Let me provide a few comments. My degree is in electrical engineering, but I am actually a bit rusty when it comes to the basics. Since differing metals placed in salt water
create a battery
electrons migrate from one electrode to the other. But not only do electrons migrate but also some of the electrodes metal will dissolve and migrate to the other. We use zincs since they act as a primary electrode and break down in the process protecting the ‘good’ metal on our boats. As current increases, the overall process increases or speeds up. So increased current means the zincs break down quicker. Often a boat with experiencing hastened zinc reduction the issue is due to bad wiring
particularly open or bare wires or connectors especially in the bilge
which adds to the current flow through the zincs due to the ‘leaking’ current. In the case of shore power
, voltages and currents are increased and if there is ‘leaking’ zincs will be lost
faster. And the goal in the case of a ‘hot’ dock is to locate increased current or current loss causing the premature zinc reduction.
There are a few likely causes. From the marina standpoint, the areas of direct responsibility are in the wiring
and pedestals. Specifically check if each circuit isolated (any voltage/current on circuits not in use) and if each neutral and ground clean and properly grounded (check for high resistance and/or voltage drops). Unfortunately for the marina the usual culprit in a **‘hot’ dock is a wiring issue with one of the boats or improper shore power
hookup. On a recent visit to a local marina I noticed one guy had what appeared to be a basic extension cord running from a pedestal
into his boat with it running through the water between boat and doc.
A few thoughts on troubleshooting and isolating the issue. There should be a region of the marina that appears as hot (more zincs being rapidly depleted compared to others). Of course this depends on observations and reports from the customer base. If you have individual meters on the pedestals than you may be able to find a specific circuit and/or boat with a high usage. If there is no noticeable concentration of zincs being lost
the issue most likely is either dock wiring where one or more circuits are compromised and serving multiple locations, or a frequently overlooked issue – power spikes or surges. Surges tend to be very difficult to troubleshoot since they are intermittent and are the result of a boater’s equipment.
Once the issue(s) is found, the fixes should be straight forward. From the marina standpoint, addressing bad wiring or pedestals is normal stuff. Adding surge protection, especially at the pedestals, may be rather effective but may be costly. The use of a monitoring box(es) that record
usage and max power may prove beneficial not only to help isolate issue location(s) but also to assist if the issue lies with a boat and not directly the marina.
Sorry about being long winded.
Hope that helps, at least to get the thoughts focused.