Dynamically Adjustable Hot Water Heater?

[superdave]

It occurred to me that combining really cold water with really hot water to get warm water is inefficient. Why not have a device that supplies water to the faucet at the exact temperature that I want? Does such a device exist?

I'm looking for something that allows me to connect a cold water supply line to a "heater" and then to a faucet (special, regular, whatever gets the job done). This device would then have a temperature control (ideally next to the faucet) so it could vary the temperature that comes out of the "heater" from cold (ideally as cold as the supply line) all the way to hot (say 120F or so).

 

[Matt30]

Not very common but I have seen little instant hot water tankless systems under sinks, fed to a single faucet mounted beside the regular faucet.

 

[KULTULZ]

Not very common but I have seen little instant hot water tankless systems under sinks, fed to a single faucet mounted beside the regular faucet

And you can take it one step further as a faucet is available to dispense both hot and/or cold water from an under sink water heater and/or carbon filter or reverse osmosis setup.

 

[frodo]

I have an insta hot on my kitchen sink, LOVE IT

If i need boiling water, i just lift a handle, it makes cooking a lot easier

 

[frodo]

want you are refering to is a mixing valve,

 

[superdave]

Not very common but I have seen little instant hot water tankless systems under sinks, fed to a single faucet mounted beside the regular faucet.

This sounds like I would always get very hot water at the faucet. Is that correct?

What I'm looking for is a way to get hot, cold, and everything in between without mixing cold and hot water together. Something that would heat the cold water to exactly the temperature I choose via some control near the faucet.

 

[Matt30]

what is it you are looking to save with this set up? And what fixture are you going to use it on?

 

[frodo]

you will have to research the different units. some only dispense hot water, others dispense warm to hot water

check big box stores,

 

[KULTULZ]

It occurred to me that combining really cold water with really hot water to get warm water is inefficient. Why not have a device that supplies water to the faucet at the exact temperature that I want? Does such a device exist?

I'm looking for something that allows me to connect a cold water supply line to a "heater" and then to a faucet (special, regular, whatever gets the job done). This device would then have a temperature control (ideally next to the faucet) so it could vary the temperature that comes out of the "heater" from cold (ideally as cold as the supply line) all the way to hot (say 120F or so).

What I'm looking for is a way to get hot, cold, and everything in between without mixing cold and hot water together. Something that would heat the cold water to exactly the temperature I choose via some control near the faucet.

I think this is what you are looking for. The TEMP adjustment is on the tank (mounted under sink), not at the faucet-

This will give you both FILTERED COLD and HOT water separate.

-CLICK HERE--- Instant Hot Water Dispensers ----

BOSCH also makes some nice units.

 

[superdave]

KULTULZ, getting closer. The problem I see is with normal plumbing you need very hot water (125F) and very cold water (say 50F) and you combine a certain percentage of both using a normal faucet to get warm (say 80F). That's a lot of wasted energy to heat that water up so hot just to cool it down again for use. I'm looking for a solution that lets me take cold water and raise its temperature to 80F (or any other temperature between 50F and 125F).

If I were to hack this together, I might take an instant hot water heater, hack into the temperature controls, and move them to the faucet so I could control the temperature that the heater was putting out in real time.

 

[KULTULZ]

OK... I think it finally sank in as to what you want to do.

You need (IMO) -

ECO Point of Use Tankless Water Heater-

ECO3.5POU 110V 30A GFCI Circuit (#10 2 Wire w/GRD).

There is no HOT and COLD mixing. The dialup temp is on the unit which can be mounted easy to reach within the sink cabinet. They offer a remote but not sure if it will operate POU heater. You don't want to be touching anything electrical around a sink anyways.

Am I getting closer?

 

[phishfood]

Electric water heaters with resistance heating elements are pretty much 100% efficient, meaning they transform all of the energy used to heat in the water.

One of the most common units of energy measurement here in the US is a British Thermal Unit, or
BTU.

1 BTU will heat 1 pound of water 1 degree Fahrenheit. So it takes pretty much the same amount of energy to heat water from 70 degrees up to, say, 95 degrees, as it does to heat the same amount of water from 95 degrees up to 120 degrees. So there would be no real energy savings strictly from heating the water only to the end use temperature.

There might be some very minor savings due to the reduced temperature gradient between the hot water and the air surrounding the water heater tank, and the hot piping from the tank to the faucet. But that would be very minimal, and probably wouldn't be worth the effort.

So, in my semi professional opinion, if you were to want to do something like this for a fun project, go ahead, but be safe. Just don't expect to save any kind of money if you do come up with a workable model.

 

[frodo]

http://www.bosch-climate.us/products-bosch-thermotechnology/electric-tankless-water-heaters/bosch-tronic-3000-point-of-use.html


same same as the one above, different manufacture,
temp range is 56 degrees f to 145degrees f

buy one for each fixture

 

[KULTULZ]

It occurred to me that combining really cold water with really hot water to get warm water is inefficient. Why not have a device that supplies water to the faucet at the exact temperature that I want? Does such a device exist?

I'm looking for something that allows me to connect a cold water supply line to a "heater" and then to a faucet (special, regular, whatever gets the job done). This device would then have a temperature control (ideally next to the faucet) so it could vary the temperature that comes out of the "heater" from cold (ideally as cold as the supply line) all the way to hot (say 120F or so).

what is it you are looking to save with this set up? And what fixture are you going to use it on?

Never answered.

I would a$$-u-me the heater is wanted for the kitchen sink for food prep (through a separate faucet). The tankless will supply hot water to 145 degrees while the tank model will deliver up to 200 degrees (is this allowed by code w/o some type of tempering valve usage?). Just another factor to consider.

I also noticed the tank model(s) have a T&P relief valve. How would you supply a safe drain to that under the sink?

 

[KULTULZ]

I also noticed the tank model(s) have a T&P relief valve. How would you supply a safe drain to that under the sink?

Excerpt From BOSCH INSTALL INSTRUCTION SHEET-

3.3 Closed system thermal expansion

Periodic discharge of the temperature and pressure relief valve or failure
of the element gasket may be due to thermal expansion in a closed water
supply system. The water utility supply meter may contain a check valve,
backflow preventer or water pressure reducing valve which will create a
closed water system.

During the heating cycle of the water heater, the water expands causing
pressure inside the water heater to increase. The temperature and
pressure relief valve may discharge hot water under these conditions
which results in a loss of energy and a build-up of lime on the relief valve
seat.

To prevent this from happening, there are two recommendations:

1. Install a diaphragm-type expansion tank that is suitable for potable
water on the cold water supply line. A minimum 0.5 gallon expansion
tank should be used.

2. Contact the local water supplier or plumbing inspector for information
on how to control this situation. Do not plug the temperature and
pressure relief valve.

 

[superdave]

My apologies for not answering the question where will it be used. I am looking for more of a general solution. This would ideally work with showers, kitchen sink, bathroom sink, etc.

I understand the heating efficiency of an electric element is very high, but the fact that it has to bring the water to a very high temp in the first place makes the system as a whole less efficient I would think.

The Bosch Tronic 3000T comes close where it has the variable temperature control on the device.

Please excuse the crude drawing. I've tried to drawn up what I'm looking for. The top drawing is a normal setup where there is a cold and hot water feed to the sink/faucet. The bottom drawing is what I'm looking for. A device (hot water heater?) that takes cold water in and supplies hot/cold/all temps in between water to the sink/faucet. The temperature control for the heater would be located at the sink for easy access.

 

[frodo]

I disagree with its use at the kitchen, you need hot water to kill salmonella
bathroom also. get the poo poo off your hands

if you want to save energy, turn the water heater down. install a circ pump, hooked up to the bathroom light

when you enter the bathroom, pump turns on you have hot water, when you leave,turn off light, pump stops

the circ process,

 

[KULTULZ]

My apologies for not answering the question where will it be used. I am looking for more of a general solution. This would ideally work with showers, kitchen sink, bathroom sink, etc.

I understand the heating efficiency of an electric element is very high, but the fact that it has to bring the water to a very high temp in the first place makes the system as a whole less efficient I would think.

The Bosch Tronic 3000T comes close where it has the variable temperature control on the device.

Please excuse the crude drawing. I've tried to drawn up what I'm looking for. The top drawing is a normal setup where there is a cold and hot water feed to the sink/faucet. The bottom drawing is what I'm looking for. A device (hot water heater?) that takes cold water in and supplies hot/cold/all temps in between water to the sink/faucet. The temperature control for the heater would be located at the sink for easy access.

This post illustrates a completely different scenario than what I was originally thinking about. I was describing POU (Point of Use) water heaters (both tank and tankless).

What you want to do makes it a whole lot more complex. You want a hot water delivery system for the whole house and not just a kitchen sink dedicated supply.

Code isn't going to allow you to do what you are describing I believe. All faucets are limited to 120 degree to prevent possible scalding and/or thermal shock. Much different than just a hot cup of coffee.

And again, you don't want electricity near a sink/tub. Bad mojo.

 

[phishfood]

My apologies for not answering the question where will it be used. I am looking for more of a general solution. This would ideally work with showers, kitchen sink, bathroom sink, etc.

I understand the heating efficiency of an electric element is very high, but the fact that it has to bring the water to a very high temp in the first place makes the system as a whole less efficient I would think.

The Bosch Tronic 3000T comes close where it has the variable temperature control on the device.

Please excuse the crude drawing. I've tried to drawn up what I'm looking for. The top drawing is a normal setup where there is a cold and hot water feed to the sink/faucet. The bottom drawing is what I'm looking for. A device (hot water heater?) that takes cold water in and supplies hot/cold/all temps in between water to the sink/faucet. The temperature control for the heater would be located at the sink for easy access.

I tried to cover that with this part of my earlier post. Probably wasn't the best explanation.

1 BTU will heat 1 pound of water 1 degree Fahrenheit. So it takes pretty much the same amount of energy to heat water from 70 degrees up to, say, 95 degrees, as it does to heat the same amount of water from 95 degrees up to 120 degrees. So there would be no real energy savings strictly from heating the water only to the end use temperature.

What I was trying to say is that it really doesn't take any more energy to heat water to a higher temp and then mix it with cold water to get to your target temp than it does to just heat it to your target temp. As long as you are using the same amount of water at the same target temperature, you will be using the same amount of energy to heat the water.

 

[superdave]

The drawing I made represents each POC. So if I had a kitchen sink, a shower, and a bathroom sink, I would have 3 of these. Not looking for a whole house setup. I know that would be extremely complicated.

The setup would be able to deliver very hot water and very cold water depending on what the temperature control setting was adjusted to.

Let me see if I can describe it another way. Imagine a normal POC electric instant hot water heater for a kitchen sink. This would have a cold feed that goes directly to the faucet and a cold feed that goes to the POC heater then the faucet. Now, remove the plumbing for the first cold water feed; so now there is only the cold water feed that goes to the POC hot water heater and then to the faucet. Now take the temperature controls off the actual POC unit and make them accessible near the faucet. The controls would allow the POC heater to go from cold to its hottest setting (say 125F).

Phishfood, that is interesting! I just did the calculations that compare heating water using the "mix" method (normal plumbing) and the method that I am suggesting (heat the cold water up to just the right temp). I found (assuming my math is right), that it's exactly the same amount of energy for either method. Maybe this is why what I am looking for doesn't really exist.

My other thought with the "just heat the water up to the right temp" method is to reduce complexity. There would only need to be 1 line going to the faucet instead of 2 and the faucet could simply be an on/off valve instead of a mixing valve. Maybe this is also a moot point as maybe it doesn't save that much in complexity.