240 V water heater ground and neutral

No neutral required, and I would do as you suggest, 8ga and 50 amp breaker.
If this is a dual element water heater, sometimes the top element is just for short low demand operation and switched over to lower for large demand, shower etc.
M.

 

You require a 4 pin socket.
Usually a dryer requires 240v 120v Neutral and GND (4 pin plug/socket).
You should be able to read the 240v and 120v with a Fluke meter.
Do not ground to any other connection than a properly ran earth GND conductor originating at the panel.
IOW you need 3 wire and GND cable.
M..

 

You should really consult a qualified electrician.
You may not need to upsize as many heaters only energize one element at a time alternating between the two. Thats likely why it's only rated 4500w.
But don't guess at it, consult someone qualified who's there to actually look things over.

You currently have a safety concern protecting 10 awg wire with a 40a breaker.

What other safety concerns or violations are there in the house?

Do you have the required disconnecting means or have a lockable breaker if the panel is not within site of the hot water tank?

Have you properly bonded the water pipes feeding it to the grounding electrode system?

Did you size the dryer circuit properly?

What you can't see (or are ignorant to) can kill.

 

As Tha fios says! Consult a qualified electrician.

But I am curious. What country are you in? I am only qualified and have worked on UK mains electric and I note your unusual terminology. "Hot" -- ? You probably mean "Line". Wire gauge in awg ? Here in the UK and Europe we specify wire size in csa in square mm. No neutral? Never heard of it on single phase, so are you working with 3 phase? But how with only two elements?

But the answer from me is that if you need to ask the question then you shouldn't be doing it. Think how many lives depend on you getting it right.

 

His avatar shows USA.
Ah yes, when I took my UK training it was 3/029 and 7/029 for principle residential conductors!
That was half a life time away.
M.

 

Yes, Hot or ungrounded line conductor.
(You'd probably call it "mains")
Awg is American wire guage. We also use circular mils, usually for larger wire sizes.
10awg is equal to 10380cmil, or just under 5 sq mm.
Neutral is a term often (mis)used in single phase but it is not actually a neutral conductor when only 2 conductors are involved . A neutral is a grounded conductor that has an equal potential difference between it and two or more line conductors.

Not 3 phase.
Over here, we use single phase 240v and ground it in the middle of the secondary winding which splits the phase into 120v on each line with respect to the grounded neutral.
In this case he only needs the outer 240v line conductors, and doesn't need the neutral tapped between it.

 

Neutral is also used as a term for the star point in a three phase transformer, which is what jurisdictions such as UK and Australia etc use. where a phase and the star point neutral forms the 230v 1ph service, also the neutral is earth grounded at the star point.
M.