What happens to a mixing valve when the hot water temp drops?

[emesine]

The 5000 series TACO mixing valve states that "the hot supply must be 20F above the set mixing temperature." What happens when the hot supply temperature drops?

For example, if my mixing temperature is set to 120F, what will happen when my storage tank cools down and is only giving me 130F supply water?

Will the hot port shut down and give me cold water at the mixing valve? Will the cold port shut down and give me 130F water at the mixing side?

Andrew

 

[Nofossil]

The 5000 series TACO mixing valve states that "the hot supply must be 20F above the set mixing temperature." What happens when the hot supply temperature drops?

For example, if my mixing temperature is set to 120F, what will happen when my storage tank cools down and is only giving me 130F supply water?

Will the hot port shut down and give me cold water at the mixing valve? Will the cold port shut down and give me 130F water at the mixing side?

Andrew

What basically happens is that the mix outlet can never be closer than 20F to the hot inlet. It might actually be a little better than that, but the mixing valve stops being able to maintain the selected outlet temp if it doesn't have some room to work. If you're set for 120, the outlet temp will start to drop off when the hot inlet falls below 140.

This is why I always suggest the Honeywell AM101 series valves for DHW - they work to within 3 degrees of the hot inlet temp.