220v Waterheater and 70 amp Subpanel

Reply

  #1  
Old 02-01-09, 01:45 PM
A
Member
Thread Starter
Join Date: Feb 2009
Location: Florida
Posts: 51
Received 0 Votes on 0 Posts
220v Waterheater and 70 amp Subpanel

I have a small apartment in back of my house that has a subpanel running off my main house's 200 amp service. The breaker going to the subpanel is a dual pole 70 amp breaker. For years (it would appear, built 1957) there has been a 220v single element (2500w) 30 gallon water heater in use without problem. I want to replace it with a low boy. When I went to disconnect it there were only two wires going to it (both inside a single casing) one to the red and one to the black. I flipped off what I thought was the breaker in the subpanel (20amp), but that only turned off one wire, another 20 amp breaker next to the first one turned off the other wire. The water heater is the only thing on each of those breakers and no other significant appliances are in the building.

What if anything should I do to correct the above if it is in fact a problem? Can the arrangement support a single 220v 3500w element? How about a water heater with two 220v 3500w elements (the low boy I want)?

Thanks you for any input.
 

Last edited by ArchStanton; 02-01-09 at 01:48 PM. Reason: Spelling
Sponsored Links
  #2  
Old 02-01-09, 06:16 PM
F
Member
Join Date: Mar 2006
Location: NE Wis / Paris France{ In France for now }
Posts: 4,807
Received 0 Votes on 0 Posts
What namebrand is that breaker is ?

Somecase it will be much wiser to get a true two pole breaker to get the power shut off for waterheater.


For 3500 watt waterheater you should be ok on #12 AWG size with 20 amp breaker { for me I will replace the wire if it is a questionable condtion and run new one with #10 AWG due some of the new waterheaters do have 4500 or 5500 watt elements in there}

the other thing is in the code is if you are not in sight of breaker box a simple Air Condteing pullout or disconnection switch will meet this code requirement.


If ya have more question just holler one of us will help ya

Merci,Marc
 
  #3  
Old 02-02-09, 12:46 PM
A
Member
Thread Starter
Join Date: Feb 2009
Location: Florida
Posts: 51
Received 0 Votes on 0 Posts
Thank you...

The brand is Stab Lock. Ominously, see the picutre and article here:

What is an FPE Service Panel and why is it dangerous? - My Electrician Online

I guess I should probably replace the panel and breakers to be safe?

Also, am I correct that a dual pole breaker (220v) should cover 4400 watts?
 
  #4  
Old 02-02-09, 01:43 PM
I
Forum Topic Moderator
Join Date: Feb 2005
Location: Near Lansing, Michigan
Posts: 10,943
Received 43 Votes on 41 Posts
Originally Posted by ArchStanton View Post
The brand is Stab Lock...
I guess I should probably replace the panel and breakers to be safe?
Yes, the FPE Stab-lok breaker panels in the USA (Canadian FPE is okay) should be replaced as they are a known fire hazard.

Also, am I correct that a dual pole breaker (220v) should cover 4400 watts?
A 4400W water heater should be on #10 wire with a 25A or 30A breaker.
 
  #5  
Old 02-02-09, 04:18 PM
A
Member
Thread Starter
Join Date: Feb 2009
Location: Florida
Posts: 51
Received 0 Votes on 0 Posts
The water heater is 3500w

Thank you. I will replace the panel and breakers. The water heater is 3500w. It has upper and lower elements but it is my understanding that they do not operate at the same time. Will 20amp do for that?
 
  #6  
Old 02-02-09, 04:33 PM
F
Member
Join Date: Mar 2006
Location: NE Wis / Paris France{ In France for now }
Posts: 4,807
Received 0 Votes on 0 Posts
Originally Posted by ArchStanton View Post
Thank you. I will replace the panel and breakers. The water heater is 3500w. It has upper and lower elements but it is my understanding that they do not operate at the same time. Will 20amp do for that?
Majorty of resdentail tank waterheater do not have both upper and lower on the same time due the double pole double throw thermosat so if upper element is on the lower one is locked out until the upper element is done heating up the water then switch over to lower element.

3500 watts @ 240 volts = 14.5 amp

You can use 20 amp breaker however for most of electricians rather run with #10-2 W/G with 25 or 30 amp breaker that will cover majorty of tank waterheater some of the elements do have 4500 or 5500 watts so that the reason why.

Merci,Marc
 
  #7  
Old 02-02-09, 06:16 PM
A
Member
Thread Starter
Join Date: Feb 2009
Location: Florida
Posts: 51
Received 0 Votes on 0 Posts
30amp it is

Originally Posted by french277V View Post
Majorty of resdentail tank waterheater do not have both upper and lower on the same time due the double pole double throw thermosat so if upper element is on the lower one is locked out until the upper element is done heating up the water then switch over to lower element.

3500 watts @ 240 volts = 14.5 amp

You can use 20 amp breaker however for most of electricians rather run with #10-2 W/G with 25 or 30 amp breaker that will cover majorty of tank waterheater some of the elements do have 4500 or 5500 watts so that the reason why.

Merci,Marc
Thank you so much for your quick replies.

Tom
 
  #8  
Old 02-03-09, 09:28 AM
I
Forum Topic Moderator
Join Date: Feb 2005
Location: Near Lansing, Michigan
Posts: 10,943
Received 43 Votes on 41 Posts
Originally Posted by ArchStanton View Post
Can the arrangement support a single 220v 3500w element? How about a water heater with two 220v 3500w elements (the low boy I want)?
Also, am I correct that a dual pole breaker (220v) should cover 4400 watts?
The water heater is 3500w. It has upper and lower elements but it is my understanding that they do not operate at the same time. Will 20amp do for that?
So which size is it? If you know that the thermostat on the heater only operates one element at a time, you can design the circuit based on the size of one element. It should be the larger of the two if the elements are mismatched. If both operate at the same time, then obviously the circuit needs to be sized for the sum of the elements.

A 20A circuit with #12 wire is okay for up to a 3850W heater.

A 25A circuit with #10 wire is okay for up to 4800W heater.

A 30A circuit with #10 wire is okay for up to 5760W heater.
 
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
 
Ask a Question
Question Title:
Description:
Your question will be posted in: