Cookers & RCD's

[Rick Hughes]

I started a thread about 2 months back over whether to have cooker on RCD or not ....

New cooker installed (Leisure 110 Classic dual Fuel range) and hooked up via an RCD .... all seemed to be working OK, except a few days into use we started using the grill .... each time 30 - 40 secs into use the RCD would trip.

Manufacturer sent out engineer today and he swapped the dual grill elements and problem cleared - did a quick impedance test on them, and they seem OK ... must be conductor moving and shorting to earth as it expands with heat.

The point to me telling you this - if it was not on an RCD I would not have witnessed this problem, and I guess we have 2 possibilities .... the element eventually failed early in life but outside of warranty and costs me money ... or it causes a fire and then lots of money.

So perhaps the discriminating trip circuits I discussed was not such a bad idea after all.

Rick

[Christian McArdle]

Many elements get damp in storage, which leads to internal earth leakage, enough to trip an RCD. The fix is to turn them on for half an hour to bake off the excess water. Without an RCD this would happen without you even noticing, but is complicated to do if the supply has an RCD, which would need to be bridged.

Christian.

[tony sayer]

In article , Christian McArdle writes

*How do they do that then?. Their made of metal and have sealed ends?....

[Andrew Gabriel]

Why do you assume you would not have witnessed this problem?

Hum, a grill element starting a fire? What part of it do you suppose might burn?

All that would have happened is the element would have burned out.

[Christian McArdle]

The insulation is mineral based (magnesium oxide, usually) and just loves to soak up water, despite the metal casing. It only needs to be used for a bit to expel the water. This is a well known phenonemon with this type of element. I imagine a large proportion of new (i.e. stored in a damp warehouse for 3 months) cookers would exhibit this problem if installed on an RCD circuit. Indeed, it is recommended not to install cookers on a 30mA RCD due to the likelihood of nuisance RCD trips.

Christian.

[Trevor Smith]

Another tip is to put the element in a hot oven to dry it through before installing it.

Trevor Smith

[tony sayer]

In article , Christian McArdle writes

The only time I have known then is when the cooker is of some age and when a heating element is about to go pop anyway, like our grill one did a year ago, advance warning as such;)

[Christian McArdle]

I can assure you it is common in heating appliances of any age that have not been used for some time. As using the appliance is the "cure", it is actually less likely to manifest in an installed appliance (that is regularly used) than a new appliance which sits unused in a damp warehouse.

Christian.

[Peter]

No its moisture in the element, when it heats up it turns to steam and trips the RCD nothing to do with element moving/expanding or near failure. The usual cure is to disconnect the earth on the cooker and dry out the element, use of the cooker will then keep it clear of this problem.

Peter