Aqua Hot Systems

When on the road, with the engine furnishing the hot water, you can run the furnace without using either the electric element or burning extra diesel.

x2 on Dennis!

Since we live in a rather warm climate, we normally just leave the electric element turned on for hot water. When we go North, we will use the diesel burner for domestic heat and hot water. As others have said, the engine heats the boiler fluid while driving, and the unit will preheat the engine on cold mornings. If properly maintained and tuned, the exhaust is fairly clean, but if you are concerned about fumes, you can add a genturi for it also. Like others, I would never buy another coach without one.

crasster wrote:
They are excellent systems that most often run on gas & electric. The thought of a nice hot shower after some long hikes sounds appealing. One day we may buy a coach with one... Had my eye on them for some time now.

99% are Diesel and Electric, NOT "gas". For un limited Hot Water, the Diesel burner MUST be ON. The only models that can give close to unlimited on electric are the dual 120 element models which are not installed on units less than 500k. The Electric element on most is to use the electric for furnace side heating and to give about 1 gallon of hot water. The 120 side is not designed to give unlimited Hot Water. Doug

They are excellent systems that most often run on gas & electric. The thought of a nice hot shower after some long hikes sounds appealing. One day we may buy a coach with one... Had my eye on them for some time now.

My aqua hot works off electric and diesel. I leave the electric on most of the time and only turn on the diesel when we are going to use the showers. Yes, it's unlimited hot water. DW likes long showers and I can follow her without waiting for the water to heat up like a regular water heater. It also can be used to warm up the engine and the engine in turn warms up the water. The best feature is there is no furnace. The aqua hot heats the coach with almost no noise.....I would not buy another coach that did not have that feature......Dennis

freestoneangler wrote:
How about its use in hot weather -- when you want hot water but don't need heat in the coach? Also, do they tend to give off odor and more costly to maintain?

They are 2 separate systems. There is the Hot Water side and the Heating(furnace side). The Furnace side does NOT circulate hot water unless you have the wall tstat set for furnace mode. As to the exhaust. No matter what anyone says, they are a BIG disturbance to your neighbor on your drivers side. The exhaust on most is amidships and shoots out directly to your drivers side neighbor. THAT is a big no no in my opinion. But, it is the nature of the beast. The ONLY maintaining is an annual tune up that can cost about $300 max. But, the most common problems on a Aqua hot system are from LACK of use. The Diesel burner(nozzle) and the circulation pumps and check valves do not like long periods of inactivity. They tend to clog up(diesel nozzle) and the Furnace side check valves stick. Regular running of the Diesel system and furnace system, just like running the APU is a must to keep the systems from malfunctioning. Doug

freestoneangler wrote:
How about its use in hot weather -- when you want hot water but don't need heat in the coach? Also, do they tend to give off odor and more costly to maintain?

In hot weather you rarely need to turn on anything as the engine has heated the water which will last a longtime (since it's hot outside).

The only odor from an Aqua-Hot would be from the diesel exhaust. Ours runs very clean (just had it serviced) so not much of a smell. Now, if we are parked close to our neighbor, I run the Aqua-Hot on electric as not to send any fumes to the neighbors. Usually we are never parked that close to a neighbor but it has happened.

Our Aqua-Hot has the two stage electric element( 110 and HI). We can heat the coach electrically through the Aqua-Hot if it's not too cold out (40+ degrees). I have to say, that the electric elements will make the water almost scalding!

I get ours serviced every other year as every year seemed too often. After having it done every year for a couple of years the nozzle looked like brand new, I couldn't tell the difference. The fuel filter is also changed. I think it's about $250 for servicing.

MM.

How about its use in hot weather -- when you want hot water but don't need heat in the coach? Also, do they tend to give off odor and more costly to maintain?

I don't know how "Unlimited" the heat is, but it has either a 45,000 or 60,000 Btu heat input from the diesel boiler, that works out to heating about 1.5 GPM from 50F to 140F. The Aqua Hot needs to start out warm to keep up. The built in tank will cool down a bit with use, but still stay above 110F when a normal shower is done.

Fuel usage is another thing. 1 gallon of propane is about 95,000 Btu's while diesel is closer to 135,000 Btu's. My guess is a normal propane burner is about 80% efficient, while a typical diesel boiler is only about 75% efficient. So the diesel one is going to cost less per 100,000 Btu's of heat in most areas.

There is also a typical electric back up for the Aqua Heat, so you can run a 2,000 - 4,000 watt electric element (depending on model and if the RV manufacture wanted to install a 120 or 240 volt element) to warm the tank over a long time. Typically they warm 10 gallons of anti-freeze, and then there is a hot water coil that the domestic water goes through this heated (160 - 180F) tank and it will instantly warm the domestic water to 140 - 160F, then cool it with a mixing valve on the outlet to the desired 120F outlet water temp.

Many systems also include a hot water loop for the engine too. So a 3/4" heater hose line from the diesel engine will go through the Aqua Hot tank, and warm it to the engine running temp (up to about 200F) and also because the engine starts out cold, the 140F tank temp will preheat the engine quickly, then the engine will start supplying heat to the Aqua Hot after a few minutes. So with that option, you have unlimited free hot water while on the road, and about 15 gallons just after you park. Many times this allows you to not turn on the burner at all, if you are not running the furnace and don't need much hot water.

Fred.