Lightobject.com Support Forum

Hello,

I'm going to be building a TC setup for a conveyor dryer that we use to dry t-shirts. Here are a little specs.

-240V
-3000W
-13A
-Operating temp = 200*F - 400*F

The dryer is powered using 3phase 240V wiring. I live in Canada so our standard is 120V 60Hz. The 3 wires comes from the receptacle into the conveyor motor first. Out of the unit is an 3 prong computer style plug, this has a wire from the heater that plugs into it (or heater is a modular style, hence the receptacle and plug on the unit) I'm assuming that the two parallel legs are the Hots and the single is the common. To wire this setup correctly, would I require two SSR that would each get a hot leg and the common would share between the two? As for the AC input is it the same. Both hots go into the unit and the ground is put where? I have never really delt with 3 phase before so I just want to clarify I'm buying the right things. Our parts list is as follows:

-2x 40A SSR Relay - Dc In / Ac Out (i'll go 40A to keep heat low. The unit will have 3 fans for cooling
-1X 250V 16A rocker switch used for the mains turnoff.
-1X JLD614 (prefer the look over the JLD612)
-1X Standard K type 1M probe

Am I missing anything? If someone could guide me in the right direction?

Thank You Kindly,
Tessellate Printing.

Doesn't sound like real 3-phase -- you have two 120V legs that share a common and which are at 240V between the two hots -- same as in the US for household wiring of ranges and water heaters, etc. I'm not sure what you mean by "computer style" connectors... that description covers a lot of ground.

Use two SSRs -- one for each hot leg of the power line -- and use big ones -- I suggest at least 60A units even with fans, and be sure they are on heat sinks, and use a thin layer of thermal grease between the SSR and the heat sink.

I'm pretty sure the SSR output from the controller can drive the two SSRs in parallel. Each SSR's AC input gets one of the power line hot legs and the heater goes between the two SSR AC outputs, so that it gets 240V. In this case the common is used for one of the controller's AC inputs, with one of the hot legs supplying the 120V to the other controller AC input.

I strongly recommend that you get a real electrician involved in the wiring....

Hope this helps.

Ok so let me understand this correctly. I will use one hot line and the common for the main input power to the controller.

I'll split the output from the controller from two lines into four. This will go to the inputs of the ssr's.


For the outputs of the ssr's a hot will run into each ssr and the other Outputs will go to the heater. It will then use a common for a ground.

Does this sound correct?

The heater doesn't use the power line neutral, but it's case and anything else that comes into contact with people should be earth grounded as is standard practice and code. The heater element floats between the two opposite phase 120V lines, which then supply 240V to it. Of course I'm going from what you said about the heater, that it is rated for 240V at 13A = 3kW.

Ok it's just that the heater has three lines going into it. Are the top two the hot 120each lines and the bottom the white neutral?

I suppose it's possible that the heater is center-tapped, and that each 120V line powers half of the heater element. I've never seen a heater like that or even heard of one, but I don't get out much.... It may be that the white (neutral?) isn't actually connected to anything, or it might be tied to the case.

You can check the heater connections with an ohmmeter/digital multimeter. Measure the resistance across the two "hot" lines, measure each hot line to the "neutral". Also measure the resistance from each wire to the chassis. Let us know what you get.

Oh I Feel Silly....

Well Here is the update. The dryer is 240V SINGLE PHASE!!!!

SO knowing this I believe I understand the full circuit. The dryer face is capable of reaching around 1000*F in temp. It is an IR dryer so we would need to put the Thermocouple directly on the face of the dryer. Is there one you would recommend?

I think a K type thermocouple will work just fine, but getting it in the right spot could be a little tricky....