Unsatisfactory 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.

[houtrz]

I agree with Big Katuna, when I added a generator to my fifthwheel, the regulator had to be changed out to accommodate the much higher gas flow.

[funpilot]

I just sold my trailer that I installed the Truma on demand hot water heater. Simply stated, it works perfectly. I am now looking for a class B or C and will get a Truma again.

[DaHose]

Good point Katuna. Anything that has big heat output needs a really good regulator setup. I put together a tankless heater setup for my hot tub. It would freeze single regulators right up. My solution was to hook up a 3/4" line and feed it with two regulators. Worked great then.

Jose

[Big_Katuna]

Do you have a two stage LP regulator? I read that is important.

The Amazon reviews are informative. The negative ones say that if you don't have sufficient pressure and volume, you get the hot-cold-hot-cold scenario.

[Puttin]

On some earlier models venting was sometimes an issue also. If the unit was mounted too close to a slide it might not get enough direct exposure to keep the flame at a constant level.

[RckyMtnVia]

There have been lots of complaints about tankless water heaters for rvs and if you do a search on this forum, Jayco forum, Forest River forum and Winnebago forum you will see lots of issues. The main problem is that unless there is a constant, steady high flow of water into the heater, it runs hot and cold. This mainly happens when using the water pump but if a campground has low pressure or low flow of water, then it can be a problem.

[RichNewcome]

My 2016 Nexus 32SC came with an Atwood on demand water heater. The problem I've had is insects getting into the vent for the diaphram switch that is used to determine that the blower is running. For some reason they like to crawl in there and plug up the switch port with a mud-like substance. When it was partially blocked, I experienced intermittent operation like you described. When fully blocked, it would not light at all. I recently put a piece of adhesive window screen over the vent opening and it seems much better. Will know more after our next trip.