Without adding a new pipe for the loop, I cannot see how this works.
It’s driving me nuts trying to look at the scematics and visualize how cool water is circulated, until hot.
Anyone want to take a shot at it for me?
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“If you come to a fork in the road, take it”
Replies
Well, this is the way I see this gizmo working to get hot water to the fixture quickly - perhaps saving some energy, but not without water waste.
You want hot water at the sink: push the button "on", pump turns on and pumps water from the "hot" supply line and forces it into the "cold" supply line until the temperature of the water at the pump reaches 96 degrees, pump shuts off, you turn on water at sink which will be 96+.
The only problem is that your cold supply line to the same fixture is now loaded with 95 degree water - so if you want cold water for tempering - you are out of luck for a while until the cold line is flushed back to a cooler temperature. So in order to get the cold water back to temperature, you would end up wasting the water anyway.
Running an additional pipe back to the cold feed side of the HWH would eliminate the water waste factor and return tepid water into the HWH thus saving some energy in reheating.
I'm with you - I don't see how it would work well without an additional pipe run to return the cold "hot" water back to the HWH.
Further, you would have to install one of these things at every fixture requiring hot water, along with additional wiring and piping.
Looks mostly like "green" hype to me, but I have been wrong before.
Jim
Never underestimate the value of a sharp pencil or good light.
These pumps work by pumping water from the hot pipe to the cold pipe. Generally they're set to run, once triggered, until a thermostat inside detects hot water.
So, simplest case, you go into the bathroom, press a button, and then drum your fingers for 30 seconds or so until you hear the pump stop.
The units can handle several bathrooms if they're in some sort of a chain. Install the unit in the farthest bathroom and it'll work for the others closer to the water heater, if they're all on a common hot water pipe. Remote control allows the unit to be activated anywhere. Can also be set to operate on a timer, to warm things up in advance for your morning shower.
Of course, the down side is that the lukewarm water is pumped into the cold water pipe. May or may not be to your liking.
They clearly save water vs just running it down the drain, and may save a little energy, depending on how you use them. Simple convenience would be the big selling point.
I have one of these pumps, costs a quarter a month to run and saves scads of water - has a cross over from the hot to the cold side at the farthest faucet from the HW heater and it gives hot water in less than 2 seconds -- used to be 2-3 minutes -- all set up on a timer and has a thermostat so it is not running all the time
Does this device affect your ability to access cold (i.e. not mixed with hot) water?
yes
Naive but refreshing !
Like SamT said -- They don't effect cold water operation. Unless you run the pump, then want only cold water, your gonna get tepid for a few seconds
On the Kit Sink we have a Chilled water set up on a separate faucet -that also has almost boiling water too -- so we have the best of 3 worlds Hot Hot water, Chilled water and Hot water in less than two second and cold water that is tepid for a few seconds and then cold but not chilled.
I have trouble not selling this concept - my wife wanted hot water at the sink when we were re-doing our kitchen -- looking into point of use H/W heaters ( used one in Austria when I was a cabinet maker there in the 70's) but did not like the cost of purchase, installation (circuit and more replumbing that necessary compared to this small pump the size of a good size fist) -- so far we are very very pleased and my wife is demanding. I like the fact that the pump is on a timer that you set for when ever and the pump only goes on when the thermostat calls for HW - so it is off at night but the hot water is right there at 5AM when I am in the kitchen getting ready to go to work.
Lastly, the chilled/hot water cooler/heater are in the basement directly below the kitchen sink so we do not eat up valuable base kitchen space -- sort of a win-win. Don't have a refrig with the unit on the door; don't have to heat a kettle on the stove or pop a coffee cup in the micro -- it is there are ready for us to use when we want it
Thanks for the reply, Dudley. It sounds like a great product.
I'm still confused about how it works, though!
Correct me if I'm wrong, but my understanding based on comments here is that the water in the "hot" line is maintained at a pre-determined temperature based on user settings. This is accomplished by pumping the "somewhat hot" water back down the "cold" line and into the water heater. In other words, water in the "hot" line is replaced as needed (based on heat loss) to maintain the desired temperature.
So far so good. But when someone opens a faucet for cold water, doesn't all the "somewhat hot" water have to go down the sink drain before the cold line is purged, and "actual" cold water (from upstream of the water heater) reaches the tap?
Without this device, it typically seems to take about 30 seconds to purge a line. Why does it only take two or three seconds to purge the cold line of "somewhat hot" water? There must be something I'm missing.
Edited 8/29/2007 12:59 pm ET by Ragnar17
Typically you have it set up on a timer or pushbutton, so that the pump only runs when hot water is wanted. If you know you'll want cold water, don't push the button.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
That makes more sense, but the OP and SamT have both stated that you only get tepid water "for a few seconds" --- even in hot water mode. That's the part I don't understand. Seems it should take longer than that for the line to purge.
If you think about it, starting from 12 hours cold, if you have to run the hot for 30 seconds to get hot it'll run 15+ seconds cold, then slowly warm up, then get hot fairly suddenly. So you might have 10-15 seconds of tepid water in the cold line, but it will be warmest first, and only a half second or so of hot, if the thermostat is reacting fast enough.Now stick your hand in the water and run until it feels cool, and it'll probably only be 5 seconds. Of course, if you want COLD water (out of the ground), you'll have to wait 30 seconds, more or less, but you'd have had to do that even without the pump.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
Think about the situation first thing in the morning before you run any water. You have the pump set to turn off at "tepid." All the water in both hat and cold lines is at ambient temp. You turn the pump on and it starts pumping the ambient water out of the hot line into the cold line. Immediatly following that ambient water is hot water, but the first bit of hat water has to heat up the hot water line as it travels towards the pump.By the time it reaches the pump it has cooled down to just below tepid, but the next bit is still at tepid because the leading slug has prewarmed the line. The pump has to put that just-below-tepid water into the cold line so there's room for the tepid water that will turn the pump off.Now the pump is off. The hot line is heated and full of hot water, except right at the pump where the water that heated the line is sitting. This water is only tepid warm because it gave up its' heat to finish heating the line after the just below tepid water prewarmed it. Plus the water in the cold line next to the pump is the last bit of just-below-tepid that got pumped out of the hot line.Turn on either tap and the first bit of water out of each is either just below tepid or just above tepid.SamT
Sam and Dan,
Thanks for the more detailed explanation. The conditions which you describe make sense. Using the system for only "on demand" hot water (as opposed to timer applications) would greatly reduce the amount of heat getting dumped into the cold line.
I was intially thinking of timer applications -- like when a timer activates the system to get hot water ready in the line at 6:00 am -- and keep that water hot for a pre-determined period of time.
If the system is maintaining temperature in the line, it would have to shunt merely "not-so-hot" water into the cold return line.
A lot depends on the specifics of the actual hot water setting (degrees), and the rates of heat loss in both the hot and cold lines. But I think that the amount of latent heat in the cold water line is probably not as great as I first thought it might be. It probably loses its heat to the house and reaches ambient temperature pretty quickly.
Thanks again for both of your posts.
The timer is generally just used as a substitute for the push button. The thing doesn't keep running, but stops as soon as the temperature setting is reached, and won't start again until the button/timer triggers it again.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
I'm a little skeptical about mixing hot water to the freshwater supply pipe A serious case of cross contamination would result..
Before having that done, check with health department AND building dept.. Do you have a good lawyer?
Cross contamination with what? It's the same water, just some hot, some cold. When the hot water expands in the tank, some of it is forced back into the cold pipe anyway.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
Work fine.
Pumps the cold water out of the hot lines.
The 95* is an absolute cutoff, You adjust them to any cutoff temp you want below 95*. Set it to cut off at tepid.
They don't effect cold water operation. Unless you run the pump, then want only cold water, your gonna get tepid for a few seconds.
There's no cross contamination problems. If you got bad hot water you got problems everywhere without the pump.
SamT
Edited 8/29/2007 6:38 am by SamT
They work great, especially with proper planning.
Get up, press the button , take a crap, flush, the warm water in the cold line goes into the tank and keeps it from sweating, get in the shower the hot water is there.
Saves water, no sweating toilet tank, and toilet paper savings to boot!
thanks everyone!
I'll pass the info along to the interested party.
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"If you come to a fork in the road, take it"
We set one up at the kitchen sink, activated with a door bell button, it is at the end o the loop, hot water source is a tankless heater at the other end of the loop, takes a couple of minutes to fill the loop with hot water. How often do you call for hot water only, other than to run the dishwasher? Willfull waste causes woefull want somewhere down the road. Great product.