How do you change 3wire 240v to 4wire 240v. I have a hot tub that requires the neutral wire but I don't have one available and can't run 1 back to the main. Can I run 1 to the quick disconect box?

As you asked this question here, the best thing you can do, to be able to use your hot tub with no worries, is to ask a licensed electrician for advice. He or she can also quote you for installation of the correct type of GFCI outlet, the right sized wiring with separate neutral and ground wires, and the right sized 240 Volt breakers on the main supply panel to power your hot tub safely.

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If you asked this question because you have no experience of working on household power circuits and you hope to get enough information on this site to be able to do the job properly and safely, it is best to warn you not to rely on getting accurate information from this site about such a potentially dangerous subject. By asking this question you probably aren't quite ready to take on this particular task.

Really, don't do this one yourself. 240 Volts is far too dangerous to handle if don't yet know which prongs are which because you have not been trained how to do this work yet.

To meet current wiring codes/regulations for your locality (Town/State) a new Ground wire or a Ground Fault Circuit Interrupter (GFCI) - to protect you as well as the dryer - may be legally necessary, for instance. If you put just one wire in the wrong place because you do not understand how to wire a 220-240 Volt outlet or appliance correctly - which is clearly why you asked this question - you could easily kill yourself or someone else in your family, or even start a house fire.

=== === === === <><><> A 3-wire dryer or water heater outlet is only safe to use for its intended purpose: to power a dryer or a water heater.

Obviously you can attempt to use it for something else, such as a hot tub, but it is NOT SAFE to do it!

You could drive on the wrong side of the road but it is NOT SAFE to do it!

You could put your hand into a fire but it is NOT SAFE to do it!

In general the reasons for saying it is not safe to use something other than a dryer on a dryer outlet are all about being sure that the circuit you will use for a different appliance (in this case a hot tub) has: * the right size of wires to carry the current the appliance takes and

* the right size of breakers on the main supply panel to protect the appliance - and the wiring to it - from catching fire if there is ever a malfunction

* the right kind of protective outlet, such as a GFCI, to help prevent someone from getting electrocuted from water splashes or spray. Hot tubs are quite different to clothes dryers: people get wet inside them! You have to be sure you wire them up correctly and safely to avoid there being any kind of risk of anyone getting electrocuted.

You also have to be sure that the supply circuit used is of the right kind to protect the house from a house fire. That can happen if there is a malfunction in the hot tub but the circuit breakers on the main supply panel - or the wiring feeding it - are the wrong size. The circuit breakers on the main supply panel - and the wiring feeding the outlet for the hot tub - must all be properly sized and correctly and safely installed. Another important factor to bear in mind is the Wiring Codes/Regulations for your locality (Town/State). in many localities it is now illegal for anyone who is not a licensed electrician to install a 240 Volt circuit in a potentially wet area such as a kitchen, bathroom, shower room, utility room or by a pool. For more information please see the Related Questions shown below. IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOB

SAFELY AND COMPETENTLY

REFER THIS WORK TO QUALIFIED PROFESSIONALS.

If you do this work yourself, always turn off the power

at the breaker box/fuse panel BEFORE you attempt to do any work AND

always use an electrician's test meter having metal-tipped probes

(not a simple proximity voltage indicator)

to insure the circuit is, in fact, de-energized.