Bosch Tankless water heater pressure relief valve issue

[CTuna]

I have a question regarding a brand-new washer. The background is this. Before purchasing the washer I had an older Kenmore probably 22 years old. Sadly it died, and no parts were available to fix it. I also have a Bosch tankless water heater approximately 11 years old. Doing laundry with this setup, I had no problems with the Kenmore. Fast forward, and I get a new Samsung washer. One day I noticed water on the floor and tracked it down to the Hot water tank. The pressure relief valve was leaking. I installed a new valve and decided to watch the washer. In doing so I notice on the normal that has the ATC it leaked about 1 to 2 Tablespoons of water. I bought a new relief valve and again it happened. I then chose another setting without the ATC and no problems. Nothing else in the house is causing any leaking. Only when I use the Normal setting on the washer. Any idea why this is happening? I have the temp on the water tank at 120.
I read a little about the water temp but still don't understand the problem with the ATC.
Thanks for any help explaining my conundrum.

 

[Dan O.]

I don't know why it's occurring but on ATC the hot water may be cycling on and off quickly and affecting water pressure through the heater which might be activating the valve for some reason. Maybe you can try to duplicate that at a tap to see if it occurs then too to confirm it?

 

[CTuna]

Thanks for the reply. I tried what you said to do. Switching off hot and cold at the slop sink. I tried turning it off quickly and turning on the cold back and forth numerous times to fill the sink. Did not cause it to leak. Either way. I think you are right about the valve being shut quickly. I have fixed the problem by putting black tape over the Normal setting. I no longer need to see it and will switch to colored or quick setting to wash. Just wish there was a way to program the default to the quick setting. Thanks for your help!