Recirculating Pump or Point of Use tank?

[Diehard]

correct superDave
what happens is his wife starts doing dishes with hot water then the water goes cold
then heats up again.
no yum yum at midnight for hubby

That's not what RenewDave said. He made a correct analogy to, "The energy loss/use issue seems like a non-issue."
You're saying that the usable capacity of the 2.5 gal heater is not sufficient while the one gallon of cold water is entering it. Granted it has a rather small recovery rate but the amount of stored water at X temperature must be considered as well.

 

[Mikey]

And, as the POU tank draws in new water, if it draws from the hot line, you will have the hot line full of hot water (eventually), which will slowly cool off when the water use stops. Same heat-loss issue as with the on-demand circulator, as far as I can see. Only way to eliminate that is to draw from the cold supply, and you will have 2.5 gal of hot water ready... eventually. Rinse, lather, repeat.

 

[RenewDave]

Soooo many negatives in that senecio. And one more, the tank will only help(marginally) the kitchen. The recirc pump could improve the entire hot system.

 

[frodo]

And, as the POU tank draws in new water, if it draws from the hot line, you will have the hot line full of hot water (eventually), which will slowly cool off when the water use stops. Same heat-loss issue as with the on-demand circulator, as far as I can see. Only way to eliminate that is to draw from the cold supply, and you will have 2.5 gal of hot water ready... eventually. Rinse, lather, repeat.

i disagree on my circ line

I am turning on the pump. with the light switch. this gives the pump the time to return the water that has cooled to the water heater and replace it with hot water
or am i missing somthing?

 

[RenewDave]

I’m not clear on your post.

 

[frodo]

ok...you have a dedicated line from the water heater to the kitchen sink
with another line beside it as a circ line

this line will go cold from no use

when the pump is told to come on it pumps hot water to the ks
we are talking 30' of 1/2'' pipe. I think that is less than a 1/2 gallon
a taco pump that moves 300 gpm will have hot water to the sink in a second [literally]
the pump is wired to the kitchen light switch. turn on the light and open the hot valve

 

[Diehard]

LOL...You're both talking a recirc line. It's just the matter of controls now.

 

[RenewDave]

Right, that’s why I like a recirc with a timer. You can “fine tune” your demand with your use cycles. We are all pretty much creatures of habit.

 

[frodo]

hey...timer or switch. makes no diff to me. that is a home owner preference not a frodo preference

 

[Diehard]

I prefer the advantages of using all three together. Timer/Temp Sensor/Manual Switch.

 

[bowens]

I would expect a switching valve to be involved, but I haven't got that far yet. And I would think that storing/heating a 2.5g insulated tank is more efficient than what's in the copper pipe.

 

[frodo]

please explain how using electricity to keep cycle a heating element on/off
24/7 to keep 2 1/2 gallons hot will be more efficient than running a pump only when the water is needed.

now, to address the ''water in the pipe''
the pipe is also insulated like the tank..
and that water returns to the hot water tank

lemmie see...30' of 1/2'' copper pipe holds .36 gallon that is negligible

 

[bowens]

1) running the pump only when hot is needed means waiting for a gallon+ of cold to arrive (and the pipe is 3/4 for some length of the 40 feet).
2) I doubt that the pipe can be insulated as well as the small tank.
2a) I've only heard the main tank's heat pump running after I've used a few gallons or more of hot water, so it must be pretty well insulated.

I think this is a "six of one, half dozen of the other" situation, with regards to the heat loss.

 

[frodo]

1] running the pump only when hot is needed means waiting for a gallon+ of cold to arrive (and the pipe is 3/4 for some length of the 40 feet).

I think this is a "six of one, half dozen of the other" situation, with regards to the heat loss.
I agree....silly argument


3/4 copper @40' = .918 gallon

......a taco water heating circ pump
.....1/25 HP pumps 16 gpm
.....it takes 3.75 seconds to pump the water in the pipe 40'
We seem to have a misunderstanding on the cold water in the pipe,
It DOES NOT come out the faucet.
It returns to the water heater in 3.75 seconds when pump is turned on.
see drawing

I agree with Dave about the SAMMICH

 

[bowens]

there's something I'm not understanding, I guess

 

[frodo]

and that something is?

 

[bowens]

if I knew...then I would know!

 

[bowens]

First, take the switch thing off the table (personal preference; I don't want to have to school visitors on how to get hot water).

baby steps...with no pump switch, what keeps the cold water from coming out of the faucet when demand is initiated?

 

[frodo]

I am so so so sorry that your visitors are people with serious vision problems
my condolences sarc/ people usually do not need instructions to turn on the light to see

1]with out a switch to tell communicate with the pump, you will not have the energy saving option
of using power only when you want hot water
2] You would still have an energy saving option, with a timer
example... pump on at 7am...off at 9am while you are working it is off
back on at 5pm etc
most of us have predictable schedules
3] an aqua stat, a sensor on the pipe that reads the temperature, and tells the pump when to come on to keep that temperature

.with no pump switch, what keeps the cold water from coming out of the faucet when demand is initiated?

anything that turns the pump on, will also remove the cold water from the pipe in 3.75 seconds

also..a check valve is installed on the cold water heater feed where the return circ line ties back into the tank

 

[RenewDave]

Have we all “jumped the shark” here? A pump with a timer will always be more efficient than a tank running 24/7. Just make a friggin decision and be done with it. We aren’t curing cancer here.