Hi.
Anyone knows some projects to pump the cold water to the pipes until the arrival of the hot water?
When the hot water is below 38ºC, the water is derived to the pump to force the water return to
cold water pipe.
When the water is hot, start taking the bath.
The idea is in attachment, something like this.
Thanks in advance
Your question makes no sense to me. What is the point of pumping cold water when you want a hot bath? Why would the hot water ever arrive if the cold water is being pumped? Could the pump force cold water back into the hot water pipe?
What you are looking for is a thermostatic valve. No need for microprocessor control, but if it is an exercise you could look at washing machine solenoid valves and drive it from an Arduino digital output, buffered of course.
A combi boiler has a diverter valve setup which does the same thing.
OK, I am working on this in my professional rooms.
I had fitted the circulating pump which pumps hot water around the loop past all the sinks and back into the cold supply of the water heater. If this is left to run continuously, it wastes all the hot water as it cools in the pipes despite lagging, so it must be controlled "on demand". (This of course, would not matter so much if the hot water was part of the building heating, but this is a warm country. 
)
You do not actually need a valve as such, the return pump takes the water from the point at which the "hot" tap connects. You need a temperature sensor at that point. A panel on the wall nearby has a pushbutton and a RGB LED.
You push the button, it turns on the pump (which is incidentally, located at the water heater) as well as the red or orange LED and hot water circulates through until it reaches the hot tap in question where the temperature sensor is located. When the sensor detects the water is sufficiently hot, it turns the LED green and stops the pump. You can now turn on the hot tap and have a prompt supply of hot water.
It is now required to have a TMV at the heater to prevent scalding; this does not interfere with the operation of the circulating pump.
need more data.
a circulator is what is needed. common pump in every country,
a simple flapper type check valve, not spring loaded.
a temperature sensor.
hot water is 50 C ?
cold water is 10 C ?
warm to humans is 40 C ?
time sensors, occupancy sensor.
if it is in the middle of the night, don't bother.
if there is activity in the middle of the night then circulate
if you shower at 6:00 AM start to circulate at 5:30
this is pretty simple. the question is how much automation and how many sensors.
insulating pipes will also help a lot.
mbranco1975:
When the hot water is below 38ºC, the water is derived to the pump to force the water return to
cold water pipe.
I wonder if the requirement is to pump the cold water back to the reservoir so as not to waste the water that would normally be run off while waiting for the hot water to arrive?
On my off-grid system the kitchen tap wastes about 1 litre of cold water while waiting for the hot water to get to the tap - even if I only need maybe a half litre of water for the task. I have a limited supply of water so I rarely use hot water, even though the heat to make the water hot is essentially free.
...R
Robin2:
I wonder if the requirement is to pump the cold water back to the reservoir so as not to waste the water that would normally be run off while waiting for the hot water to arrive?
Exactly. But it is also the convenience of not having to wait to put the plug in the bath, or outside the shower.
In a larger building such as mine, it could well be more than a litre in the intervening pipes.
Actually, what I described above was my first concept of the system. On reconsideration, it can be substantially simplified and the temperature sensors are unnecessary!
All that is needed is to determine how long it takes the circulating pump to get the hot water from the heater to the tap (or in fact, the branch back to the circulating pump as it will not actually flow further until the tap is turned on; this branch will generally be in the ceiling above the tap). You then just need a control button to "prime" the pump to run for this period of time and stop.
I have eight rooms with sinks plus a shower so the actual times required will differ, but an Arduino can easily handle that. To avoid wiring, I am presently looking at ESP8266 "smart buttons".
You do not need a "flapper valve" - there is no impetus for the water to move on its own (the circulating pump returns the water to the heater after the cold water check valve and the pump itself may be non-return).
In some systems ,in big properties , the “dead leg” from the hot tank to the tap can mean it takes an age for the hot water to come through .
What the OP is asking for( I’m assuming ) is a system to over come this , as suggested above- you just need a pump running a loop and the taps draw from that - you can have a timer/thermostat or whatever to operate the pump to keep the loop
Hot with a small flow-no Arduino needed. Guess you’d need to lag all the pipe work to stop losses . It might be easier to have another hot water tank nearer the tap
Commercial example:
hammy:
Hot with a small flow-no Arduino needed. Guess you’d need to lag all the pipe work to stop losses .
And let me assure you that is just not practical, even if you pay attention to lagging every pipe, every junction including the connections to the heater itself. Lagging is never perfect.
Unless as I said, you have unlimited (free) continuous heating.
Paul__B:
And let me assure you that is just not practical, even if you pay attention to lagging every pipe, every junction including the connections to the heater itself. Lagging is never perfect.Unless as I said, you have unlimited (free) continuous heating.
the problem from the land lord point of view is that you have a tenant turn on the hot water on a far sink.
they let the water run, this moves hot water out of the heater.
the heater comes on to warm up the new water
the tenant, satisfied that the water is warm enough, satisfies their needs and turns off the water
all the water wasted,
all the heat of the water in the pipe after it has been shut off
all the tepid water as the pipe is beginning to heat
all that is wasted water and heating.
Then the problem of heating cold water and let it sit in the tank to cool.
heating recirculating pumps are common all over the planet, do not have or need much lift and are designed for hot water.
having the pump come on when the bathroom lights come on is a smart thing.
Well, the recirculating pump certainly does not save on heat, if anything it wastes more. It makes little difference in that regard whether the cold water goes down the drain or back to the heater, and in either case you are left with hot water in the pipes, cooling down and wasting the heat.
Not much you can do about that, you can lag as effectively as possible (generally using plastic foam), and limit the actual recirculation specifically to when needed which essentially requires that you "ask" for the pre-circulation which is the system on which i am working.
Running the circulation more than required results in having hot water filling the return as well as the feed piping and keeping the water in the piping hotter to lose more heat overall.
The recirculating pump is a well used system in hotels and other large premises ( I’ve seen it in large shops where the boilers and calorifiers were on the top floor, during my Gas Engineering days ) it does waste some heat , but is the only solution if you want rapid response for hot water from your tap unless you can reduce the supply distance from the hot tank.
Did anyone follow my link !!
Here’s another with how it used to be done with thermo cycling loops and no pump
hammy:
Did anyone follow my link !
Yes, a good summary.
What I have been describing is the "On-Demand Hot Water Recirculating Systems " option described there as in most of our situations, we cannot afford the continuous heat losses.
Found this which might be of interest
Health wise, the whole idea is wrong! Bacteria from your piping system should NEVER be returned to a reservoir without first being disinfected. And, YES, there are bacteria growing in both your hot and your cold water pipes. Best to discharge the excess water to your garden area.
Paul
So, you believe the "Dettol" ads, do you?
Paul__B:
So, you believe the "Dettol" ads, do you?
I believe in bacteria. I have no idea what "Dettol" is.
Paul
Copper i thought killed bacteria.
Must be American!
Paul__B:
Must be American!
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