Just installed the EcoSmart 27 electric tankless heater. When we are in the master shower and running both the sinks on hot (also in the master bathroom) the shower turns cold as well as when we turn the tub on while in the shower, both are cold. Also, when we run the master bathtub only, it's lost pressure. We were thinking we were having a GPM issue but when we turned the master shower on and the guest shower on, they both had very hot water. The shower only turns cold when we use the tub or sink faucets in addition. The shower also turns cold if any other sink is running hot anywhere in the house. We have the temp set to 118, the max 140. We live in Texas and typically have a high water inlet temp but it's winter here and just got really cold this weekend. Any thoughts on what the issue is?

With incoming water at 52*, that heater is rated to put out 3.5 gallon a minute(manufacturer doesn't state temper
ature rise). What's the GPM of the showerhead? The sink faucets?

GPM of the showerhead is 2.0, GPM of the sink is 1.5 We have the same showerhead in both showers meaning it's able to keep up with 4.0 (both showers at once) but not 5.0 (1 shower and 2 sinks) I guess. I just went and turned the shower on and only one faucet and they both had hot water. It was when I added the 2nd sink running that the shower got cold. So maybe if we reduce the flow on the hot water handles on the sinks we may be able to run 2 at once with the shower. Also, we can up the temp higher than the 118 if the shower turns cold we can just turn it hotter. Thank you for your help! I guess I just needed to talk it out.

"Doctor it hurts when I do this", doctor relies, "Well... Don't do that".

I also have an EcoSmart 27, and live in Texas. and I also experienced a performance loss during winter. Turning the temp up on the unit will not help, as this is a temperature rise issue with the volume of water you are trying to heat. If it can't get to 118*, it won't be able to get higher.

For your info, here is the temp rise performance numbers of the unit:

GPM -- Temp Rise
1 ------ 184
1.5 ---- 123
2 ------ 92
2.5 ---- 73
3 ------ 61
3.5 ---- 52
4 ------ 46
4.5 ---- 41
5 ------ 37
5.5 ---- 33
6 ------ 31
6.5 ---- 28
7 ------ 25
7.5 ---- 20

So at 5gpm, you'll get a 37* rise. So to obtain 105* water with 5gpm flow, the ground water temps needs to be 68*F or higher. You're having this issue because the ground water temp has dropped, and your heater can't keep up.

To fix this, I ended up piping something unique. My house had 2 tank water heaters. One feeds the master bathroom and the kitchen, and the other feeds everything else. I replaced the master tank with the EcoSmart.

So when I experienced this, I ended up installing a thermostatic mixing valve on the inlet of the tankless, and then ran the cold into one side and a feed from the hot water tank to the other. I then set the temp of the mixing valve to 87*. This ensures my inlet temp on the tankless is always 87*; which means I can flow 7gpm through it, and still get 107* water out. But in the summer, when ground water can reach the 80's, very little is being bled from the tank.

Here's an image to help understand:



If you only have one hot water heater, you could do something similar and install a small (ie: 10, 20, 30 gallon) tank, set it to heat to 150* (make sure you have an expansion tank installed with it), and then use a mixing valve to control the tankless inlet temp by supplementing with the tank's hot water. In the summer, you will probably not bleed much off, but in the winter, it'll make sure you don't get a cold water surprise when someone uses a sink, or does laundry.