Buffer tank, DSH and a hot water recirculator pump

There is more than one bathroom connected to the loop, so a motion is no good. I'll have one of my zwave contacts in there shortly so it'll turn on and off based on a bunch of conditions (motion, home/away alarm status, time of day/week, etc). Either way it doesn't change the fact that it should be plumbed "correctly"

 

Put the motion sensors in each bathroom to the on/off switch. If you need it I will draw it for you.

Good idea Curt.

 

I'll be pretty close to that anyway as my z-wave controller is also my alarm and it has access to the motion detectors all over the house.

Thanks for the offer to draw it - but with a z-wave module hard wired prior to the pump I won't need to change any other wiring to implement this.

Is anyone suggesting that I should be going back to plumbing this to the buffer tank instead of the finish tank based on turning the pump off during unused times?

 

Unless you also have logic which shuts off the circulator once it's up to temp, plumbing to the finishing tank is still the way to go, in my opinion.

Think of it this way: suppose you rig up the circulator to run for a minute after a motion sensor trips. If the the sensors are continually tripped over the course of a half hour (as the occupant(s) of bathrooms move around during the course of their morning routine), then the circulator could be running almost continuously for the same time. If the buffer tank is cold, this may be enough runtime to seriously dilute the existing hot water so as to equalise the temps in both tanks - which would be bad.

Only if your control logic can limit circulator usage to the first minute or so of that half hour activity period (the window of time in which the hot water loop is actually cold) would it make sense to plumb to the buffer tank. This can be done (as I mentioned earlier) with an aquastat that disables the circulator if the plumbing is already hot. The occasional hot water usage events during this half hour period will be enough to keep the plumbing hot.

 

Plumb recirc to finishing tank.