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Old 03-17-2008, 06:12 PM   #1
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Ele hot water tank and welder sharing circuit


My electric hot water tank is in the garage. It's wired with 240 volt 30 amp.
I have a mig weld that requires 240v 30 amp.
What I'm thinking of doing is to instal a 240v 30 amp plug on the hat water tank. (dryer plug) then wire a matching receptical on the wall. So when I want to use the welder I would unplug the tank and plug in the welder. I use the welder once a month or less. I just need to remember to plug the tank back in.

I guess what I need to know is it OK to have the hot water tank on a plug?

Thanks

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Old 03-17-2008, 06:38 PM   #2
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Ele hot water tank and welder sharing circuit


Considering they are both straight 240v appliances I'd say you are fine doing this. I like the fact that they cannot both be powered at the same time.

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Old 03-17-2008, 07:43 PM   #3
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Ele hot water tank and welder sharing circuit


Just a thought worth thinking about. The hot water tank requires a disconnect other than the breaker in a lot of situations. You could purchase a 30 amp double throw disconnect and wire the receptacle off that. This would satisfy the disconnect requirement for the hot water tank and allow you an either one or the other option but not both.
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Old 03-17-2008, 07:57 PM   #4
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Ele hot water tank and welder sharing circuit


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Originally Posted by Stubbie View Post
Just a thought worth thinking about. The hot water tank requires a disconnect other than the breaker in a lot of situations. You could purchase a 30 amp double throw disconnect and wire the receptacle off that. This would satisfy the disconnect requirement for the hot water tank and allow you an either one or the other option but not both.
I'm not sure I follow you. Would the receptacle be hot at all times and the disconnect would turn the tank on and off?

I was wondering about pluging in the tank, if the tank is calling for heat wouldn't that be a bad thing. At least the welder is in an off state when you plug it in. The tank has no off position.
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Old 03-17-2008, 08:07 PM   #5
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Ele hot water tank and welder sharing circuit


No the switch has two on positions with the middle being off. the hot water tank would be permanently connected to one load side of the switch and the receptacle to the other load side of the switch. In one position the hot water tank operates only... throw the switch to the other on position and the receptacle for the welder is energized but not both. You select which one you want operating with the switch.
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Old 03-17-2008, 08:11 PM   #6
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Ele hot water tank and welder sharing circuit


Other than the fact that unless you throw the breaker you would be plugging in the water heater under load, the receptacle/plug setup would itself be the disconnect.
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Old 03-17-2008, 08:16 PM   #7
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Ele hot water tank and welder sharing circuit


Yes Speedy is correct I failed to mention that a shared receptacle would also satisfy the disconnect requirement. I was simply looking at it as a bit more convenient to use a switch.
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Old 03-17-2008, 08:18 PM   #8
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Ele hot water tank and welder sharing circuit


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Originally Posted by Stubbie View Post
No the switch has two on positions with the middle being off. the hot water tank would be permanently connected to one load side of the switch and the receptacle to the other load side of the switch. In one position the hot water tank operates only... throw the switch to the other on position and the receptacle for the welder is energized but not both. You select which one you want operating with the switch.
now I get it. I like this idea. where do I get a switch like this? Lowes? Homedepot?

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Old 03-17-2008, 08:19 PM   #9
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Ele hot water tank and welder sharing circuit


Correct me if I'm wrong gentlemen, but take a look at NEC 400.7 (A) 8. Is a water heater intended to be connected with a flexible cord? I would be concerned with the temperature rating of the cord and the conductors insulation. I don't consider plumbing as "readily removable." Maybe I'm way off base and these are non issues, I've just never seen a resi water heater wired with drop cord.
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Old 03-17-2008, 09:38 PM   #10
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Ele hot water tank and welder sharing circuit


This argument always comes up when this cord and plug of a storable hot water tank is brought up. 422.16 also addresses this issue of cord and plug appliances that are fastened in place. The key issue here is "if the manufacturer lists the hot water tank as cord and plug. Many are but they are usually the 20 gal variety. However it would be prudent to verify the acceptance of cord and plug for this hot water tank. I believe you will find that hard unless the op has the install instructions. That said I am not aware of any hot water tanks that are 40 gal. or larger in storage gallons that are listed for cord and plug. After reviewing the code I would have to agree that cord and plug is not allowed for the larger storage electric hot water heaters unless listed for cord and plug. There have been proposals to add this to just about every code cycle for clarification for quite some time. this is the latest proposal I am aware of and the cmp rejected the clarification as not needed.... stating that hot water heaters are not intended for cord and plug. So I would say that the connection of this hot water tank to a dryer plug would be non-compliant unless listed.

The use of a switch would allow you to comply with a fixed wiring method for the hot water heater and cord and plug for the welder.

17-19 Log #2729 NEC-P17 Final Action: Reject

(422.16(B)(5))
__________________________________________________ _____________
Submitter: Doug Boggus, City of Grand Prairie

Recommendation: Revise text to read:
422.16(B) Specific Appliances
(5) Water Heaters. Water heaters shall be permitted to be cord-and-plug
connected with a flexible cord identified as suitable for use on water heaters in
the installation instructions of the appliance manufacturer, where all of the
following conditions are met:
(1) The flexible cord is terminated with a grounding-type attachment plug.
(2) The length of the cord is not less than 610 mm (2 ft) and not more than
1.8 m (6 ft).
(3) The receptacle is accessible.
(4) The flexible cord is not subject to physical damage.
(5) The flexible cord has a temperature rating not less than that marked on
the appliance nameplate or in the appliance’s connection wiring compartment.
(6) The water heater is identified for cord-and-plug connection.

Substantiation: Throughout the US, jurisdictions are constantly approached to
allow water heaters to be connected to 120-volt and 240-volt power supply
through plug-and-cord connection in violation of 422.16(A) as such appliances
are generally not identified for flexible cord connection. The most commonly
proposed type cord is “dryer cords” rated at 30-amperes for connections to 30-
50 gallon storage type units. This is because of local demand for a quick and
safe way to facilitate removal and replacement of such appliances. The
proposed wording is intended to set necessary requirements for installations
where cord-and-plug connection of a water heater is chosen as the connection
wiring method. Such specific requirements will allow cord manufacturers to
address this issue with properly rated cord insulation and connections while
also allowing manufacturers of water heater appliances to be able to allow a
connection method that is favored by both electricians and plumbers making
new installations and by plumbers and homeowners replacing such appliances.

Panel Meeting Action: Reject

Panel Statement: The submitter has not substantiated a need for an exception
to 400.8(1): “…cords shall not be used…as a substitute for fixed wiring of a
structure.” The panel notes that water heaters are often installed near other
heating equipment or in areas used for storage of tools and other implements
that can damage cords. They are infrequently replaced, have no vibration
concerns, and can be serviced in place. Cellar installation of water heaters may
also necessitate that the cord be plugged into a ceiling receptacle, requiring a
cord longer than proposed and increasing the risk of cord damage.

Number Eligible to Vote: 14
Ballot Results: Affirmative: 14




Last edited by Stubbie; 03-17-2008 at 10:03 PM.
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Old 03-17-2008, 09:42 PM   #11
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Ele hot water tank and welder sharing circuit


Quote:
Originally Posted by junkcollector View Post
Correct me if I'm wrong gentlemen, but take a look at NEC 400.7 (A) 8. Is a water heater intended to be connected with a flexible cord? I would be concerned with the temperature rating of the cord and the conductors insulation. I don't consider plumbing as "readily removable." Maybe I'm way off base and these are non issues, I've just never seen a resi water heater wired with drop cord.
Your correct, also a dryer cord is not listed for anything other than a dryer...IMO...

Last edited by chris75; 03-17-2008 at 09:45 PM.
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Old 03-17-2008, 09:56 PM   #12
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Ele hot water tank and welder sharing circuit


I don't think you will find one at lowes. I would drop in to an electrical supply and see what they have in 30 amp double throw safety switches. Or try e-bay but you need to know what your looking for. Online is good also. This is what they will be similar to...

There are several varieties and many applications I would just tell the guys at the counter what your wanting to do and see what they have.

Some are wired two sources or two loads you want one configured for two loads at 240 volts single phase.

I also agree with Chris about the dryer cord pigtail. I was thinking in terms of a soow industrial cord.
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Last edited by Stubbie; 03-17-2008 at 10:08 PM.
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Old 03-17-2008, 11:39 PM   #13
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Ele hot water tank and welder sharing circuit


You know, I've always liked the idea of a cord and plug connected water heater. You would not use a dryer cord, you would use a NEMA 6-30. However, like stated above, it may not be legal. Code aside, I know that I have read the stickers or instructions that came with water heaters that said they are not listed for use with a cord.

However, I am not giving advice that is against Code, but I personally think that this is a non-issue. If this were my setup, and I had no other way to do it, I might just put a plug on my water heater.

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Old 03-18-2008, 12:07 AM   #14
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Ele hot water tank and welder sharing circuit


This used to be a very common practice to cord and plug water heaters and I believe some areas still allow you to do so. Unfortunately I would have to say code doesn't allow it unless listed and I can't say as I have seen it listed. I checked A.O. Smith and Reliance web sites and they don't say one way or the other but only show a armor flex or rigid method. If your good enough friends with your inspector then maybe........

As for flexible cords there is no doubt that if you get the right one it isn't going to burn up on connection to a hot water tank. I think the issue is physical damage and the length of the cord.

Last edited by Stubbie; 03-18-2008 at 12:12 AM.
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Old 03-18-2008, 01:24 AM   #15
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Ele hot water tank and welder sharing circuit


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Originally Posted by Stubbie View Post

As for flexible cords there is no doubt that if you get the right one it isn't going to burn up on connection to a hot water tank. I think the issue is physical damage and the length of the cord.

yeah it kinda common i did see alot of resdentail area i know one place they really fill the room to the top and cant find the electric water heater took me and the plummer about 1.5 hours just get in there and make a path to drag the old tank out [ btw that is a 80 gallon tank ] and they did have a dryer cord on that and part of the cord wire is allready burnted so end up put in flex and disconnect switch to meet the code.

Merci,Marc

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