House ampage increase??

'68 Fastback

Hi all,

I've recently installed a ceramic kiln(oven for pottery, fires to about 1300c) in my pottery workshop at home. Its a single phase kiln and is rated for 6kw but its tripping out before it reaches full temperature. The kiln runs off the house supply.

I've heard that its possible to have the supply increased in a residential home witout having to go for the full 3 phase conversion. Is this true? Is it a big job?

Thanks

Jnealon

Thats roughly 30 amps, what is the breaker rated at on the fuseboard.
My guess is that the circuit is under rated

Randyleprechaun

6KW should not pose any problem to your existing supply.

Most showers are up on 9 and 10KW afterall.

You should be using 6mm2 cable connected to a 32A SP B MCB.

2011

The resistance of the heating element increases as it gets hotter. When you turn it on first the lower resistance of the element causes a higher current to flow. The chances are this higher initial current is causing you this problem (assuming that the MCB is sized correctly). Once it is up to temperature the current drawn would be reduced. If the MCB was a C type rather than the domestic standard B type it would help. A lower earth fault loop impedence value is required for a C type which is code for you may need a larger earth cable.

6 kW is 26.1 Amps for a pure resistive load, which is pretty much what you have. If a 32A B type MCB is not doing the job for you I would try a 32 A C type. Cable size should be a minimum of 6 mm^2

'68 Fastback

Thanks for the quick responses.

I'll have to check everyting again to be double sure.
I replaced some broken elements with new ones that the previous owner had bought, so i think that they might be too heavy a gauge and pulling more power than the original ones. TBH its an old kiln and I have to replace all the cabling at the back as the insulation has perished with the heat so there are a few other things to try.

M cebee

i've wired a few .

don't recall using C types- but there may be an 'inrush'

there's prob a big saving to be made on dual-tarriff(i'm dubious about the domestic dual-tarriff idea)-industry is different

sustained heating load anyhow so all switches etc. need to be well-rated

M cebee

2011 wrote: »

The resistance of the heating element increases as it gets hotter. When you turn it on first the lower resistance of the element causes a higher current to flow. The chances are this higher initial current is causing you this problem (assuming that the MCB is sized correctly). Once it is up to temperature the current drawn would be reduced. If the MCB was a C type rather than the domestic standard B type it would help. A lower earth fault loop impedence value is required for a C type which is code for you may need a larger earth cable.

6 kW is 26.1 Amps for a pure resistive load, which is pretty much what you have. If a 32A B type MCB is not doing the job for you I would try a 32 A C type. Cable size should be a minimum of 6 mm^2

immersion heaters (for sure) and storage heaters afair you can do the basic v2/r with a multimeter to get the wattage.

light bulbs- there's an inrush so 'cold resistance' is much lower

2011

immersion heaters (for sure) and storage heaters afair you can do the basic v2/r with a multimeter to get the wattage.

light bulbs- there's an inrush so 'cold resistance' is much lower

My point is that a higher current will flow if resistance is lower if everything else remains equal. It is not as dramatic as a motor starting. I am suggesting that if the MCB is sized correctly that this might be the reason. The cold resistance of an immersion and a buld is less that the hot resistance. The resistance of most conductors increases as their temperature increases.

If you were to put three 500 watt halogen lamps on one switch on one circuit there is a good chance that switching them on together would trip a 10A B type MCB. Why is this, they only draw 6.5 amps? It is because their combined cold resistance is so low.

2011

http://www.creative-science.org.uk/RS3therm.html

The link above shows how the fact that a tungsten lamp's element changes resistance with temperature can be used to measure temperature.

'68 Fastback

Thanks again for the responses.

Had a mate measure how much the Kiln is pulling over the weekend, 70amps with the new elements!! We put back some of the old but working elements and got it down to 50ish, so its definately the gauge of the new elements. The Kiln worked untill the new elements went in.

2011

OK that explains it! Your main fuse is normally 63 amps

Bruthal

2011 wrote: »

My point is that a higher current will flow if resistance is lower if everything else remains equal. It is not as dramatic as a motor starting. I am suggesting that if the MCB is sized correctly that this might be the reason. The cold resistance of an immersion and a buld is less that the hot resistance. The resistance of most conductors increases as their temperature increases.

If you were to put three 500 watt halogen lamps on one switch on one circuit there is a good chance that switching them on together would trip a 10A B type MCB. Why is this, they only draw 6.5 amps? It is because their combined cold resistance is so low.

Lamps are a bit different, they go from cold to white hot almost instantly and are rated at the hot running wattage. Heating elements are rated at the cold resistance i would of thought. Anytime ye measure the resistance of an immersion element it is at the rated wattage. An incandescent bulb is of a higher starting current order than a motor. I think a 60w bulb has about 60 ohm impedence, that would be 4 amps, which would be nearly a kw. But this reduces far faster than a motor start current would, (the start currents in motors and bulbs are for completely different reasons obviously)
I would`t say the heating elements of cookers or ovens would change near as much as an incandescent bulb filiament anyway. Would be an interesting test.
A normal 32 amp breaker and dedicated 6 square circuit and it should be fine with this oven/kiln