240V (ac) stat

Jerry_15

You can break one leg to control, but interesting things sometime happen if youre trying to work on the unit with one leg still hot. I always use a double pole stat or switch on 240.

Paul Rohrs_4

why

Does a 240V (ac) line feeding this floor heating stat not need a neutral? Both 120V hot lines feed terminals 1 & 2 from the 240V, but I can just wire-nut off the White Common? This stat is feeding two electric infloor radiant heat cables and it is wired correctly, I am just curious about the neutral on the 240V.

(Power then feeds from terminal 3 to the load and 4 is the neutral.)

Regards,

PR

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Big Ed

240V

The system needs to be grounded but there is no nutral like on a 120V...Also you only need to break one leg to control..

Mike T., Swampeast MO

It's all about alternating current. 240VAC uses two alternating 110V sources that are 180° out of phase--when one is going "hot" the other is going "neutral" and vice-versa. The third wire is a true safety ground--that's why it's usually just screwed to the metal frame of the heater or appliance.

Four wires are now required on some 220V appliances like driers and ovens because the timers/clocks/lights/etc. are frequently 110V and there's a very remote chance of a shock hazard without a separate neutral for the 110V portions. If EVERYTHING about the appliance/heater is 220V there's no need for the fourth wire.

Rich W

I was thinking one leg was +120 and the other leg was -120. This gives the 240-volt potential difference. Checking either leg to ground should read 120 volts. I'm guessing there is a DPST relay behind terminals 3&4 and the stat controls the relay coil. There are a number of different ways to wire this. What's behind the terminal strip? Here is one of many ways to wire this A/C (haven't worked on much 240volt DC lately)circuit.

bob_50

Rich

you are showing the elements in series . Pauls diagram has them in parallel.

Rich W

series

It's just a representation of the circuit. Each element connected to 3 and 4 must be a 240volt load whether it's 1 or 10 elements- as long as you don't exceed the load limits. Or you could have two 120volt loads in series thus giving the correct voltage drop. Here's a link to 240volt DC circuits- it's been awhile since we used these

http://www.sparknotes.com/biography/edison/section6.rhtml

Techman

Unused Neutral!

Hi Paul.Is this the "feed wirers"that you are talking about ? The heat works fine .If its any kind of "jacketed" feed the white wire is just an extra ,in order to have two hots , BLACK ,RED .?????????????Just courius !