I have a holiday flat in Spain. The supply is 25A and it would be both difficult and expensive to upgrade. In addition to my incoming 25A breaker and 25A ELCB with the consumer unit in the flat, there is a limiting box outside by the meter. The idea of the box is to stop me using more than my contracted power.
My main problem is that if the oven is in use along with three or more of the rings on the ceramic hob the aformentioned box removes my supply for about 10 minutes.
What I would like to do is shed the power to the cooker when ever the hob draws more than either 15 or 20A. Thus saving me from loosing my supply.
I know that there are load shedding circuit breakers available. However the only ones I can find details of shed the load for 5 or 10 minutes which is far too long as I would wish the oven to be reconnected as soon as the thermostats turn off the elements on the hob.
Some one mentioned using a protection relay to remove the power to the oven when the hob current exceeded my 15A. The only ones of these I can find are designed for protecting motors.
Can anyone help me with finding the correct unit for either of these solutions or even suggest another way of achieving what I want?
Yes even the oldest of installations were 85A here in the UK. The more we use the more we pay. But in Spain you contract for a certain rate (in this case 3.3 or 5.5 KW or 15 & 25 A). Then pay a charge which increases with the contracted rate. For a higher current I would have to pay the supplier for the cable and gear to be replaced and contract for a higher rate.
I did not realise it was a US board mainly because I confused ECN with ECA (Electrical contractors association). However there may well be some well informed person who can give me an answer.
This may sound odd on a electrical forum , but if it were me, [and assuming this is a separate oven-hob worktop /counter setup], I'd take the easy option and dump the electric hob and fit a bottled LPG gas one instead, [Butano]. I believe you need to get the setup approved by a bottled gas supplier in Spain, [mandatory health and safety insurance inspection] when you sign the contract for bottle supply, which makes sense. The inspection is free. You'll be surprised at the speed, better performance and economy of gas, now on a par with electicity btu-v-btu. The whole setup with the new hob, regulator and a gas bottle will come in somewhere around €200 depending on model, and automatically unload your oven's electical demand. If you live in the flat [US = apartment] 365 dpy, I doubt you'd use two 13kg bottles pa.
If anyone has more information on 'load misers' I would be grateful. There are several web pages giving acounts of a home made miser but they seem to be light on details of actual sensors and relays used.
In reply to Alan. I had the flat inspected after purchase. The gas (Butano) installations were heavy critised. This has led me to put a new gas water boiler outside and change from the previous gas hob to an electric one and the start of my problem!! I don't wish to go back as my wife does not like gas or the smell of butane and I would also have to install extra ventilation when I am trying to cut draughts and would loose space in an already small kitchen storing the gas bottle. However I have retained the gas hob in the loft as a desperate last resort.
About a home-made solution, there is a current sensing relay that has an adjustable range. It's a small current transformer that slips over one conductor and has contacts built in; and, I'm pretty sure that you can find a normally closed contactor with a high enough rating for the non-preferred load. I've used these relays in condos to control exhaust fans when the dryer starts and to monitor exhaust fans in commercial kitchens. The set points aren't real accurate, but they have a range between 5 and 40 amps. I checked availability a couple weeks ago and, even here, they are only a day away. So, I assume they are everywhere.
If your power supply has wide fluctuations, you might consider adding in a timer so, when the relay cuts in, it holds the non-preferred load off for several seconds to prevent contact chatter.