Continuous HWH woes. Suburban IW60

[ElDorado]

We have a 2019 Rockwood 5th Wheel and had the hot water heater upgraded to a tankless Suburban IW60 (90% Sure re: model).

We live in it and it took some troubleshooting after we took delivery to get the heater to work, but for the last couple of days, it has been driving us nuts.

First some background. We live in the Sierra Nevada region at 3600 feet not too many miles from the Rubicon River and Trail. The cold season is upon us. Also, being so rural, our water is from a well which is shared by us and three other households. One of those was added last spring.

About the middle of this last summer, the heater would refuse to make the shower or bathroom sink water hot. However, if we turn on the kitchen hot water, or start the stove, it seems to prime the propane and the bathroom hot water starts working. We've always had SOME issues with getting hot water temperature to stay consistent, but usually with only slightly unpleasant variations. Inconsistent water temperature seems to be remedied by making sure the tanks are full.

Now that temps are dipping to freezing for the first time this year, the variation is from too hot, to freezing cold and back again for the last two days.

What is the most likely culprit? low water pressure? something with the propane? something I'm not catching?

[NMWildcat]

I'm not familiar with the Suburban tankless, but the most important factor in most tankless water heaters is water flow rate. That's why you leave the cold water off and turn on the hot water valve 100%. If it's not warm enough, you turn down the valve to slow the flow rate, allowing the water to stay in the heater longer. But if you turn the flow rate down too much, it will turn off the burner. And if you open the cold water valve, you usually mess up the flow rate through the heater, causing the hot/cold cycling.
Our old tankless usually works great unless the incoming water temp is too warm, then the temp is too hot. So when at hookups, we open the bathroom sink hot water valve to a trickle while using our shower. The flow rate is increased though the heater and the water temp is cooler. And we don't have the temp cycling caused by opening the cold water valve.
If after experimenting with flow rates, you can't regulate the temp sufficiently, you might have an RV tech familiar with Suburban come and see if any sensors or such need adjusting.

[NavyLCDR]

I would be looking at the flow sensor in the water heater. I'm not sure if they are adjustable or not and just needs to be replaced. The flow sensor determines when there is water flowing through the water heater which signals a demand for hot water to ignite the burner. Have a second person stand by the water heater and listen for the burner to come on as you slowly open the hot water in the shower. The water heater burner should kick on when the shower hot water faucet is open about 1/2 way.

Personally, I've always turned hot water on 100% and used cold water valve to regulate temperature. I know my starting settings are hot water 100% and cold water about 1/8-1/4 turn back from 100%, then adjust the cold water valve for desired final temperature.

[pagescanz]

Did you ever get this resolved|?
Having the exact same issue.

[5picker]

Originally Posted by pagescanz

Did you ever get this resolved|?
Having the exact same issue.

Welcome to the forum, I see it is your 1st post.

As mentioned, water flow is often an issue with tankless models.

What is YOUR water source?

Is this a new issue (worked OK before) or has this happened since day one?
A clogged filter(s) can create low flow.

I don't see your R/V year/make/model listed nor anything in your profile.

[Cruzrtwdgt]

We have a Furrion but same principle of operation. If kitchen sink works OK but bathroom sink and shower don't, look for a kinked hose in that area or debris in the strainer and shower head restricting hot flow.


As for extreme temperature fluctuations, we have had this issue a few times. We'll have the water heater set for 124 and all is good until we turn on the cold to adjust the temp. This causes reduced flow through the water heater and it goes nuts, hot/cold/hot/cold. Our solution was to set temp to our desired shower temp (108 for me and 113 for my wife) and just use hot water for shower, no cold.