View Single Post
Old 10-20-2020, 05:22 PM   #11
O C Diver
Guru
 
O C Diver's Avatar
 
City: Fort Myers, FL... Summers in the Great Lakes
Vessel Name: Slow Hand
Vessel Model: Cherubini Independence 45
Join Date: Dec 2010
Posts: 12,834
Quote:
Originally Posted by DavidM View Post
I don't understand. You can run 14 gauge wire 50' (in one direction) as is done in most all houses, and keep the voltage drop down to less than 3%. 100' if it is 220V. AC is a different animal than DC.

David
Quote:
Originally Posted by mvweebles View Post
I'd keep the switch if it's near the water heater. If not, I'd lose the switch and butt-splice in a junction box. David is correct - assuming 1500-watts of heater, 10ga wire is over-kill. 14-ga is code for 15A circuits (1800w); 12-ga is code for 20A circuits (2400w). I don't remember how big 10A goes, but it's what I ran for a 240v pool pump recently.

The reason I like a switch near a water heater is if the water heater is empty and you flip the breaker, you will burn-out the heating elements in a few seconds. Typically, the water heater is only empty for winterizing or swap-out. With the switch right there, you can manually disconnect and not forget later. It also may be a building code item to have a switch right there, but not positive.

Peter
Regarding wire size:

14 gauge has a length limit relative to amperage. Depending on the wire it also has a temperature limit for the amperage. The limits also consider whether a single cable or a bundle of cables in a conduit or other confined space that limits heat dissipation.

In my calculation, I considered it passing through an engine room (120 degree temperature), incorporated in a bundle of wires and certainly wouldn't design a circuit with a 3% voltage drop in a marine environment.

Further, house wiring is designed with an unlimited source of power other than the circuit breakers. Being on a boat with a much more limited amount of power (on the generator), it's conceivable that there is already 3% or move voltage loss between the generator and breaker panel when the generator is seeing 75% load before the water heater.

Finally, without knowing the length of the run from the generator to the breaker panel and the existing run to the switch, it would be difficult to justify reducing the wire by 2 sizes while increasing length by 15'. If the current wire is original, clearly the boat manufacturer had a reason for spending modestly more on increased wire size.

Ted
__________________
Blog: mvslowhand.com
I'm tired of fast moves, I've got a slow groove, on my mind.....
I want to spend some time, Not come and go in a heated rush.....
"Slow Hand" by The Pointer Sisters
O C Diver is offline   Reply With Quote