Electric Water Heater Wiring - Electrical - DIY Chatroom Home Improvement Forum

 DIY Chatroom Home Improvement Forum Electric Water Heater Wiring
 User Name Remember Me? Password
 Register Blogs Articles Rewards Search Today's Posts Mark Forums Read

 Thread Tools Display Modes
09-22-2011, 08:23 PM   #1
Newbie

Join Date: Sep 2011
Posts: 7
Rewards Points: 10

## Electric Water Heater Wiring

Hi, new here but it seems like a knowledgeable site.

Ive been looking into a water heater timer, and upon locating the circuit found out it still has aluminum wiring. Its a fuse panel so there was one 20A fuse on each side used to give 240v. This wiring is 14ga BX at best..though it looks thinner than the 14ga copper conductors. The water heater has 3000w upper and 3000w lower elements, non simultaneous operation, though it says max 4500w...not sure if this is actual or maybe the tank itself isnt fix for an element larger than that.

A friend of mine whos an electrician here in Ontario (canada) told me that code states here that you cannot exceed 75% of current overload device(Im taking this as fuse/breaker). That said, and assuming the wiring is #14, the fuse should be 15A, 75%15A=11.25A. When i clamp meter the hots they're 12A...thus making 15A fuse inadequate, while a 20A fuse on #14 is also wrong.

So, ideally I would need to have 20A fuses with #12 BX? OR am I way off in my calculations LOL

09-22-2011, 08:44 PM   #2
Member

Join Date: Nov 2007
Location: Nashua, NH, USA
Posts: 7,971
Rewards Points: 1,548

1. Aluminum wire generally must be one size larger than copper wire for a given amperage (breaker rating), for example 15 amps needs 12 gauge aluminum versus 14 gauge copper. The actual criteria involve resistance per foot.

2. The U.S. NEC calls for 80% circuit loading (12 amps maximum draw on 15 amp breakered circuits) for "continuous" usage which means appliances and equipment likely to be on for more than 3 hours at a time. The kinds of appliances are named in the code; I don't recall what water heaters are. Intermittent usage may use the full amperage rating.

3. Wires handle the same number of amperes at 240 volts as they do at 120 volts.

Canadian rules (CEC) may differ.

__________________
The good conscientious technician or serviceperson will carry extra oils and lubricants in case the new pump did not come with oil or the oil was accidentally spilled, so the service call can be completed without an extra visit.

Last edited by AllanJ; 09-22-2011 at 08:49 PM.

09-23-2011, 04:36 AM   #3
Member

Join Date: May 2009
Location: Easton MD
Posts: 1,893
Rewards Points: 1,104

Quote:
 Originally Posted by AllanJ 2. The U.S. NEC calls for 80% circuit loading (12 amps maximum draw on 15 amp breakered circuits) for "continuous" usage which means appliances and equipment likely to be on for more than 3 hours at a time. The kinds of appliances are named in the code; I don't recall what water heaters are. Intermittent usage may use the full amperage rating.

422.13 Storage-Type Water Heaters. A fixed storage-type
water heater that has a capacity of 450 L (120 gal) or less shall
be considered a continuous load for the purposes of sizing
branch circuits.

 The Following User Says Thank You to Code05 For This Useful Post: NJMarine (09-23-2011)

 09-23-2011, 06:08 AM #4 Member   Join Date: Jun 2011 Location: Plattsburgh, NY Posts: 249 Rewards Points: 162 Yikes... time to fix that asap. Is the whole house aluminum or just that line? I just installed a 40 gallon hot water heater. 30 amp dual throw breaker with 10/2 NM. 2 20 amp fuses with 12/2 NM is probably fine but it couldn't hurt to have slightly bigger wiring.
09-23-2011, 07:23 AM   #5
Electrical Contractor

Join Date: Sep 2008
Location: Delmarva
Posts: 3,368
Rewards Points: 2,000

Quote:
 Originally Posted by matt151617 .... I just installed a 40 gallon hot water heater. 30 amp dual throw breaker with 10/2 NM. 2 20 amp fuses with 12/2 NM is probably fine but it couldn't hurt to have slightly bigger wiring.
You will need at least a 25 Amp OCP with a #10 wire if that water heater has 4500 watt elements in it.
__________________
-KB

Life is uncertain -- eat dessert first!!

 09-23-2011, 01:43 PM #6 Newbie   Join Date: Sep 2011 Posts: 7 Rewards Points: 10 I plan to fix it this weekend! I just discovered it. The rest of the house is old copper. I plan to run 12/2 bx and surface mount an outlet. In regards to the outlet and the heater cord itself - currently its bx out the top of the water heater with a T slot plug end attached...bx to plug end doesn't seem right to me...? I m wondering if a piece of #12 kavtar with either tslot or 20Atwist is allowable in this case as a permenant solution? On a side note, I checked things out this morning after a shower and the fuse cartridge was quite warm.. I m assuming this is normal as this has nothing to do with the wiring. the terminal screws and conductors were slightly warm but nothing to be alarmed about.
09-23-2011, 01:53 PM   #7
A "Handy Husband"

Join Date: Feb 2007
Location: South Carolina Low Country
Posts: 7,589
Rewards Points: 4,260

Do yourself a favor and run 10-2 directly (hard wire) to the WH. Eliminate the plug and cord. Install a disconnect if the WH is out of sight of the fuse pane.

Next project is to install a modern circuit breaker panel.

__________________
Location:
Coastal South Carolina

 The Following User Says Thank You to rjniles For This Useful Post: Code05 (09-23-2011)

 Tags heater , water , water heater

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are Off Pingbacks are Off Refbacks are Off Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post crankbait09 Plumbing 18 04-18-2011 11:35 AM supermaxhd Plumbing 24 11-28-2010 12:11 PM makunag Plumbing 15 08-27-2010 11:00 PM mw2727 Plumbing 4 08-21-2008 01:51 PM alexz Plumbing 3 08-15-2006 10:31 AM

Top of Page | View New Posts