Power upgrade decisions

[getblown5.9]

I have a 50x36 garage with 16' ceilings and plenty of space and yet the previous owners powered this "shop" with a 70amp subpanel, off of a 100amp subpanel that is in the pool house.

Anyway, I need POWER. I have a 220v compressor, and have future plans for a lift, decent sized 240v welder, plasma cutter etc.

I have done some research and in order to run a separate 200amp service to the garage I would either need to upgrade the house to 400amp, then run new lines to garage (pain in the ****, requires lots of precarious excavation around pool, pool house etc.). I would rather run a straight line for 200amp service to the garage but power company would consider it a commercial building and charge me a higher rate for power. The distance would be roughly 380-400' from street to garage that would need to be trenched which included some very large tree roots.

My other option is to go with a propane powered genset for the garage and plumb it to the already installed 500 gallon propane tank that is buried next to the building for the furnace. I would then run new lines within the garage to add some 220v outlets for the lift, welder, etc.

I have a feeling that both will run about the same cost by the time the quotes come in, and generator power would not be affected by my unreliable power service. We live on a peninsula in the sticks, and there is a tendency for power to go out quite often, hence why the house already has a generac home generator.

Anyone have thoughts?

 

[DSMR]

That is interesting that they would consider that commercial. That may be a rule based off of your location. I have a 200A feed to my garage with no issues(single phase 240).

One question though... If you would be considered commercial, does that mean you would be offered 3 phase power? If so, I would love to have some 208 in my garage. That may be worth a little extra cost.

 

[md21722]

Where I used to live the garage was also considered commercial. 200A panels in both the home and the garage. The difference in rate was not worth circumventing it. I have also known people over the years that had solar & diesel gensets with the propane refrigerators and they all said the same thing, make it if you have to, buy it if you can... I would only make my own if the cost of bringing in the power was excessive. In one case, an out building would've been hundreds of feet up a ravine... the power company would've laid the lines and put a pad transformer if I trenched it for them. It still would've been cheaper than putting a big diesel genset up there... What happens if the genset goes down for maintenance or repairs and how will you get the fuel deliveries? You almost need 2 gensets for reliability. Hard to be utility power if available.... Pay once, cry once...

 

[bjcouche]

How do you know you need more power? You can do a lot with a 70A feed. A friend of mine runs 2 knee mills, 1 CNC lathe, an air compressor plus lights and other tools, all on a 70A feed. We need more info on exactly what types of equipment that you intend on using and which ones you need to run simultaneously. Also, it would be helpful to know the wire gauge that is run between the pool house and shop, and from the house to the pool house. And because the shop feeds from the pool house, what the loads are in the pool house.... Like for example if you had a 15,000W (63A) electric pool heater to heat the pool.... Also the length of the wire is important, so the distance between the pool house panel and shop panel , and house panel to pool panel.

Based on the little info you gave, I'd say you are fine with 70A because the only large loads that will be used simultaneously will be when plasma cutting, which would be the plasma cutter, and air compressor. However if you are starting a metal fabrication business in your shop and will be having 5 guys working, and 3 of them welding simultaneously.... If you were building a new shop I'd certainly go bigger, but I would not tear up the yard to upgrade it if what's already there will suffice.

Oh, and for the record, A generator would not be such a good idea, you'd need to size it significantly larger than necessary due to the large starting currents of air compressors, etc. It's an impedance thing.

Brian

 

[Fixin'Stuff]

Anyway, I need POWER. I have a 220v compressor, and have future plans for a lift, decent sized 240v welder, plasma cutter etc.

You won't be welding while using the lift, or while cutting, etc. You only need enough power for the things that you use ALL at the same time. A brief overload while the compressor spins up won't kick out the breaker unless it's already overloaded. They only trip instantly when they detect a huge overcurrent.

My other option is to go with a propane powered genset for the garage and plumb it to the already installed 500 gallon propane tank that is buried next to the building for the furnace.

Anyone have thoughts?

A decent size generator will **** that propane tank dry so fast that it will make your head explode.

Run your wire, install your outlets and see what transpires. Odds are pretty good that you'll be able to do much more in your shop than you think, without tripping breakers.

 

[sberry]

I agree, the 70 may work.

 

[theoldwizard1]

As long as you are a "one man" operation, 70A should be fine.

If you add a heat pump or A/C, worst case would be turning them off while you are using the plasma cutter.

 

[shillamus]

70 Amp Panel at 240 V? That is 16.8 kVA

Your welder is likely your biggest load.. say 50 Amps at 240V or 12 kVA

http://www.rapidtables.com/calc/electric/Amp_to_kVA_Calculator.htm

You could juggle your loads before upgrading.. possibly supplement with a generator if you need it (then you have some back up when grid has failed) for awhile.

Another kluge would be to run another feed wire from the shed to the garage and upgrade to 100 amp service from there... maybe the wire is big enough already???

 

[06 DIESEL]

He does have heat and A/C in the garage and it runs when the weather conditions need it to. Welder and plasma cutter will likely be used at the same time as we work on projects there with several guys that are capable of doing more than one task at the same time.

I think it comes down to the fact that 70A, while it will power the garage and a tool or two at a time, is not enough to be able to use what you want when you want and not have to deal with the constantly turning off the heat or A/C, not using the plasma and welder at the same time, not using two welders at the same time, etc.

 

[acer66]

As long as you are a "one man" operation, 70A should be fine.

If you add a heat pump or A/C, worst case would be turning them off while you are using the plasma cutter.

 

[ddawg16]

The first question to be answered....is the existing 70A 120 only or 240Vac?

If just 120Vac.....then an upgrade is in order

BTW....50A for a welder is a BIG welder.

 

[johnnynightstick]

The first question to be answered....is the existing 70A 120 only or 240Vac?

If just 120Vac.....then an upgrade is in order

BTW....50A for a welder is a BIG welder.

Not really. You fuse the amps for the plug not the actual welder draw.
My old 185A Forney C5 has a three wire NEMA 6-50R 50A plug so I wired a 50A socket. Current on the C5 is probably 30 amps. My new 210amp inverter is 50A but it's a four wire NEMA 14-50 plug.


Sent from my SM-P605V using Tapatalk

 

[Falcon67]

I'm 960 sq/ft - two AC units, big 240V compressor, welder, 2 HP 240V 12x36 lathe, small 120v lathe, 3 phase mill, metal saw, band saw, lights, TV, 240V well pump, 240V electric heat, blast cabinet - all kinds of stuff. Feed is fused at 70A, never a trip.

>That is interesting that they would consider that commercial.
Not sure where the OP is but the PUC in Texas allows a provider to charge commercial rates for a 2nd meter at an address. That was the deal at our old house - the drop to the shop was from a pole right across the alley, easy-peasy. But the bill was $40+/mth because it was billed commercial including minimums. Didn't take very long to pay back the cost of running a feed from the house to drop the 2nd meter.

 

[getblown5.9]

I am an admitted "electrical illiterate" and much of what has been asked here are things I can not answer. It seems I have come to the right place though, as I was under the impression that the current 70A power was way undersized for what I want to do.

The current power is 240v 70A. The only 240v items currently hooked up are the AC unit and the compressor, which I used the disconnect box that was slated for a future Instant-water heater to save running new lines. I can deal with not having hot water, but must have the compressor.

The only two 240v items that will HAVE to be run simultaneously may be the compressor and plasma cutter, which will be used sparingly as I am a hobby fabricator/welder that may use it a few times a year.

I need to bring in an electrician buddy of mine and have him look over the incoming lines, and current panel and see what he thinks about adding some 240v circuits routed to various places in the garage where they will be needed for the lift and welder/plasma. As stated, I will not be raising a vehicle while the welder is running, so I should be fine.

Thanks for the insight fellas, this is great news for my wallet and means we may be getting the lift in sooner rather than later if we aren't spending $5k+ on a power upgrade.

 

[ddawg16]

You have plenty of power. A decent 240Vac compressor is going to only pull about 10a max....anything more and you're wasting compressor.

My plasma cutter runs off a 120Vac line. If you have a 240Vac one, I doubt it will pull more than 5-6a.

Your lift is not going to take much....and you're not going to be using the plasma or welder while you're raising a car.

 

[Fixin'Stuff]

The first question to be answered....is the existing 70A 120 only or 240Vac?

Single phase subpanels must be fed with 240 volts. Otherwise half of the breaker slots won't have any power. The breaker slots are arranged such that the power lug is fed from the opposite leg between every slot. This way, you can install a single breaker in any slot and it will pickup 120 volts from one leg or the other (could be L1 or L2. Either will supply 120 volts between it and neutral). When you install a double breaker one side is fed from L1 and the other side is fed from L2 (no neutral involved. Connect a load between them and you get 240 volts).

 

[James-W]

Most times I am working alone in the garage and my power consumption is rather small. But every once in awhile I will have a friend stop by with a project he wants to work on, like the time a buddy and his son brought over their trailer to be worked on. They needed a bunch of welding done, so they were using two of my stick welders. At the time it happened that I had a couple people over and we were shooting the bull, so they decided to help out with the trailer project. They were using angle grinders and we were running the air-compressor. I was using the lathe and my oldest daughter was using the mill as a drill press for a project she had going. The air-conditioning was running.

Now granted, this much activity going on simultaneously in the garage is a very rare occurrence, possibly that one time is the only time I will be using that much power at once. But since we have a separate 200 amp service for the garage it isn't even an issue. Personally, I would go with a separate 200 amp service if the cost is not terribly excessive.

 

[sberry]

You eluded to the point. No reason to toss 5K at it at this point. 70A is a lot of poop and I have wired several and never had a call about tripping a 60. I have really seen 100 do some work and worked a gang from it for a year, got a bud with a weld shop does. Many modern welders now use 1/2 the input of the old one

 

[ddawg16]

Single phase subpanels must be fed with 240 volts. Otherwise half of the breaker slots won't have any power. The breaker slots are arranged such that the power lug is fed from the opposite leg between every slot. This way, you can install a single breaker in any slot and it will pickup 120 volts from one leg or the other (could be L1 or L2. Either will supply 120 volts between it and neutral). When you install a double breaker one side is fed from L1 and the other side is fed from L2 (no neutral involved. Connect a load between them and you get 240 volts).

Not totally true.

First off, you can get 120Vac only panels....all the breakers on one lug.

Second....it's not unusual for someone to feed a 240Vac panel with 120Vac and tie both lugs together

 

[theoldwizard1]

Not really. You fuse the amps for the plug not the actual welder draw.

I have beat this horse so many times it should be dead !

The reason "medium" size welder have a 6-50 plug is that most welding shop have 6-50 receptacles installed ! So to save the customer a few bucks (and prevent customer screw ups !) that is what they have molded on to the end of the cord.

Of course, the cord is sized for the machine ! If the welding machine does NOT have some type of on-board breaker/fuse the cord becomes the fuse !

I don't like this. If I ever acquire a welder I will put a more appropriate plug on the cord. You have to remember, because the duty cycle of any "non-production" welding machine is likely <50% (maybe even <30%) you can likely run a machine that is rated at 25a on a 20A circuit at low duty cycle.

 

[theoldwizard1]

The only two 240v items that will HAVE to be run simultaneously may be the compressor and plasma cutter, which will be used sparingly as I am a hobby fabricator/welder that may use it a few times a year.

Your good to go, even when running the A/C !

Now if a buddy comes over and want to fire up a welder while you are cutting with the plasma, well, one of your should wait or turn off the A/C !

 

[bjcouche]

Just install the lift. My 10,000lb Mohawk lift has its motor on a 20A (240V) breaker and the nameplate on the motor says 11.2A. You're not likely welding while lifting a vehicle, and both welding and vehicle lifting has a very low duty cycle. I asked questions before because the size of wire and distance affects voltage drop... If it were me, spend all your money filling your shop with tools. If you ever start tripping breakers, then think about spending money on upgrading the power feed then, but not before. A correction from another post.. A 5HP air compressor will take about 30A. I believe a plasma cutter will operate with a 3HP or smaller air compressor just fine...

If you spend all your money on tools, and your buddys come over, they'll drool over them. If you spend all your money upgrading your power feed, do you think your buddys are going to come over and drool over your power feed?

Brian