Joining 4 x 10mm conductors?

[Vortigern]

The thing about kilns is they are very demanding current wise in the sense that they draw full current for hours at a time while getting up to temperature so the supply cable must really be adequate for this. While you would be getting circa 20a per phase on three phase you would notionally be drawing 52 amps on a single phase. The last kiln I put in it seemed by calculation I should use 6mm for a 35a load. I went up to 10mm as the manufacturer recommended that size.

 

[pc1966]

Yes, on reflection I would be replacing the flexible lead and having L1-L2-L3 linked in the kiln, instead of joining cores (unless it really is 10mm already).

What I wonder is the choice of cable. H07RN-F is usually 60C max which seems low for an oven/kiln, even if it is far from the heated section as I expect it gets pretty warm inside!

6242B is avaiable to 10mm and rated to 90C but not that flexible, so if it is fairly static like a cooker then maybe that would be acceptable?

I know you can get silicone rubber flex but personally never seen it above about 2.5mm which ain't going to do 52A.

 

[Mike Johnson]

I don't know anything about Kilns, but should not the heat be inside, so the cable should not see that type of temperature?

Just a thought.

 

[pc1966]

Sure it won't be the 400C or whatever is inside! But I imagine it is going to be warm still. Maybe there is something on the specs or drawing to indicate what rating of cable is needed?

 

[HappyHippyDad]

Sure it won't be the 400C or whatever is inside! But I imagine it is going to be warm still. Maybe there is something on the specs or drawing to indicate what rating of cable is needed?

1800°C... pretty hot!

 

[HappyHippyDad]

Usually on dual types of supply like that i.e. three phase/single phase, there is a plate inside the equipment that lets you configure the wiring for single phase supply or three phase, so that you get a two core and earth supply and reconfigure the links inside the appliance rather than try to link one single phase wire to the five core cable. So at your switch you would have a cable coming out from say a rotary isolator straight to the appliance. From there you would have a cable that would go directly to the links. Configuring the links is key to this. Or...three phase rotary isolator and the five core goes into that with a link to each of the L1-L2-L3 at the supply side. I suspect you need to link at where that five core goes to and inspect the arrangement. I have been caught out by this before by assuming the links were configured for three phase and they weren't. So you would need to see how the links are configured and be sure you are linking in properly.

Thanks Vortigern. I'm guessing this plate would have be located on the 4 way connector block in the picture below? is this something that is usually removeable (i.e able to be lost), or attached to the block permanently?



Now my next question is going to be is there some kind of 60A + copper link available? Just like you have in cookers sometimes. This will be much neater than a separate junction box joining the 5 core cable to 3 core.

 

[Dave OCD]

If you're using a 60 amp rotary isolator HHD you could quite possibly connect the flex as you normally would on the outgoing side to L1,L2,L3 and N but link out L1,L2 and L3 on the incoming supply side. Although even at 60 amp rating those isolators aren't exactly roomy inside.

 

[HappyHippyDad]

If you're using a 60 amp rotary isolator HHD you could quite possibly connect the flex as you normally would on the outgoing side to L1,L2,L3 and N but link out L1,L2 and L3 on the incoming supply side. Although even at 60 amp rating those isolators aren't exactly roomy inside.

Now that's an idea ?
Thanks Dave.

 

[Vortigern]

Now that's an idea

Yeh he pinched from my script earlier

 

[Vortigern]

Actually it would be good to see that plate in picture form on the kiln. I think you need to change the 5 core cable to 2 core and earth 10mm or 16mm (??) to be totally safe. You might find that the plate/link is already on there and just has to be moved. The cable on the kiln is 90c cable flexible. So if you bought that it would be quite expensive to be sure. There must be a lot of heat radiated as the kiln manufacturer said you must have 18 in space all around the kiln so no wonder 90c cable. The rotary isolator is a Scame and plenty of room to do whatever you decide inside it.

 

[HappyHippyDad]

Yeh he pinched from my script earlier

I've just re-read yours more thoroughly. You did indeed mention that! Thankyou ?

 

[Lucien Nunes]

If there are links they will probably be ordinary flat bits of brass with two holes, like the links in a motor terminal box. You could make your own.

Thinking about the cable and my earlier comment about flexible conduit, I would probably still do it that way. Galvanised flexible with tri-rated singles, rated to 105 deg.C but also resistant to burns if something hot touches the exterior.

 

[Dave OCD]

Yeh he pinched from my script earlier

I honestly didn't read your post mate, thought I was having a good idea. ?

 

[Vortigern]

That's perfectly ok @Dave OCD, just thought I would get my patent in before you got all the kudos, petty jealousy I am sorry to say. I guessed you hadn't read my post and why would anyone anyway, boring! I know I do witter on a bit sometimes.