# Wire size for 120V water heater?

Discussion in 'Electrical Forum discussion & Blog' started by Artie, Oct 3, 2010.

1. ### ArtieNew Member

Joined:
Nov 6, 2009
Location:
Jacksonville, Fl
I want to run this water heater, (10 gal., 120VAC, 1650W), at a remote location. (Approximately 20ft. from the breaker box.) Would 12-2 be sufficient?

2. ### jimboPlumber

Joined:
Aug 31, 2004
Location:
San Diego
1650 watts is about 13 amps. 12 guage wire is fine.

4. ### ThatguyHomeowner

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Aug 27, 2008
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A bounty hunter like in "Raising Arizona"
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MD
If you have an ohmmeter, before you install this heater check that the element resistance is at approx. (120v^2)/1650w = 8.7 ohms.
It can't hurt to make sure.

Their kwh rating for a year is based on it being on 17% of the time. I guess this is some consumer average usage.

5. ### ArtieNew Member

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Nov 6, 2009
Location:
Jacksonville, Fl
Thanks guys.

6. ### hjModerator & Master PlumberStaff Member

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Plumber
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Cave Creek, Arizona
The KW for a heater is the "actual" wattage, not a "kw per year" statistic. The "kw/yr" number creates the "annual cost of operating the heater" which is a completely different thing.

7. ### ThatguyHomeowner

Joined:
Aug 27, 2008
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A bounty hunter like in "Raising Arizona"
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MD
Speaking of power usage,
since the element runs on 120v, wiring an electromechanical analog clock across the element for 24 hours or so will tell the heat loss through his R8 insulation.
If the clock advances 5 minutes every 600 minutes with no hot water being used then his loss is 1650w(5m/600m) = 14 w = 48 BTU/hr.

I definitely have to find a day job. . .

8. ### ArtieNew Member

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Nov 6, 2009
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Jacksonville, Fl
Thanks. 1650 is the "watts @ 120VAC". 2523 is the Kw hours per year.

9. ### jwelectricElectrical Contractor/Instructor

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Instructor
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North Carolina
A #12 on a 20 amp breaker is just what the doctor (NEC) ordered.

10. ### Jim PortElectrical Contractor

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Electrical Contractor
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Maryland
Do you really think all this effort is worth it? Do you really think someone wants to go without hot water just to find out heat loss? Since heat loss should already be figured into the operating cost the energy star label should already tell whether the heater is efficient compared to other heaters.

11. ### nukemanNuclear Engineer

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Nov 20, 2009
Occupation:
Nuclear Engineer
Location:
VA
It is only something us engineer types would be interested in.

Anyway, if the OP wanted to know the heat loss, there is no need to do the test for 24hr. You could simply do it say overnight (or while at work). Just need to ratio the time the clock runs to the total time that has past and multiply by the heater power. Testing over a longer time would give a better average heat loss estimate, but the loss shouldn't change much unless you have the WH in an unconditioned space such as an attic or garage. In this case, the heat loss can be quite different than what the unit is spec'd at depending on climate and time of day/year.

The test doesn't get you much except for the knowledge of how much heat is being lost. It is good info to have as a baseline to see what impact insulating the piping, replacing with a new unit, etc. has. You could also use this to show others (and yourself) that the standby loss in a tank-type WH (especially electric ones) is quite small and that a tankless type is not going to save a ton of money by not "heating water around the clock".

12. ### ThatguyHomeowner

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A bounty hunter like in "Raising Arizona"
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MD
Mr. Port, as a courtesy to you I must tell you that you are on my ignore list.

If this were the real world you would, right now, be a defendant in an action for harassment and defamation, at the very least.

13. ### ballvalveGeneral Engineering Contractor

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Dec 28, 2009
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"retired" and still building and troubleshooting
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northfork, california
If he is on your ignore list, be sure not to respond when he defames you again.

But I am more on Mr. Ports side. No one has the time for that except a high school energy class.

Tankless water heaters are pretty much a joke when compared to an electric rig. You can bury an electric water heater in all your old winter jackets and get the standby losses to near zero.

And I think the Indian-Indonesian anti-defamation league will soon be contacting you about that kid in a bowl about to be eaten by a snake.

14. ### hjModerator & Master PlumberStaff Member

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Occupation:
Plumber
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Cave Creek, Arizona
A 24 hour reading would only tell you the TOTAL time the heater ran, including replenishing the hot water used, unless the system were not used during that time period. If the heater is in an "unconditioned location" such as a garage, the heat loss will fluctuate according to the ambient temperature, which could change hourly, and would definitely change during the various seasons.

15. ### ArtieNew Member

Joined:
Nov 6, 2009
Location:
Jacksonville, Fl
I'm interested in all opinions here. My situation is that this old house's water heater is too far from the kitchen sink. I hate the fact that I must wait 5 minutes to get hot water from the kitchen sink. I was thinking of doing a small dedicated heater just for the sink. On the other hand, I don't want to spend \$400/yr to do that. But I might, for the "luxury" of psuedo-instant hot water. All opinions and ideas welcome.

16. ### Jim PortElectrical Contractor

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Electrical Contractor
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Maryland
You could see about adding a recirculator pump on the hot water line. This way you should not need to wait so long for hot water.

17. ### ThatguyHomeowner

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Aug 27, 2008
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A bounty hunter like in "Raising Arizona"
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MD
Last edited: Oct 6, 2010
18. ### ballvalveGeneral Engineering Contractor

Joined:
Dec 28, 2009
Occupation:
"retired" and still building and troubleshooting
Location:
northfork, california
Its a pity that a 10 gallon water heater costs more than a 50 gallon job.

You can find a 20 gallon mobile home one for 250\$ or look at motor home water heaters, and get a small 120 volt element, maybe 1200 or 1500 watts, and you could plug it in under the sink without more wiring. That would likely be cheaper than a recirc system, and you can super insulate the unit too.

If you use a lot of water at that sink, your incoming cold could be the HOT in from the water heater. That should fill in the "lag" time

19. ### ThatguyHomeowner

Joined:
Aug 27, 2008
Occupation:
A bounty hunter like in "Raising Arizona"
Location:
MD
You only have to make up 1 gallon of cold water per 100' of 1/2" ID pipe. It's ~800 BTU for a 90F rise, so using 1200 W it'd take ~11 minutes to recover.

You probably have the whole morning to recover. A 120w heater will take 1.8 hours to recover.

Decide on what tradeoffs you can make and then hope somebody makes a heater that does this.

8.3 pounds/gal
90 F rise
747 =BTU

according to
http://www.onlineconversion.com/
this many BTU per hour equals
219 watts

with 1200 w
this takes
0.1825 hour
10.95 =minutes

Last edited: Oct 7, 2010
20. ### ballvalveGeneral Engineering Contractor

Joined:
Dec 28, 2009
Occupation:
"retired" and still building and troubleshooting
Location:
northfork, california
Right, so a 1200w or less 5 or 10 gallon WH under his sink, with the hot from normal heater as infeed would solve his issue pretty cheaply with less issues than recirc.

Would also keep his undersink warm and dry, an advantage toward cabinet survival.

21. ### ThatguyHomeowner

Joined:
Aug 27, 2008
Occupation:
A bounty hunter like in "Raising Arizona"
Location:
MD
Yes, I hope we find out how it finally worked out. The OP certainly has all the facts by now.

Mr. Valve, you are definitely not a run-of-the-mill electrician.

Good. You can make up for the [name deleted] types in this world.

Last edited: Oct 10, 2010