dishwasher/disposal

[kwired]

Personally, I call it a design issue. Poor design = poor performance. Article 90 is pretty blunt- the NEC is about a practical, minimum amount of safety- and not at all interested that things work well.

It is a design issue. Having a dishwasher and disposer on the same branch circuit is not necessarily a poor design in most cases. I have seen it done countless times and can not recall ever having performance issues, so what does it take for it to be a poor design?

The circuit possibly draws more than 20 amps fully loaded, but this seldom happens and when it does it is for a very short time.

 

[Gregg Harris]

Here is what it said in 1987 NEC:


Here is what it said in 1993 NEC:


I don't have 1990 NEC but I think it was similar to 1987 wording.
1996 wording is similar to 1993 wording.

For some reason I can't find my 1999 NEC so I don't know what is in there.

2002 wording is similar to what is in 2011 and is likely similar in those between.

So we have gone from NEC telling us what kind of cord is acceptable to the manufacturer telling us what cord is acceptable, and just like the classified breaker issue, why would the manufacturer suggest anything but what they sell? There is a good chance many manufacturers all have their acceptable cords made at the same place to the same specifications, only difference is the name on the packaging.:happysad:

1990 is when the listing of the type of cord that could be used, SE,SEO,SO, etc. under 428-8(d)(1)

1992
422.16 Flexible Cords. (A) General. Flexible cord shall be permitted (1) for the connection of appliances to facilitate their frequent interchange or to prevent the transmission of noise or vibration or (2) to facilitate the removal or disconnection of appliances that are fastened in place, where the fastening means and mechanical connections are specifically designed to permit ready removal for maintenance or repair and the appliance is intended or identified for flexible cord connection.

(B) Specific Appliances.

(1) Electrically Operated Kitchen Waste Disposers. Electrically operated kitchen waste disposers shall be permitted to be cord-and-plug connected with a flexible cord identified as suitable for the purpose in the installation instructions of the appliance manufacturer, where all of the following conditions are met.

(1) The flexible cord shall be terminated with a grounding type attachment plug.

Exception: A listed kitchen waste disposer distinctly marked to identify it as protected by a system of double insulation, or its equivalent, shall not be required to be terminated with a grounding-type attachment plug.

(2) The length of the cord shall not be less than 450 mm (18 in.) and not over 900 mm (36 in.).

(3) Receptacles shall be located to avoid physical damage to the flexible cord.

(4) The receptacle shall be accessible.

(2) Built-in Dishwashers and Trash Compactors. Built-in dishwashers and trash compactors shall be permitted to be cord-and-plug connected with a flexible cord identified as suitable for the purpose in the installation instructions of the appliance manufacturer where all of the following conditions are met.

(1) The flexible cord shall be terminated with a grounding-type attachment plug.

Exception: A listed dishwasher or trash compactor distinctly marked to identify it as protected by a system of double insulation, or its equivalent, shall not be required to be terminated with a grounding-type attachment plug.

(2) The length of the cord shall be 0.9 m to 1.2 m (3 ft to 4 ft) measured from the face of the attachment plug to the plane of the rear of the appliance.

(3) Receptacles shall be located to avoid physical damage to the flexible cord.

(4) The receptacle shall be located in the space occupied by the appliance or adjacent thereto.

(5) The receptacle shall be accessible.

(3) Wall-Mounted Ovens and Counter-Mounted Cooking Units. Wall-mounted ovens and counter-mounted cooking units complete with provisions for mounting and for making electrical connections shall be permitted to be permanently connected or, only for ease in servicing or for installation, cord-and-plug connected.

A separable connector or a plug and receptacle combination in the supply line to an oven or cooking unit shall be approved for the temperature of the space in which it is located.



Range hoods added to cord and plug for 2005

2008
422.16 Flexible Cords. (A) General. Flexible cord shall be permitted (1) for the connection of appliances to facilitate their frequent interchange or to prevent the transmission of noise or vibration or (2) to facilitate the removal or disconnection of appliances that are fastened in place, where the fastening means and mechanical connections are specifically designed to permit ready removal for maintenance or repair and the appliance is intended or identified for flexible cord connection.

It should be understood that a cord-connected appliance is required to be specifically designed, mechanically and electrically, to be readily removable for maintenance and repair.


(B) Specific Appliances.

(1) Electrically Operated Kitchen Waste Disposers. Electrically operated kitchen waste disposers shall be permitted to be cord-and-plug-connected with a flexible cord identified as suitable for the purpose in the installation instructions of the appliance manufacturer, where all of the following conditions are met:


(1)

The flexible cord shall be terminated with a grounding-type attachment plug.

Exception: A listed kitchen waste disposer distinctly marked to identify it as protected by a system of double insulation, or its equivalent, shall not be required to be terminated with a grounding-type attachment plug.

(2)

The length of the cord shall not be less than 450 mm (18 in.) and not over 900 mm (36 in.).

(3)

Receptacles shall be located to avoid physical damage to the flexible cord.

(4)

The receptacle shall be accessible.

 

[Blaer]

I've taken a liking to Reno - his posts seem to me like they were written by another woman. Maybe that's why you guys sometimes can't seem to catch his (?) points.

When he posted "Poor design = poor performance," it sounded to me like it was a general statement, and not anykind of implied criticism of any particular practice. Like he meant to say 'if you make the wrong call, you'll hear about it.' It's still your call to make.

That's how i read it.

 

[tortuga]

I can not see in the code an exemption of a Disposal from art 430.
If I am not corrected here next;
If I was inspecting a disposal and a DW on a shared 20A circuit weather both are hard wired or cord and plug:
I would look at the HP of the disposal and see that it is probably between 1/5 and 1/2 HP
that's 7.2 to 9.8A per T4230.248
Next I would cite the disposal in violation of 450.53 (A)(1).

[QUOTE="2011 NEC (C) NFPA]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(D) and in 430.53(A),
(B), or (C). The branch-circuit protective device shall be
fuses or inverse time circuit breakers.
(A) Not Over 1 Horsepower. Several motors, each not ex-
ceeding 1 hp in rating, shall be permitted on a nominal 120-
volt branch circuit protected at not over 20 amperes or a
branch circuit of 600 volts, nominal, or less, protected at not
over 15 amperes, if all of the following conditions are met:
(1) The full-load rating of each motor does not exceed 6
amperes.
[/QUOTE]

 

[kwired]

I can not see in the code an exemption of a Disposal from art 430.
If I am not corrected here next;
If I was inspecting a disposal and a DW on a shared 20A circuit weather both are hard wired or cord and plug:
I would look at the HP of the disposal and see that it is probably between 1/5 and 1/2 HP
that's 7.2 to 9.8A per T4230.248
Next I would cite the disposal in violation of 450.53 (A)(1).

If the disposer is allowed to be cord and plug connected with a 5-15 cord cap what code section prohibits the receptacle from being on a 20 amp circuit other than if it is a single 15 amp receptacle?

Now "direct wire" same disposer and you may be able to claim that violation, even though it doesn't seem to make a lot of sense.

I also still think that 430.53(B) would still allow the install.

Funny thing here is between 430.53(A)(1) and 430.53(B), 120 volt motors would need to be 6 amps or less under (A)(1), but under (B) they would have to be 8 amps or more to be on a 20 amp circuit, so it appears anything between 6 and 8 amps on a 120 volt circuit is not allowed on a multiple motor circuit between those two sections, but either up to 6 or 8-20 amps is allowed?

 

[renosteinke]

I disregard the 'horsepower' rating on disposals, just as I ignore the markings on power tools.

There is more pure poppycock in horsepower ratings than in any other rating. Even with "real" industrial motors, even the reputable motor manufacturers have no qualms about deliberately ms-labeling motor nameplate horsepower.

I've had to replace far too many industrial motors where the motor maker has provided 'identical replacements' with entirely different ratings. With consumer products, the horsepower rating is pure marketing fiction.

Instead, I go by the FLA - then pick the horsepower in the chart that matches. That's the only way I can reconcile plugging most any Craftsman power tool into an ordinary 15-A receptacle.

 

[tortuga]

I would need more info on there UL listing of dishwashers to see anything other than 430.53(A) fitting.

I disregard the 'horsepower' rating on disposals, just as I ignore the markings on power tools.

I think that is what 430.6 Ex NO. 2 is about.

The disposal and DW fall under 430.6 Ex NO. 3 so going with the nameplate is fine no need to go to the tables.

I also still think that 430.53(B) would still allow the install.

Funny thing here is between 430.53(A)(1) and 430.53(B), 120 volt motors would need to be 6 amps or less under (A)(1), but under (B) they would have to be 8 amps or more to be on a 20 amp circuit, so it appears anything between 6 and 8 amps on a 120 volt circuit is not allowed on a multiple motor circuit between those two sections, but either up to 6 or 8-20 amps is allowed?

It took me a second to see how you got to 8A 20A/250% = 8A
That little red button on the bottom of disposals apears to be overload protection so I see (B) would apply if the DW pump is protected internally.

(C) Other Group Installations. Two or more motors of
any rating or one or more motors and other load(s), with
each motor having individual overload protection, shall be
permitted to be connected to one branch circuit where the
motor controller(s) and overload device(s) are (1) installed
as a listed factory assembly and the motor branch-circuit
short-circuit and ground-fault protective device either is pro-
vided as part of the assembly or is specified by a marking on
the assembly, or (2) the motor branch-circuit short-circuit

Looking at the underlined part I think (C) would apply. As long as the Dishwashers pump motor has short-circuit and ground-fault protective device part of the UL listing.

430.42 if in fact the DW and disposal have an overload device that is "required".
Perhaps it is required by the paragraph (1) of 430.53(C) quoted above?

(C) Cord-and-Plug-Connected. Where a motor is con-
nected to a branch circuit by means of an attachment plug
and a receptacle or a cord connector, and individual overload
protection is omitted as provided in 430.42(A), the rating of
the attachment plug and receptacle or cord connector shall
not exceed 15 amperes at 125 volts or 250 volts. Where indi-
vidual overload protection is required as provided in
430.42(B) for a motor or motor-operated appliance that is
attached to the branch circuit through an attachment plug
and a receptacle or a cord connector, the overload device
shall be an integral part of the motor or of the appliance. The
rating of the attachment plug and receptacle or the cord con-
nector shall determine the rating of the circuit to which the
motor may be connected, as provided in 210.21(B).

So to go back to the original topic question I now think it is all hinging on the dishwasher Pump motor having overload protection and Ground Fault protection provided by appliance (since we can see the reset button on the disposal).

I have run into issues with small pumps and this 430.53(A) in the past so thats what made me think of it.

 

[kwired]

I did not review before posting, but we also need to remember that a dishwasher falls under 422 appliances. Some parts of 422 do send you to art 430. Whether or not the disposer is strictly a 430 application or if it is a 422 application is not really all that clear (I think) what is printed on nameplate and any listings maybe are determining factors?

I did look again at the art 100 definition of appliance - and it would seem to me that unless you had a one of a kind disposer that they are covered by that definition.

Appliance. Utilization equipment, generally other than industrial, that is normally built in standardized sizes or types and is installed or connected as a unit to perform one or more functions such as clothes washing, air conditioning, food mixing, deep frying, and so forth.

 

[tortuga]

Good point.

422.3 Other Articles
The requirements of Article 430 shall apply to the installa-
tion of motor-operated appliances, ..<snip>.., except
as specifically amended in this article.

Looks like 430 does apply however 422.11(G) requires our dishwasher to have overload protection:

(G) Motor-Operated Appliances. Motors of motor-
operated appliances shall be provided with overload protec-
tion in accordance with Part III of Article 430....<snip>

So if we can meet 430.53(C) were good
However the logic in that first sentance in 430.53(C) is confusing
The sentance is broken up into 1 or 2 and 3
The way I am reading the logic in that first sentance is if item 1 is true then we are good, even if 3 is false, since 3 can only be invoked by 2.

The OP states he is going to a split duplex receptacle:

... jbox undersink with a split recept, switched on one hot on the other.Pigtails through the cabinet. First time I've ever heard this request.

Based on that I think the answer to his question:

where in nec does it state garbage disposal and dishwasher can't share a circuit, or that I must provide one for that matter?

I stand corrected it is allowed.

 

[Gregg Harris]

I did not review before posting, but we also need to remember that a dishwasher falls under 422 appliances. Some parts of 422 do send you to art 430. Whether or not the disposer is strictly a 430 application or if it is a 422 application is not really all that clear (I think) what is printed on nameplate and any listings maybe are determining factors?

I did look again at the art 100 definition of appliance - and it would seem to me that unless you had a one of a kind disposer that they are covered by that definition.

Both disposals and dishwashers fall under 422 appliances and both are required to have thermal overload protection.
Garbage disposals manual under UL 430 and automatic for dishwashers under UL 749.