Re-purposing a common (white) wire for 2nd pole of a 220 V circuit

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dsteinhorn

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I am adding a point of use water heater under my kitchen sink because it takes over a minute of running water to get hot water to the faucet. There is currently a pair of unused 12 ga white-black conductors wired to the main panel with a 20 amp breaker. There is a separate ground wire running to the dead-ended box where the unused circuit terminates. It was apparently intended for some future use, but is not pulled through a conduit, so I cannot replace it.

-> is it permissible by code and good practice to re-purpose the white conductor (painting it red in the main panel to indicate it is now a hot lead) to a 2nd pole breaker (installing a new two-pole breaker) and use it for the 2nd pole of a 220 v 20 amp circuit? That would increase the wattage I can support at the under-sink heater.

Is that question clear?

Thanks for your thoughts and comments.
 
I’m not a pro and there should be some pros along shortly.



My non-pro opinion is it would likely work ok and as you mentioned you would put red tape on both ends to identify it as a hot leg.



I would think it will depend on the device you buy if it requires 3 conductors and a ground. Things like 240v cloths dryers used to be 3 wires but now want that white wire as well. Last drier we bought I had a plug and 3 wire pigtail and the delivery guys would not set it up for my 3 prong outlet.



12-2/G should be good for the 20a and has a 600v rating.



Take a look at the device you plan to use and see if it for some reason needs the white wire.



Lets see what the pros say.
 
Were it I, and it isn't, why, when you have an existing 120v system, in place, would you go to the additional expense of changing to an 240v system with a likely requirement of an 240v AFCI breaker?

After all, your lag time is only 1min, and most of the point-of-use systems are flow-thru, and shut off when the incoming water temp. overcomes/equals the devices preset operating temp.
 
If the white is in the same cable as the black then it is permissible to colour it red at both ends and use the white(red) and black as a 240 volt source on a double pole breaker.
 
Were it I, and it isn't, why, when you have an existing 120v system, in place, would you go to the additional expense of changing to an 240v system with a likely requirement of an 240v AFCI breaker?

After all, your lag time is only 1min, and most of the point-of-use systems are flow-thru, and shut off when the incoming water temp. overcomes/equals the devices preset operating temp.
I hate to waste a couple of gallons of water waiting for the hot water in drought-beset California and wasting heat in the pipes under the slab. My wife turns the hot water on for 10 seconds to rinse something and the hot water never arrives.
 
I understand that frustration, however, there are many 120v systems available. The tricky part to all of these systems, to me, is, for those that have them, the TPR.
 
There is another option and it is what I would likely do given what you have. There is a small pump you install under the sink and when you need hot water you push a small button you install at a convenient location and the pump starts and takes water from the hot water line and sends it back the cold water line. It has a temp sensor and when the hot water reaches the pump it shuts off and you have your hot water with no wasted water. They have showcased this system on This Old House a few times.



Here is a video of all the methods of circulating hot water and the end of the video shows the one I’m talking about.



 
There is another option and it is what I would likely do given what you have. There is a small pump you install under the sink and when you need hot water you push a small button you install at a convenient location and the pump starts and takes water from the hot water line and sends it back the cold water line. It has a temp sensor and when the hot water reaches the pump it shuts off and you have your hot water with no wasted water. They have showcased this system on This Old House a few times.



Here is a video of all the methods of circulating hot water and the end of the video shows the one I’m talking about.




Yes. An option for predictable timing use of hot water like a morning shower between 6-7 am. Because electric heater are very efficient with little loss in long pipe runs and we have solar, I am still leaning towards a point-of-use heater. Going with 20 amp 120 V unit will limit the flow rate and temperature rise compared with a 20 amp 220 V unit. That is why I am leaning towards the 220 V opition
 
I understand that frustration, however, there are many 120v systems available. The tricky part to all of these systems, to me, is, for those that have them, the TPR.
Does TPR refer to temperature?
 
TPR is the TemperaturePressure Relief valve, which some of these systems have, and while you likely may already have 1 or 2 in your water system, those that do, are a mfg. safety system, which, in some cases, is addressed by an expansion tank.

Most of the 240v models I've looked at require #10AWG, which implies a 30A circuit, which your #12AWG won't support.

So, now given the evolution of the thread, I'll revise my initial suggestion to a similar to bud16415, but to that which I'm familiar with, by GRUNDFOS; https://www.amazon.com/Watts-500800-Instant-Recirculating-Install/dp/B000E78XHG/ref=sr_1_5?crid=3I00XVQVHEMLY&dib=eyJ2IjoiMSJ9.q2dEfQMq5635mu0eeJi9RUeaL-jv5XIybe0UeuR8H7Wcnu_zEQwsUrxu1J1dzKV6UvfUMc3njShFXZAYy3-U0mQ66wWWTobSrXj0AUcWmWsrV74DZ1egtDbCTf2JZzaWmiergoe7it9QaaSfkEbRD8T64ukFh77lyZ7lGMRUWq-eJA39638M8ooxQsb-aGLV4gymbscmgFbPZjx6ucs_--iuHUWSY1-cRBNNPlEfvD99zdZzdMpS7SgXySVnZ3ojPtgZLYSftJuFIFE5l_VCP9Hs0cI8EWiq7EI7T44L4b4.iqNOkFPsM6CLRGkBDZqFI1SDrZzyWjGxyM9__y_eBn0&dib_tag=se&keywords=grundfos+hot+water+recirculating+pump+system+with+built-in+timer&qid=1715182763&sprefix=Grundfos+water+recirculating+system,aps,103&sr=8-5

As your use is defined, the run periods can be
adjusted.
 
Yes. An option for predictable timing use of hot water like a morning shower between 6-7 am. Because electric heater are very efficient with little loss in long pipe runs and we have solar, I am still leaning towards a point-of-use heater. Going with 20 amp 120 V unit will limit the flow rate and temperature rise compared with a 20 amp 220 V unit. That is why I am leaning towards the 220 V opition
The system I was suggesting is not at all time dependent and doesn’t affect the whole house only the one sink it is installed on. You have a button most likely attached thru the cabinet the sink is in and you simply push the button when you want hot water and the small 120v pump under circulates water from the hot line to the cold line. In the same amount of time or less you normally would run clean water down the drain the pump will stop and now you have instant hot water to be used without wasting a drop. This is circulating water to just one device and only when you need it. The whole house systems are similar to what hotels use and run water around in a circle 24-7 so that when someone needs it, it is there. Most home systems for a whole house have timers so you can turn it off over night etc. Still they run a lot for the water savings all the normal hours of the day.
 
The system I was suggesting is not at all time dependent and doesn’t affect the whole house only the one sink it is installed on. You have a button most likely attached thru the cabinet the sink is in and you simply push the button when you want hot water and the small 120v pump under circulates water from the hot line to the cold line. In the same amount of time or less you normally would run clean water down the drain the pump will stop and now you have instant hot water to be used without wasting a drop. This is circulating water to just one device and only when you need it. The whole house systems are similar to what hotels use and run water around in a circle 24-7 so that when someone needs it, it is there. Most home systems for a whole house have timers so you can turn it off over night etc. Still they run a lot for the water savings all the normal hours of the day.
The disadvantage in the under sink models, especially in CA is that the piping is beneath the slab, with multiple branches to fixtures dislocated from the recirc. location, and while there will be, depending upon the branch, a reduced wait time. You'll also need a GFCI recep. at each, if you choose multiple units.

I installed 2 of the GRUNDFOS recirc. fixture devises in a residence, in CA, who's fixture groups were 35' apart.
 
The disadvantage in the under sink models, especially in CA is that the piping is beneath the slab, with multiple branches to fixtures dislocated from the recirc. location, and while there will be, depending upon the branch, a reduced wait time. You'll also need a GFCI recep. at each, if you choose multiple units.

I installed 2 of the GRUNDFOS recirc. fixture devises in a residence, in CA, who's fixture groups were 35' apart.
I agree the whole house units with the timers have their place. I was just at a doctors enormous home and in touring his basement I saw he had two of the whole house units and I saw they were powered down. He said they are nice but they run all the time and I’m heating all this water just to pipe it a mile around the house cooling it down just to heat it again. He said he has a well and his waste water goes back into the earth at his house. So he said I would rather wait a minute for my hot water to come than deal with the pumps.



If the OP runs power to the sink for a point of use water heater or a single circulation pump putting a GFCI to plug it into is not an issue for me.



When I plumed my house with PEX I made one critical mistake. I made a manifold in the basement and ran .5” as homeruns to every first floor device. The second floor has one bath with toilet, sink, and tub. rather than running 6 lines I thought I will run 2 but for more supply I will run .75” and once up there branch off with .5”. That was stupid as all it did was make twice the amount of cold water to purge from the longest run of all and more than one thing being used at the same time will never happen and if it did likely .5” would handle it.



What I like about the point of use circulation is if the plumbing is done homerun style the whole hot water piping for the house being purged isn’t required just the one leg hot back to cold.
 
Manifolding is always interesting. In this house the, "lic. B-general", who I'm of the opinion was obtained at an F.W. Woolworth, weekend sale, didn't comprehend, and just added piping. There's roughly 60' extra of 1/2" copper.

Which equip. you select will need to be balanced, by you, and will needed to be adjusted too, and dictated by your families social demands.

I favor the other, with the use of the GRUNDFOS crossovers.
 
I am adding a point of use water heater under my kitchen sink because it takes over a minute of running water to get hot water to the faucet. There is currently a pair of unused 12 ga white-black conductors wired to the main panel with a 20 amp breaker. There is a separate ground wire running to the dead-ended box where the unused circuit terminates. It was apparently intended for some future use, but is not pulled through a conduit, so I cannot replace it.

-> is it permissible by code and good practice to re-purpose the white conductor (painting it red in the main panel to indicate it is now a hot lead) to a 2nd pole breaker (installing a new two-pole breaker) and use it for the 2nd pole of a 220 v 20 amp circuit? That would increase the wattage I can support at the under-sink heater.

Is that question clear?

Thanks for your thoughts and comments.
Hello Dsteinhorn!

Above, JoeD mentioned recolouring the wire is OK for your use. I noticed his proper spelling of "colour" & guess Joe's not in the U.S. where we spell it wrong. Here's the U.S.'s NEC (NFPA 70) take on it:

As long as the conductors are in a multi-conductor cable all the way, it's OK by NFPA 70 to do as you propose unless local code contradicts. If, at some point in the run, the cable switches to conduit with individual conductors, it's Not allowed to change the color of the white # 12. (those rules change with wire size)

Don't ever re-color the bare ground. It's for grounding (earthing) only.

Make certain that any place the conductors are exposed are colored. Example: If there is a junction box along the way to the final destination & the jacket is stripped in the box. I suggest permanent marker or paint marker instead of tape which can fall off, confusing someone later.

Note that the rules differ a bit regarding re-coloring for 3 and 4-way switches. SEE NFPA 70 200.7 for that variously interpreted section.

Not That You Asked-
It's not my business & I hope you don't mind a suggestion, but 20 amps is a generous circuit. You may find a 120 volt point-of-use that will suffice for your needs. This will save you some money on circuit breaker & save you some time.

Also, people I know have installed point-of-use on the hot water line & asked why they get instant hot water, then a minute or so of cold, then hot again. Phas 1: Hot from the Instant heater Pahse 2: Cold from water that was dormant in the supply pipes. Phase 3: Hot from the water heater

Paul

PS: Do you know why we spell words such as "color" and "favorite" wrong in the U. S.?
Grade school English class taught us that Benjamin Franklin decided our use of the English language was "terribly inefficient", so he went on an extensive publicity campaign to ditch the extra letters. Nothing else to worry about, I guess!
 
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My kitchen is about 80' from my hot water heater. I also use the Grundfos recirc pump and the little sensor "doohickey" under the kitchen sink. I have a programmable timer on the water heater so I can preset the times where the hot water in the kitchen is needed. It has worked great for the last 8 years living at this house. As a side note, I am also in So Cal, where water costs are always a concern, and this was the cheapest solution not to waste water by dumping it down the drain as the water warms up.
 
As often as not, in CA. the under slab piping is a series of connected loops, so finding the last fixture group and installing the GRUNDFOS recirc. devise there, will give you hot water at all the fixtures, in a relatively short time frame.
 
With respect to all the folks who recommended the recirculating system, doesn't that lead to warm "cold water" when brushing teeth unless there is a separate return line for the recirculated hot water line?
 
That's why the use of the system, needs to be adjusted to your, specific, social needs, because while that may be a marginal affect at the location of the, temperature regulated GRUNDFOS, others, unless you are on a continuous loop, will only be marginally affected.
 
When you walk up to the sink both the hot and cold taps have water in them that is room temp. When you push the button the room temp hot water displaces the room temp cold water. At some point new water from your water heater reaches the pump and the pump shuts off. Unless it over shoots there shouldn’t be very much if any hot in the cold line. The same water wasting can take place if you have a long run from say a well in hot climate and you want an ice cold drink of water you could well be clearing out the warmer cold water.



Personally I wouldn’t mind the water a little warmer for teeth brushing. I’m always being reminded I’m strange as I mix hot and cold for the sensitive teeth.
 

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