Wiring with 120V AC, advice requested - Vacuuforming related

Sulla

Sulla

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With all the recent posts on everyone’s great vacuuform machines, I thought I might re-tool my existing vacuuform box or even build a new one. My old box is not held down and is not mounted to anything so it tends to slide around a bit when working with it. And the shop vac has a rough rubber switch to contend with that takes one person to operate the shop vac while the other applies the hot plastic from the oven.

I want to take away the difficult switching, reduce the persons needed to operate the machine to one (me), and centralize it all away from my kitchen. Going on some of the design elements of “Ralis Kahn’s” vacuum former set up, I wanted to make it so that I could plug the shop vac into the machine when needed but still have an easy SPDT on/off switch and have a simple store bought heating element for small time vacuuforming.

At this point I have a preliminary design question regarding wiring. I plan on using my 3.5 HP shop vac to draw down the plastic, but I also want to use the shop vac as a shop vac, so integrating it into the machine is not an option. I want to use the wide wall light switches that I could bump with an elbow or knee if needed. I wanted to be able to use this in the garage.

Here are the two designs I sketched out. One without fuses, one with. Sorry for the roughness, I only have MS Paint here at work. I was also thinking of installing a “master kill switch’ in between the 120VAC in and the fuse box/vac & heating element. I have never built anything that wasn’t battery powered.

What fuses would I need? Do I need the large fuse blocks you would get for your house's fuse box with the big throw switch, or just the little blade type fuses and fuse blocks? And please let me know if I am totally going about this the wrong way.

View attachment 17171View attachment 17172
 
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Your house wiring already has a 15/20 amp breaker on it.

Only reason to add additional fuses would be if you want it below that rating.


Kitchen circuits tend to run 20 amps.
 
Lots of logistics to consider the biggest being the vacuum and heating element most likely draw in excess of 15 or even 20 amps when on, that will kill almost all residential wiring circuits as is combine both and you will almost certain pop the fuse... You should consider drawing from two circuits...

You don't need any additional fuses if you are plugging in to existing duplexes in the house...

Two extension cords so you can reach two different circuits, and then just common light switches... Get a 4 gang box, two switches and two duplexes (plug ins) Look for 20 amp rated switches and duplexes they are just a little bit more money but built much better...

1. Wire the black on the extension cord to one switch, come off the other side with more black wire to the duplex, run the white on the extension cord directly to the duplex...

2. Repeat above for other set of switch and duplex...

3. All green wires should be connected and if you use a metal box grounded to that, if not then the green should be split and connected to each switch and duplex individually but still all common...

And it should work...
 
Oh! Thanks exoray, I think I get it... Please forgive my ignorance, but the green wires - If I use a metal 4 gang box, I can just screw all the green wires from both extension cords onto the box, or onto a ground bus of some sort (or one ground bus for each chord)?

The green wires are just grounds right? The 'third pole' on the plug end of the extension cord?
 
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Yea, ground all the green terminals on the switches and the extension cord to the box usually via a green ground screw on a 4 square metallic box. Be sure to check that the wire size in your extension cord is rated to the correct amperage. If your shooing for 15 amp circuit #14 or for a 20amp circuit go with #12. Pay attention to your breaker size you don't want to overload the circuit. good luck..
 
I have piles of extension chords and 'chords with plugs' I've cut from dead fans and appliances like old vacuums. I check the breaker size in the garage, match accordingly, and post here about it before I go plugging things in.
 
Sulla said:
If I use a metal 4 gang box, I can just screw all the green wires from both extension cords onto the box, or onto a ground bus of some sort (or one ground bus for each chord)?
Click to expand...

Just tie all the greens together and 'pigtail' them to the box if you are using a metal box...

Outlets and switches are designed to ground automatically to the metal box when screwed down... But if you use plastic boxes each unit requires it's own ground...

They actually sell little green pigtails at most hardware stores with the included screw that should screw right into one of the holes on the back of the box, sometimes this hole is on a raised 'pucker' in the box so that the screw doesn't poke out the back of the box... Basically take a wire nut and twist all the greens together with the pigtail and then screw it to the box...
 
exoray said:
Lots of logistics to consider the biggest being the vacuum and heating element most likely draw in excess of 15 or even 20 amps when on, that will kill almost all residential wiring circuits as is combine both and you will almost certain pop the fuse... You should consider drawing from two circuits...

You don't need any additional fuses if you are plugging in to existing duplexes in the house...

Two extension cords so you can reach two different circuits, and then just common light switches... Get a 4 gang box, two switches and two duplexes (plug ins) Look for 20 amp rated switches and duplexes they are just a little bit more money but built much better...

1. Wire the black on the extension cord to one switch, come off the other side with more black wire to the duplex, run the white on the extension cord directly to the duplex...

2. Repeat above for other set of switch and duplex...

3. All green wires should be connected and if you use a metal box grounded to that, if not then the green should be split and connected to each switch and duplex individually but still all common...

And it should work...
Click to expand...
Agree with all of the above, but also consider that the Shop-Vac will have a large inrush current. By that I mean there will be an instantaneous current spike when you turn the vac on that may be much greater than the rating printed on the motor. Think of how the lights in a room momentarily dim when you switch on the vac. So, if the nominal current draw is 15-20 A like exoray suggests, use a circuit that can take 30 A or more.
 
You can always split them on different circuits too.

Larger amp circuits tend to be for things like electric stoves/dryers/ac units.

Putting a large amp breaker on a small gauge wiring is a no-no.
 
I got my hands on two of these Farberware rotisserie heating elements for a song last night. I also plundered my dad's shop and came away with wiring, aluminum angle stock, gang boxes, outlets and switches that should work with this set up, and a ton of fasteners and little do-dads to help out it all together.

One of these days I am gonna' borrow everything in his shop and he'll have to come to mine to use anything! :)

This is a pic of the actual rotisserie. All I got were the heating elements you see inside the cooker below.

View attachment 17197
 
Thanks! I've already poured over your site many times, bought the Thurston James book in January as well as Vincent Gingery's. Thanks for all you've made available to beginners like me.
 
OK, If I understood you correctly exoray, here is the crude wiring diagram showing two plug in and on/off switch assemblies for the shop vac and door the single heating element. This image presumes that the 120V AC socket in the wall is rated for 15-20 Amps and it will be plugged into the wall socket in the garage that has the built in protection – a tripper switch or fuse or however that works.

*added* Sorry, I forgot to draw in the common grounds all being connected between the heater/vac plug in's and their respective 120V AC in from the wall-cords.*added*

View attachment 17198

But what if I want to use the two heating elements together? Is there a way to wire it up so that I still only have 120V AC coming in from the two wall plugs and one switch to turn both the heating elements on or off, and one for the shop vac?

*added* though I would rather have one of the large flat wall switches, I wonder if a surge protector with a built in on/off switch could do the job?

View attachment 17199
*added*
 
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Here's some help.

Even though electricity knows no color, make sure your polarity is correct.




 
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noble's pictures are perfect... And your pictures show you have the idea...

Remember unlike noble's picture green can simply be attached to the metal box in your case...
 
Thanks guys you rock!

How about the surge protector idea? If I use something akin to noble's great images, would plugging two 120V AC heating elements into a surge protector, which is plugged into the Heating element circuit would I have troubles?
 
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Sulla said:
Thanks guys you rock!

How about the surge protector idea? If I use something akin to noble's great images, would plugging two 120V AC heating elements into a surge protector, which is plugged into the Heating element circuit would I have troubles?
Click to expand...

My advise skip the surge protector as it will probably blow it's internal fuse more often then you want to deal with, just use a three plug heavy duty extension cord or one of the three plug adapters... The houses fuses are a little more tolerant of well surges, then the ones built into the surge protectors... The heat and vacuum will both surge when first turned on, house fuses (breakers) will almost always tolerate this short burst/surge, but on surge protectors in many cases they will trip and shut off... You can try it and see if it works, it won't harm anything and might save you the trouble of tripping the house breaker if you do max out...
 
I concur. Skip the Surge idea.

You are welcome for the drawings.


Used to be an electrician,then alarm tech in my early years before being an industrial designer.
 
Sulla said:
How about the surge protector idea? If I use something akin to noble's great images, would plugging two 120V AC heating elements into a surge protector, which is plugged into the Heating element circuit would I have troubles?
Click to expand...
Agree with the others to skip the surge protector, as it isn't really necessary. As long as the fuses/breakers for the circuit(s) you are using can handle the load, that's all that's really necessary.
 
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