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# Thread: Wire size for 120V water heater?

1. ## Wire size for 120V water heater?

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. 1650 watts is about 13 amps. 12 guage wire is fine.

3. 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.

4. Thanks guys.

5. 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.

6. 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. . .

7. Thanks. 1650 is the "watts @ 120VAC". 2523 is the Kw hours per year.

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

9. Originally Posted by Thatguy
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. . .
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.

10. 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".

11. 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.

12. 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.

13. 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.

14. 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.

15. 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.

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