Power Setup for Home Shop

[Ed from NY]

Howdy,

I'm sorry if this is a stupid question... here we go...

I'm shopping for a new home and one of my concerns is to have a nice space for the workshop and adequate power. I'll probably have 1/2 a full walkout basement which should be enough to (after the finances get back on track) get a full size used mill, lathe, and a 60-Amp plasma cutter and eventually DIY CNC them.

I figure I would plan ahead and see if I can get 3-phase in there, but since I never messed with it before I'm unsure if I should ask for 3-phase 230V or 460V. Not even sure if 460V is available in residential areas Would have 3-phase 230V give me a leg up when it comes to running used machinery I may pick up at auction or some other place later or is it a waste? What amperage would be good for a couple of beefy machines?

I'll try to get a couple of 240V circuits and one or two 120V circuits as well. I figure 20 Amps for the 120V. What amperage should I go for the 240V?

Do I need to get a 60-Amp 240V line for the cutter which is rated at 60 Amps... not sure... that sounds like a lot!

Thanks!

[Karl_T]

You're extremely unlikely to find 3 phase in a residential area.

Just make sure you have a 200 amp sevice (standard) and an electrical box with a huge area for adding more circuit breakers.

Tell the electrician you want a 60 amp welder here, a 50 amp air compressor there, and a 50 amp ? there, etc. Put in plenty, very hard to wire after sheetrock is up.

You'll end up running 3 phase equipment off a three phase motor/converter. You can build it yourself. My shop is the baesment and tuck under garage - sounds about like what you're doing. I only run one 3 phase machine at a time ( out of 8) off a 220 V 30 amp circuit.

Karl

[diarmaid]

I contacted my electricity supplier last year about getting a 3 phase connection in my house for a workshop (Residential area) and they said that it was no problem, and sent me the form. The cost was €800 (About $1000). Of course this is Ireland, so it may be different where you are, and Im near the capital city so the necessary networks were probably already in place in the area. I ended up not getting it done because we were going to move house and didn't want someone else to have the luxury of my €800 expense!!

[epineh]

Speaking as a sparky, although your system is different to what we have here, maybe consider getting a sub board installed in the workshop area, makes for easier additions later on, closer to reset tripped breakers without affecting the rest of the house... just a thought.

Russell.

[Al_The_Man]

Originally Posted by diarmaid I contacted my electricity supplier last year about getting a 3 phase connection in my house for a workshop (Residential area) and they said that it was no problem, and sent me the form.

Yeah, your fortunate that probabally like the UK, residential areas have three phase distrubution, (one phase per dwelling), so it is relatively easy to bring in three phase, unlike N. America that uses single phase only for residential areas.
Al.

[epineh]

Originally Posted by Al_The_Man Yeah, your fortunate that probabally like the UK, residential areas have three phase distrubution, (one phase per dwelling), so it is relatively easy to bring in three phase, unlike N. America that uses single phase only for residential areas. Al.

So your residential distribution uses one phase ? How big an area are we talking (on average) per phase, seems like that would make it hard to get even distribution of load using that approach (from a supply point of view).

Do you have floating neutral problems often by any chance ?

Russell.

[Geof]

Originally Posted by epineh So your residential distribution uses one phase ? How big an area are we talking (on average) per phase, seems like that would make it hard to get even distribution of load using that approach (from a supply point of view). Do you have floating neutral problems often by any chance ? Russell.

I don't know how they work it in Al's area but we have three phase 7200volts running down the street. Every so often a domestic supply 50kva transformer is tapped between one phase and ground. The transformer secondary is center tapped to give 240/120 with the neutral again at ground. It seems four or five houses are supplied by each transformer with a typical house supply in our area 100amps; newer houses are normally 200amps.

So I have three phase about 180 feet from my home workshop but the last time I enquired about getting a three phase supply I was told that mixed service; single phase and three phase is not provided to a single location and three phase is not supplied to a residential address.

What's a floating neutral? Our neutral is obviously the ground and considering I live on an island in a river delta about 10 inches above high tide I am almost floating but I don't think that is what you mean

[epineh]

Originally Posted by Geof What's a floating neutral? Our neutral is obviously the ground and considering I live on an island in a river delta about 10 inches above high tide I am almost floating but I don't think that is what you mean

Lol yeah that isn't what I meant, sounds like your distribution is "same but different" to what we have. Transmission is usually done at higher voltages (here street HV is 22 000 Volts) to cut down on losses caused by conductors carrying current, basically the higher the voltage the lower the current for the same given power.

Our setup is generally 3 phase HV (22000) using three phase Trannies (not the cross dressing type ) of whatever size 50-500 KVA and 3 phase and neutral LV (415 between phases, 240 between phase/neutral) distribution along the streets, be it domestic or industrial.

By floating neutral I meant that sometimes when a supply grid or large installation has a major imbalance on one or two phases (usually overloaded) the neutral point can tend to "float", causes havoc with 3 phase and single phase equipment, in worst case neutral can burn away, causing all sorts of fun stuff, water pipes becoming "live", anything metallic and previously grounded is at line potential.

Happened at my sisters place recently after our last cyclone (google cyclone Larry), combination of neutral burning out and 300km/hr winds disconnected the neutral to the house (overhead connection), as she had 2 phases coming in to the house with no neutral, when power was restored (1 week later), she noticed something strange going on with the power, went to check breakers and got booted from the metallic switchboard. Blew 2 computers, air conditioners and so on, basically they were on something between 240 and 415 volts, not good.

That is the basic version of what I meant, I could go on but I think I have hijacked Ed's thread enough, sorry bout that Ed...

Russell.

[Al_The_Man]

Russell , As you are an Electrician from down under, out of curiosity I have a question regarding Grounding there for you.
In Australia does the service company provide a Ground conductor, or do you have to set a local one up, isolated from the neutral?
Al.

[Adobe Machine]

Most residential in the Southwest "bond " the neutral to the ground, and on new housing, the ground can be attached to rebar in the slab.
There can be a situation where a neutral floats if there is poor bonding, or the neutral is lost to the power company ( wind etc ) and as stated pure havoc ...will go through water heaters, pipes , even water..happened to me years ago in the shower..still carry scars.
For a price ($12000.00), plus the cost of wiring from the transformer to the home shop, about another $3500.00 we could have 3 phase in our new home. Those VFD and phase converters work real well for a home shop !

Adobe (old as dirt)

[epineh]

Originally Posted by Al_The_Man In Australia does the service company provide a Ground conductor, or do you have to set a local one up, isolated from the neutral? Al.

Hi Al, we have a system called MEN or multiple earth/neutral. Basically an active and neutral comes in off the street overhead or underground, there is an earth stake usually at or near the switchboard installed by the installing electrician, the conductor from this connects directly to the neutral at the MEN point. Usually we have a equipotential bond to the incoming water service, at the hot water system, though plastic pipes are taking over...

Russell.

[Al_The_Man]

Russel, Thanks, I presume the star point (neutral) at the distribution transformer is grounded?
Al.