Despite disagreements on whether they are actually green or not, whole-house hot water recirculation is becoming increasingly popular in new home buildings and retrofits. On the side of "green" is that you don't waste all that cold water running down the drain while you wait for the shower to warm up (to the tune of hundreds of gallons per year), while the anti- crowd complains that you heat water that is frequently not used.
Me, I just like the hotel idea of hot-water at the ready, all the time. Especially in the winter - I mean really - who wants to be standing around waiting for the shower to get warm?
In my attempt to split the difference, last year (pre-SmartThings), I found the Redy-Temp HW recirculator pump (http://www.redytemp.com/). This device offers several innovative and energy-saving features, including:
* Thermostatically-controlled return, with auto-shut off when return reaches a target temperature
* Momentary contact relay to signal HW demand, suitable for automation with X10 (then) or SmartThings (now)
I first installed using X10 motion sensors as described on the web site, but early in 2014 I got hooked on SmartThings and transitioned over to using a MIMOlite to signal HW demand, activated by a variety of ST actions, events and Hello, Home Activities. Initially, I used stock SmartApps (Light Turn on Motion, etc.) to automate the HW demand, but over time having 5 or 6 different Smart Apps associated with the HW demand switch got too complicated.
So I wrote this Smart App as a single place to control ALL aspects of HW demand that I can imagine, supporting both momentary contact initiators (like the RedyTemp) as well as always-on pumps controlled by a SmartThings switch, plug or outlet. I think I've captured pretty much every use case imaginable.
Supported Use Cases for HW Recirculation Demand
On with Motion: Select as many motion sensors as you'd like. If people are moving inside the house, the water will always be hot. Optionally stop demand when they stop moving.
On when Open: When any specified door opens, turn on demand. The idea is opening the laundry room door means you will soon need hot water. Optionally stop the demand when the door is closed.
On when Closed: The inverse of the above - closing the bathroom door creates the demand (e.g., shower time). Optionally stop demand when the door is opened again.
On/Off with a Switch: A virtual (or real) switch can signal demand - this can be used to link demand with things like IFTTT. Supports demand when open and/or when closed.
Something moves: Turn On demand when acceleration is detected (e.g., SmartThings Multi is "active"). Optionally turns Off demand when it stops moving
Scheduled demand: Turn on demand every XX minutes.
Location mode changes: Turn on/off demand when the Hello, Home mode changes (e.g., On for "Home", Off when Away or Night)
What's cool is that you can use practically any combination of the above. In addition there are a few overrides that further optimize things:
* Stop demand after XX minutes
* Block ALL demand while location.mode is Away or Night (for me, this means "sleeping")
* Stop demand when Temperature Sensor sees a specified temp. For now, this one is experimental - I'm trying to use a SmartThings Multi-Sensor to mimic the thermostatic control of the Redy-Temp. It's definitivbely not as sensitive or quick to respond, but you eventually can find a "Hot" reading (mine gets no warmer than 84F)
* Start demand when the Temperature Sensor falls below a specified temperature
With all these options, you can pretty much customize your house's recirculation pump recipe, no matter what kind of circulation pump you have (momentary contact or unswitched plug-in) - so long as you can control it with a ST-supported Z-wave or Zigbee switch, plug or outlet.
Caveats
Some things to note/consider:
* Using the Open/Closed contact sensors. For simplicity, you can select more than one door (contact sensor); if any of them opens, HW Demand is made; and if you enable the Off-on-Close, ANY of them closing will stop HW demand (if you have a constant-on switchh controlling your recirculator). With the RedyTemp, this isn't an issue (the app doesn't even ask about turning the pump Off if you declare it is a momentary switch).
* For many people, running the HW Demand longer isn't A Bad Thing - once the entire loop is heated, the HW heater will likely stop heating.
* That said, using Timed Off or a ST Thermometer will limit the time the pump runs, saving that electricity as well.
* If multiple doors are opened before the Timed Off event, they don't extend the Off Timer - any door closing (or any other Off event, for that matter) will turn off the (constant-on) recirculator switch.
* In fact, every HW Demand call will check first to see if the Recirculator pump switch is already on, and if so it will not send another demand call. Note that if you are using a momentary-switched device like the RedyTemp setup I have, the switch will (almost always) immediately revert to Off() after turning On().
IMHO, (and FWIW), HW Recirclation works best when you have a complete loop in the HW piping. The alternative is to install these bypass valves that use the cold water pipes as the return. Unfortunately, this means that your cold water is always warm after HW Demand; you might minimize this by putting the SmartSense multi thermometer on the cold water pipe under the sink at the most distant bypass valve (I personally have not tried this).
My Own Recipe
For those that are interested, here's how I use this app with my own RedyTemp pump (with dedicated return):
* Recirculation only while Home, not while Away or Night
* Home starts when motion is detected in the Master Bath after 4:30AM; Night starts When Things Quiet Down
* HW Demand is requested on any change to "Home" (like when we get home from work in the evening - the water is warm pretty much by the time we get up the stairs).
* HW Demand whenever motion detected in the kitchen or the Master Bath
* HW Demand when the laundry room light is turned on or off (so the washer has HW), and when the door is opened or closed
* HW Demand when the Guest Bathroom door is closed or opened (so guests have warm water in the sinks AND instantly hot showers)
* HW Demand when the pocket door to the downstairs lavatory starts moving (so people have warm water to wash their hands)
* RedyTemp set to momentary demand (with a MIMOlite), and auto-stop when return water reaches 105F (source is 120F).
This works for me, but your own recipe can differ...try it, you might like it!
Barry