Microwave ovens and isolated outlets

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#1624814 6-Sep-2016 21:07

solutionz:
"To turn this apparatus off completely, you must disconnect it from the wall outlet. Consequently, the wall outlet and power plug must be readily accessible at all times."

I wonder how closely that's followed though. Just thinking of the most obvious thing, the TV cabinet, have you ever seen any electrical connections on those that that are readily accessible? The whole point of the cabinet is to keep all that out of sight. So it seems like it's something that's either widely ignored, or has "readily accessible" defined in a very flexible manner (e.g. "readily accessible" means "accessible without the use of power tools, or more than ten minutes manual labour").

There'd also be a difference between "readily accessible with the powered device switched off" and "readily accessible with the powered device in flames" :-).

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#1624821 6-Sep-2016 21:30

neb:
solutionz:

"To turn this apparatus off completely, you must disconnect it from the wall outlet. Consequently, the wall outlet and power plug must be readily accessible at all times."

I wonder how closely that's followed though. Just thinking of the most obvious thing, the TV cabinet, have you ever seen any electrical connections on those that that are readily accessible? The whole point of the cabinet is to keep all that out of sight. So it seems like it's something that's either widely ignored, or has "readily accessible" defined in a very flexible manner (e.g. "readily accessible" means "accessible without the use of power tools, or more than ten minutes manual labour"). There'd also be a difference between "readily accessible with the powered device switched off" and "readily accessible with the powered device in flames" :-).

It's all about CYA; that clause limits manufacturer liability in the event of an accident, notwithstanding being sensible advise.

As an end user you can choose to accept the risk and ignore it however commercial kitchen fitters, electricians etc have a duty to follow cautionary advise labels, obtain SDoCs etc.

nigelj

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#1624848 6-Sep-2016 22:27

Our Microwave is in a cubby directly above an "appliance garage", which is in turn just right of the fridge, so what we have is a PDL double switch (i.e. the light switch types) in the back of the appliance garage one disconnects the Fridge power, the other does the Microwave since the power sockets for both would be generally awkward to access.

This was a design implemented by Kitchen Studio & their contractors numerous years ago.

Bung

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#1624866 7-Sep-2016 00:24

In AS/NZS 3000 the clause requiring a readily accessible switch beside open cook tops has a sub clause making it clear that this requirement does not apply to enclosed ovens or microwave ovens.

I don't think the electrical safety standards were written with ease of being able to stop the drain of built in clocks and standby circuits as a priority but I'm not an electrician.

mdooher

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#1624881 7-Sep-2016 07:47

solutionz:

Having just taken a product though standards testing I can tell you that "Household and similar electrical appliances" are required to have an accessible means of disconnection ("isolation") for safety being either:

A) Approved appliance mains inlet switch (microwaves don't usually have these).

B) Physical disconnection from supply lead (microwaves usually have fixed lead)

C) Physical disconnection from mains outlet (probably inaccessible due to inset cabinet).

D) Approved mains outlet switch (your only remaining option).

Yes @neb same goes for all those other appliances. The approved user manuals will all contain a clause to the effect of:

"To turn this apparatus off completely, you must disconnect it from the wall outlet. Consequently, the wall outlet and power plug must be readily accessible at all times."

The appliance approval standard relates to the appliance and in this case "accessible" means you can't direct wire it (like a towel rail) and not have a switch somewhere. There is a big difference between "accessible" (normally able to be accessed without tools) and "readily accessible".

The placement of any socket outlets within the electrical installation is outside its scope. Consequently you can put a socket outlet behind your TV, in the ceiling space to run a masthead amplifier, in the cupboard under a sink to run your dishwasher and waste disposal , and yes even behind your microwave. The user manuals may say something else...but fortunately Sony, Haier and Panasonic don't write our laws.

Don't forget, you can always turn the appliance off at the circuit breaker or main installation isolator if you really need to.

Matthew

mdooher

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#1624883 7-Sep-2016 07:53

Bung: In AS/NZS 3000 the clause requiring a readily accessible switch beside open cook tops has a sub clause making it clear that this requirement does not apply to enclosed ovens or microwave ovens.

I don't think the electrical safety standards were written with ease of being able to stop the drain of built in clocks and standby circuits as a priority but I'm not an electrician.

Correct, the hob isolator is only required because in the event of a fire on the hob you may not be able to reach the element switch. This is why the isolator is not allowed to be directly behind the hob.

As an interesting aside, the standard also states that an isolation switch should not be used under load (this exam question comes up almost every year)... So what is the point of the hob isolator then?

Matthew

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#1624900 7-Sep-2016 08:19

mdooher:

The appliance approval standard relates to the appliance and in this case "accessible" means you can't direct wire it (like a towel rail) and not have a switch somewhere. There is a big difference between "accessible" (normally able to be accessed without tools) and "readily accessible".

The placement of any socket outlets within the electrical installation is outside its scope. Consequently you can put a socket outlet behind your TV, in the ceiling space to run a masthead amplifier, in the cupboard under a sink to run your dishwasher and waste disposal , and yes even behind your microwave. The user manuals may say something else...but fortunately Sony, Haier and Panasonic don't write our laws.

Don't forget, you can always turn the appliance off at the circuit breaker or main installation isolator if you really need to.

Refer my last comment. It follows as such:

- It is "our law" which requires most appliances to be approved under a relevant test standard.

- Most of the relevant test standards including AS/NZS 60335 for Household & Similar Appliances require an approved method of disconnection.

- Simplest way for manufacturer to meet this requirement is by putting the appropriate the clause in the user manual requiring accessible outlet to be unplugged / switched off when not in use etc.

- The user manual forms part of the approval and must be supplied with the product (with the intention that all cautionary advise is followed).

- As above, most users choose to ignore some of this advise however it would be a risky move for a commercial operator to do so as they would be incurring relevant liability. (Just like how a Mr Joe Homeowner can freely change a light fitting but Mr Sparky required SDoC's for his CoC's).

- The rationale behind independent standards testing is that it also limits liability of the manufacturer. "We manufactured our product independently tested to your country's approved standard and someone got hurt? Either your standard is flawed or the user didn't follow the instructions."

[Source: Registered electrical worker & have recently taken a product through this process.]

Not saying this is rationale of the the kitchen fitters, they may have other reasons, however it ought to be a consideration.

@Bung: AS/NZS 3000 is irrelevant to this as it relates to fixed wired installations.

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#1624908 7-Sep-2016 08:49

mdooher:

As an interesting aside, the standard also states that an isolation switch should not be used under load (this exam question comes up almost every year)... So what is the point of the hob isolator then?

Have you noticed that sometimes when you turn a switch off you see a spark, that's a load been broken, it causes ionisation which under high loads can cause a flash over. A switch may be rated at lets say 10amps which means it can carry 10amps under normal operating conditions, but it MAY NOT be rated for load breaking at 10amps, this is where "circuit breakers" come in to place, they are rated as load break switches (although they are set to automatically break the load under certain conditions).

mdooher

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#1624911 7-Sep-2016 08:58

solutionz:

- Most of the relevant test standards including AS/NZS 60335 for Household & Similar Appliances require an approved method of disconnection.

Yep this... and an approved method of disconnection is an "accessible" plug on the end of a cord...not a "Readily accessible" plug. So if you are planning on putting the microwave on a shelf with the plug behind it that's fine. Putting trim around it so you can't access the plug without...different.

The reason we don't need to follow the manufactures instructions is because they become so risk averse they put things in like "always turn of your appliance at the wall when not in use" and "don't use your keyboard for long periods" and "never use your weed-eater in wet grass" (I'm not joking) and my personal favorite "always wear safety glasses when using a screwdriver"

Matthew

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#1624914 7-Sep-2016 09:11

Aside from the legalities it's practical to have an isolation switch for the microwave somewhere, accessible.

This doesn't need to be a separate switch plate. When we redid the kitchen in our former house the isolation switches (3) were able to be installed as a third, labelled switch on double outlet plates on the splash-back.

Mike

mdooher

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#1624915 7-Sep-2016 09:11

gregmcc:

mdooher:

As an interesting aside, the standard also states that an isolation switch should not be used under load (this exam question comes up almost every year)... So what is the point of the hob isolator then?

Have you noticed that sometimes when you turn a switch off you see a spark, that's a load been broken, it causes ionisation which under high loads can cause a flash over. A switch may be rated at lets say 10amps which means it can carry 10amps under normal operating conditions, but it MAY NOT be rated for load breaking at 10amps, this is where "circuit breakers" come in to place, they are rated as load break switches (although they are set to automatically break the load under certain conditions).

A switch that is rated at 10 amps is most definitely rated to switch 10A. This is why some are rated say 10Aac or only 10Adc or not for inductive loads etc

an "isolator" may not be rated to switch the full load current... but an "isolating switch" is

What I am getting at is, if the hob isolator isn't rated to break the full load current of the hob... this being the switch you use when you can access the element switch because it is on fire...then...

Matthew

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#1624917 7-Sep-2016 09:13

mdooher:

The reason we don't need to follow the manufactures instructions is because they become so risk averse they put things in like "always turn of your appliance at the wall when not in use" and "don't use your keyboard for long periods" and "never use your weed-eater in wet grass" (I'm not joking) and my personal favorite "always wear safety glasses when using a screwdriver"

Yeah we had to put lots of lovely statements on our product such as;

- "Must only be moved by trained professionals" (Otherwise we had to put lifting instructions etc and would be liable for customer injury.)

- "Must be securely mounted by a qualified engineer" (Relating to wall mounting.)

MikeB4

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#1624942 7-Sep-2016 09:51

Thanks guys for all the interesting info, home improvements are a minefield and why I always use professionals.

Next challenge doing all the work that trades don't do in my condition

richms

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#1624968 7-Sep-2016 10:16

Just stick in a socket on the counter with an extra switch on it for the microwave. You can even splash out on the marked one that says microwave on it if you really want.

Its useful to turn them off when you are cleaning them etc and want to leave it open to dry out without the light running all night.

Richard rich.ms

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#1624976 7-Sep-2016 10:37

Just for clarity (I hope): A switch and an isolator are different things. A switch has to be able to break the full load current. An isolator is designed to make a device safe - it is made so that in the OPEN position the contacts must be physically separated.

Most switches are also isolators but not always. You can't assume that a switch sitting in the OFF position has made a circuit safe. For example if the contacts are welded together it might still be possible to move it to the OFF position. An isolator won't let you do that.

A cooking device has to have a SWITCH, not an isolator.

Similarly a light SWITCH is not necessarily isolator - something to keep in mind when you change a lamp.

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