On the manual diagram the power supply shows l1 and l2 neutral and hot wire manual is in black and white need to know where does the hot wire go to l1 or l2 because the manual does not specify and

SOURCE: Installing a Dayton G73

If that is a 240V unit then you are correct wiring L1 and L2 to black and red. Unless the unit uses 120V for something like a control panel, it doesn't need the neutral.

SOURCE: Need to know were to hook up, pressure switch

Black wire to L-1, White wire to L-2 Green is ground and also bonds to green wire in the switch.

SOURCE: Mini Split Heat Pump wiring

Check to make sure it is single phase, should be stamped on unit. Is this wiring coming from what use to be there?

If you replaced the old unit with this one, you can trace the wires back to the breaker box. If you are Electrically inclined or you know someone who is.
Remove the panel and trace the nuetral and ground wire to the bus termination.

Some States require or use to require that the nuetral
and ground wire be tied together. 230 is 230v ,2hot and a ground.

My guess is you tie nuetral and ground together or
I wouldnt use white wire and I would disconnect
from both ends.

If you are uneasy about electricity, talk to a certified
electrician. Contact City Electrical Inspector. Dont get hurt!

SOURCE: 120v hot tub wiring diagram

I would expect your tub is either 110 or 220. Currently you are set up for 110. Based on that ... you disregard the red wire.

If your tub can run on 220, you should run it on 220 as this is more economical.

You should probably have an electrician check this out and make any changes to assure proper and SAFE operation of your tub. You are using a GFI, correct?

Thanks for your interest in FixYa.com

SOURCE: Hi.i got a new dryer and its 3 prong but the house

Ok. Let's simplify this for you. First and foremost you will want to remove the copper strip that goes from your center cord post the to case/cabinet of the dryer. This is to seperate your neutral and grounds within the machine. Some models used a green jumper wire instead of a copper strip but the idea is the same.
Now on the new cord the green (ground) wire is supposed to go to the connection point the copper strip used to go to on the cabinet. The white wire (neautral) is supposed to go to the center terminal connection on the terminal block and the red and black (L1 and L2) wires can go to either of the outside terminals.
The only difference in a four wire cord application is the segregation of the electrical neutral and the ground wires.
Good luck, hope this helps you!