Cold-water side makes the hot water heater come on.

[Boudreaux]

OK,
We have experienced something this past weekend that makes no sense at all. First off we have a 2016 Grayhawk 29MV. It has the limitless Water Heater That has worked well for 4-plus years. This weekend that all changed.

We parked the coach at the campground on Friday. Used the Toilet, the lavatory and the sink, using the cold water side without issues on Friday. On Saturday, we noticed that every time we used the cold water side, the hot- water heater would come on momentarily, but the water was still cold because it was being used on the cold waterside.

By midday Saturday, the sink was working properly when we used the cold- water side, but using the toilet and the lavatory on the cold water side would make the hot water heater come on momentarily.
By Sunday morning using the toilet would make the hot water heater come on, the lavatory and the sink worked fine on the cold-water side..

Now keep in mind the shower worked fine on the hot-water side.

[JimD]

For an on-demand water heater to come on it requires a good amount of water flow through it before the burner will activate. If you try to get hot water by just barely opening a faucet, the heater will not come on.

Try turning on a hot water faucet just a little bit and see if the heater fires up. It should not until you get a good flow going.

I would suspect your water flow sensor may be flaky. Maybe when you turn on the cold water it pulses the line just enough to trigger the flow sensor causing the unit to fire up. As far as I know this is what determines when the water heater should activate.

I have attached the manual for the on-demand water heater that was in my 2017 Greyhawk. I say WAS because I recently yanked that sucker out of there because I absolutely hated it. We dry camp mostly and it wastes a lot of water and doesn't work near as well as a tank style.

[Bullitt6283]

Originally Posted by Boudreaux

OK,
We have experienced something this past weekend that makes no sense at all. First off we have a 2016 Grayhawk 29MV. It has the limitless Water Heater That has worked well for 4-plus years. This weekend that all changed.

We parked the coach at the campground on Friday. Used the Toilet, the lavatory and the sink, using the cold water side without issues on Friday. On Saturday, we noticed that every time we used the cold water side, the hot- water heater would come on momentarily, but the water was still cold because it was being used on the cold waterside.

By midday Saturday, the sink was working properly when we used the cold- water side, but using the toilet and the lavatory on the cold water side would make the hot water heater come on momentarily.
By Sunday morning using the toilet would make the hot water heater come on, the lavatory and the sink worked fine on the cold-water side..

Now keep in mind the shower worked fine on the hot-water side.

I also have a 2016 29MV with that water heater (I hate it).
I suspect there is some trapped air in the line somewhere. Momentary backflow through the hot water line due to trapped air could cause the heater to come on.
Bleed the air out of the water lines going to the outdoor shower. The outdoor shower plumbing is the furthest point from the hot water heater.


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[Boudreaux]

I FIXED IT ....

Someone mentioned the possibility of air in the lines. The wife and I connected a water line to the coach, opened "every faucet in the coach" at once, and let water flow for about three minutes. Yes, there was air in the lines.

I used air to blow out the lines last November for winterizing. Apparently, it does "a very good job" of clearing the waterlines.

SO, if you have a tankless water heater, and the water heater is activated from the cold water side (after winterizing), you may very well have air in your lines (somewhere).

Thanks to all ......

[Bullitt6283]

You're Welcome.




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