On-demand water heaters

[rogerddd]

On-demand water heaters – do they work?

We have a new Thor brand class C Motorhome with an tankless Girard Brand RV water heater. In the shower the water will temporarily turn warm after the hot water faucet is on and run for a while, but it cycles between warm and cold, so we end up showering with mostly cold water. Both the manufacturer and RV repair facility tell us the same thing: run the faucet until warm water flows, then reduce the flow to sustain the warm temperature. When hooked up to city water, this almost works but with dry camping it does not work well and takes too much water to sustain even water occasionally warm. Washing dishes offers a similar experience. Anyone have good success with tankless water heater in their motorhome? Is so, how did you get it work?

[Flarpswitch]

My impression is that how the tankless system is installed makes for better results. We have a Truma AquaGo and so far it has been pretty good. We have about 50 days of use so far on the new rig so I may have a different opinion in a year or two. Our system does have two recirculating loops; one to the kitchen and one to the bath. When the control is turned to normal, the heater starts and shuts off when the temperature rises in the loops. This provides near instant hot water and almost no waste. If hot water use is anticipated, normal is selected and hot water is ready in a minute or two. The Truma is so quiet that you have to stand right next to it to even detect that it is on, unlike the jet plane roar of the water heater in our previous motorhome. There is an Eco mode that maintains a minimum temperature in the system which is advisable in cold weather. Forgetting to switch to Eco mode will leave the heater to cycle on and off to keep the water hot in the lines wasting fuel and consuming battery power when dry camping. The true test is the shower. Previously, I had a heck of a time getting the water to the right temperature. Trying to conserve water by using the switch on the shower handle just caused the cold water to back up into the hot water line. Turning on the water again, you had to let it run for the hot water to come back. Now, once the single handle faucet is set to the right temp, I can control the flow from off to full flow and the temperature remains constant with no waste down the drain. With a water connection and the grey tank open, I could have hot water until the propane tank runs out. There was one issue so far. The pilot light on the control knob started flashing to indicate a fault. The fault code can be retrieved by observing the pilot light on the water heater with the door open. The fault code was not in the book, so I contacted Truma by email and they told me that the fault code I read indicated a program error in the control module. They sent me a new one which took all of five minutes to swap out. The old unit was returned in the provided shipping box. The Truma is expensive, however if it continues to perform as it has so far, I would not hesitate to recommend it on a new RV or as a replacement for a conventional heater. I would qualify that recommendation by saying that the recirculating feature is a must have to avoid water waste and to have consistent temperatures. There does have to be a minimum water flow before the heater kicks in, so without the recirculating system feature, there is no distinct advantage over a conventional heater.

[Farmboy666]

kerrlakeRoo wrote:
I have one in my home (S&B) and dont like it. We have to trickle water from the bathroom sink to keep the volume through the water heater high enough to keep the unit from switching off. Being on a well my pressure fluctuates between 45 and 65 PSI, and tankless units want a perfectly constant flow to maintain a temp so its not a good match. And an RV has the added issue of limited storage for both fresh and gray water making that even more problematic.

I don’t know what brand or how old your heater is but you have a problem. Yes you need a certain flow to kick it on but you shouldn’t need to open another faucet. They don’t need a perfectly constant flow as you said, just enough flow to kick the burner on.
I have a Noritz and am on a well and have zero problems. Rv system is a different story.

[paddykernahan]

FunTwoDrv wrote:
Another option we have seen is to install a recirculating system. This would flow through the heater even with the faucet off. They can be controlled by a simple switch so they aren't on continuously. Just a thought...

Gary

I made a valve controlled connection from the hot water low point drain (winterizing valve) to the fresh water winterizing drain. With the valve opened the pump runs constantly taking the on demand heated water through the hot water system.

Once the shower head is cleared of cold water, you have constant hot water.

When done with shower mode, turn off water pump until recirculating valve is turned of and the system put back in normal mode.

[T18skyguy]

The previous generation of Girard tankless had a recall for defective gas valves. My 2017 has the correct valves marked with with a white plastic circle around the top of them. Look at the unit and you should see the two valves on the lower left of the unit. Tankless is not the best for dry camping as said above, but if your on hookups, this is my method that works fine for me.

1. Purchase a high quality Rinaldo adjustable water pressure gauge. You can get it on Amazon. I set mine at 60psi and I usually see a running pressure of about 40psi. The standard regulators sometimes keep the pressure too low.
2. Set the water temperature at the wall to 105 degrees
3. Use only hot water no cold. You don't need to mix in cold cause the water temperature is set.
4. Turn your hot water on full in the shower and leave it there. No on and off because the unit will cycle on/off and you get uneven cycle. Don't even touch the cold water in the shower.
5. Go to camping world and get a black water cap that has the built in hose connector. Connect a hose and just leave your grey valve open and drain the water down the sewer. At the end of your trip go back to the solid cap and collect some grey water so you can fill the black tank with fresh water/chemical. Hope it works for you. I'm happy not to use the campground showers anymore.

[FunTwoDrv]

Another option we have seen is to install a recirculating system. This would flow through the heater even with the faucet off. They can be controlled by a simple switch so they aren't on continuously. Just a thought...

Gary

[Oldtymeflyr]

We are thinking about switching out our tankless to a more standard tank unit.

Rick

[ScottG]

I used one in a friend's house (showers, etc) that worked great. Can't tell any difference from a tank system.
So it gives me hope that they can eventually come up with a workable system.

As I have posted before, the new Atwood tankless is very promising because it addresses the usual shortcomings with two levels of burner heat (15K & 50K). So it should work at both very low flow and higher flow. Reviews seem to be very mixed though and it would be great to hear form someone on the forum that has used this model.

[3oaks]

midnightsadie wrote:
just my .02 worth they were never made for rv,s and most of them don,t work great in a house ,you gotta run a lot a water down the drain, for it to work correctly..

I'll add my .02.
My same thoughts. Now you have .04 cents worth. 🙂

The tankless on-demand hot water system works just fine in our house, but I can see where it wouldn't be a good fit for RV use.

[kerrlakeRoo]

I have one in my home (S&B) and dont like it. We have to trickle water from the bathroom sink to keep the volume through the water heater high enough to keep the unit from switching off. Being on a well my pressure fluctuates between 45 and 65 PSI, and tankless units want a perfectly constant flow to maintain a temp so its not a good match. And an RV has the added issue of limited storage for both fresh and gray water making that even more problematic.

[MDKMDK]

Some folks do like them, but it appears to be make/model specific.
http://www.irv2.com/forums/f52/truma-aquago-instant-hot-water-heater-251183.html

[Dick_B]

For previous posts search this Forum for `tankless' or `on demand', etc.
Unless there has been a vast improvement in the design the only time they would work well is if one is connected to campground water and the gray tank valve is open. That's my $.03 adjusted for inflation.

[Desert_Captain]

The problem with the on demand water heaters is that they only work to capacity when you have full hook ups. There just is no free lunch here. Without water and electric you will quickly deplete you fresh water supply {and dent your battery bank} as that 6 amp+ an hour water pump runs and runs while you await a steady stream of hot water.

At the same time, you are quickly filling your gray tank which, if you have a proper sewer hook up, will necessitate frequent trips out to the dump hose to open the valve and drain the tank. I doubt that these systems use significantly more propane {if any} than conventional water heaters but not having the electric option ultimately costs more over time {there are lots of CG's and RV Parks that provide electric even absent full hook ups. Additionally these are usually cheaper than the full hook up park down the road}.

Off the grid, the performance issues noted by the OP seem to be common. On demand systems work well in residential applications but unless you always have full hookups they have their limitations in the RV world.

My bride and I have no problem getting nearly instant hot water from our 6 gallon propane/electric water heater. It comes out of the galley faucet steaming hot in mere seconds {the water heater is located directly beneath the galley sink}. We can both take short but very hot showers back to back without exhausting our hot water.

As always... Opinions and YMMV.

:C

[ScottG]

Well this is discouraging! I keep hoping to hear some good reports about these but it doesn't seem to happen.
Good luck and welcome to the forum.

Scott

(PS, btw, your not allowed to post the same thing in multiple threads.)

[MDKMDK]

Perhaps this will help. I'm not familiar with the brand you mentioned.
https://www.youtube.com/watch?v=eE89B4zQoKc

Here's another
https://www.youtube.com/watch?v=1-6YQUuVyqM

And yet another
https://www.youtube.com/watch?v=cZ5i8FzU4UE