On 01/01/2014 20:47, Bill Wright wrote:
Adrian Brentnall wrote:
HI Folks
Some advice please.
I'm working on the control gear for a homebuilt glass-fusing kiln.
It's using a commercial digital controller, which provides a switched
output @ 12v DC.
Final load is two resistive wire elements, each rated @ 240v / 15A.

I can either feed the controller output through a small relay, to
provide a switched 240v AC,

Double pole relays rated at 240V/15A per pole or better will do it. Use
both poles in parallel. I made a gadget for switching the caravan
electrics automatically between two supplies using relays, and it's been
fine for 10 years.

Bill
HI Bill
I'm always a bit nervous of the 'commoned-contacts' approach, as
Murphy's Law suggests that one set of contracts will operate slightly in
advance of the other set, and will end up making or breaking the lion's
share of the current.

I'm deliberately over-engineering this project! (Partly because I want
it to be reliable, and partly for safety reasons - as it's a box of
heat, operating unsupervised, in a timber workshop.
For this reason I'm forgoing the usual 'let's see what's in the junk
box' approach, and speccing / buying new components. Call me paranoid!

Thanks
Adrian