water heater bonding and more

Reply

  #1  
Old 05-27-06, 02:12 PM
Member
Thread Starter
Join Date: Oct 2005
Location: USA
Posts: 1,188
water heater bonding and more

A couple of questions;

I see references to bonding across the water heater input to output piping. is this always required with metal piping? Since the heater tank is metal, why is external bonding necessary? I read 250.104, and it's not clear to me..

Second; I've got a 3800watt heater, with no nameplate indicating max OCP. I've got 10/2 NM feeding. I read i'm in violation if I use a 30a breaker. True? I must use either a 20a or a 25a breaker. My load amps are 3800/240= 15.8a. 125% is then 19.8a, which would be the min ampacity, and 150% is 23.8a which would be my max OCP. Does this look reasonable?

thanks!
 
Sponsored Links
  #2  
Old 05-27-06, 04:03 PM
nap's Avatar
nap
nap is offline
New Member
Join Date: May 2006
Location: north
Posts: 4,163
Originally Posted by telecom guy
A couple of questions;

I see references to bonding across the water heater input to output piping. is this always required with metal piping? Since the heater tank is metal, why is external bonding necessary? I read 250.104, and it's not clear to me..

Second; I've got a 3800watt heater, with no nameplate indicating max OCP. I've got 10/2 NM feeding. I read i'm in violation if I use a 30a breaker. True? I must use either a 20a or a 25a breaker. My load amps are 3800/240= 15.8a. 125% is then 19.8a, which would be the min ampacity, and 150% is 23.8a which would be my max OCP. Does this look reasonable?

thanks!
The bonding is required because if the water heater is removed, you lose that continuity.
Additionally, the wate pipe connections may be insulative and not reliable as a means of bonding.



curious as to where you read the possible violation.
 
  #3  
Old 05-27-06, 04:14 PM
Member
Join Date: Jan 2004
Location: Oregon
Posts: 1,219
Many hot water heaters have dielectric unions between the external and internal piping. These are insulating fittings which reduce corrosion caused by electrolytic action. You need to use a bonding jumper between the hot and cold water pipes to make sure that the entire metal piping system is electrically bonded.

I presume that you are reading the 150% number from 422.10(E). I tend to agree with you that 30A would be a violation for your water heater circuit, however 30A circuits are so common and standard for water heater heaters that I wonder if either the name plate fell off, or the name plate was damaged The wattage of your water heater seems to have been selected to just make a 20A breaker and wiring acceptable.

If your water heater manual or name-plate permits the use of higher wattage elements, I'd be strongly tempted to use 4500W elements and a 30A breaker.

-Jon
 
  #4  
Old 05-27-06, 04:50 PM
Member
Thread Starter
Join Date: Oct 2005
Location: USA
Posts: 1,188
thanks

I completely ignored any possibility of removing the water heater, leaving the hot pipes floating.

also, my heater does have a dual wattage lower element, but i'm keeping the low watts due to the hurricane/generator issue.

thanks for the response..
 
  #5  
Old 05-27-06, 05:23 PM
nap's Avatar
nap
nap is offline
New Member
Join Date: May 2006
Location: north
Posts: 4,163
How about this

422.11(E)(3)

not exceed 150 percent of the appliance rating if the ocp rating is not marked and the appliance is rated over 13.3 amp (applies here). Where 150 percent of the appliance rating does not correspond to a standard oc device ampere rating, the next higher standard rating shall be permitted.
since 25 amp rating is considered a standard, then 25 would be allowed. Still #10 wire. (150% is 23.8a )

Not being argumentative, just anal.
 
  #6  
Old 05-27-06, 07:39 PM
Speedy Petey's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Nov 2003
Posts: 2,455
In most homes there is no reason to add an intentional jumper between hot and cold pipes. The water heater is only one device with both pipes on it. The boiler, shower valves, faucets, all typically have continuity.
I have yet to see a house without continuity to the hot pipes. I have however seen many cheap plastic filters installed with NO jumper added, and that IS in the code. I think THIS is a much more serious issue.
 
  #7  
Old 05-28-06, 07:00 AM
nap's Avatar
nap
nap is offline
New Member
Join Date: May 2006
Location: north
Posts: 4,163
=Speedy Petey]In most homes there is no reason to add an intentional jumper between hot and cold pipes. The water heater is only one device with both pipes on it. The boiler, shower valves, faucets, all typically have continuity.
NEC 2005 250.104(B) FPN states that "bonding all piping and metal air ducts within the premises will provide additional safety". I know of no other section similar for bonding the water pipes but in my locality, the inspectors have required a bonding jumper across the water heater. Additionally, in this age of plastic, many faucets and shower valves are plastic and therefore provide no continuity for plumbing systems and I do not have a boiler, I'm sure many others don't as well.. We always deal with possibilities. This just prevents a bad situation if certain possibilities do happen. Better safe than sorry.
I have yet to see a house without continuity to the hot pipes. I have however seen many cheap plastic filters installed with NO jumper added, and that IS in the code. I think THIS is a much more serious issue.[
I don't disagree, but as posted above, better safe than sorry when dealing with electricity. The code is a minimum requirement code. While it only requires the minimums, you can always add to it.
 
Reply

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 Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes