Tankless Water Heater Issue - Not getting hot in shower

[hlmmay05]

Hi,
We just took delivery of our 2021 Flying Cloud with the tankless water heater. I have a few questions about some issues we are having.

I turn on the water heater and set it to the temperature that I want, then turn on the shower to full hot, but the shower water never reads above 102 degrees when the tank is set to 120. (yes I know that is too hot for a shower).

If I turn on the faucet to hot in bathroom sink while the shower is running, the temperature gets hot in bathroom sink faucet and the shower, but the shower pressure decreases.

If I turn off the bathroom sink faucet , the shower water decreases in temperature again down to less than 100 degrees.

Same test scenario with the kitchen sink. Any ideas? Do we have a kink in the line somewhere? This has happened both when boondocking and plugged into shore power with water hook-ups.

Any ideas?

Thanks!

[jondrew55]

I assume you are hoooked up to city water or are you running of the internal water pump. We had a similar situation and it turned out my daughter had turned the water valve at the pedestal outside the trailer almost completely off. So water would run, but not enough pressure for the on demand water heater to operate properly. So make sure you have the water all the way on coming into the trailer. If you have water in the fresh water tank, the internal water pump should give you enough pressure for the HW heater to work properly.

Look at the display in lavatory when the hot water is running. It will show the flame icon for a few seconds, then that will go out and the entire display will go off if you have insufficient water pressure.

[JonDNC]

It sounds like water heater is making hot water so the issue maybe you shower valve. Most of them have a “safety” setting that won’t let the water get fully hot. You need to remove the handle and adjust the hot water setting to allow full hot. Didn’t have that issue on our Airstream but did one new shower faucets at home when we did a remodel.

[jondrew55]

Originally Posted by jondrew55

I assume you are hoooked up to city water or are you running of the internal water pump. We had a similar situation and it turned out my daughter had turned the water valve at the pedestal outside the trailer almost completely off. So water would run, but not enough pressure for the on demand water heater to operate properly. So make sure you have the water all the way on coming into the trailer. If you have water in the fresh water tank, the internal water pump should give you enough pressure for the HW heater to work properly.

Look at the display in lavatory when the hot water is running. It will show the flame icon for a few seconds, then that will go out and the entire display will go off if you have insufficient water pressure.

Also, if you have the shower running and then open a faucet in the lavatory or kitchen, the water pressure will probably drop to where the system turns the heater off. You can monitor it on that little panel. when the flame icon goes out, it's no longer heating.

[Doc Savage]

Not that I know anything about Tankless water heaters, I did notice from a video install that there was a flow restrictor, white knob at water inlet, on the backside bottom corner that the owner could adjust. You could check to see if set to minimum or average flow. Just a thought.

[LilPeanut]

We used to have to run the faucet while we took a shower in a house we had to keep the water hot. Instant hot water is different that a tank. In a tank, the water temp is always hot and you adjust the flow to adjust the shower temp. In a tankless, the water is cold and flow determines how much heat is used.

This is especially true when you have low flow shower fixtures or like us, when you let the shower fast trickle instead of open flow to conserve grey tank. The reduced demand tells the I stand hot water heater that not much hot water is needed so don’t do much. People react by turning up the temp on the hot water heater. That makes them turn the temp at the shower cooler and further reduces demand. Eventually you end up cycling between all cold and all hot with no happy medium. Some people think that the water ‘gets cold’ in the lines when they stop the shower in a navy shower. What is really happening is the water heater is turning off.

So you need to either increase the flow (remove all restricted sim the head and everywhere else) and/or turn DOWN the temp to match the shower temp you want to take. Then set the knob to full hot and ALL the flow will be hot water flow, I creasing demand even more. If you set the hot water temp to be too hot, you don’t demand enough hot water because you are mixing it with cold (not the OP’s problem but a real thing) and the water heater turns off.

[etheroner]

I really appreciate this tip from LilPeanut... We've been trying to get used to our tankless water heater when staying at State Parks that only have electric hookups. Will definitely give this a shot. Thanks!


"So you need to either increase the flow (remove all restricted sim the head and everywhere else) and/or turn DOWN the temp to match the shower temp you want to take. Then set the knob to full hot and ALL the flow will be hot water flow, I creasing demand even more. If you set the hot water temp to be too hot, you don’t demand enough hot water because you are mixing it with cold (not the OP’s problem but a real thing) and the water heater turns off."

[jondrew55]

Unfortunately the OP has not weighed in to tell us if any of these comments have helped. In my 2021 Globetrotter I set the temp to a comfortable number (like 112 deg or so) and run the shower at full hot. Seems to work fine for me. The shower in this GT has the best pressure of just about any RV I've ever known. Either when using city water or the internal tank. No evidence of any restrictors.

[gln826]

Sounds to me like you need to adjust the anti scald device on the shower handle. Google the youTube video on how to do it

[27ftToaster]

Another possibility that hasn't been mentioned, is that it seems that the shower flow is greater than the heater can heat. That would be a tankless heater gas burner issue. That should be checked.

Our 2021 27' FC has tankless also. It is finicky, especially with low water pressure. We set our water temp to 108 to 110 and run the shower only on full hot (It cools down several degrees before reaching skin!) But it is consistent.

If a cold water faucet is opened or toilet using cold water is flushed, then that will prioritize over the water heater and the heater will not have enough flow, so it shuts off. It will immediately resume heating water again after the cold flow is shut off. But the shower taker is now the recipient of cold water and the 30 seconds required to heat it up to comfort again. That'll wake you up!

The OP stated that all tests are run with hot water running in the other faucets. It seems that perhaps the heater can only provide a faucet quantity of hot water, but not a shower quantity of hot water.

Perhaps they have some special shower head that maximizes flow?

[jamieb1086]

This may be a shot in the dark but check that both hot and cold handles on the outside shower are closed and the on demand button on the shower head is open. Saw this issue on you tube when the rv geeks had this issue.

[hlmmay05]

Hi everyone.

Thanks for all the great ideas. Sorry for the delay in responding. I’m not on here as much as I should be I guess. We haven’t had a chance to try all these great ideas. Our trailer is stored off site, but we will have it back this weekend and will try these suggestions.

A couple notes. Out trip last weekend was boondocking, so using the water pump and battery. The bath sink worked perfectly. Great pressure and rose to temp as it should. Both kitchen and shower just never got to temp, until we turn on the bath faucet at the same time, then both the kitchen and shower faucets rose to temp. Very odd.

We’ll try some of these ideas and let you know how it goes.

Thanks everyone!

PS - I originally was just running the shower and couldn’t get it to warm past about 97 degrees. When I turned on the sink, the shower got warmer, but the pressure dropped. As soon as I turned off the sink going back to just the shower, the temperature dropped again.

[jondrew55]

See if it behaves the same hooked up to city water. If there actually is an issue, it may be any of the things people have suggested (flow restrictors, low water pressure, shower mixing/anti scald valve).

Originally Posted by hlmmay05

Hi everyone.

Thanks for all the great ideas. Sorry for the delay in responding. I’m not on here as much as I should be I guess. We haven’t had a chance to try all these great ideas. Our trailer is stored off site, but we will have it back this weekend and will try these suggestions.

A couple notes. Out trip last weekend was boondocking, so using the water pump and battery. The bath sink worked perfectly. Great pressure and rose to temp as it should. Both kitchen and shower just never got to temp, until we turn on the bath faucet at the same time, then both the kitchen and shower faucets rose to temp. Very odd.

We’ll try some of these ideas and let you know how it goes.

Thanks everyone!

PS - I originally was just running the shower and couldn’t get it to warm past about 97 degrees. When I turned on the sink, the shower got warmer, but the pressure dropped. As soon as I turned off the sink going back to just the shower, the temperature dropped again.

[s1000pre]

There is a flow rate adjustment on the water heater. I didn’t need to adjust mine, I remember seeing it on an Atwood video. As others have stated and from personal experience with our 2021 30bunk. It takes 30-40 seconds to get warm-hot water. Get used to washing hand and dishes with cold water, especially when boondocking. Just like the convection microwave, as much as I didn’t like it at first, the on-demand is growing on me.

[jondrew55]

Originally Posted by s1000pre

There is a flow rate adjustment on the water heater. I didn’t need to adjust mine, I remember seeing it on an Atwood video. As others have stated and from personal experience with our 2021 30bunk. It takes 30-40 seconds to get warm-hot water. Get used to washing hand and dishes with cold water, especially when boondocking. Just like the convection microwave, as much as I didn’t like it at first, the on-demand is growing on me.

We really don't boondock, but certainly like to minimize the trips to the dump station with the portable tank when we stay places with no sewer hook up. But yes, I like the on-demand heater so far. I'd have been perfectly happy with the standard 6 gallon propane/electric WH from a simplicity standpoint. Same thing with the Reflex awning, I'd have preferred a manual awning.

[Paul May]

Hey everyone.

I’m fortunate to be married to hlmmay05. We took our trailer out this weekend, in the northern Utah mountains. We did some highly unscientific tests, to get a baseline on what is happening. Here is what we found.

12 volt, fresh water tank

bathroom
1. Temp set at 115
2. Display show flame, temp building stops 97 never goes higher

Kitchen sink
1. Temp at 115
2. Display shows flame, building never past 104 water felt warm

Shower/ all way on is hot
1. Temp at 115
2. Display shows flame, building temp never goes past 97

Test 2
Kitchen sink and bathroom sink both on same time
1. Kitchen pressure decreased bathroom sink strong
2. Temp at 115
3. Display show building get to 92
4. Stop bathroom kitchen build to 104

Test 3
Bathroom sink and shower on
1. Temp at 115
2. Shower pressure decreased
3. Display get to 92
4. Bathroom sink stoop
5. Shower to 97

Connected to shore power

Bathroom
1. Temp set to 115
2. Display shows building gets to 101 and stops warming

Kitchen sink
1. Temp at 115
2. Display show building gets to 106

Shower
1. Temp at 115
2. Display shows building, gets to 97 and stops

Bathroom and sink
1. Temp at 115
2. Pressure drops on kitchen
3. Display shows building gets to 92
4. Stop bathroom
5. Pressure up
6. Gets to 104

Bathroom and shower
1. Temp at 115
2. Pressure shower decreases
3. Display shows building get to 92
4. Sink stopped
5. Display shows 97

Connected to shore power and water

Bathroom
1. Temp set to 115
2. Display shows building gets to 111 and stops warming

Kitchen sink
1. Temp at 115
2. Display show building gets to 113

Shower
1. Temp at 115
2. Display shows building, gets to 108 and stops

Bathroom and sink
1. Temp at 115
2. Pressure drops on kitchen
3. Display shows building gets to 101
4. Stop bathroom
5. Pressure up
6. Gets to 111

Bathroom and shower
1. Temp at 115
2. Pressure shower decreases
3. Display shows building get to 97
4. Sink stopped
5. Display shows 106

So we learned a couple things. Two valves open is too much flow. It overwhelms the heater and pump. Voltage doesn’t seem to change outcome on fresh water tank, but shore water/no pump does some.

I did a revolutionary thing. I opened the instructions they gave us on the heater and pump. Optimal heather performance is at 45 psi. The Shur flow pump runs at 40 psi. Seems like an obvious problem, so I bet I have something wrong here.

The heater performance diagram maxed out at 4000 feet of elevation. We were at 5600. That most definitely has an effect on temps. But I don’t think it is the root one.

We ran out of time to sort out restrictors or scald valves, etc. so we’ll do that next outing.

Thanks for all the help!

[jondrew55]

We just got back from our 3rd outing in our 2021 Globetrotter. The tankless heater does seem a bit finicky. I cranked the temp up to 125 to wash our griddle in the kitchen sink. It did get pretty hot. When I took a shower later I turned it down to 113 since that seemed like a comfortable temp. Instead, the water got super hot in the shower and then I heard a beeping coming from the controller in the lavatory. The temp was back up at 125. And there were a few more instances of odd behavior when my wife said the water was not very hot but when I tried it, it seemed to work fine.

Gimme my old tank system and a manual awning.

[precipice]

We’ve had the same problem with our 2021 FC 30 Bunk. I’ve taken in for service on this issue three or four times and have gotten “cannot reproduce” replies each time. I took a video using an instant-read thermometer showing the issue and still got no help.

The only thing I noticed was that it happened a lot more consistently in a cold outside environment than a hot one. Once the outside temperature was hot, I couldn’t reproduce the problem, either.

Since it’s been summer, it’s happened less often for us. Sounds like that’s a difference from your case. Please keep the thread posted and I’ll keep my fingers crossed for you.

[Life is a Highway]

There is a water flow adjust open the compartment find the
Water heater adjuster is on the back side. If the flow is to slow it does not heat

QUOTE=hlmmay05;2527243]Hi,
We just took delivery of our 2021 Flying Cloud with the tankless water heater. I have a few questions about some issues we are having.

I turn on the water heater and set it to the temperature that I want, then turn on the shower to full hot, but the shower water never reads above 102 degrees when the tank is set to 120. (yes I know that is too hot for a shower).

If I turn on the faucet to hot in bathroom sink while the shower is running, the temperature gets hot in bathroom sink faucet and the shower, but the shower pressure decreases.

If I turn off the bathroom sink faucet , the shower water decreases in temperature again down to less than 100 degrees.

Same test scenario with the kitchen sink. Any ideas? Do we have a kink in the line somewhere? This has happened both when boondocking and plugged into shore power with water hook-ups.

Any ideas?

Thanks![/QUOTE]

[chrispe]

Very interesting!
We were really happy with it in the beginning, set to like 104F and used shower all hot and worked perfectly fine. Until recently when there is for whatever reason all of the sudden very hot water coming while showering mixed then with cooler phases again etc, but def exceeding the set 104F.
I have no idea what changed as it used to work nicely for weeks and month...

Originally Posted by jondrew55

We just got back from our 3rd outing in our 2021 Globetrotter. The tankless heater does seem a bit finicky. I cranked the temp up to 125 to wash our griddle in the kitchen sink. It did get pretty hot. When I took a shower later I turned it down to 113 since that seemed like a comfortable temp. Instead, the water got super hot in the shower and then I heard a beeping coming from the controller in the lavatory. The temp was back up at 125. And there were a few more instances of odd behavior when my wife said the water was not very hot but when I tried it, it seemed to work fine.

Gimme my old tank system and a manual awning.