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[Shadysprings]

Lets back up a bit and think about why we use these hot water recirculation systems.  There are two main advantages.  One is that we avoid having to waste water while waiting for it to warm up.  Another is that we can turn on the hot water tap and have warm water instantly.

In our house it takes about 70 seconds for the Grundfos pump to refresh hot water in the loop.  If we went to the on-demand type of system, that would mean waiting up to a minute every time we wanted hot water.  Since we use water randomly throughout the day, I chose to keep the pipes always warm, and heavily insulate them to minimize loss.

The Ocelot runs the pump for 70 seconds every 15 minutes.  I could stretch that out, but now there is little difference in temperature regardless of where it is in that 15 minute period.  As a result, the shower temperature usually does not have to be readjusted as the water flows.  The cycle only runs from dawn to 11:15PM, so there is some additional savings by not running the pump at night.

The advantage of this type of scheme is instant hot water throughout the day, and no wasted water while waiting for it to warm up.  Because the pump runs at only a 8% duty cycle, this is much more efficient than the basic 24 hour timer that Grundfos normally uses.

Jeff

Hi Jeff,
Actually this is pretty much my identical setup.  I've got a Taco pump and timer.  The timer is very basic and that is what I want to replace. 
when i run the pump 24/7, both gas and electricity bill rises.  The gas bill is 5-7x.  So my goal is to convert from a timed system to on demand. 

Our household does not have a single pattern that I can set the timer to match up to.  Without pump running, the water will never heat up fully.  Not even after 20 minutes of running.  I don't know why. 

So My goal is to have a manual switch next to each bath tub/shower, and sink.  Hit the button, pump turns on for a say 10 minutes, then goes back to sleep. 

So In my case, I don't use the pump for instant hot water, I use it because without it, my water never heats up fully.

Thanks

[hot4X10]

The cold water sandwich problem you speak ofcan be remedied by installing a small 6 gallon utility heater that installs just after the tankless system.  The initial blast of cold water is absorbed into the small utility heater and no more cold water sandwiching problem.

[hot4X10]

Going through 3 chilipepper's must of been a headache.  I think the perfect solution would be for you to install one of Redytemp's TLC-X1 circ controllers.  http://www.redytemp.com/efficienthotwatercirculation.htm You would plug your pumps power cord into the control box then use the controllers phone jack and a UM506 module.  Using a TM751 and and push-buttons at each location you'd be able to activate the pump on demand.  It would then turn the pump off once hot water had reached the sink.  We have a Redytemp TL5000 and feel spoiled everytime we use it.