wiring for an xmt??

[Clutch Cargo]

I am inthe process of putting together an xmt setup and am not exactly sure of what the requirements are for electricity. It will most likely be a xmt 304 setup on a 220 single phase.

I have needed to re-wire my garage (detached) since we bought the house a year and a half ago but am just now moving it to the higher end of the priority list.

I have a 200amp service into the house and there is a sub panel in the garage now with 2- 20 amp circuits. I am pretty sure that a 60 amp dedicated circuit for the welder is not going to be nearly enough but not sure if my welding requirements might not push me to the higher end of the machine.

Most of what I do is smaller projects on thicknesses up to 1/2" max. but most of the material will be 3/8 and under. As far as the size rod I would use, mostly will be 3/32 7018 and 1/8 7018.

Look forward to hearing any and all recommendations. Hope I gave enough info. Thanks

[awright]

The brochure for the Miller XMT 304 (http://www.millerwelds.com/pdf/spec_sheets/DC18-8.pdf)
states that the power requirements on single-phase, 230 volt power are 47.5 amps max., so I think a 60 amp 230 volt circuit dedicated to the welder would be fine. What makes you think 60 amps would not be adequate?

With 200 amp service to your house, you have all the power you need to supply the max demand of the welder. The two items you have to consider are wire size feeding the garage load center and the breaker size at your main service panel feeding the garage load center.

WARNING! I am not an electrician! But I did wire my garage with a 125 amp subpanel supplying a 90 amp circuit to my stick/tig welder with the help of my electrician friend, and I love it! If you are not familiar with power wiring, you may be well advised to have an electrician at least advise you on wire size, etc. Let us know if you want more detailed advice.

One item to look into is whether the wiring to your garage load center is in metal conduit or is unshielded Romex or open wires on poles. Especially with a multi-process machine having HF, the supply wiring should be shielded, as in EMT or rigid metal conduit. Unshielded wiring can radiate lots of RF noise that can cause problems with your neighbors or your family.

Enjoy your XMT.

awright

[Clutch Cargo]

The only reason I didn't know if 60 amps would be adequate was due to the 5-400 amp rating on the machine. Before I go any further, I'm a retard when it comes to electricity. For some reason I have a major mental block when it comes to dealing with it. I even read the page you linked in your post at least 10 times prior to you linking it and I was still scratching my head. I have a couple electrician friends that owe me a favor or two but I'm trying to do some reasearch on this on my own ahead of time. Not to mention my dad is/was a lineman for 20 years prior to moving into line dept. management.

The wiring to the sub panel runs through the basement and is in pvc conduit underground to the garage. I know going into this that the new circuit will require upsizing the supply line to the garage, so that is basically a given for my situation.

Thanks for the help, greatly appreciate it.

[robbbby]

The machines "output" is rated at 5-400A.

Your 240V input is transformed down to a lower voltage to deliver that kind of high current while still only drawing a max of 60A on your primary (240V going in).

So the 400A that it is outputting at say 30V for example, is only using up 60A at the 240V input.

[riley mcmillan]

I have a miller 330 a b/p. On full power it will put out over 400 amps. At 240 volts, it pulls about 100 amps primary. Since moving from Texas to Pennsylvania and deciding to just use my midrange, about 250 amps, a 60 amp breaker has done me proud. Hope that helps.

[awright]

Well, Clutch Cargo, I tried to cut and paste the relevant section of the Miller brochure describing input power requirements, but failed. It came out unformatted and impossible to interpret.

However, the important portion for your evaluation is the "XMT 304 CC/CV Specifications" table on page 2 of the Miller brochure. Notice that on the "Single Phase" line under, "Amps Input at Rated Load Output, 60 Hz," below "230 V" it says that rated input current is 47.4 amps. This is the maximum draw of your unit on 230 volt power and is what your wiring and circuit breakers must be sized for. Wiring for 50 or 60 amps will be fine for this welder. Think about running wires for a larger welder in the future. I am an advocate of overkill for present requirements in recognition of the lust of welders for ever more powerful equipment or a really good deal on a giant welder.

I don't know what the electrical noise situation is for wiring in underground PVC conduit. Here's where the advice of an experienced industrial electrician may be valuable because the PVC is probably necessary for waterproof, corrosion resistant conduit but it doesn't provide any shielding for radiated electrical noise. (I've heard electricians say that an underground conduit eventually ends up filled with water after a few years anyway due to condensation.) On the other hand, 18 inches of damp earth may provide some shielding for radiated noise. I do not know. Maybe the Miller technical department would be able to advise you on that.

You may be able to pull larger wires required for your 60 amp service to the garage through the existing conduit using the old wires for the two 20-amp circuits, but it depends upon the size of the buried conduit. There are wire size requirements for a given current in buried conduit and there are limits of the permissible fill of conduit by numbers of wires of a given size in conduit of a given size that have to be reconciled. This is a job for an experienced electrician familiar with your local code.

As a little background on current requirements, real power equals amps times volts (for current in-phase with voltage). Output power equals input power times efficiency. The weakness of using this formula for welder input requirements is that the output voltage varies and is a rather soft number, and we don't know the phase shift at all loads or the efficiency of the transformer. But if we use the specified output under "Rated Output at 60% Duty Cycle" of 225 A at 29 VDC, output power is about 6525 watts. 6525 watts divided by typical efficiency for transformers of 90% is 7250 watts input power. At an input voltage of 230 volts, the input current would be (7250/230) = 31.5 amps. This current could be further increased by phase shift between current and voltage due to lack of power factor correction on a transformer type machine. So the rated supply current draw of 47.4 amps in the Miller brochure seems realistic and conservative. They test the product in a laboratory environment under specific loads, so their numbers are credible.

Hope this helps understand the input power requirements.

awright

[Clutch Cargo]

Thank you very much, it is starting to become much clearer to me now. After reading the miller brochure that you linked I saw the input plain as day. Felt stupid for even asking the question when it was right there in front of me all along. Glad I did ask though because the miller link didn't have that info you just shared. With the minimal amount I do understand and what you just posted I think I'm starting to understand a lot better.

Thanks

[awright]

I'm busy backtracking on my recommendations to Jammer on wiring for his 250 DX Synchrowave and, now, to you. My entire response to Jammer is shown below:

Wiring up a 250 DX

--------------------------------------------------------------------------------

Jammer, thanks for your kind words. However, this is a good lesson on taking amateur advice on important matters as the last word.

Having responded to a couple of such requests, I thought, "Surely the manufacturers must offer advice on installation." So I used the, "Miller Contact Us," form at www.millerwelds.com to inquire about just what the several different entries in the eletrical input characteristics meant and how they related to the input power requirements. The response came in a couple of days and is reproduced below:

"Dear awright,

These ratings are for the same machine at different voltages (28 and 30 VAc), different duty cycles ( 60% and 40% )
Do not use these values to determine how to wire your shop.
The wiring and breaker size/ information can be found in our owners manuals.
To get this information go to our web site: millerwelds.com
Select "product" in pull down menu
Scroll alphabetically to locate Syncrowave 250 DX
Select owners manual for this machine
Find "electrical connection"
There will be a chart describing breaker size, and wire sizes.
If you have any further questions please let me know .

In case you are having trouble finding this information here are the recommneded breaker and wire sizes for a Syncrowave 250DX

On 230 volt single phase primary power use a 125 amp time delay breaker.
If you will not require full output of the machine you can use a 100 amp time delay breaker.
Wire size for 230 volt primary should be 6 gauge.
Thank you for contacting Miller


Jack Fulcer
Business Development Manager
Miller Electric Mfg Company- Tig Business
N822 Communication Drive
Appleton, WI 54914
Business: 920-954-3616
FAX : 920-954-3633
E-mail : Jfulce@millerwelds.com

>>> "Miller Contact Us" <aiaw@earthlink.net> 3/1/2006 10:52:55 AM >>>
Technical Assistance inquiry from the web

Subject: 250DX data sheet
Comments: I note that your 250 DX product data sheet shows two entries in
the "Rated Output" column, one for 200 A, 28 VAC, 60% Duty Cycle and
another for 250 A, 30 VAC, 40% Duty Cycle. My question is, are these two
entries for different models or versions of the machine or are the two
entries for two different modes of use by the operator? In other words,
if I am sizing my power to the machine, do I decide how I will typically
use it and provide maximum current accordingly, or do I select a specific
machine and provide the power for that machine?

Thanks.
awright"

So my advice to all inquiries about how to wire for a given machine is now, "Get the owner's manual and follow the wiring directions therein."

I do note that Mr. Fulcer doesn't make a distinction between 50Hz, 60Hz, and 50/60Hz models or between machines with or without Power Factor Correction. However, page 30 of the owner's manual DOES make a distinction. I still don't know how to place a properly formatted page of a PDF file here, but it says that the recommendation is for a time-delay breaker of 125 amps with #6 wire for a machine without PFC and a 90 amp time-delay breaker with #8 wire for a machine with PFC. That's for 77 input amps without PFC and 61 input amps with PFC at rated output.

There you have it from the horses mouth.

The owner's manuals also show proper wiring and grounding techniques.

Have fun with your new machine.

awright"

The comments above refer to the 250 DX, not your XMT 304. Page 14 of the owner's manual for the XMT 304 cites 31 amps input current at rated output and recommends a 35 amp time-delay breaker and #10 wire.

Enjoy your XMT

awright

[Clutch Cargo]

Wow, that's very good to know. I was planning on downloading the owners manual as soon as I got the welder. I actually just won one on ebay today so I will most likely dload that tomorrow. Thank you very much for doing that little bit of leg work. I do appreciate it. I think I am still going to run a 60 amp circuit for the welder and then with that I should still have plenty of room for a 220 air compressor.

Thanks again

[tensefan]

I have a 304 wired on a 60 amp breaker and have not hade any problems with it but i've never had it above 200 amps i cant thank of any material that i weld that would need 400 amps

[Doolittle]

Originally Posted by tensefan

I have a 304 wired on a 60 amp breaker and have not hade any problems with it but i've never had it above 200 amps i cant thank of any material that i weld that would need 400 amps

I was wondering the same thing.. When would you require 400 amps? What material and electrode size would you be using? (Yes, its a serious question).
Maybe like 3/4 inch stainless or something?

[awright]

I can't speak from experience, as I've never had my 450 amp welder cranked above about 150 amps. But don't forget that industry and heavy machinery builders and structural steel welders and shipbuilders and others have use for these high currents routinely. That's why the welder manufacturers make them - they fulfill the demands of users other than guys like me who pick up heavy iron at auction to play around with in their garages.

awright

[tensefan]

just how long do you thank a 1/8 7018 would last at 400 amps