I think I just talked myself into using the generic Taco 003 pump without the priority zoning functionality.

Here's the pump: http://www.taco-hvac.com/uploads/FileLibrary/101-061.pdf\

Sorry for the confusion.

I am not a huge fan of circulating pumps because of the standby heat loss. Too often they just compensate for really shabby design (like making a long pipe run through a slab with no insulation)

However, you seem to have thought through the issues so that you have as little loss as possible and still get the instant hot water.

The only other thing I would suggest is to be sure that you insulate the hot water lines.

Good Job.

Jake,

Thanks for the response.

Copy standby losses. I intend on insulating the hot water lines.

My biggest challenge right now is figuring out the best motion control system. I want to control one pump with motion detectors in two different rooms. If I wire the detectors in series, what happens if motion is sensed in both rooms at the same time? Can this be done?

Anyone have suggestions?

Thanks-
Scott

No problem, You would wire them in parallel, not series. If wired in series they would both have to be activated in order to turn on the pump. Thats not what you want.

Connected in parallel, any one of them would activate the pump.

got it. Makes perfect sense. Thanks again Jake!

You're doing something very similar to what I've set up. Instead of motion sensors, I've got an extra wall switch to signal a timer to turn the pump on. What you propose sounds fine, with the correction proposed by Jake.

It nevrr ceases to amaze me how people can take the simplest things and make them complex.

While a motion detector in each bathroom would turn the pump on thier is no way to determine if that motion in the bathroom would really require hot water or did someone just step in to grab a towel or the laundry hamper. On the other hand, would this insure a ready source of hot water to the kitchen?

The simple method is to install a thermostat on the return line in the immediate vicinity of the pump. For maximum energy conservation the thermostat can be wired in series with a timer so that the system can be timed out during periods of non-use such as Midnight till 5Am or in households were both parents work and the children are in school we could time out 9AM to 2PM.

lazypup,

You bring up some great points. However, my solution I think to be better for my application because:
1. My water heater is within about 7-8 feet of the kitchen sink and so I never have to wait for hot water there.

2. The upstairs bathrooms will get very few visits throughout the day, but when it is used, the times are often quite different. Our schedule is rarely the same. The downstairs bathroom is used mostly throughout the day and won't have / doesn't need a sensor. In the end, I'm betting that the pump will run less for our application by being controlled by motion detectors than with a timer / aquastat sensor.

.....and it's entirely possible I could be absolutely wrong, at which point I'll eat crow as I'm removing the sensors and installing the thermostat / timer.

-Scott