On Demand Hot Water Concern

[Jeff & Deb M.]

Hello,
We're new to the group, just joined today and excited to be here! We just bought a new 3920fb and hope to begin our full-time adventure in the near future! My question is: On our way home from picking up our new 5th wheel, we spent a couple overnights along the way, and the first night everything was fine, but on night #2 the on demand hot water wouldn't stay on. It would give us hot water for about 20-30 seconds, then shut down. The on-demand display panel threw a code "E2". I haven't contacted the manufacturer yet, but will in the next couple days when we're home & unpacked. Has anyone else experienced this? If so, can you tell me what the issue was?
Thank you
Jeff & Deb

[martyperu]

We have just purchased a 3920fb and have been in it a couple of weeks. The hot water did give E2 once. I found it impossible to find out what that meant also. I did the old turn off turn on routine and it has been working great for some time. I feel it was either to low of water flow or the propane missed igniting. At any rate turn off and on works although not nice if you are in shower!!!
We also found it takes some getting used to as far as tap settings. General have hot on full and adjust with cold. Does vary for some reason. Is very nice to have unlimited hot water.

[masterdrago]

Not sure what model you are referring to. I did not know that On Demand Water Heaters were even an option in 5r. We are seriously looking at a Montana for our first rv purchase. I can possibly give you an idea on the shut down. Most on demand units will call for a minimum flow rate to keep the burner on. Pressur input or restricted flow anywhere. I once had our outdoor shower have the same issue. It turned out the hand shower want had a crimped hose. Fixing that solved the issue.

[martyperu]

The on demand heater is a Suburban. I have found out exactly what you stated. You need sufficient flow rate then heater works perfect. They are just starting to put tankless heaters in 5th wheels. This model 3920fb has a bath tub so need lots of hot water. Motor home have had on demand heaters for sometime.

[masterdrago]

Because of their complexity, compared to a simple gas unit, they have always been something I preferred to not own. I have worked on them for ~40 years. I recently installed an outdoor Noritz NR501 for an outdoor shower. I have truly changed my mind about them. I've taken about 30-40 showers using a single 5 gallon LP grill tank and have yet to exhaust the tank. Very efficient. I'll look for the options in my hunt.

[Jeff & Deb M.]

Thanks again Marty. Since some time has passed since our purchase, we have learned quite a bit about our on demand hot water system. Basically, it needs a minimum amount of water flow to operate, so we turn the hot water all the way on and adjust temperature with the cold. However, this doesn't work for the bathtub because the heater is capable of heating a maximum of 1.5 gals. per minute & the tub draws more than that. Before we learned this, we were unsatisfied with the tub because the water was only luke warm. Now we turn the hot water faucet for the tub about 1/3 on and we get very hot water!

[martyperu]

Good information Jeff. My wife figured that out
through expermintation also.
On thing about rving if you have some imagination, ambition and a little luck you can figure most things out.
Thanks again.

[Jeff & Deb M.]

You are so right Marty! Glad this thread has been helpful to both of us. Happy Travels!

[DQDick]

Don't know what brand of heater they had, but it got real cold for a week this winter when we were in New Mexico and two rigs on our block had continuous hat water heaters and the best they could get out of them was luke warm. They called the company that made them and were told the water coming is was too cold so warm was the best it would do.

[Mikendebbie]

Here is a report on our experience and use...
We bought 3921FB on January 27, 2018, and it has been fantastic so far.
DW loves the tub. The long hot showers are great for me. I bought adjustable water regulator and have it set at ~56 psi.

The heater thermostat is set at 128 degrees. I let the shower water run for maybe 30 seconds until hot water flows, then temper with cold.
DW always supplements the tub with a teapot or pan full of near-boiling water to get the water temp up to her preferred level. Seems like it takes 5 to 8 minutes to fill the tub.

We lived in the unit full time for 7 weeks (last week January+February+half of March) after we bought it using shower and tub every day + dish washing etc. with no problems. We do not have washer/dryer installed yet.
We went out again for 7 days last week with no problems.

Low temps in the DFW area during our 7 week stay were in the 20's and 30's and we did not experience any water temperature problems. Water came out hot and on demand. I give it a thumbs-up!