# How much power for the shop



## Papa Charlie (Aug 26, 2020)

Ok, I know the first response will be "depends" and that would be correct. In another thread regarding a 211 miller welder and powering it, the subject came up on the circuit and power available.

The wife and I are planning on building our retirement home on some land. This will include a separate shop, maybe 40x30 metal building. I have been thinking about how much power (amps) I will need. That's where the "Depends!" comes into play.

Hard to say at this stage, I know what I would like to have as far as equipment, but that most likely is not going to be the case. As a rough I figure worse case power use at any given time could be as follows:

120/240 Volt, Single Phase System
Shop Lighting 15 amps
AC or Heater 15 amps
Air Compressor 30 amps (Edited 9:26AM from 20 amps to 30 amps for 3.5 HP compressor)
Metal Machine 30 amps
Total 90 amps plus 10% = 99 amps (Edited 9:26AM added summary)

So in my mind if the shop has 100amp service it should be covered for just about anything. I won't have other people in the shop working, this is my shop so won't have multiple equipment running other than what I projected above.

What do you guys think?


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## macardoso (Aug 26, 2020)

I have 30A 240V service and 20A 120V service in my basement. I run a small CNC (30A @ 240V max) and a 12x36" lathe (1.5HP @ 240V). All the lighting is LED and I run a small 1.5 HP compressor on the 120V line. Never tripped a breaker yet.


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## nnam (Aug 26, 2020)

As much as you can afford, and your service entrance provide, 200 amps?

You will want compressor, welder, lathe, mills, grinders, who knows what you'll like next 

Seriously, that's how I think.  If you can find large cable for going to your shop for good price, I would start there.

Most likely, you don't use them in a same time.  But it can be cheaper now to lay the cable.  It depends on the distance and the cost would dictate your decision.

I have a couple 15 hp compressors that I can't run currently.

I also just get a large welder running, so it takes alot of amps.  You don't want take all house hold current though.


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## FOMOGO (Aug 26, 2020)

The difference in cost in new construction will be minimal. 100amp would be the least I would consider. I had a separate 200amp service run to my shop and I'm glad that I did. Mike


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## DavidR8 (Aug 26, 2020)

I have a 60 A service running into my shop. 
One way I reduced amp load is by running machines on 220v. So my mill, table-saw and compressor all run on 220v. The biggest draw is my TIG welder which has a theoretical max draw of 40A. 
The other way I reduced load was by using LED lights. My whole shop uses less than 5A for lights. 


Sent from my iPhone using Tapatalk


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## BGHansen (Aug 26, 2020)

I have 200 A in my shop.  You should be fine with what you have listed there at 100 A.  I didn't see any welders listed which will probably be around 40 A 220V.  Like you mentioned, one-person shop not running an electric heat treat furnace and a 5 HP compressor and a 7.5 HP VMC and a . . .  you get the point.

Bruce


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## mksj (Aug 26, 2020)

I would go with Mike's recommendation, minimum 100A and preferably 200A. If you have a 5-7.5Hp compressor running on in the background, you are welding and have an AC unit/heater going you are already punching through 100A. The typical 100A sub-panel you are also limited to the number of breakers, I put one in my garage/shop and quickly maxed out all the slots even with 1/2 size breakers. I like to also have each of my machines on a dedicated breaker or outlets sized for 20A, 30A and 50A 240VAC. Add AC/heating a say two banks of 120 sockets, lighting, etc. you are going to want the additional breaker slots. In my new garage/shop I probably have at least 12 breakers coming off of two 200A panels that also service the rest of the house. The 120VAC sockets are 20A, the 240VAC sockets are all twist lock type with the exception of the 50A for the compressor welder.


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## Alcap (Aug 26, 2020)

Are you having separate meters for the house and garage ?   The house we now live in has separate 100 amp services we want to upgrade the house to 200 so we will need a new meter pan and more $$$ work  .  When the electrician changed the garages 100 amp fuse panel to one with circuit breakers he just pulled the meter swapped and reconnected no outside upgrades needed  . What I'm getting at is get a price for a few different   ways and see if spending a little more now instead of more $$ if you ever have to change


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## Daligas (Aug 26, 2020)

200 amp on the house and 200 amp for the shop, the additional cost up front is minimal compared to trying to add amperage later.


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## Aukai (Aug 26, 2020)

Putting it in new is easier than adding it in later. Put the 100 house 200 shop on the build list, if you need to trim costs at design time you can change some items then.


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## NCjeeper (Aug 26, 2020)

I am putting in 400 in my new shop and I had 200 at my old shop. You can fill up a 200 amp box quick. Lights on, fans running, stereo playing, frig keeping your drinks cold. Welder or plasma on plus the compressor running you are probably over 100 amps now.


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## CluelessNewB (Aug 26, 2020)

My shop has a 100 amp sub panel feed from the house.  Every breaker is slot is used,  I sure wish I had 200 amp service and a bigger panel.  It's only a 24x24ft shop.   Cry once, do it right 200 amp minimum.   Don't forget things like lots of 120V outlets (can't have too many)  smoke detectors, exterior outlets, exterior lights, garage door openers (if you have overhead doors) and remember 220V circuits use up 2 slots.


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## AGCB97 (Aug 26, 2020)

I have a sub panel that runs the machine shop and garage. It is fed by a double 60 amp breaker in the house, I have welders and machines for myself alone. No problem.

But I would at least run the main wire size for the next step up. The rest is easy after the fact.
My 2 cents
Aaron


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## middle.road (Aug 26, 2020)

If the budget allows - 200A. 
Have to have room for additional equipment.
Because as soon as retirement sets in you'll be expanding your shop inventory.
Then if you've only gone with 100A you'll hit the limit and be kicking yourself for not going with 200A service.
Buy Once - Cry Once really applies to this.


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## Reddinr (Aug 26, 2020)

Puget Sound Energy now charges a separate "base fee" for each meter, at least where I am.  If your shop is reasonably close, consider a large panel in the house, a 100A or higher feed to the shop and just one meter at the house.  About 90% of my shop electricity cost is in the base fee.  I think it is about $300 per year in base fee, but I have not looked lately.  Always ticks me off when I do because they changed the policy after I built my shop with its own meter.


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## samstu (Aug 26, 2020)

My prior shop was barely adequate and had significant voltage drop as it was run off house meter.  I upgraded to 400 amp in shop and moved meter from house to a detached garage so that I split the distance and only had to upgrade shop, not house.  

I would certainly only go with one meter but might put at site of biggest load (shop) so that upgrades are simple and don't affect look of house.  Buried electric to house is also nice.   Don't forget to also consider water, septic, compressed air, natural gas, Cat 6 and network cable in that ditch.....or at least a big conduit to add these later.  Your wife will thank you for compressed air in her garage at house.

A 50 amp RV plug also can be handy if you like visitors.....

My father ran his shop off an old RV generator.  Another friend has 2 10k military generators which he uses only when running a large boring machine (each burning multiple gallons per hour).  Old noisy generators often go for little more than scrap prices and can give you both extra power when u need it and prime power during an outage.


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## Logan 400 (Aug 26, 2020)

For what you have listed 100 amp is more than adequate. It's not clear if it will be a separate meter for the shop. Overhead or underground service? If you are feeding it from the house service you could use a 200 amp mlo 40 circuit panel in the shop. Then if you decide to have a separate service for the shop you would just have the service and meter/disconnect to add. If you have a plan listing loads I could do a load calc if you want. The Service overcurrent protection is calculated at 125% of total calculated load per NEC.
Jay


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## Papa Charlie (Aug 26, 2020)

Some really good advice here. Got me thinking. I do not want two meters as I know there will be a monthly base charge on each. I hadn't thought about running the line from the utility to the shop and then feed the house from there. I would think it will depend on which will be closer to the utility line.

Also, we plan to have an RV which I would like to keep plugged in. We also could get family with their RV and it would be nice to plug them in and not have them in the house. It's the wife's family not mine. Love my wife, feel she had to have been adopted. As for 50 amps, that isn't going to happen, it will be a 30 amp outlet. Don't want them to stay too long. 

I want a generator on the house. Planning on a 22kw unit with autostart. That shouldn't be an issue as we can put the transfer switch between the shop and house panels. Some of this will be restricted or stipulated by code and as we do not have the land picked out, it is hard to do any real serious planning. But good to think about options. However we set this up, I want to ensure that the house and the well will be fed by the genset.

I will have to see what the costs are in the area for either path, 200 or 400 amp. I agree that installing 400 up front is going to be a lot less than changing it down the road. As you say, I may end up buying a lot more equipment after retirement, either that or a part time job which I don't really want. I don't plan on being a production shop, but hope to do jobs for companies and individuals in the county that don't want to go to the larger shop(s).

Thanks again for the great input guys. A lot of things to consider and take into account.


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## Saguaro Slim (Aug 26, 2020)

20 years ago we did a remodel, adding a 2 car garage (now the shop), master suite and dining room.
I had updated the house service to 200 amps shortly after I bought it in the mid 80s.
If I was doing this again:
Task lighting, especially in the kitchen.
Sub panel in the garage - I don't have enough 125V circuits in the shop and it's a challenge to get more now. There's plenty of slots in the main panel, no easy way to get them in use. The welder (250V) and little air compressor were planned at construction, the lathe, the overflow freezer and the A/V equipment were not foreseen.


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## DavidR8 (Aug 26, 2020)

If your code is anything like the code here in Canada, a 400 amp service can’t always be run to a residence, sometimes it has to be terminated in a non-occupied space. 
My niece and her husband own a place with 400 A service and it terminates in an outbuilding in front of their house. 


Sent from my iPhone using Tapatalk


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## Papa Charlie (Aug 26, 2020)

DavidR8 said:


> If your code is anything like the code here in Canada, a 400 amp service can’t always be run to a residence, sometimes it has to be terminated in a non-occupied space.
> My niece and her husband own a place with 400 A service and it terminates in an outbuilding in front of their house.
> 
> 
> Sent from my iPhone using Tapatalk



I have seen something like this on several properties. They set up a central location for the service to come in with two distribution breakers. These are set up to feed  a house and a shop. They didn't have an out building. It was on a pole with a rain shield over the box and meter. Also allowed the meter reader to get to it without having to come up to the house.


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## projectnut (Aug 26, 2020)

Another vote for a 200 amp service.  While you might not need the whole 200 amps at any one time it's nice to have separate  circuits for  machines, or only a couple on the same circuit.  You want separate circuits for lighting, another 1 or 2 for 110 wall outlets, several for 220 outlets, one for a welder, and a sufficient additional number of circuits so there room to expand in the future. 

Think of how many machines you might have running at one time, and make sure they are all on different circuits.  It's not uncommon to be using a bandsaw or power hacksaw at the same time you're using a mill or a lathe.  The compressor might also kick in when one or more machines are running.  You want them powered separately from each other so if for instance if you're taking a hard cut on the lathe or mill and the air compressor does kick in it won't blow a breaker and shut down anything else.

Our house was originally wired with a 200 amp service.  I've added a 100 amp sub panel in the shop, and another in the garage.  All the outlets and lighting in the shop are powered through the original service.  The additional sub panel powers all the machines.  All the slots in the main panel are  used and there are only a handful left in the sub panel.  There are still a few machines I'd like to add to the mix.  Should they come along they can have their own dedicated circuits.

It might sound like a stretch of the pocket book to install a larger service now, but it won't be less expensive to have it done in the future, and depending on how you finish the walls and ceiling in the shop it might be a bigger PITA to do it later.

As for your "planned" RV I would have both a 30 amp 110 outlet, and a 50 amp 220 outlet.  When we bought our first motorhome the standard was a 30 amp 110 service.  50 amp units were around, but fairly uncommon.  Fast forward 20+ years and a 50 amp is the standard with some newer units  needing a 100 amp service.  Part of the sub panel in the garage powers the outlets for our RV.  I also use the 30 amp outlet to run an industrial pressure washer.


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## Bi11Hudson (Aug 26, 2020)

As an electrician, I concur with the "buy once, cry once" crowd. My usage has tapered off in recent years. Not only am I using less but the utility is getting greedier by the day. I have three total outbuildings. And a 220 Amp residental service. 

The feed to the shop is 150 Amp wire and a 200 Amp breaker box. But only a 75 Amp breaker in the main panel. The shop has an "upgrade" service, sort of like a mobile home setup. Both the shop and the barn have a feed from that box. 150 Amp in the shop and 100 amp in the barn. But limited by the breaker in the house. 

I work alone so have *never* tripped anything off. But the wiring and panels will support heavier usage just by changing a breaker, if necessary. The barn has the torch and welder. A tractor shop is just a shed and feeds a couple of 120 volt outlets from the barn.

.


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## Aaron_W (Aug 26, 2020)

I went with a 60 amp subpanel but they used a 100 amp box with a 60 amp breaker to give me more slots. 

I'm in a basement though so a lot of my infrastructure is covered by the main panel, hvac, a lot of the lights, some 20 amp outlets etc.

Agree with LED lights, we've been replacing lights in the house with LED which really knocks down the lighting draw.


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## matthewsx (Aug 27, 2020)

All of it.


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## Alcap (Aug 27, 2020)

After reading all the good ideas here I'll ask the electrician if when we do upgrade the house from 100 amp to 200 would it be more cost effective to put a 300 amp panel in the house the go underground to feed the garage off the house instead of having it's own meter . Like what was mentioned right now it doesn't cost much more  getting two bills but maybe in the future it will change ?


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## gwade (Aug 27, 2020)

I researched this a few years ago.  I had 200 amp service to my house and got a 40x60 shop building built.  The best for me was to have 400 amp service run to the house with a separate box with two breakers each 200 amp service.  The big advantage of this set-up is one meter and a residential rate.  If you have a separate meter then it goes to commercial rate with a minimum monthly charge (at least in my area).  The only draw-back is the shop has to be fairly close to the house with this set-up.  Something like within 100'.  Mine is 85' and the set-up works great.


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## pontiac428 (Aug 27, 2020)

I have a 60A panel for the house (plenty for our tiny place) and a 100A panel in the shop on a 250A service and single meter.  I don't think I'll hit my limit because I don't need climate control.  I put in excess insulation to keep it that way.  So it's just me, the lights, and one machine at a time (plus 5hp compressor for plasma).  If I wanted more service, I'd need to replace my ducts and wire from the out building to the panel.  I'm not worried about it, though.  I've got 24 single breaker slots in my shop panel, breaker slots can be increased with a bigger panel.  I think there is a 36-slot version from Square D, so breaker slots should not be an issue.  You can always add a sub panel off of one or two breaker slots to add more.  Slimline double breakers can replace all your 20A outlet breakers to make more room.

The buy once, cry once rule is absolutely true.  I didn't pull 200A worth of wire and didn't have a big enough service (overhead/aerial distro area), so I saved myself a few thousand dollars at the cost of limiting my shop to a one-man operation.  Actually not much of a limitation, my biggest power hogs are welders, a compressor, and machine tools, and I can only use one of those at a time.  The rest is lights and 110v outlets.  I might peak out at 50-70A if I'm trying hard to do it.  But I sure would feel the regret if I ever had to upgrade.  If you think you need it, do it now.


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## Tim9 (Aug 28, 2020)

I seldom have more than one machine running at a time. If I’m welding, the lathes or mill isn’t running. i don’t have a big compressor anymore. Not really running a lot of air tools. I use air to supply the air gun more than anything else. So a little Makita compressor has been more than sufficient for me. I have a 100 amp sub panel in my shop. I have more than what I need in my opinion. My Miller 211 is more than happy.  Now, if I had a 5000 sf shop...yeah, I’d have a 200 amp serviced. But I’d also have climate control in at least 1500 sf of it too.
  FWIW... I just found some real narrow air supply line which is designed for air cylinders. I’m probably going to run some copper pipe on the ceiling and branch down with the poly lines to supply my air guns at each machine. I’m tired of tripping over the damned air hose.


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## kb58 (Aug 28, 2020)

Well, without reading this entire thread, just keep in mind that you aren't using everything at the same time. Some yes, most no. Only add up all the stuff that will be running concurrently. I have a welder, lathe, mill, band saw, and air compressor, all on 230V, everything else is on 115, all running from a 100A service for the entire house, haven't popped a breaker yet.


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## projectnut (Aug 29, 2020)

Tim9 said:


> I seldom have more than one machine running at a time. If I’m welding, the lathes or mill isn’t running. i don’t have a big compressor anymore. Not really running a lot of air tools. I use air to supply the air gun more than anything else. So a little Makita compressor has been more than sufficient for me. I have a 100 amp sub panel in my shop. I have more than what I need in my opinion. My Miller 211 is more than happy.  Now, if I had a 5000 sf shop...yeah, I’d have a 200 amp serviced. But I’d also have climate control in at least 1500 sf of it too.
> *FWIW... I just found some real narrow air supply line which is designed for air cylinders. I’m probably going to run some copper pipe on the ceiling and branch down with the poly lines to supply my air guns at each machine.* I’m tired of tripping over the damned air hose.



You might want to try the Rapid Air system for your shop.  It's relatively inexpensive and a starter kit comes with enough tube and fittings for 2 outlets.  I bought 2 starter kits for my shop from our local farm store when they were on sale for $69.00 each.  It took about a day to install all the outlets and plumb them to the compressor.

Here's a link to the system I purchased.  They do go on sale from time to time.






						RapidAir 1/2in. 100ft. Master Compressed Air Piping Kit, Model# 90500 | Northern Tool
					

The RapidAir 1/2in. 100ft. Master Kit is a compressed air piping system designed for automotive and woodworking shops, trailers or home garages. Us...




					www.northerntool.com


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## Papa Charlie (Aug 29, 2020)

projectnut said:


> You might want to try the Rapid Air system for your shop.  It's relatively inexpensive and a starter kit comes with enough tube and fittings for 2 outlets.  I bought 2 starter kits for my shop from our local farm store when they were on sale for $69.00 each.  It took about a day to install all the outlets and plumb them to the compressor.
> 
> Here's a link to the system I purchased.  They do go on sale from time to time.
> 
> ...



That is an interesting system. Limit of run from compressor to the farthest point must be 50 feet or less. The hose ID is 3/8" which is comparable to a rubber air hose. Depending on how you install it, would be fine for a very small shop as long as you can protect the lines.

A couple of concerns I have with something like this and these are just my concerns as I have designed and built several commercial shops:

1) There will be a pretty good loss of pressure over the length of the PEX type hose. Then you you will have the length of rubber hose from the bib to the tool. This will also effect the flow of air.

2) Having the PEX type hose exposed also puts you at risk of damaging/puncturing the hose and if you have every been near a hose/pipe that lets go it is not a good place. I was lucky once when a ABS pipe was hit by a cylinder head being put on the bench next to me by a coworker. Luckily, I had a face shield on because I was grinding at the time. Still hurt like hell.

3) No where in the system that they are dipicting do they provide water drains. Moisture builds up in air systems as the compressed air cools. We all know this. Generally one would expect the water to remain in the tank but it doesn't. When I have designed air systems I run the lines high on the wall horizontally then drop to the outlet but carry the line at least 2 feet below the bib. I then terminate the extension with a drain value, usually a ball valve. I have also added drop lines with drain valves near the compressor to act as distrillery cooling tubes, usually copper to help remove the moisture before it reaches my tools.


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## Papa Charlie (Aug 29, 2020)

A lot of great thoughts provided here. Thank you very much. Has given me a lot to think about and a lot of questions that I will need to pose to the electricians and county in the planning stages once we have identified the property.


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## Flyinfool (Aug 29, 2020)

I used 1/2 id rubber air hose from HF to plumb my shop air. I just cut it to length and installed barbed tees and fittings with hose clamps as required. This the same hose you would have on the floor walking on dropping things on etc. I ran it along the very corner of the wall and joists so it is hard to get to with anything that might damage it, and there is a clamp at every joist so that if it is cut or punctured, the whipping snake is not very long. I ran all 1/2 lines to reduce pressure drop, My shop is only a 20 x 30 basement and a lot of that is taken by furnace, water heater, washer, dryer, laundry tub.
But now I think I will need to add some drains, I never thought of that. Simple, just a few more barbed fittings and hose clamps


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## projectnut (Aug 29, 2020)

That is an interesting system. Limit of run from compressor to the farthest point must be 50 feet or less. The hose ID is 3/8" which is comparable to a rubber air hose. Depending on how you install it, would be fine for a very small shop as long as you can protect the lines.

A couple of concerns I have with something like this and these are just my concerns as I have designed and built several commercial shops:

*1) There will be a pretty good loss of pressure over the length of the PEX type hose. Then you you will have the length of rubber hose from the bib to the tool. This will also effect the flow of air.*

I have one outlet approximately 40' from the compressor without any problems of pressure or volume loss. The feed line runs along a joist and drops to the outlet. There is over 50' of Nylon tube if you include right angle turns and the vertical sections. The basic kit comes with 100' of tubing

*2) Having the PEX type hose exposed also puts you at risk of damaging/puncturing the hose and if you have every been near a hose/pipe that lets go it is not a good place. I was lucky once when a ABS pipe was hit by a cylinder head being put on the bench next to me by a coworker. Luckily, I had a face shield on because I was grinding at the time. Still hurt like hell.*

As mentioned earlier the main line runs along a joist with drops to the outlets. The outlets in my shop are all about 6' off the floor. Each has a quick connect fitting and a coiled hose. There is another quick connect fitting at the operator end. The only outlet that's near a bench is on the wall . The bench itself is 36" wide so there's little chance of running into a feed line.


*3) No where in the system that they are dipicting do they provide water drains. Moisture builds up in air systems as the compressed air cools. We all know this. Generally one would expect the water to remain in the tank but it doesn't. When I have designed air systems I run the lines high on the wall horizontally then drop to the outlet but carry the line at least 2 feet below the bib. I then terminate the extension with a drain value, usually a ball valve. I have also added drop lines with drain valves near the compressor to act as distrillery cooling tubes, usually copper to help remove the moisture before it reaches my tools.*

There is a drain on the compressor, a dryer just down stream, and a drain at each outlet. If you look at the parts list it includes a manifold, outlets, and fittings. The drains are some of the fittings included. About the only additional items needed are the quick connectors, and the brackets to hold the line to the wall or ceiling.


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## Papa Charlie (Aug 29, 2020)

Well we all have our own ideas when it comes to air systems. I am not saying that anyone is doing it wrong, as it is obvious that there are many ways to skin the cat in this situation.


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## Tim9 (Aug 30, 2020)

projectnut said:


> You might want to try the Rapid Air system for your shop.  It's relatively inexpensive and a starter kit comes with enough tube and fittings for 2 outlets.  I bought 2 starter kits for my shop from our local farm store when they were on sale for $69.00 each.  It took about a day to install all the outlets and plumb them to the compressor.
> 
> Here's a link to the system I purchased.  They do go on sale from time to time.
> 
> ...


I really like the Rapid Air system. And I’d go that route if I have my “dedicated shop” but.... I’m kind of in the mindset that everything I’m doing now is temporary. What I have now is small...just half a carport. Plus, I moved in my mothers house because she’s up in age now and just needed help. So it’s like  I always have this feeling that sometime in the next year or three....I’m going to have to move when she passes. Because  my siblings are going to want me out so they can sell the house. It is what it is.
   So.... I’m just going to go with what I have. I have the copper...have the poly hose...and the entire run to both lathe and mill is less than 20‘


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## Papa Charlie (Aug 31, 2020)

Tim9 said:


> I really like the Rapid Air system. And I’d go that route if I have my “dedicated shop” but.... I’m kind of in the mindset that everything I’m doing now is temporary. What I have now is small...just half a carport. Plus, I moved in my mothers house because she’s up in age now and just needed help. So it’s like  I always have this feeling that sometime in the next year or three....I’m going to have to move when she passes. Because  my siblings are going to want me out so they can sell the house. It is what it is.
> So.... I’m just going to go with what I have. I have the copper...have the poly hose...and the entire run to both lathe and mill is less than 20‘



Sorry to hear of your mothers failing health.

Your run is so short you could run a single hose to the tool you are using for now. But, it is hard not to want to make those improvements.


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