Hot Water Recirculating Pumps

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Not a really good solution if you have an instant hot water system.
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Han
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On 2/16/2012 1:53 PM, Han wrote:

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Well anyone who has those needs to have their head examined anyway. What a waste of dollars for luke warm water.
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Steve Barker
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You're barking up the wrong tree. Instant hot water systems can be very energy efficient.
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Han
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What parameters was that based on? Like RBM said, I think those are just nuts. First, if you're comparing using a push button type pump with no pump at all, the savings in gas is minimal.
With no pump, you have to heat enough incoming cold water to replace the water that is in the hot water pipe between the water heater and the point of use. That's not a lot of water. With a pump, you have to heat enough returned water to replace the water that is in the hot water pipe. So, the difference is in heating a gallon or two of water either from about 45F or about 65F. The other small savings would be in the cost of the gallon or two of water that goes down the drain.
My whole gas bill in summer, which is just for the water heater, is only $17 or so.
If you're comparing a push button system to one that already has a pump and keeps it circulating 24/7, then it would be more substantial, but still, those numbers are hard to believe.
The biggest drawback to these systems, which I bet TOH never mentioned, is that unless you install a seperate return line from the points of use back to the water heater, the stale, tepid water is going back into the cold water line. There it will be available for anyone who draws a glass of what they think is cold fresh water. That person could be at the point-of-use where the pump is or anywhere else along the path of the cold water pipe going back to the water heater. Meaning if you're drawing a pitcher of water to mix the kids some Koolaide in the kitchen, you could be in for a surprise. Before installing one, I'd analyze what else is on the cold water line and figure out hot to install a new line if necessary,.

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wrote:

In addition. no one (including ATOH) ever mentions the cost of running power for the pump.
On the ATOH episode in question, there was clearly a brand new receptacle shown inside the vanity where the pump was placed.
Depending on the current electrical situation and homeowner's skill level, the installation of the receptacle could add significant cost (percentage wise and payback wise) to the installation.
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That's a good point. I guess in some cases you could manage to get the pump cord to a nearby outlet without it looking like hell. But as you say, in the ones I've seen installed, they always seem to have that receptacle right there in the vanity. Another problem could be if you don't have a vanity, ie pedestal sinks.
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wrote:

I was going to mention pedestal sinks (since I have one) but I chose not to.
That adds another level of complexity since you now need to figure out where to put the pump (in a closet? in the basement?) and then figure out how to plumb it so that it turns off when hot water is at the sink (not just at the pump) and run the wires for the push button or hope the remote (Honey, where is the remote for the sink?) can turn it on and...and...and.
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wrote:

T4-
My apologies.... I don't believe their "savings numbers" either.
I was just throwing out some general concepts about where the savings would come from. I think they might have been double dipping on their energy savings.
Looks like no one visited
http://www.builditsolar.com/Projects/Conservation/Recirc/RecircEnergy.htm
the author did a decent energy analysis 24/7 small recirc pump ~ 500 to 1000 kwh per year ~200 gallons of propane per year (about 256 therms equivalent)
About a 1/3 of this waste can be eliminated by using a timer, more by having some sort of temp sensor. Even more by doing the push button thing.
A lot of work & expense to have "instant water".
The "best" solution is thermo-syphon with well insulated hot water lines.
cheers Bob
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