The dryer electric driagram identifies a RED L1 wire, a WHITE LN one, and other Black as L2.
The suplpy cord has a RED, WHITE and BLACK wires and the green ground as well.
How should I connect the wires to have the 240 V from the wall outlet and the 120V trough a 240 to 120 transfo?
I have a 120/240 dryer from Canada, and want to use it in a 240v country.
120-240vdryer
Related Solutions
Without being able to see the cables as they enter the cabinet; or the ability to touch or trace them, here is what I assume is going on.
Definitions:
Grounded (neutral) from the service
A typical single split phase service is made up of 3 wires. Two ungrounded (hot) conductors, and one grounded (neutral) conductor. The ungrounded (hot) conductors will connect to the main service panel through a disconnect (usually a large breaker), while the grounded (neutral) connects to the neutral lug. The neutral lug will be bonded (electrically connected) to the neutral bus bar, and all grounded (neutral) branch circuit conductors will terminate at the neutral bus.
Grounding Electrode Conductor
This conductor is used to connect the grounding electrode (ground rod, etc.), to the grounding bus in the panel. All equipment grounding conductors will be connected to this bus.
Bonding Jumper
The bonding jumper is used to bond (electrically connect), the un-energized metal parts of the panel to the grounding system.
Assumption:
Since it appears that (what I assume is) the grounding electrode conductor terminates at the neutral bus, I'm also assuming that this is the main service disconnect. This leads me to believe that the neutral and grounding buses are bonded (electrically connected). In which case, technically, grounded (neutral) branch circuit conductors can terminate at the grounding bus.
So you have two options:
Terminate the grounded (neutral) from the new circuit to the grounding bus.
Move the green wire that is terminated on the neutral bus, to the grounding bus. Then terminate the grounded (neutral) from the new circuit, to the freed up slot on the neutral bus.
Additional Information and Code Compliance:
Number of Conductors
Since this is a new circuit, it has to be installed to current code standards.
National Electrical Code 2011
ARTICLE 250 — GROUNDING AND BONDING
VI. Equipment Grounding and Equipment Grounding Conductors
250.140 Frames of Ranges and Clothes Dryers. Frames of electric ranges, wall-mounted ovens, counter-mounted cooking units, clothes dryers, and outlet or junction boxes that are part of the circuit for these appliances shall be connected to the equipment grounding conductor in the manner specified by 250.134 or 250.138.
Which in this case means installing a NEMA 14 receptacle for the dryer, and a proper grounding conductor.
You'll have to follow the dryer manufacturers installation instructions for upgrading to a 4 wire cord. For more information see this answer, and this answer.
Since you've said that you're already using 4 wire cable, you'll simply have to terminate the grounding conductor in the cable to the grounding bus in the service panel. Then connect the other end of the grounding conductor to the grounding terminal in the dryer receptacle.
Size of Conductors
You'll also want to be sure that you're using the proper size breaker and conductors. In the case of a dryer, you'll typically use a 30 ampere breaker and 10 AWG conductors (depending on the length of the run). However, you'll want to check the dryer manufacturers installation instructions to verify this.
The NEC expressly permits 120v & 240v loads on mwbc (multi-wire branch circuit) provided both legs are disconnected at the same time. This point is moot since the same is required for just a 240v circuit.
Related Topic
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Best Answer
Very often, these types of dryers are also marketed in Pacific Rim markets where only 240V is available. In this case, they build the dryer slightly differently, adding an internal 240V/120V transformer for the small number of 120V loads inside the machine (typically the motor).
I would start by getting the schematic for the 240V version of this dryer. Then compare it to the 120V schematic, and see what needs to change.
DO NOT - DO NOT - use a "step down" transformer without extreme care for how neutrals are bonded in the dryer and with your power supply. If a step-down transformer isn't applied painstakingly correctly, it would end up energizing the chassis of your dryer at 230V.