Superheated Water

[MFFJC]

We just started camping in 108 degree heat in our 2022 Flying Cloud. After a long, hot day my wife took a shower. The Girard tankless water heater was set to 102 degrees, but it was delivering water between 110 and 116. We ran the water for several minutes in case the water had superheated in our supply hose. No change. The “cold” water was not too cold, but it certainly wasn’t over 100 degrees.

I turned it down to it’s lowest setting (95), and the water delivered was being superheated to 124 degrees!

Is this a common problem attributed to pre-heated water or is something wrong with our water heater?

[Jcondon]

The lowest fire rate on the Girard tankless is about 15K BTU's. With the incoming water so warm the water heater is on low fire and the water temp may exceed the setpoint. The only thing the water heater could do is shut off and you probably don't want that? More flow through the heater will help.

[MFFJC]

I tried resetting the water heater by turning it off for 10 minutes, then turning it back on. No change. I removed the fuse as another method of resetting. Same.

I called our dealer, and Service told me that they had not heard of such an occurrence. I called Girard Products and spoke to a tankless water heater technician. He said that there is no programming reset for the Girard tankless water heaters (I was hoping for one of those “Press and hold both the up and down arrows for 6 seconds. When the display starts to flash, …). He offered two possible culprits:

1. Low water flow - he said low flow can cause the heater to be erratic.
2. Warm water entering system- if the water is warm when it enters the heater, inaccurate readings are possible.

I believe we may have both conditions. The pressure of the water coming out of the spigot is probably below normal, and the extreme heat here may play a role as well. We tried turning the pump on, which does indeed boost the pressure coming out of our faucets and shower head, but that did not fix the problem. What is interesting, though, is that when we add the pump to the equation, the temperature still soars to 107 to 109, but then stays there (when set to 102 degrees). I guess we won’t know for sure until we get home a week from now.

[MFFJC]

UPDATE
We are now camping in more temperate climates and the problem has resolved. It was due to low pressure and/or extremely hot water coming into our rig.

[Saluda372]

Appreciate the update.

[99TJSE]

Our Girard water heater does this as well when it gets hot enough out. These water heaters seem a bit quirky to me.

Sometimes you can coax a shower out of one under these circumstances by adjust the water mix in the shower. Add cold water until the Girard shuts off due to low flow, then back off until it kicks in again. Turn the flow off when it gets to warm, and back on again. It's a total pain, but you get clean.

[Mollysdad]

In the old fashioned tank water heaters the temperature is set at 160º.
Then there's bypass plumbing so the super hot water is mixed with cold and made tolerable. Why can't tankless systems do that?

[99TJSE]

Originally Posted by Mollysdad

In the old fashioned tank water heaters the temperature is set at 160º.
Then there's bypass plumbing so the super hot water is mixed with cold and made tolerable. Why can't tankless systems do that?

My guess is that would make the flow rate through the on demand water heater fall below the minimum required for safe operation. You absolutely don't want to get anywhere near a situation where that water decides to flash into steam. Much excitement would ensue.