Demand-Sensing Hot Water Recirculation Control

Smart Aquastat Recirculation Pump Control for Homes with a Dedicated Recirculation Loop

Satisfies CA Title 24 requirements

Smart Aquastat Control 32 for Tankless Water Heaters from Leridian Dynamics

The Smart Aquastat Control 32 is an “on-demand” smart hot water recirculating pump controller for homes with a Navien combi unit and a dedicated recirculation loop. The other application is for tankless water heaters that don’t modulate flow to provide hot water at the temperature set point. If you don’t have a dedicated recirculation loop check out our Smart Thermostatic Control

The Smart Aquastat Control differs from the Smart Recirculation Control in that it has only a single temperature sensor and turns the pump off when the single sensor reaches the configured temperature rather than run the pump until the temperature difference between the water heater outflow and the return line are within the defined tolerance.

It is designed to sense when hot water is drawn from any plumbing fixture and to run the recirculation pump until the water in the recirculation loop reaches the programmed temperature. The microprocessor-based design monitors the temperature of the water returning in the recirculation loop to ensure the water in the loop stays hot while hot water is being used. 

Tankless water heaters are good at producing a never-ending supply of hot water however, they are only capable of increasing the temperature of the water at a certain rate. If water is pulled through them too quickly they will not product hot water at their temperature set point. Most modern tankless water heaters will modulate (reduce) the rate of flow so that the output water is at the set temperature. If your unit does modulate the flow then you can use the Smart Recirculation Control 32 which uses the temperature difference between the water coming out of the water heater and the temperature of the water returning in the recirculation loop to know when the water it hot and turn the pump off.

If your tankless water heater does not modulate the flow of hot water then you will need to use the Smart Aquastat Control 32 to prevent the pump from cycling on and off while the loop is heating up.

how smart on demand hot water controllers workTo operate go to any faucet and turn the hot water on, then off.  The Smart Aquastat Control senses this minimal draw checks the water temperature in the loop, and if necessary, starts the pump running.  Within seconds the water loop is hot and you are able to draw hot water. 

Because the Smart Aquastat Control uses the demand of hot water to know when to run the pump, it works even when your washing machine or dishwasher needs hot water. 

Unlike other on-demand hot water systems, there is no need to install switches or sensors at each faucet location and run wires or maintain wireless transceivers.  

The Smart Aquastat Control also has a set of Smart Timers that can be used to heat the recirculation line on a schedule. 

The Smart Controller only runs the pump until the line is heated up to the programmed temperature.  

Of course, outside of the timer periods, the controller will still run the pump on demand.

The “Smart Timers” are disabled if the controller doesn’t sense a hot water draw within 24 hours.  So if you go on vacation and forget to manually disable them, no worries, they will turn themselves off and re-enable as soon as it senses a hot water draw.  The “Smart Timers”  are set via your Android or iPhone smart device.

Leridian Dynamics also makes a LEED for Homes v4 compliant on-demand Smart Aquastat Control 32.

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  1. This setup is great. My water heater is quite a distance from the kitchen sink. We used to have to run the water a while to get the water hot. I was considering an undersink water heater when I found this. Makes more sense and doesn’t waste water.

  2. I will start out by saying this is a great system and it is working very well and as designed. We had a different idea for the water system in our house. Our kitchen/washer/dishwasher was on the opposite side of the house (50 feet) from the Hot Water heater. We wanted to install a recirc system to speed up the time it took to get hot water to that end of the house and to save water, but we did not have an installed recirc loop. We also did not want a system that required Alexa, a pushbutton, or a phone app to start the recirc. Looking on the Internet, we found this smart recirculation system. Working with Dave, we agreed this system would meet our needs. One difference is we installed the flowmeter in the kitchen hot water line and not on the cold water line to the hot water heater. I installed a new recirculation loop and connected it to the cold water return line to the hot water heater. The flowmeter is rated for hot water temperatures (120F) and has worked great with no problems since it was installed. After installation, I observed the hot water loop increased in temperature without the pump running. This is where Dave excelled. Even during the holidays, Dave responded to numerous emails to help us troubleshoot the system. We finally determined it had to be thermal convection from the hot water heater was causing the flow. I ordered a spring loaded check valve with a 0.4 psig cracking pressure and installed in the recirc return line. This solved the continuous flow problem and the system has been working flawlessly since. I can’t complement Dave enough for his response to our problem and his support. I would also add that the pump is super quiet and cannot be heard when the system operates.

  3. Works as advertised, love the controls in the app!

  4. For my particular case, it has far more features than necessary. Ideally, for me, I would prefer a simple turn the hot water on then off, then the pump would run for two and a half minutes. That’s it, all I need. No need for a temperature sensor, just want to keep the 6 – 8 gallons of water it takes before hot water gets to the back shower from going down the drain. To make sure the pump turns off, I put the sensor on the hot water pipe (not the return – to do that correctly, I would have to run 50 feet of phone wire, which I tried with some wire I had, but it did not work).