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Does anybody know about electrical relays, please? Bi-Switching Circuit Needed to Control 2 x 1000w Kilns On and Off. Answered

I have a workshop which has 2 x 1000w kilns. To fire my pottery etc, I need to put a kiln on for about 12 hours. No ordinary cheapo timer can handle the wattage load and so I am thinking of using a heavy-duty relay. Are you good with relays? If so, I would value your help, please. What I want to do is plug my timer into the mains socket, have the relay connected to the timer so that it knows when to switch on and off, and then I need two outlets (one for each kiln) so that when one is switched on, the other is off, and so on. I have thought of a 30A, 240v relay which is SPDT. I have deliberately over-specified the relay because I want it to be safe and to last, as well as use the thing for other applications where there may be a large inductive load (as opposed to resistive load). I can provide a link to the relay, but I'm not sure if this allowed. Many thanks. Kevin



Not to be picky here,

but this is not nearly the optimal solution.

you need to be present when a kiln shuts off/on. this is a major safty issue.
are you firing a sitter kiln? or a controller kiln?

if you are firing free kilns, you need to be present to view the witness cones. firing times varey greatly depending on the weather, humidity, load density etc. and only a cone series will tell you if tyhe pottery has firied correctly.

a sitter kiln will turn itself off, but it really need to soak 24 hours before being opened..

same with a controller kiln.

the biggest problem with the situation you present is operator safty.

if you are unloading/loading the "off" kiln and the relay fails for some reason, the elments in your inactive kiln comes on. with you working in it...
manual control for operator safty.

and really, if you need to fire round the clock, you need a bigger kiln- or a series kiln, or, gasp, a Gas kiln.

now, im not saying not to do it, but I dont see where it;s pratacable or safe.

sam gueydan
Moose Studios Pottery

Please link the part Kev. You're in the UK, yes...so your mains are 240 single phase... I'll assume your heaters are as well works out to ~5A. A relatively low load. In general, 30A 240V relay should be fine for the resistive use. You need a fuse or circuit breaker on your inlet to the relay, and ideally over current protection (fuse or circuit breaker) on the outlet to each kiln. However, I don't see any mention of temperature control. Assuming the timer and relay are AC operated:

Note that for inductive loads, a "best solution" will require the use of a relay rated for use with motors...

Use the output of your timer to connect the appropriate juice to your relay's coil. If the relay coil is driven by mains then the output from the timer directly to the coil terminals like appolo says but if your relay coil takes 12 or perhaps 24 volts then you simply need an adaptor that outputs this and plug this adaptor into the timer and connect its output to the coil of your relay. I have a similar arangement on my bathroom lights with a switch on the wall of the bathroom that carries only 12v that drives a relay that connects the mains to the main lights supply.


8 years ago

Have I got this correct... You switch number 1 kiln ON for 12 hours, while number 2 is OFF. At the end of the 12 hour period, Kiln one is switched OFF and kiln 2 is ON. The cycle repeats every 12 hours unless time periods are terminated. Your relay would handle over 7kW so more than enough, but is the coil low voltage or mains energised? If it's mains energised then the output of the timer can connect directly to the relay, in which case being a double pole type you can use one pole to feed a live connection to each switched pole, so as the pole toggles it switches a LIVE connection to either kiln. If this arrangement is what you are trying to achieve then wire the relays with a suitable cable rated to carry the power. Make sure your connections are good and tight and wiring and components are fully enclosed and protected_to be safe. Hope this helps Regards