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#146238 - 11/20/06 03:14 AM Timed circuits for stoves & ovens  
32VAC  Offline
Joined: Jun 2004
Posts: 202
Alice Springs, NT, Australia
Recent discussions with electricians in Central Australia bought up an interesting topic regading the installations of timers for stoves & hotplate circuits in dwellings located in remote communities.

The reason this is being done was two-fold: firstly for safety where people were leaving the cooking appliances on & going to town & also to reduce the occurance of clocking up large power bills as most of these dwellings are fitted with credit power meters.

The wiring is centered around a contactor for the control of the supply to the cooking appliances. A two hour timer is installed in the kitchen where the occupants press the button to operate the timer, which in turn operates the contactor to supply the power to the cooking appliances.

Has anyone else ever seen such a set-up used elsewhere? An isolating switch is still used as in a normal installation to interrupt the power if the need arises (maintenance or fire for example)

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#146239 - 11/20/06 06:39 AM Re: Timed circuits for stoves & ovens  
pauluk  Offline
Joined: Aug 2001
Posts: 7,520
Norfolk, England
Stoves with integral timers to turn the oven on and off at preset times have been used here for decades, but I've never seen anything like the system you describe.

#146240 - 11/20/06 11:38 AM Re: Timed circuits for stoves & ovens  
EV607797  Offline
Joined: Oct 2006
Posts: 745
Fredericksburg, VA, USA
I have done something similar to this, but it was for safety reasons. A family had an elderly parent living in a basement apartment who was continously leaving the oven on after using it. We installed a wall-type one hour timer that controlled a contactor at the panel. She would just turn the timer on and she then had one hour to do her cooking. If she needed more time, she could just turn the timer up, so this insured that she would have to stay nearby when cooking.


"But the guy at Home Depot said it would work."

#146241 - 11/20/06 03:37 PM Re: Timed circuits for stoves & ovens  
djk  Offline
Joined: Dec 2002
Posts: 1,237
Sounds like a sensible sollution.

We purchased a fairly sophisticated induction hob for an elderly relative because of safety concerns too.
It has a lot of safety features:

1) It can detect boiling over and will stop heating.
2) It will not allow you to leave it on if there is no pot/pan present. (there's nothing to pick up the magnetic field)
3) It can detect boiling dry / and will cancel cooking
4) Limited residual heat (only the pot/pan gets hot)
5) In the even to of a fire (oil) the cooking surface isn't too hot and also the unit will detect a sudden temprature rise and cancel cooking.

I know it might be a pricy alternative, but if there is no cost limitation they're actually a very safe alternative to traditional gas or radiant/conduction based electric cookers.

#146242 - 11/21/06 12:17 AM Re: Timed circuits for stoves & ovens  
EV607797  Offline
Joined: Oct 2006
Posts: 745
Fredericksburg, VA, USA
Yes, induction cooking is likely to be the wave of the future IF the prices for the appliances come down. Many commercial kitchens use this now in my area, mostly national chains since they are the only customers who can afford them. Some of our school systems are also using them.

Since they are nearly 100% efficient, it doesn't take a rocket scientist to understand the 30%+ increase in efficiency over other burner types. Believe it or not, gas is only 68% efficient, long-believed to be the best. Heating with induction provides true instant heat and the heat stops the second that the pot/pan is removed. Precision control is provided down to the single-degree level.

Unfortunately, I priced out a new range for my home with an induction cooktop and it was nearly three-times the cost of a standard radiant smooth-top. Even though this technology has been around for quite a while, it wasn't until natural gas prices spiked dramatically that interest in induction cooking got the people paying the bills to take another look.

My son is attending a culinary arts program and they have a separate class for this. They developed this class to learn the difference between gas and induction cooking. He said it's pretty amazing, but similar to driving a stick-shift vs: automatic transmission. They are learning to "dance the pan" so that 100% contact isn't made until they get used to it. Since induction is a lot faster, they have to be careful about burning the food.

I have seen them demonstrated, I have connected these cooktops using traditional cooktop wiring, and I have even tried using them at a home/kitchen show. It is absolutely amazing. Not only is it just about as efficient as you can get, but it's amazingly safe and completely fool-proof.

By the way, I do not sell these cooktops, I simply speak from my exposure to them.

[This message has been edited by EV607797 (edited 11-21-2006).]

[This message has been edited by EV607797 (edited 11-21-2006).]


"But the guy at Home Depot said it would work."

#146243 - 11/21/06 12:28 AM Re: Timed circuits for stoves & ovens  
aussie240  Offline
Joined: Jul 2005
Posts: 223
Blue Mountains, NSW, Australia
I've been using a time switch with electric blankets for years. It eliminates the problems of accidentally leaving them on and the associated fire hazard.
What I have contemplated with other heating appliances which are not used at set times, such as fan heaters, soldering irons etc, is a PIR sensor that keeps resetting a timer (say for 15 mins). This would be located in the room where the appliance is located so that while ever someone was 'supervising' the appliance it would work normally. If they left the room and forgot about it, then it would be disconnected. As we know, it's the unattended appliances that cause the most damage.

#146244 - 11/21/06 03:32 PM Re: Timed circuits for stoves & ovens  
C-H  Offline
Joined: Sep 2002
Posts: 1,497
Stockholm, Sweden
I've seen similar setups in Sweden. A timer for the stove is now standard in kitchens that will be used by senior citizens.

The exact reasoning has already been given by EV607797. :-)

#146245 - 11/22/06 01:52 AM Re: Timed circuits for stoves & ovens  
Trumpy  Offline

Joined: Jul 2002
Posts: 8,223
SI,New Zealand
What is it we need here?.
A timer to turn a load off in case no human intervention occurs?,
Or should we be looking at the real cause, is that people forget to turn things off if they may suffer from the early stages of dementia.
We will all get old, that is for sure, some of us could be run over by a bus tomorrow too.
There was a system here that included a smoke detector and a contactor that shut off the power to a range and any other such loads.
I just can't remember the brand name of it.
As a Fire Officer, this concerns me some, not because of the fire risk, but because if a person walks out of a block of flats with the range still going, to do the shopping, could that person also be driving a vehicle?.
I'm not trying to be funny at all here, there have been "doubles" like this here before.
By Double I mean 2 incidents related to the same person.

#146246 - 11/22/06 10:15 AM Re: Timed circuits for stoves & ovens  
32VAC  Offline
Joined: Jun 2004
Posts: 202
Alice Springs, NT, Australia
The dwellings are of besser-block (concerte "breeze blocks") with tin roof construction with usually 3 to 5 bedrooms depending on the occupants place in the tribal structure.

The tribal Elders take off for days at a time on "walkabout" for hunting & gathering. Most cooking is done on an open fire (goannas, kangaroos & wallabies)
with the occasional beef dish done in the oven or on the hotplates.

Modern life hasn't quite reached some of the remote communities of Central Australia as quick as petrol sniffing & alochol has so measures have been put in place to help the homes occupants see another day. Sad story but true...

[This message has been edited by 32VAC (edited 11-22-2006).]

#146247 - 11/27/06 03:36 AM Re: Timed circuits for stoves & ovens  
kiwi  Offline
Joined: Dec 2004
Posts: 354
christchurch new zealand
32VAC, sad story indeed.

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