screen printing > Equipment
Will the Real Electrician Please Stand Up
blue moon:
--- Quote from: screenxpress on June 14, 2011, 12:08:28 PM ---You lost me on the 7.5 for Flash and A/C.
If plugged into a 110V circuit and tagged for 15A, how does it drop down to 7.5?
--- End quote ---
sorry, 15A at 110v is same as 7.5 at 220. I was upconverting to 220v amp count.
tpitman:
One thing to think about is as you stress the system, efficiency drops, I think, even if the breakers don't trip. I'm no electrician either, by the way, but I did wire my garage with a new panel, lighting circuit, wall outlet circuit, water heater, 220 dryer, 220 flash, and a dedicated 15 amp circuit for my exposure unit. One question I have is, why the #12 cable? I assume the 3 #8's are the two hots and neutral? Is the #12 a ground back to the panel at the house?
Otherwise, I'd be inclined to use the 110v ac unit, simply to save some juice for everything else.
One other thing. Living in Orlando, I know what you mean by hot. I installed an "attic" vent/fan in the roof of my garage that is supposed to change the air about every 3 minutes. My garage has no attic, just an open shed-type roof that goes from 8 feet to 12 feet. I used to just have a box fan blowing out one window with the other window open, but noticed that, if I got on a ladder, as soon as I went up a couple of steps, the heat was trapped in the "ceiling" as it were, and was hotter than hell. That roof vent/fan makes a difference, and I've got to either keep two windows open, or a window and side door to feed the fan. I also have a small a/c unit in another window, but unless I'm standing right in front of it, it does little to cool the garage so I pretty much don't use it. My garage is also shaded quite a bit, so that might be a factor that you don't have, so the roof vent/fan is just an alternative to think about.
screenxpress:
--- Quote from: tpitman on June 14, 2011, 12:28:43 PM --- One question I have is, why the #12 cable? I assume the 3 #8's are the two hots and neutral? Is the #12 a ground back to the panel at the house?
--- End quote ---
Correct. Since there is a secondary breaker box, the ground has to be isolated from the typical neutral bar in the second box. But is okay (code wise) to be on the neutral bar (which has a line to a ground rod) in the primary box. It was a toss up as to whether I needed to run #8 for a ground fault, so I just kept the #12 that was previously there.
What is the total amps to your garage breaker box?
Northland:
I'll take a stab at this one... I happen to be a licensed Master electrician in the state of Minnesota.
If you used THHN (90 degree C) insulated wire, a #8 conductor is rated for 55 amps.
However, because it is terminated on 75 degree C devices (receptacles) we must use the 75 degree columb of table 310-15.
So, step one... YOU ARE CORRECT, your wires are rated for 50 amps (as you stated).
I think it's most helpful to look at the load in wattage terms:
Conveyor dryer.... probably 7200 watts (30 amps X 240 volts).
Flash dryer..... 1800 watts ( 15 amps X 120 volts). Put this on an odd number circuit breaker.
Air conditioning.... 1800 watts (15 amps X 120 volts). Put this on an even number circuit breaker (to help balance the load).
Lighting... 600 watts (5 amps at 120 volts).
Step two.... Total load..... 11400 watts
Because this is continous duty load the ratings should be multiplied by a service factor of 1.25
Step three.... to be code legal you'd need a minimum of 14,250 watts of capacity (1.25 X 11,400 watts).
Step four..... you've got 12,000 watts available (50 amps X 240 volts).
So, to satisfy the code requirements you'd need a larger feeder wire.
#6 THHN is rated for 65 amps.... (15,600 watts).
The reality is... because the dryer, flash and air conditioning all "cycle" you will usually not be drawing full load current.
The voltage drop you experience from being 125 feet away from your service panel would be offset by the 1.25 service factor rating.
You could possibly limp along on #8 wire, but it would not be code compliant.
Sorry.... you're probably going to need to upgrade your feeder going to the garage. A 100 amp circuit would be most practical.
Another option would be to downsize your conveyor dryer to 3600 watts which would probably cure about 100 shirts/hour (that still fits the need of most manual shops). If you have two heat panels in your dryer... disconnect one and then slow down your belt speed.
Also..... an 1800 watt air conditioner would only be about .5 ton of cooling (6000 btu).
screenxpress:
Thanks Northland, and the other responders.
The Flash is rated at 110V/20A (I called Workhorse) which makes your numbers even a little worse.
Here's what I've decided. Since pulling the #8s and #12 through the existing 3/4 conduit that partially went underground and was such a PITA with seven 90 degree turns , I'm not going to pull it out and try to re-pull #6s. I don't think they would make the turns.
I'm going to get the 110V/15A A/C (15,000 BTU) and see what happens. If I do have problems, I can run a new conduit line using a driveway spacer crack to the garage and pull #10 with G for the A/C. That will drop 15A and I should be well under the max.
Oh, and I know the real world is 120/240 now. It's just that all my life it was 110/220 and it's hard to break old habits.
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