Heat treat oven wiring

Kevin McGovern

Kevin McGovern

Joined
Jul 31, 2015
Messages
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I am using the diagram in the stickies to wire my oven (220v, pid, 2 SSRs). One thing it seams to be lacking is notations for grounding. So one of my switches has a ground terminal, and of course I want to ground the chassis and door. It does not appear that the PID or SSRs have provisions for grounding. So I'm thinking if it can be grounded, it should be grounded to the ground wire in my main power plug coming in. So at this point, tie in the chassis, door and the switch that has a ground terminal to the ground coming in. Make sense?
 
The shell and door should be grounded to the incoming green (ground) wire. The PID does not need a ground. SSRs are usually internal components, so they are grounded by the heat sinks being bolted to the control box. Switches are rarely grounded unless the ground provides a path for a lamp. That terminal is usually a neutral, not a ground.
 
Can someone please point me to these stickies? I am trying to wire up an old kiln with a PID circuit. Want to go 220 volt and was wondering why you would need 2 SSR's? Is it one per leg and how do you hook then up to the PID. Thank's guys!
 
It is best to use two SSRs, one per leg. A 3phase SSR also works good. All they are is three SSRs in a single package. Just use two of the legs and the third can turn on/off a red "HEAT" indicator light. The 3phase units are very low cost and often come with a heat sink. You can usually get one with heat sink for less than $30 on eBay.
 
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