Marey Gas 10L on demand water heater

I'm currently installing a Marey 10L (3 gallon/minute, 65,000 BTU) on-demand in a Spartan Tandem 30' trailer which is still under construction. I have installed and used a few different on-demand LPG heaters. As you would expect I have some opinions on the subject.

Marey is a quality product, they have been around since 1955, and meet ISO 9001 quality standards. Just a suggestion, they are widely sold by many different retailers. If you buy one, and it does not work, it would be expensive shipping it back. Home Depot sells them "on-line" and offers free shipping to your local store for will call pick up. This also makes it more convenient if you have a problem.

Every different brand LPG on-demand water heater I have looked at "with the cover off" looks like it was made in the same factory! I do not know this to be true, but it all looks the same to me. The capacity sizes, and volume ratings are different, but they look like they were all made in the same factory but with different brand names used.

It's of interest that they list about twenty different important specifications on the outside of the box, but nowhere on the box is it printed about not using it at high altitudes. Every instruction manual I have read states the same thing about using it below 2000 feet. I have regularly used my Marey at Big Bear Lake about "mile high" without any air/fuel ratio problems. It only makes sense that if you have less air density at high altitude you should have a way (it would be expensive) to automatically reduce the fuel to thin air ratio. Auto manufacturers finely got around the carburetor high altitude problems when they adopted electronic fuel injection.

It's important to remember that the on-demand heaters are just raising the temperature of the water that flows into the heater. If you camp in the desert and the ambient shore water temperature going into the heater is "let's say" 70 degrees and the heater can warm it up by 50 degrees (just a guess), you will have nice warm 120-degree hot water. But when you camp at Big Bear (mile high) and they are pumping 40 degrees well water, your heater might not be as efficient (high altitude) and only warms the water by 40 degrees, you will have "not so warm" 80-degree water coming out of the faucet. I'm sure my actual numbers are off, but I hope my explanation is still understandable. In actual practice, my water is not as warm at Big Bear, but it is not so objectionable that I need to reset the controls. They do have winter/summer temperature controls to slow down the flow to give the heater more time to heat the colder water.

IMO, proper venting of the heater is very important. I vent all of my installations to the outside side wall. Due to the tight quarters in a trailer, you should pay close attention to the distance from the hot exhaust pipe to any combustible material. They sell a "Double Wall" vent tube called "B-Vent" which will allow you to only need one inch of clearance to a combustible material. It's commonly available at your local HD.

The on-demand heaters have several safety features, one is a water control valve that prevents the heater from turning on until the valve senses actual water flow. This works well, but sometimes with the new "low water flow" faucets, the heater will not turn on because the flow is "too slow". It's an easy remedy to remove or modify the screen in the faucet nozzle.

If you're really concerned about the altitude issue, just buy it and test it at altitude "before you install it into your trailer. It can be run off of a Bar-B-Que LPG tank as long as you have a regulator in line.

One additional thing, they use "Electronic Ignition".  This is a Pezo spark lighter like you would have in a Bar-B-Que and is fired by two "D-Sized" batteries.  I camp about ten times each year, and the batteries have not been changed in six years.  It's a proven system.

All and all, I would highly recommend the LPG on-demand water heaters. I would not recommend an electric On-Demand heater.

John Palmer