We found out its the park PSI causing the issue. It has to be between 45 and 60 PSI. anything higher and it pushes water through the water heater faster than it can heat it.

Suburban's manual is nothing like a home tankless waterheater. It hardly gives the model number. They also will not give specs over the phone. I think we figured out that as long as we keep the incoming water pressure between 45-55 psi, it functions properly.

Wonky for sure.

I thought that too, until I turned on both sink faucets and got the same result. If i decrease the demand on the hot water, the temp goes up. However, the specs of the water say it should be able to flow 140 degrees well above what one rig could possible use. Suburban will not talk details with customers, you have to go to a service center. they also will not tell me what sensors or controllers are used.

Thanks. we ordered the part you suggested.

Great information. Ill check that out. Ours seems to do it running on the fresh tank as well, but ill double check it.

That’s what I think. I wish they would tell me if it has a flow sensor. That would be a great place to start looking.

What we think we have figured out it this: The incoming water pressure is the problem. The water heater wants to see between 45-55 PSI. Anything over that pushes the water through the waterheater faster than it can warm it. Using a lower flowing faucet, like the shower wand or a single sink, slows the incoming water and it can keep up. Really the water heater should have a sensor to adjust as the water flow changes. We are at a park that has perfect 45psi to the rig and we are not having a problem. Our pressure regulator is set to 65. The last three parks we were at, where the problem started, had high pressure in the 80's.

Thank you

We found that if we set the pressure regulator outside to 45-55 PSI, we dont have a problem at all. So what we did was put the pressure regulator on the end of the water filter. Then connect the hose to it that leads to the 5th wheel. This way if the filter is clogged it will show on the regulator and we dont leave it at the park.

I agree but the temp will also drop the 100 degrees if we run both bathroom sink faucets as well. Just on will go to 120 degrees. Same with the shower the wand will go to 120 degrees but the shower head will only go to 100

I would think that if it can reach 120 with just one faucet on, then its not clogged or blocked in any way. Unless it does have an obstruction that only shows up when the flow increases. I had not thought of that. Ill go outside and see if there is anything abnormal.

thanks brother.

that is our next step after we figure out what the actual issue is. If they only made a black one that would fit.

I agree. What we have found out is that the incoming PSI is the culprit. As long as we stay between 45 and 55 PSI we can run multiple faucets and stay at 120. I'm trying to find out now if the Suburban has a sensor that monitors the incoming water pressure to adjust the amount of heat supplied or if its fixed and we are stuck with 45-55 PSI

we figured ours out. Its due to high pressure. Water pressure needs to be between 45 and 55 PSI. have not had a problem since the change.

I would tend to agree with you except, when the two bathroom faucets are on, we can duplicate the issue of just the main shower head. If it were the shower diverter, I would think that the sink faucets would not have an issue. I think it has to do with a water flow sensor in the tank. I can't get the specs form Suburban though to see if there is a sensor that would control it. thanks for the comment, hoping someone posts something that leads to a solution.

The diverter valve might not help with the feeling of cold water at the the shower head but the temperature you're seeing drop on the display is what's leaving the water heater before it ever makes it to the shower head.

I would agree, but we bought the 5th wheel brand new. This just started about 3 weeks ago. We have always used a 2 stage 2 micron filter. The 5th wheel is 5 months old now. Not to mention we get the same results if we turn on the 2 bathroom sink faucets.

What we found was the PSI was too high on the inlet, pushing the water too fast through the unit. We are hoping that a 2.6 gpm shower head will resolve the issue, or changing the setting on our pressure regulator. Thank for the support and comment.

@OurRoadLessTraveled will depend on the BTU rating of the unit. If you know the rating, you can calculate the maximum allowable flows given you know the inlet water Temps.

@@travisbreeden1825 its supposed to be 60k BTU.

@OurRoadLessTraveled with a 60k btu unit, and an inlet water temp of 65 F, a 2.6 gpm flow will get you in the range of ~111 F for your shower water temp. Also keep in mind that a 65F inlet water temp is on the high end of what you'll normally see, depending on where you're at... this can be closer to 50F to 55F, which will lower your shower water temp 10 to 15 degrees. To get closer to 120F water temp range, you'll need a flow of 2gpm or less, depending on the inlet water temp.