Recirculating Pump Selection for Residential Hot Water

I am considering adding a hot-water recirculation system to a residential re-piping job I am planning for my home. Due to the design of the home (two stories with full basement and full attic), the re-piping will serve the second floor from an attic manifold (near the water heater)and the first floor from a basement manifold (17' distant from the water heater). The water heater is located on the second floor.
I need to know what pump (specs, brand/model, if possible) should be selected for a 3/4" recirculation loop, where the lowest point of the loop will be approximately 17' below the water heater return. Also, where should such a pump be placed, at the top of the loop or bottom, or does it not matter? Any other considerations?
P.S. Code does not permit second water heater in basement, due to waterfront flood zone, so that solution is out.
Thanks in advance.
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(with possible editing):

Mine is a TACO Cartridge Circulator Model 006-84 - (very small even though it is a 28 room home). You might want to put a dial indicating thermometer on the return line. That will help you set the frequency and "on" time. You can have multiple returns. The pump is controlled by the computer on the boiler (in my case a Buderus). Mine runs a few times each hour for a short period of time and shuts off at night. It does not matter where you place the pump (since it's a closed system), but near the water heater is a logical place. Obviously it makes sense to insulate both hot water feed and return lines.
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Larry
Email to rapp at lmr dot com
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Tacker-
I've only had one house w/ a hot water recirc pump. It was located right at the water heater & plumbed into the water heater drain port.
I didn't do the installation, it was "professionally" done whne the house was built
It was a Grundfo, as far as I know they're somewhat pricey but the one I had ran 24/7 for the 13 years I owned the place with no problems.
here's a link to a pretty good supplier
http://www.plumbingsupply.com/circpump.html
the pump in the photo looks just like mine. the install shown has a timer AND a thermostat..............mine just ran all the time
The site has a general installationscheme but maybe you can ask them about your special sitiation. IMO the far left hand point of the sketch looks like the right place for your pump, if you can easily put it there.
pumps work best at (near) the low point of the loop (my w/h was the low point)
ideally, the sensor for the thermostat should be at the hot water delivery point second choice would at the water returning to the w/h
the return water should be dumped into either the drain port? (as was done in my install) but my gut tells me it makes better sense to dump it back via the cold water inlet (a check valve might be a good idea) but it probably doens't make much difference since my old install worked fine
my pump was very low powered, you don't need much plus you want to keep the electrical cost low.
wrt to pump specs, since it's a closed loop you really don't need much hp, you're just overcoming the friction losses due to flow
I'd ask them what pump they sugggest, you'll just need to know the loop length, tube material & sizes.
cheers Bob
Do you want those Wirsbo tables?
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Thanks. Would love those tables via e-mail.
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I believe the pump goes in the return pipe near the storage tank. I believe they are quite small pumps and if you put them in the feed they can reduce the flow.
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From what I have seen, the kind of pumps HD, or Lowes has, use a smaller hose than 3/4". What I have seen gets the pump mounted at the farthest source for hot water, and the return line from the pump goes back to the hw tank. The diameter would probably have to do with the distance involved. The pump runs all the time. Can you just recirculate from manifold to manifold? Not sure what the lengths of runs off of the manifold are, but that would make a difference too.
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tacker wrote:

I installed one of these in my house
http://www.lainginc.com/act303.htm
about 4 years ago. I've been very happy with it runs silently and it was very simple to install. IRC it was just over $200.
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Art

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