In need of some direction/pointers

[compunerdy]

I am looking to convert a cres-cor food warmer into a powder coating oven. The oven is 23"w x 35"d x 43" or 50" tall depending on if I use the lower control box.




It looks like 240v has already been run out to the garage and I just need to hookup a plug.

At garage



So here are my questions.

1. What do you think needs to be done to the food warmer to make it adequate for occasional plating.

2. How many and what rating elements should I use.

3. How would I hookup a 240 plug to the outside electrical box. It looks like the left breaker is the 240 one and has nothing going to it currently.

4. Will I need to upgrade the 30A breaker at the main box and if so what should I change it to?

Thanks, Tim

[ed_denu]

Tim,
It's kind of hard to tell how the garage panel is wired from the picture.
You need to check a couple of things.

I believe from your post that there is a 30 amp breaker in the house controlling this sub panel. You cannot change that breaker to a larger one without increasing the wire size going to the garage. See if you can read in the garage panel what the wire gauge is coming in. It should be 10ga. Regardless of the wire gauge, there are other considerations such as the garage distance from the house which can limit the load.

Normally a remote garage panel will have a master disconnect breaker to control all distribution breakers. This installation doesn't appear to have that. There are also 2 additional 15 amp breakers on this panel. My best estimate is that you will be limited to the existing 20 amp 240 VAC breaker already installed. You really need to have a qualified electrician look at this however.

20 amps will limit you to 4800 watts maximum in heating elements. Probably best to stay at 80% of that or 3480 watts. That would require a new branch circuit run with 12 ga wire and a 240 VAC 20 amp receptacle.

From the picture, these walls appear to be rather thin. For safety and to allow the oven to heat to the 400 degree range I think you will need to frame another sheet metal layer, either inside or outside with insulation between. Look at the oven calculator at the top of this forum. It will give you an idea of how effective 3480 watts will heat your oven.

[CarWiz]

That looks like a start for a dandy oven. You could probably get by with a single 3kw heater. You'll need to add some insulation and possibly an exterior wall.

Your electrical box appears to be supplied with 240v but it's split into two segments or legs of 120v. Both breakers look to be 120v. You can't just plug in a larger breaker until you check the use of the other two lines on the right. The supply line to box looks like 10ga. wire and you've got more than half of it's capability used up on those two circuits. On top of that, the two 120v circuits are running off one leg. They should be balanced across the feed.


To get 240v, you need both legs available for a breaker and that box doesn't look like it will take a 240v breaker unless you pull the two that are in there now. That will kill the two circuits on the right. It may take a 240v breaker in the middle and two singe 120v breakers on either side of that though. I can't see the runners in the box. Even so, you don't want to overload the supply line.

You need to go back to the box that supplies that box and see how it's being fed. A 3kw heater will draw 12.5A but you need to allow some margin. I'd say a minimum of a 20A breaker. The other two circuits are 15A each so you're really over the maximum for that feed line at 50A total. That would be living on the edge if the other two circuits are being used.

[CarWiz]

Ops, sorry Ed. I guess we were typing at the same time. Good coverage though.

[compunerdy]

The 20a breaker on the left states 120/240 on it. The 15a breaker/breakers on the right are for the garage outlets and lights. This sub box is about 30-40 feet from the main box. What other info could I get to help?

Here are more pics of the box




I dont plan to use the old element box. I doubt the controls and such would survive 400 degrees. Is the hole in the back enough ventilation?

Is there any kind of insulation panels I could just glue/attach to the outside?

[CarWiz]

Originally Posted by compunerdy

The 20a breaker on the left states 120/240 on it.

And that means what?
It could say 360/480 on it but the way it's mounted in that box, it's 120. The only way you're going to get 240 out of that box is if the circuit breaker is making runner contact with BOTH the red and black wire at the top.

That means the 240v breaker has to go in the middle and two singles on either side for the current outlets and lights. You need to buy two single breakers to replace the one on the right. If you use the 20A on the left for 240, you need to pin the two levers together also.

[compunerdy]

OK OK...obviously I dont have a clue.

If it was you what would you do? Should I change out this box to one with a master switch etc..?

[ed_denu]

It appears that the 20amp breaker is a double pole 240 volt breaker which could possibly be used as is. The easiest thing would be to test this with a multimeter to see if it reads 240 volts. Alternately you could pull the breaker to see if the panel is constructed such that it allows both 120 volt line feeds to hit the 20 amp 2 pole breaker. However as you don't have a lot of electrical experience I would recommend that you get a qualified electrician to look at it for you.

I'm not aware of any insulation panels that you could use internally. Perhaps you could attach something like rock wool to the outside without covering it with sheet metal.

[blackandredwarrior]

I'm new here (this is my first post) so I hope you don't mind me chiming in. I'm not a certified electrician, but I'm a draftsman for an electrical contractor. As with everyone else you really should have a qualified electrician take a look at that box.

First thing the feeder is 10 AWG (orange type NM "Romex" is 10 AWG, and most likely this was installed 2001 or later). If anyone is interested search for "type NM cable color" on Google (or any search engine) for color codes for type NM cable aka "Romex."

I'm not sure what that box is, but it almost looks like a home made contraption. I would have a qualified electrician replace that with something like a SquareD QO612L100 would work great for that. You could then even reuse that twin breaker (+/- $35). Just because that panel is rated for 100A, doesn't mean you can't feed it with something LESS. We've used that panel full of QOT breakers when we've needed a lot of circuits in a small package.

It appears it's already burnt something once. I believe the left breaker is a SquareD QOT2020 (stab on, twin 20A) breaker. These can be used as a 2 pole (240V) breaker with the proper handle tie QOTHT installed. I don't believe that panel can be used as a 240V panel unless you pulled out both of those twin breakers and installed a standard 30A 2 pole breaker (SquareD #QO230).

At the least the grounding needs to be fixed. That single lug should be replaced by a ground bus bar (much like the neutral bus bar on the right side.) That lug is triple lugged. And I think even the wire is under it's min. size. Even that neutral bus bar doesn't look right. If it's screwed to the enclosure directly that's bad. A qualified electrician should look at that panel no mater what.

You may be in luck that the #10 NM cable is in conduit (shouldn't be) and maybe that goes back to the main panel. If that is the case, it should be "fairly easy" to pull out the NM cable and pull in larger building wire. The NM cable exiting the right upper side might also be in conduit, but I can't tell. The bottom exiting NM appears to correctly use a Romex connector. Those could probably both be #14 AWG (or #12.)

Hopefully that's helpful to you. And good luck with the oven build.