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maticus 01-01-2008 10:00 PM

2 100 amp services in a barn
I have a house trailer that has a 100 amp service ran to it that I'm getting rid of. It sets next to my barn and it has a separate 100 amp service ran to it.
My question is: can I run this other 100 amp service to my barn instead of paying a lot more to upgrade my barn to a 200 amp service. I will be running woodworking machinery that will require a 200 amp service.

Stubbie 01-02-2008 10:29 AM

When you say a separate 100 service are you saying a meter at the barn and a meter at the house trailer?

Or are you saying you have a pole or pedestal with one meter and 100 amp panels at the trailer and barn?

J. V. 01-02-2008 10:46 AM

I'm not sure I understand your question. Lets see if I have it right.
You have a barn and a trailer. Both have seperate services rated at 100 amp. You want to remove the trailer and keep the barn. You then want to bring the trailers 100 amp service to the barn. Thus having two seperate 100 amp services in the barn. Is this what you mean? Do you have two meters or one meter.
You say you need 200 amp service in the barn. How do you know this? Many homes operate satisfactory with 100 amp services.
Please clarify my questions. Then I or someone else can help.

maticus 01-02-2008 11:16 AM

Hi Stubbie!

I have the meter on a pole and 2 100 amp panels on the pole, one inline with the other.

So, that's were the problem arises. Is there a way to branch off the meter to 2 100 amp panels on the pole?

maticus 01-02-2008 11:23 AM

J.V. , you bring up an important point: Is 200 amp needed? I believe it is since I'm purchasing some powerful woodworking machines to run and I have an on demand water heater that takes 3 double pole 40 amp breakers as well.

Andy in ATL 01-02-2008 03:03 PM


Originally Posted by maticus (Post 84779)
I have an on demand water heater that takes 3 double pole 40 amp breakers as well.


Holy crap! I wanna see a picture of that water heater.:laughing:

frenchelectrican 01-02-2008 03:18 PM

on demand waterheater is a fastest way to raise red flag fast.

you denfiney need a 200 amp service min size those thing is power hog and i did hook up few allready and personally i dont like it when the comuster asked me what went wrong with their main breaker tripped i say " 100 amp is too small " they reply to me this one :censored: that all they will say to me and uselly have to upsized the service entrance.

i know the last 2 i did have to boot up to 400 amp service for this matter and to make it worst one POCO transfomer went up smoke from that.

the lights will flicker someway it will do that when the on demand waterheater kick in in stages those unit can be big as 20 KW [ this is not a misprint ] yeah 20,000 watts just like 2 or 3 electric stove run full speed at the same time.

Merci, Marc

maticus 01-02-2008 04:51 PM

Here you go Andy.

maticus 01-02-2008 05:00 PM

OK, so with an amp hog water heater and a 5 horse cabinet saw that is arriving next week, I need more juice. I figured since I have 2 buried 100 amp lines I could run them both to my barn instead of uprooting them both and putting in a whole new line. Is this possible?

Stubbie 01-02-2008 05:05 PM

Hello Maticus

Sorry I had to step out for the afternoon and was unable to reply till now. The simplest way to find out what service you have is a call to the power company.

If the panels are both fed from the meter or if one panel has feed thru lugs then you likely already have 200 amp service. However if a second panel was added and is fed from a breaker installed in the panel ahead of it then you likely only have 100 amp service.

1.) Do both panels have main breakers in them?
2.) Is there possibly one or two main disconnects that are between the panels and the meter?

Assuming you only have 100 amp service I'm trying to figure out how you are operating 120 amps of hot water heat with out tripping a main disconnect breaker. Maybe you have it set real low on temperature?

Anyway take a look at the pole panels and make sure the main breakers or seperate disconnects are 100 amps.

I'm also curious how the branch circuits are run normally on farm poles they will have a main disconnect(s) on the pole right after the meter.. then feeders ran to the barn and trailer and panels located either on the outside or inside those structures.

So I guess my question is.... are the panels with the branch circuit breakers on the pole or at the barn and house trailer?

Point is... regardless what you have the change over is rather straight forward if you already have 200 amp service. If you only have 100 amp service then you will have to request a service upgrade from the power company which will require a new meter base most of the time. The simplest way to handle a farm pole 200 amp service is to have a 200 amp disconnect hung on the pole with a underground 4 wire feeder to a main lug
200 amp panel inside the barn.

If you are wanting to keep what you have and 120 amps of tankless heat you would almost certainly have an existing 200 amp service and main disconnect. Otherwise you should be tripping a 100 amp breaker if the heater is operating at factory set amps.

So I think your best bet is to verify your service for us and we will go from there.

maticus 01-02-2008 05:21 PM

Hi Stubbie!

I have 100 amp service. I have two 100 amp breaker boxes on the meter pole. The first one runs down the pole and under ground to the trailer and also out the side to the other 100 amp breaker box that goes under ground to the barn. Both are ran to 100 amp breaker boxes inside.

I haven't hooked up the water heater yet. I just got it out of the box. I have to run two 8G-3 wire runs to the panel box for it yet.

Stubbie 01-02-2008 06:24 PM

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Are you just using the barn for storage and your wood working or are you going to convert it to a dwelling?

You definitely will need at least a 200 amp service so your going to have to coordinate with the power company on that issue. Their going to require permits for an upgrade unless your in one of those resident owned and operated power company coop districts. You cannot run two feeders to the barn. It doesn't serve your purposes anyway with only 100 amp service. Best bet is have the power company bring in 200 amp service then hang whatever they will allow on the pole for a main disconnect then a 4 wire feeder to the barn to a 200 amp mlo panel or come off your new meter base with a direct 3 wire underground feed into the barn to a 200 amp main breaker panel. Then add a 60 amp or 100 amp sub-panel to your shop area fed from the 200 amp panel. There is a bunch to know about this project so you need to do your homework.

As for your hot water heater you are going to need 3 complete circuits ran to that heaters terminal block. Each of those 40 amp double poles require two hots and a ground if you use cables. However, these large electric tankless water heaters are usually done in conduit. You will need 6 hots and one ground if you use conduit. Hots need to be #8 copper thhn/thwn and the ground needs to be a #10 awg. You don't have any issues with derating the wires in this application.

maticus 01-02-2008 06:51 PM

Thanks for the reply, Stubbie.

So if the power co. upgrades me to 200 amp service, will I still be able to use the wire I have in the ground now? You mention a main disconnect then a 4 wire feeder to the barn to a 200 amp mlo panel.

I have two 3-wire feeders to both panels. Couldn't I use 4 of the 6 wires that I have in the ground now? The reason is it's a 150' run from the pole to the barn. I'd be pretty pricey to run all new wire.

As for the water heater wire, I was going to run 8G/3 wire so I can get it wired in 2 runs instead of 3 runs with 8G/2 wire. Is this OK?

jerryh3 01-02-2008 07:47 PM

Can you clarify the three grounds vs. one ground if in conduit for me. If the feeds were run in pvc conduit you're saying use three grounds and if metal conduit is used, use one ground?

HouseHelper 01-02-2008 08:00 PM


Originally Posted by jerryh3 (Post 84954)
Can you clarify the three grounds vs. one ground if in conduit for me. If the feeds were run in pvc conduit you're saying use three grounds and if metal conduit is used, use one ground?

If run in conduit, you would run 6 individual THWN hots and one ground. That would apply if using metal or PVC.

Maticus: You cannot run two 8/3 runs to feed this heater. You will need three runs of 8/2 or six individual wires as stated above.

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