Diy portable sub panel?

I'm looking to power 3 1000w hids from a 50amp dryer outlet. Someone advised that I may need to build a sub panel to power it instead of just running a plug converter to a 3500w power strip(fans will be run independently on a different circuit)

Pretty sure this is the right equipment but need verification.

This is what I was planning on using

We used to build these back in the day, called them "freedom boards".

Run a dryer cord to a intermatic DPST timer (40 amp), then feed receptacles off the timer. I preferred to put a six space homeline subpanel off the timer and then feed receptacles off that.

Typically configure the panel with three double pole 20a breakers, feed those each to a box with two duplex 20a receptacles for ballasts. You can use whatever style of receptacle matches your cords but I like to use orange receptacles if they are wired for 240v and using NEMA 5-20R receptacles.

Sometimes you want a blower off the timer as well so IF the dryer outlet has the 4 prong receptacle with a neutral then you can use some 120 volt receptacles on your system with single pole breakers.

Make sure the timer you get runs off the 240 volts if you don't have the neutral. The intermatic digital 40 amp double pole timers always gave me trouble, end up resetting out of nowhere and losing all their programming. So I stick with the mechanical timer and the motor power is either 240, 120 or 277 volts depending on what model. So if I remember right the T-103 has to have the neutral (120vac clock motor) and the T-104 doesn't need the neutral (240 volt clock motor).

Ok so I've got the t104 timer ordered.
Looking at a few sub panels but I'm not 100% sure what I'll need. It goes dryer plug(50amp 3 prong) to sub panel/with breakers to timer to outlet(would i run 2 outlets off the timer? I've got 3 1000w ballasts to power.

If the dryer receptacle in the home is a 30 amp then you want a #10 gauge dryer cord minimum (#8 isn't required for 30 amp and is harder to wire into the timer anyhow) and #10 wiring through the timer to the subpanel. If using 20 amp feeds off the subpanel then use #12 wire off the 20 amp breakers to the receptacles for the ballasts. If using 15 amp feeds off the subpanel then #14 wire is good.

Already wrote the above and saw your post:

Lenin1917 said:

It goes dryer plug(50amp 3 prong) to sub panel/with breakers to timer to outlet(would i run 2 outlets off the timer?

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You have a 50 amp dryer outlet in your home? Usually thats for an electric range. If thats the case you will need to downsize it to a 40 amp breaker feeding that receptacle since thats the max rating on the timer contacts. #8 from the timer to the subpanel for 40 amp. For three 1kW ballasts you won't need 50 amps anyway.

Lenin1917 said:

Looking at a few sub panels but I'm not 100% sure what I'll need.

Click to expand...

That one is a surface mount version so it won't have the corners sticking out off the cover like a flush mount one.

You will need to get a ground bar for it too:


Use proper size wire and fittings to go through the boxes and make the board neat. Metal Clad would be advisable.

The board is going to be a small wooden buffet table. Its an older house. Its either a 30 amp or 50 amp. My main is one of those old school bulb fuse boxes but I think you're right and the 50watt may be running to my oven while the 30 is supposed to be for a dryer. Thanks for the help.

Lenin1917 said:

It goes dryer plug(50amp 3 prong) to sub panel/with breakers to timer to outlet(would i run 2 outlets off the timer?

Click to expand...

It goes dryer cord to TIMER, then to the subpanel, then with breakers to the receptacles for ballasts. The whole subpanel is timed power.

If you use surface mount metal boxes for your receptacles it will be easiest.

It is indeed a 30amp outlet
Old ass fuse box

Well you won't have a neutral so just get a dryer cord that matches that receptacle and the T-104 timer. The subpanel off the timer will only support 240 volt feeds with double pole breakers. You could even skip the ground bus bar and use the one provided for the neutral.

If you use the neutral bus as the ground bus you should install the green bonding screw that connects the neutral bus to the panel ground. Normally we would only use the bonding screw at the service entrance but in the case of using the neutral bus as the ground bus we want to ground the panel.

Looks like I'm going to lowes later.

If you have questions on what parts you will need now is the time to ask lol. Otherwise you are stuck with the lowes help.

It gets costly to use metal clad for such short runs since they usually wont cut it for you, you have to buy a whole roll. Many just use non metallic cable (NM-B or Romex is a brand) on the board with the clamp style box connectors. You will want #10 wire for the subpanel to the subpanel, it will likely have orange insulation, 10-2 is all you need for that since you have no neutral you don't need the 10-3. You will use the white conductor for your other phase and typically the ends of the wires used in this fashion will be marked with red or black electrical tape to indicate that it's a hot wire and not a neutral. For the runs off the subpanel you have options, since you want to power three ballasts you have the option of a dedicated receptacle for each. That would max out the panel spaces but still leave the room for adding a few more lights. With only 30 amp capacity you can probably just run a single duplex receptacle for each circuit, that way you can plug in two ballasts per breaker. 20 amp breakers, 12-2 wire (yellow) and get the 20 amp receptacles, yeah they cost more but they are better. you can only ever run 5 maybe 6 lights on the 30 amp dryer outlet so two lights per 20 amp breaker on your subpanel...

Intermatic T-104 timer (DPST 240 volt timer motor) Has to be a double pole version to switch both hots.
Small roll of 10-2 (orange) and 12-2 (yellow) nm cable
9 clamp style box connectors (for the timer, subpanel and surface mount boxes), I think like 9 of them, may want a 3/4 incher for the dryer cord to the timer and 1/2" for all the nm runs.
6 space surface mount homeline panel
3 x 20 amp double pole breakers for the homeline panel
3 x 20 amp receptacles (maybe orange or red) get the ones that match the ballast power cords.
3 x surface mount square boxes (could use two and put two duplex's in one box but it gets more crowded)
3 x duplex covers for the square boxes
Some short like 1/2 inch) wood screws to mount everything to your board

Maybe a cable clamp for the dryer cord, you could use a strap for 1/2" EMT conduit for that probably. The two hole style would offer more stability for this application.

Oh and you will probably need a couple wire nuts in the timer for the neutral and ground junctions. The neutral and ground just pass through to the subpanel but you do connect the ground to the timer, it has a little green screw, a #12 bare copper pigtail is good enough for that screw to the junction where you twist up the ground from the dryer cord to the timer ground and the ground that goes from the timer to the sub panel. It's easier to junction that with another wire nut since it has the stranded cable from the dryer cable. The red wire nuts usually suffice, not sure there is even room in the timer housing for a blue one.

Just make sure to punch the correct knockouts for your intended layout. Sucks to have to fill the empty hole but they do make little snap in metal hole fillers in the event you end up punching the wrong hole lol.

These for the #10 and #10 wire:


One of these probably the best fit for the dryer cord going into the timer.


For the receptacles:

Double check on the timer too, make sure the timer is double pole and that the timer doesn't require a neutral for the timer motor. Thats critical.

Renfro said:

These for the #10 and #10 wire:

Click to expand...

Meant #10 and #12

Thanks for the input. I only had kind of vague idea of what all was needed. And this is probably one of those things where kinda knowing would've set my house on fie.