heat controller wiring for sub press

[prospectsnow]

Hey guys.
I have a sublimation press in the works. Just about got this bad boy done. I'm hoping I can get some advice from the guys that know electricity.

The posts from Brazen and Nightmare were absolutely key. Thanks guys.

I am having some electrical issues. The heat blanket is a bit more powerful than what most of us use in our presses. I have a 4000w blanket heating up a 1/2 plate of aluminum. It converts to 18amps at 220V

The problem I'm having is that it is blowing fuses. The controller is based on happy monkey, but uses 1 pid and blanket.

I'm using 2 fuses:
Coming in after the switch (before ssr and pid) tried 20amp and 30amp
Going into the heat blanket (after ssr and pid) 20 amp
My outlet is good for 40 amps.

I'm blowing the fuses before the pid and ssr. After both 20 and 30 amp.
The fuses stay on for a few minutes and the blanket heats up for a while, but then they poop out. With the 30 amp it got up to 150c turned on and off a few times then blew.

Is the PID and and SSR consuming that much current? (An extra 10 amps)?

I'll post up my build notes for everyone to benefit
. It really isnt' too technical, but the project does take some jing.

[skimann20]

Can you post a picture of inside your controller or draw out your wire configuration?

[prospectsnow]

The fuse circled in blue is the one that blows as the temp ramps up close to the target temp.

Forgot to label that the blanket is at 18amps.

https://fbcdn-sphotos-h-a.akamaihd.net/ ... 7516_n.jpg

[Brazen]

Yea, I'm not the guy to be definitive on this HOWEVER, I would take that fuse out. I didn't run with one in that position and problems equaled exactly none. And that's a cool lookin' press!

[skimann20]

I'm no electrician. but if it were me I would remove that fuse. I do not have a fuse there on my controller. It does concern me that you have a 25amp switch and your burning out a 30amp fuse... also make sure your are not grounding out somewhere.

[troublemaker]

Is this exactly how it is wired? Looks like your diagram is missing some wires.

[prospectsnow]

I too am not an electrician.
I'm going take that fuse out. I think it will be fine.
I have a line going to ground that I didn't include.
I don't have the box in front of me. other than that ground I think that is the wire up. Am I missing something?

I followed the schematic on the how to page
http://skibuilders.com/articles/heatedpress.shtml

[falls]

It looks like there is a wire missing associated with the SSR. The SSR should be placed in one of the legs of the high voltage current. Then the PID's control breaks and completes the high voltage circuit for the blanket. You show a wire leaving the SSR to the blanket, and one returning from the blanket to your contactor, but no connection from the wire with your 30 amp fuse to the SSR.
The high voltage current shouldn't run through your PID to the SSR.

[prospectsnow]

Yeah my diagram is wrong. Sorry guys. I appreciate the help. Took a closer look this is how im wired.

[troublemaker]

So you have two hot wires going to your PID? 240VAC right? I fuse both L1 and L2 between the SSR and the mat, and also the other leg and switch.

[falls]

Mine is wired like your freehand sketch. I have just one fuse in the same position as your 30A fuse. Never blown a fuse.
Either you are drawing more than 30A or the fuses aren't what they are meant to be.
The only other thing is that you can get fast blow and slow blow fuses for the same amp rating. Maybe a different type of 30A fuse might be better?

[falls]

I think I am using slow blow fuses from memory after discussion with electrician (marked with a T rather than an F for fast).
They will allow some excess current for a short time before blowing.

The only thing is that your setup shouldn't be drawing 30A at all.

[prospectsnow]

I pulled the 30 amp fuse. I'm not blowing fuses anymore, but I'm

Now I am getting a strange electrical click/spark sound.
Thinking it is overloading my 25amp SSR and should upgrade to 40amp?

Troublemaker, Yes. 240, 2 hot wires, and both do go into the PID. I'm not sure what you mean by fusing them. Can you be more specific?

Falls, I am using a slow blow fuse now as well. It seems to help.

Posts are a sloppy. My shop computer is down at the moment so none of this stuff is in front of me to see. Thanks guys.

[prospectsnow]

I got some answers from a bud that is an electrician.
The short, just over engineer the circuit. 40amp SSR, heavier wire, and no need for that fuse that was blowing.

Some explanation:
As wires and circuit heats up resistance goes up as well so it takes more amps to power.

The heat also causes disimilar metals to expand and contract at different rates.

Conclusion:
The heavier wire will keep the circuit low temp and won't draw extra current.
The 40 amp SSR will take the inefficiencies since it is built tougher.
Sparking sound is basically caused at the joints. Either I didn't tighten it down well enough or the heat is causing the materials to not conduct well enough. Probably making extra resistance, extra heat, extra current load.

Anyone have anything to add?

[troublemaker]

What kind of PID do you have that takes 240VAC? The ones I build use one leg, 120VAC. On my 240VAC systems I fuse all legs before and after the SSR without any problems. Oh, I also use ceramic slow blow fuses.