990s are equipped with a heating system similar to Hydro-Hot, but different in operation and maintenance. The information contained in this article covers Hydro-Hot, built by Vehicle Systems, Inc.
When interior coach heating is desired, all you need to do is select the diesel burner, electric element, or both, and set the thermostat. Hydro-Hot is draft free and quiet and separate heating zones throughout the system will allow independent room temperature control. Fresh water storage tank freezing can be prevented by setting a bay-heat thermostat to forty degrees Fahrenheit.
“Hydro-Hot offers unlimited domestic hot water and zoned interior coach heating.”
The Electronic Controller faceplate, registering working and non-working components, can be used to operate and troubleshoot the Hydro-Hot system. To check for loose connections or plugs, remove the cover panel by unscrewing the four cover screws. To inspect for loose connections on the diesel burner control unit, remove the access cover on the front of Hydro-Hot.
Hydro-Hot uses a 50,000 BTU diesel burner and a 120-Volt electric heating element. Both systems will automatically heat and maintain temperature of the heat storage tank. A switch panel in the RV allows you to choose heating with diesel, electric or both. Warming up the system utilizing the diesel burner will take 10-20 minutes. Continuing to operate with the diesel burner will only require low volumes of fuel, probably one gallon per day. The diesel burner is supplied directly from the engine’s main fuel tank, so for safety’s sake, the Hydro-Hot system should always be turned off prior to filling the main fuel tank.
Use of the electric heating element requires shore power or the generator. The electric heating element is not connected to the inverter. Powering the system through the electric heating element will require 1-2 hours for the system to reach operating temperature. The electric element, which offers 1/10th the power of the diesel burner, is designed for lighter heating loads. If you are plugged into good shore power, and the weather is mild, it is appropriate to turn off the diesel burner and utilize the electric element for low heat requirements. In extreme cold temperatures, or when taking long showers, the diesel burner should be used for more efficient heating.
Interior heating will go on stand-by whenever there is a demand for hot water. Once the hot water valve is turned off, interior heating will automatically resume. This priority routine insures that the Hydro-Hot user never runs out of hot water. Tests conducted have found that during a thirty-five minute shower, when interior heating was suspended, interior coach temperature dropped only four degrees during a cold winter day. Due to this minimal temperature drop, heating the coach and hot water at the same time is impractical in terms of a larger system requiring more storage space.
"Hydro-Hot is... quiet and separate heating zones throughout the system will allow independent room temperature control."
An adequate 12-Volt electrical system is necessary for operation of the diesel burner, electric heating element, circulation pumps and the fan for the heat exchangers of Hydro-Hot. If the batteries are disconnected or discharged too low for the system to properly operate, a red light will illuminate the low battery voltage reset light on the Electronic Controller panel. Once proper DC voltage has returned, the fault must be manually reset for operation to resume. Push the Low Voltage Reset button on the controller’s PC board with a thin, straight object.
The RV engine is automatically heating the Hydro-Hot system as you drive. By harnessing this free energy, the supplemental heat will reduce the heating requirements of the diesel burner and electric element as the engine’s heat transfers to the Hydro-Hot’s heat tank.
The optional engine preheat feature will assist with easier start up of the RV during cold weather conditions. For most efficient engine preheating, run the Hydro-Hot system on the diesel-fired burner and engage the engine preheat switch a few hours before starting the engine. Remember to turn off the engine preheat switch once engine preheat is complete. If this feature is not available on your present system, it may have been pre-wired for later addition.
A temperature controlled mixer valve has been installed behind Hydro-Hot. This valve can be adjusted but extreme caution must be used as this is not an anti-scald valve and incorrect settings may cause severe burns from overly hot water temperatures. Contact the Hydro-Hot manufacturer for step by step instructions on adjusting this valve, or with any other maintenance questions.
“The RV engine is automatically heating the Hydro-Hot system as you drive.”
To keep Hydro-Hot running at peak performance, have the system tuned up annually, replacing the fuel nozzle and filter, as well as thoroughly cleaning the combustion chamber. Have all components of the system thoroughly inspected for wear and tear and confirm that hoses and connections are snug and tight. While it is appropriate to wipe away grime from the component with a dry rag, never spray direct water pressure onto Hydro-Hot. Always disconnect the system prior to performing maintenance by turning off Hydro-Hot and pulling the wire harness of the diesel burner. It is recommended to carry a spare fuel nozzle and fuel filter as these parts are often not readily available for immediate retail purchase.
Winterize the fresh water system by first completely draining the RV’s fresh water system. Remove the water pump’s line from the fresh water tank and attach a piece of hose onto the suction side of the domestic water demand pump. Place the other end of the hose into approximately two gallons of FDA approved RV antifreeze. Going from faucet to faucet, exterior and interior, hot and cold, open each faucet and run until only antifreeze is present, then close the faucet. Wipe surfaces clean to prevent staining from the antifreeze. After performing this task, remove the hose from the antifreeze and reconnect the water pump’s suction line to the fresh water tank. If you do not intend to use Hydro-Hot to heat the RV during storage, turn off all electrical power supplies to the system while in storage.
When removing the RV from storage and preparing it for use, fill the fresh water tank with fresh water and flush the water lines by opening all faucets, exterior and interior, hot and cold, until clear water is present. If the electrical power to the system was disconnected for storage, the Electronic Controller will require reset by using a thin straight object to depress the Low Voltage Reset button through the small hole on the faceplate.
"Using Hydro-Hot's controlled interior heating and unlimited hot water make extended stays in the RV more pleasurable than ever."
Preventive maintenance includes running the diesel burner solo, for a minimum of ten minutes on a monthly basis. During cold start up, expect minimal exhaust, but extended smoke should be inspected for potential problems. When using Hydro-Hot for prolonged camping, beware of excess exhaust. If this occurs, check the batteries as less power for the fan may be creating less air for the system to operate.
Cold and discomfort conspire to eliminate enjoyment in camping. Using Hydro-Hot's controlled interior heating and unlimited hot water make extended stays in the RV more pleasurable than ever. While the prospect of a single component offering so much seems unimaginable, understanding the intricate features of Hydro-Hot will put everything into perspective and assist you in maintaining this dual furnace and hot water heater to provide years of comfortable service. |
