Dishwasher and Disposal wiring.

[jwelectric]

I had a call once about the dish washer smoking so I told them to turn the power off till I got there. I arrived about an hour latter and now the disposal is smoking. They were wired on a three way.

Personally I think that this type of installation is as about as silly as trying to siphon gas up hill.

 

[George Stolz]

Ah, but is it a legal way to avoid pulling two circuits, that is the question.

IMO: No.

Furnaces and AC's are specifically permitted to be on the same circuit; I don't see any switching provisions mentioned. It's assumed that one will be off when the other is on.

IMO.

 

[iwire]

Ah, but is it a legal way to avoid pulling two circuits, that is the question.

IMO: No.

George neither of the circuits in question are NEC required circuits. We don't have to pull any circuits.

If the customer is happy with one circuit for both so be it.

The use of a SPDT switch prohibits the circuit from overload.

IMO it is NEC compliant.

You know you have to cite a code section that prohibits it. 8)

Now that said...

A SPDT switch may be a workable sulotion. But in my oppinion not a practical one. Pepole buying homes at todays prices should be able to run a dishwasher washer and disposal at the same time if they chose to do so.

I agree with Romeo, it is a poor solution.

 

[allenwayne]

Not any more non compliant then having 30 outlets on one circuit.In residential that is :wink: Personally I pull 6 kitchen circuits.1 fridge,1 d/w,1 disposal,1micro,2 SA circuitsthen depending on the home and extras the amount of circuits are pulled acordingly.

 

[dlhoule]

romeo wrote:
A SPDT switch may be a workable solution. But in my opinion not a practical one. People buying homes at todays prices should be able to run a dishwasher washer and disposal at the same time if they chose to do so.

I agree wholeheartedly. In certain subdivisions where I have done service work, 3 ways were a common practice. The only problem I encountered was when HO tried tapping off at switch location for a light and complained of light dimming when starting the disposal.

I don't like the idea though, I believe it is legal.

 

[LarryFine]

The only problem I encountered was when HO tried tapping off at switch location for a light and complained of light dimming when starting the disposal.

We have the same problem with people who replace range hoods with microwaves in older homes.

 

[George Stolz]

George neither of the circuits in question are NEC required circuits. We don't have to pull any circuits.

Not exactly true. 210.50(C) requires us to install an outlet within 6' of an appliance. That entails a circuit to power the outlet. Which, by a meandering path, entails that we have a circuit of some type required.

You know you have to cite a code section that prohibits it. 8)

I stick with 210.20(A).

There is a subtle difference between the way 210.19(A)(1) is worded and 210.20(A) is worded. 210.19(A)(1) is saying, under no circumstances is the ampacity of a conductor to be exceeded. That does not prevent a 40 amp breaker on a 12 guage wire. It does prevent the connected load from exceeding what the 12 can handle.

On the other hand, 210.20(A) is giving us a method to comply with. Add all the continuous loads, and count them at 125%. On top of that, add all the non-continuous loads at 100%. I see no relief for non-simultaneous loads.

A disposal is a non-continuous load, as is the dishwasher. So we can add them together and equal our OCPD rating. But we cannot exceed it, because 210.20(A) has tunnel-vision, either intentionally or unintentionally.

220.60 allows us to ignore non-coincident loads at the feeder/service level, but no relief for branch circuits.

440.33 and .34's exceptions lend credibility to the principle, but don't apply to our situation.

Tired, or I'd look for more relevant sections.

 

[iwire]

George neither of the circuits in question are NEC required circuits. We don't have to pull any circuits.

Not exactly true. 210.50(C) requires us to install an outlet within 6' of an appliance. That entails a circuit to power the outlet. Which, by a meandering path, entails that we have a circuit of some type required.

You need to read that again using Charlie's rules.

That section does not require an outlet at all.

That section requires that if we install an appliance outlet it will be within 6' of the appliance.

You know you have to cite a code section that prohibits it. 8)

I stick with 210.20(A).

IMO 210.20(A) does not support your position.


If a SPDT is used as described above the branch circuit does not, it can not, supply a load at any time which is greater than the OCPD rating.

At no time is the breaker electrically connected to both loads at the same time.

It's that simple.

Your over thinking this big time. :lol:

Let me ask you to think on this.

What is the electrical hazard that you see that I and others in this thread do not see?

Keep in mind...

The purpose of this Code is the practical safeguarding of persons and property from hazards arising from the use of electricity.


Compliance therewith and proper maintenance will result in an installation that is essentially free from hazard but not necessarily efficient, convenient, or adequate for good service or future expansion of electrical use.

 

[jwelectric]

Before using a three way switch to control two pieces of equipment I think some thought should be given to:

404.6 Position and Connection of Switches
(B) Double-Throw Knife Switches Double-throw knife switches shall be permitted to be mounted so that the throw is either vertical or horizontal. Where the throw is vertical, integral mechanical means shall be provided to hold the blades in the open position when so set.

And

404.7 Indicating
General-use and motor-circuit switches, circuit breakers, and molded case switches, where mounted in an enclosure as described in 404.3, shall clearly indicate whether they are in the open (off) or closed (on) position.
Where these switch or circuit breaker handles are operated vertically rather than rotationally or horizontally, the up position of the handle shall be the (on) position.
Exception No. 1: Vertically operated double-throw switches shall be permitted to be in the closed (on) position with the handle in either the up or down position.


Three way switches do not have an off position nor can they be locked in the center position therefore I would use the sections above to reject this installation.

 

[dnem]

Three way switches do not have an off position nor can they be locked in the center position therefore I would use the sections above to reject this installation.

I don't buy that argument because it would prevent 3ways from being used for anything. Depending on the position of the other switch(es), a 3way could turn on a light in any room by moving the toggle down.

If the dishwasher is cord and plug connected, then you have a disconnect for the dishwasher under the sink. I can't see that the position of the switch would matter.

Using a 3way for the dishwasher and disposal is a bad design, but the 3way could get you out of a pinch on a final if the dishwasher is found to require a dedicated circuit.

David

 

[dlhoule]

Mike Whitt said:

Three way switches do not have an off position nor can they be locked in the center position therefore I would use the sections above to reject this installation.

Gee Mike, I sure am glad I don't work in your area. Actually they at least at one time made a device to lock any switch in the center position. Of course, then and now, I would never have trusted them to keep sw from moving enough to energize what I didn't want energized. And you could lock the switch either up or down depending on what you want to work on.
Just unplug the disposal 1st so it doesn't run while working on DW. Course if it were me I'd just unplug the DW and let them run the disposal if they wanted to.

I still think it is a poor design.

 

[jwelectric]

When using a three way switch as it is listed to be used then there is an off for the light.

When using the three way as a way to switch from one load to the other the switch is being used out of it?s intended use and then would be required to conform to the rules of a double throw switch.

One of the rules mandate that a locking means be provided integral to the switch.

Another is that the off position be marked on the switch.

I would stand on these as reasons to post a ?Does Not Comply? sticker on the job.

 

[infinity]

What does 404.6 have to do with a 3-way switch? A 3-way is not a knife switch. Also 404.7 doesn't seem to apply to 3-way switches either. A 3-way switch is a snap switch which isn't on the list.

 

[dlhoule]

Before using a three way switch to control two pieces of equipment I think some thought should be given to:

404.6 Position and Connection of Switches
(B) Double-Throw Knife Switches Double-throw knife switches shall be permitted to be mounted so that the throw is either vertical or horizontal. Where the throw is vertical, integral mechanical means shall be provided to hold the blades in the open position when so set.

Inre to 404.6 they are not talking about a knife switch.

And
404.7 Indicating
General-use and motor-circuit switches, circuit breakers, and molded case switches, where mounted in an enclosure as described in 404.3, shall clearly indicate whether they are in the open (off) or closed (on) position.
Where these switch or circuit breaker handles are operated vertically rather than rotationally or horizontally, the up position of the handle shall be the (on) position.
Exception No. 1: Vertically operated double-throw switches shall be permitted to be in the closed (on) position with the handle in either the up or down position.

In terms of 404.7: If you are using this to reject the 3 way, how do they control the stair lighting in your area? Both are general use switches.

Will you let me control a duplex in LR from a 3 way. I want one side to control top and one side to control bottom of duplex.

A 3 way controlling duplex under sink for disposal and DW isn't any different as far as I can tell.



Three way switches do not have an off position nor can they be locked in the center position therefore I would use the sections above to reject this installation.

 

[dnem]

What does 404.6 have to do with a 3-way switch? A 3-way is not a knife switch. Also 404.7 doesn't seem to apply to 3-way switches either. A 3-way switch is a snap switch which isn't on the list.

I agree.
404.6 only applies to knife switches and 404.7 only applies to switches that have on and off positions. A 3way doesn't have on and off positions.

When using a three way switch as it is listed to be used then there is an off for the light.

When using the three way as a way to switch from one load to the other the switch is being used out of it?s intended use and then would be required to conform to the rules of a double throw switch.

How is a 3way listed to be used ?
What is the intended use of a 3way ?
Trevor posted earlier on this thread:

A 3-way switch is in fact an SPDT switch. A single pole double throw switch has one common terminal, the pole (or black screw on the 3-way). The "throw" is the number of positions it has that will connect to the common pole. So a SPDT has one pole or common and two positions that the common can connect to.

"the number of positions it has that will connect to the common pole"
So the 3way doesn't turn anything off, it only switches the connection to the common pole between 2 possible other terminals. It has no "on" and "off" positions.

There is no specific intended use. I'm not sure what is specified in the test lab listing. But I'll bet somebody will post it.

David

 

[iwire]

IMO Mike (jwelectric) is partially correct.

The SPDT switch (3-way) can not be used as the required disconnecting means as it is not indicating.

Using it as described in this thread it is not being used as the required disconnecting means and does not have to be indicting.

 

[dlhoule]

yep, it is still legal and still a poor design.

 

[George Stolz]

(210.50(C))
You need to read that again using Charlie's rules.

That section does not require an outlet at all.

Good call. You're right.

On the other part, if what you are thinking to be true is true, then the exceptions to 440.33 and 440.34 are pointless, because it's already allowed. Why would we need these exceptions if threeways (or relays) allow us to "over" load a circuit?

 

[dlhoule]

georgestolz said:

On the other part, if what you are thinking to be true is true, then the exceptions to 440.33 and 440.34 are pointless, because it's already allowed. Why would we need these exceptions if threeways (or relays) allow us to "over" load a circuit?

What does air conditioning and refrigeration equipment have to do with our subject?

I am sometimes very slow, will you explain how the circuit would be overloaded? :?

 

[dana1028]

Original Post:

".... I wired a Dishwasher and a Disposal on the same 20A ckt. The inspector says that I need seperate ckts to each of these. The dishwasher has a FLA of 9.6A with 2.7 of that being the motor The disposal has a FLA of 6.7 all of which is the motor... Any one tell me why I can't put these on the same Ckt. The Inspector sites article 210.23 (a) (2). However there are no other loads on this ckt.

Stu Goforth
Contractor


Your post indicates your garbage disposal has a FLA of 6.7A.


430.53 Several Motors or Loads on One Branch Circuit
"Two or more motors or one or more motors and other loads shall be permitted to be connected to the same branch circuit under conditions specified in 430.53(A), (B), (C) or (D)....."

430.53(A) - "....motors...shall be permitted on a nominal 120v branch circuit protected at not over 20A....if all of the following conditions are met:
(1) The full-load rating of each motor does not exceed 6 amperes."


Am I misreading this section? Someone cited this code section when I said, "Show me".

As I understand this code section, you are permitted to have a motor and 'other' loads on the same 20A, 120v branch circuit IF the motor load does exceed 6A.