Electricians. 240 volt SINGLE PHASE heater?

[cstreit]

Hey gang,

I'm currently wiring the new shop up and decided I was going to by an Oulette 240 volt 10k Watt heater for it. However as I started researching it to figure out what wiring I'd need to pull through that circuit I saw that it was listed as 240 volt 1 Phase.

Now I THOUGHT that US residential power was either 120volt single phase or 240 volt 2 phase power... In other words by the time it hits the house through the breaker (I'm running from the house to the new shop) power was stepped down to 120 volts...

So am I crazy, or is this impossible (or impractical anyway) for a residential appliance?

[RM512]

No such thing as 2 phase power, only single phase or 3 phase. Most residential hook-ups will not be 3 phase.
You need to run 2 hot leads to the heater off a 2 pole breaker rated for the amp draw on the heater. Then match the wire size for the breaker, i.e. 20amp=12ga., 30amp=10ga.,etc.

[red-beard]

Sure there is 2 phase power. A lot of transformers are setup this way for 180 out 2 phase power.



Lets say you 13.8KV input and a turns ratio of 57.5, then each leg to ground will produce 120VAC. If you wire across the top and bottom legs, then you get 240VAC.

I expect that you have a true 180 degree 2 phase power in your house.

If you have 2 phases of 3 phase power (single phase being 120V), then you only get 208V if you go hot to hot.

see split phase below:

[cstreit]

Ooof...

Okay guys, I should add. I'm only a step above the "White wire is common and goes to the silver connector" level. I've run conduit and pt the load-center in m shop, wired in the 120v wall outlets and putting in 3/4" conduit for thr 240 run. That's a big breakthrough for this schmoe.

So I guess the question is... Is 240 Single phase possible from a standard residential load center? The dual breaker you speak of, does it run off both "sides" of the hot from the load center, or just one? Can you elaborate on how it's physically wired?

I'm going to have an electrician help me with that bit (while upgrading the house to 200Amps) but want to be sure this heater is going to work for me before running the conduit.

[red-beard]

see this

http://en.wikipedia.org/wiki/Split_phase

A split phase electricity distribution system is a 3-wire single-phase distribution system, commonly used in North America for single-family residential and light commercial (up to about 100 kVA) applications. Its primary advantage is that it saves conductor material over a single ended single phase system while only requiring single phase on the supply side of the distribution transformer. Since there are two live conductors in the system, it is sometimes incorrectly referred to as "two phase". To avoid confusion with split-phase motor start applications, it is appropriate to call this power distribution system a 3-wire, single-phase, mid-point neutral system.

better picture:

[Bill Verburg]

It's not usually caller 2 phase but I guess that description fits

you have 220-240vac coming into the hose on 4 wires. the external sheath is one, it is a ground, then there are 3 core wires, one is neutral the other 2 are hot.

There is 110-120vac difference between each hot and the neutral, there is 220-240vac difference between the 2 hots.

the 3 core wires go to the circuit breaker busses, if you use a 220-240 breaker it can only mount across the 2 hot busses similarly a 110-120vac can only mount across 1 hot and the neutral.

[cstreit]

I actually read that wiki entry earlier and sprained something in my brain.

I thought the two 120's were out of phase (hence calling it two phase) and then cumulatively you could get 240volts that way, but using BOTH to power the appliance. GOt confused when I read the product description of 1 phase.

I'm still confused... 240 volt single phase normal in the house (Yes/No?)

[Zero10]

In every house you have 2 hots and 1 neutral (and of course a ground). This is called edison three wire. If you simply run 2 hots to the heater (from different phases) then you will have 240V.
Technically the service at a house is 2-phase. You have 2 hots that are 180* out of phase and 1 neutral. However for some reason many people call this setup single phase.... don't ask me.

If you are running seperate conduit for the heater, then in this conduit you should pull 2 hots and 1 ground. Since it is 10kW, and you have a 240V supply I'd expect the heater to draw a touch over 40A. Most likely it will require a 50 or 60A breaker. For this reason you will probably want to run 2 #6's in the conduit for the power. Around here code says you should pull a #8 ground with that, but check your local code rules for the ground size. For the sake of convention you should run a red and a black in the conduit, and bring each of them off of the appropriate phase in the panel (of course from a 2-pole breaker), however again local code here (And perhaps there) will allow exceptions. For example, you can run 240V on 2-wire loomex around here, meaning that the white wire can be a hot in a 240V only system. Of course, if the heater is for continuous duty them the rules change again......

[Zero10]

Now something interesting....
My code teacher in school mentioned that they run 240V in europe, but it is not edison three wire, i.e. it is a true single phase system. Yet above it is mentioned that they run 2-phase like we do here?...

[cowtown]

Chris,
It looks like you got your question answered, but I'll throw this in:

I just got done doing high-amp 120V and 240V runs with EMT conduit and GFCI breakers, etc. etc. in my garage. I didn't know much about wiring going in, but this book was really good, and only costs $10. It taught me basically everything I needed and is updated to the latest NEC. It's very readable.


http://www.amazon.com/Wiring-House-Best-Fine-Homebuilding/dp/1561581135/sr=1-26/qid=1160002778/ref=sr_1_26/002-3469162-5337634?ie=UTF8&s=books

[cstreit]

Thanks guys...

It was the "single phase" thing that really confused me. When you use a dual-pole breaker, to me, that's two phase. As mentioned above 180 degrees out of phase 120v circuits... Meaning you use 3 wires (Hot, Hot, and neutral) rather than the two of normal appliances.

Here's the heater:

http://www.ouellet.com/commercial-heating-specs.aspx?i=10

Install guide - Useless.

http://www.ouellet.com/fd.aspx?h=/documents/products/installation_10_en.pdf