Best Hot water recirc for new construction?

I installed the the Grundfos ComfortPump when we added a new 2nd floor bathroom. It works like a charm, better than expected. Tip - insulate the hot and return lines. The pump runs very little to maintain temp at the remote faucets.

http://www.plumbingworld.com/grundfoscomfort.html
http://www.grundfos.com/web/HomeUs.nsf/Webopslag/PAVA-56TMVA

 

I was concerned about that, but higher electric bills never materialized. If anything they went down a few dollars. The system runs very little to maintain temp. Like maybe 20-30 sec. every 15 min. in the winter and every 30 min. in the summer. It has a tiny motor (1/32 hp?) and it only runs when the timer is on. I suspect the savings is because everyone is no longer running shower and sink faucets for a minute to get hot water. The other benefit was that our expensive water bill did decline. There's very few things that get me a "great idea honey" pat on the back. This is one that keeps giving.

 

Nate-
The Taco 009 is used with the tankless heater to supply enough flow to activate the heater when the temperature in the loop starts to drop. With a tank type heater you can use the Taco 003 pump. The other way to set it up with the tankless is to use the 003 pump but install a small electric 2-6 gallon water heater to maintain the temperature of the loop. I find this to be more cumbersome and costly. One side benefit of the small electric heater is that it eliminates a phenomenon inherent in the use of tankless heaters and recirc systems called the cold water sandwich. It takes about a second and a half for the tankless to fire up and start producing hot water. If the heater is set at 120 f then the water in the loop will probably run between 105 and 120 f because the tankless will not fire up for a small deltaT unless the flows are really high. When you open a faucet, cold water will enter the loop at the heater and some will pass through the heater before it fires up. This segment of cold water will travel down the line until it reaches the faucet where it will cause the temp of the water to fluctuate for a second or two. It will be less noticable if the fixture is farther from the heater because the cold water will draw heat from the pipe in the loop. The small electric heater eliminates the sandwich and maintains the loop temperature at 115 degrees. Always set the temp of the electric at a lower temp than the tankless so it only heats the loop water. I also dislike this method because it makes controlling the system less precise. The tankless gives the ability to vary the water temperature easily. I turn mine up when washing dishes to reduce run times.

On the issue of controls, I use a timer that has lots of flexibility and overrides. It has a battery backup and adjusts for DST automatically. It is about 40$. It is a Grasslin DIGI42 digital timer. The Taco 009 is 1.1 amps. The timer is rated up to 16 amps and you can get them in 120 volts or 24 volts. If you use the 24 volt model, you will only need t-stat wire run from the pump location to the timer location but you will need a 24 volt transmormer(12$) and a relay switch for the pump(18$). I like this method personally.

The shorter your loop the better for BTU losses. In colorado, the losses will benefit you more on the space heating side than they do me here in TX. (less penalty)

If you are using a tank type heater(bummer) then use the taco 003 and a 1/2 inch return line. If you use the tankless, use the taco 009 and a 3/4" return line.

There are small valves available that automatically remove air in the loop to keep it out of the pump(noisy). You will need a thermal syphon reducing loop in the cold water feed line. This just means you need to run the feed line up 36" and back down prior to the heater so the heat in the line doesn't travel into your cold water supply line. You will need a check valve to keep the cold water line from back feeding into the loop when a valve is opened. You will probably want an expansion tank in the loop although you can skip this if you are on a well or rainwater system as either of these will already have an expansion tank in the system.

The Rinnai website has plumbing diagrams to get you started. They promote the small electric heater with recirc systems to reduce the number of start stop cycles on their heaters.

The Taco pumps have a diaghram kit that can be replaced if the pump burns up due to running dry for too long. The pump is 200 the kit is 100.

The Rinnai has all replacable parts, though the service network is not well developed. The Rinnai is reliable, so you should have many years of worry free use. I install mine outside to save space and reduce installation cost. They are freeze protected to -30 degrees. If the power is out they are not freeze protected and must be drained if installed outside. There is a kit for automatically draining the heater in a power outage but I would not recommend it. In your climate, I might put it indoors and pipe the exhaust and combustion air.

OK that's a little more on the subject and I've gotta go without checking for errors. Good luck.