Weird Behavior of Tankless Water Heater

[chasfenwick]

Our 2014 Jayco Melbourne 29D came with a tankless water heater. Dealer says that it is working normally but we don't believe it for one minute.

From day one, it has been impossible to get it to put out a continuous stream of hot water for, say, 30 to 60 seconds, before water abruptly turns cold for a period of time. Then burner comes on again for a while.

When taking a typical shower, is not unusual that you would go through 3 cold-hot-cold-hot-cold-hot-cold cycles. I'm talking full water flow rate, not touching ANYTHING. Trying to mix hot and cold water makes the problem even worse, so you have to control the hot water temperature from the dial on the other side of the walkway. Of course, problem is same at the sinks, and same whether water source is tank or city.

I don't know how many different models of Class C motor home have this type of water heater, and possibly travel trailers, but we are very interested in getting some indication of whether this type of problem is generally recognized. If it is, I would think there would be a lot of squawks about it. Wish we could go back to a tank type water heater, with which we've never had any sort of problem, but I suspect that is impractical and we're stuck with this thing.

Thanks for any help you may be able to provide on this.

[hoppers4]

I had the same problem even when following the instructions to a tee which is to make sure you only turn on the hot water and then adjust temp with rotary water temp knob. It still wouldn't work for me because I use a low flow shower head. Rather than change the shower head I had a conventional DSI water heater installed. There's been much discussion about these tankless water heaters and here's a link to one of them.

http://www.jaycoowners.com/forums/f5...ing-22681.html

[us71na]

I looked into tankless water heaters a while back and decided against them. While they might save money in operating costs, I'm not sure that is ever offset by the higher initial cost. The other problems are, they can only raise the water temperature a certain amount based on the flow rate. They also need a certain flow rate to even operate. In a travel trailer, with a low flow shower head and faucets, I don't see how they would work properly.

My suggestion is to check the specifications for your unit and see what flow rate is required to trigger the burner and then check to see if you can achieve that rate of flow in your shower or any other location.

Here is what you should be looking for in your specifications:
Note that in this example, the minimum flow rate is 2.5-3 gallons per minute.