Plumbing – Flow sensor adjustment for Navien 240S natural gas fired tankless water heater

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We installed a Navien 240S natural gas in our house, and it is working fine.

Except the short range for hot water valves in the showers. So, in other words, I need to turn shower valve almost all the way on to start the hot water. This leaves us a very small range to adjust hot water when taking a shower. My plumber explained that it is because the sensor is triggered only with a certain water flow. In general, the water pressure is high already. But there is just not enough flow until I turn the faucet almost all the way on.

Is there way to adjust the flow sensitivity for the sensor in the water heater?

My plumber suggests the following:
He can install some flow controls on the cold water pipe in each shower and set them to desired temperature range.  

Is this a good solution?

I find it strange that I cannot adjust that sensor on the unit.

Best Answer

This is a common complaint for these types of water heaters.

Unfortunately, you have a model that seems to be slow to respond to water flow. I don't think any company has a way to adjust the flow sensor on their on-demand water heaters. This is not a customer adjustable function of these style of heaters.

If you're dissatisfied with this product I would suggest searching for a company/product that has positive reviews from people for the product's low-flow response rate. Some products respond even respond well to just running a hot water valve at a trickle.

Good luck!