by McDave » Tue Apr 18, 2017 4:28 pm
Hey Padilen and Tommy too,
I have experienced the extra "hot shot" as well, and just wanted to let you know what is happening and why. These units were made transfer the heat from the flame to the water as rapidly and efficiently as possible. When you stop the water flow to scrub or apply etc., the water has time to absorb all residual heat in the exchanger. So the next "shot or slug" of water will be overheated, then as the new water enters the exchanger the temp normalizes. It's the reverse of the normal domestic hot water operation where you get a "cold slug" before the hot water travels from heater to faucet.
These units don't hold a lot of water, like a cup or two, that's why it gets so hot, so fast. So, you can either leave water running and enjoy constant temp, but high usage or turn off when soaping up and just know to let that first shot NOT be aimed at your sensitive region.
If you waited long enough between the OFF and ON, the water would have time cool off, but so would you.
The only other possibility would be a really long hose between heater and wand, but you would still waste water at the start to get rid of the cold slug. You might be able to put in a bypass so the water is returned to the fresh tank when wand is off, but the pump and heater will continue to run and put hot water back into the fresh tank.
I think you will just have to remember that a hot shot is coming, and let it pass and normalize, if you forget.. you will get a reminder, every time...
McDave