Demand (Tankless) Water Heater with Thermostatic Shower Control

[TheWalkman]

Has anyone tried thermostatic shower controls with a with tankless (demand) water heaters to avoid temperature fluctuations? Any comnents/ thoughts?

Thanks!

[Wayne Whitney]

You know, I started looking into this, and now I don't understand what a "thermostatic" shower valve does. I thought it would adjust the relative flow of the incoming hot and cold water supplies to provide the desired temperature, regardless of the incoming temperatures. But I have read a number of the manuals which state that if you adjust your water heater temperature, you have to recalibrate the "thermostatic" valve. In which case it doesn't seem very thermostatic to me.

Are there any thermostatic shower mixing valves that will maintain the set temperature given fluctuating hot water supply temperatures?

Cheers, Wayne

[Wayne Whitney]

OK, I contacted Delta today for some clarification. The issue is that Delta's thermostatic valves (17T series and 18T series) have a warning in the manual that if you adjust the temperature of the hot water supply, you may need to recalibrate the thermostatic cartridges. The answer Delta gave me was that the valves are thermostatic with respect to small fluctatuations in supply temperature (a few degrees) but not in response to large fluctatuations in supply temperature (tens of degrees).

Cheers, Wayne