Wiring a 240V Appliance: Difference between revisions
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{{Hint|There are 2 distinctions - old appliances, and pure 240V systems - which used 3 wire plugs. The former is no longer allowed}} | {{Hint|There are 2 distinctions - old appliances, and pure 240V systems - which used 3 wire plugs. The former is no longer allowed, and was replaced with a 4-wire plug}} | ||
*This one has a ground and 2 hots on a modern appliance. With 3 wires, it means it has 240v only, but not 120v. [https://youtu.be/zzk7QUKqfEs?t=400] | *This one has a ground and 2 hots on a modern appliance. With 3 wires, it means it has 240v only, but not 120v. [https://youtu.be/zzk7QUKqfEs?t=400] | ||
**See Spruce for difference between 3 wire and 4 wire installation [https://www.thespruce.com/installing-a-240-volt-circuit-breaker-1824649#:~:text=In%20a%20pure%20240%2Dvolt,or%20green%20insulated%20grounding%20wire.] | **See Spruce for difference between 3 wire and 4 wire installation [https://www.thespruce.com/installing-a-240-volt-circuit-breaker-1824649#:~:text=In%20a%20pure%20240%2Dvolt,or%20green%20insulated%20grounding%20wire.] | ||
**But - older appliances which were 120/240v, not pure 240 - also had a 3-wire cord, and they combined ground with neutral. But that is no longer allowed as it appears to be less safe - for example if in a non-fault condition, the person has lower resistance than the ground. See [https://www.jadelearning.com/blog/3-wire-cords-on-modern-4-wire-appliances/#:~:text=In%20an%20existing%20installation%20(such,4%2Dwire%20cord%20and%20plug.] | **But - older appliances which were 120/240v, not pure 240 - also had a 3-wire cord, and they combined ground with neutral. But that is no longer allowed as it appears to be less safe - for example if in a non-fault condition, the person has lower resistance than the ground. See [https://www.jadelearning.com/blog/3-wire-cords-on-modern-4-wire-appliances/#:~:text=In%20an%20existing%20installation%20(such,4%2Dwire%20cord%20and%20plug.] | ||
*If you only have a 2 conductor + bare ground, mark the bare ground as a neutral and run it to | *<strike>If you only have a 2 conductor + bare ground, mark the bare ground as a neutral and run it to the neutral of the main panel if you want 240V/120V. It is not clear whether codes allow this, or whether this is allowed with subpanels. [https://forums.mikeholt.com/threads/3-wire-stove-grounding.2556425/]</strike> | ||
*Does a 3-wire 240v circuit have a grounded neutral, or a ground that is neutralized? | *Does a 3-wire 240v circuit have a grounded neutral, or a ground that is neutralized? | ||
*'''Thus: is it safe to say that any 3-wire appliance is pure 240V no 120V? | *'''Thus: is it safe to say that any 3-wire appliance is pure 240V no 120V?''' | ||
*Note: if it says 3 wire or 4 wire is ok - then the device is pure 240, no 120. In the 4 wire case, you just disconnect the neutral, so you have pure 240. Ie, you are just running a 4 wire cable with 3 wires of the 4 available - so that functionally it is identical to the 3 wire case. This is an example of a device that does this: [https://images.thdstatic.com/catalog/pdfImages/17/17ef4839-d585-4a00-bdf4-be80759b22b6.pdf]. Manual is consistent in showing 3 working wires and describing the device as 240V only. | |||
Latest revision as of 07:27, 27 April 2024
Hint: There are 2 distinctions - old appliances, and pure 240V systems - which used 3 wire plugs. The former is no longer allowed, and was replaced with a 4-wire plug
- This one has a ground and 2 hots on a modern appliance. With 3 wires, it means it has 240v only, but not 120v. [1]
- See Spruce for difference between 3 wire and 4 wire installation [2]
- But - older appliances which were 120/240v, not pure 240 - also had a 3-wire cord, and they combined ground with neutral. But that is no longer allowed as it appears to be less safe - for example if in a non-fault condition, the person has lower resistance than the ground. See [3]
If you only have a 2 conductor + bare ground, mark the bare ground as a neutral and run it to the neutral of the main panel if you want 240V/120V. It is not clear whether codes allow this, or whether this is allowed with subpanels. [4]- Does a 3-wire 240v circuit have a grounded neutral, or a ground that is neutralized?
- Thus: is it safe to say that any 3-wire appliance is pure 240V no 120V?
- Note: if it says 3 wire or 4 wire is ok - then the device is pure 240, no 120. In the 4 wire case, you just disconnect the neutral, so you have pure 240. Ie, you are just running a 4 wire cable with 3 wires of the 4 available - so that functionally it is identical to the 3 wire case. This is an example of a device that does this: [5]. Manual is consistent in showing 3 working wires and describing the device as 240V only.