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aphil138 03-25-2005 04:40 AM

Inverters and AC Transfer switch
I am considering installing a Prowatt 1750 inverter on my Pearson 424. Included in the design is a 30 Amp AC transfer switch. I am curious if anyone else that has installed an inverter has also put in the transfer switch. I know some of the more expensive models have them built in. I think the 55 dollars for the switch is cheap insurance to protect the inverter. OR is it overkill. The kind of cruising I do now is mostly 1 or 2 days at a time. I know I will at some point in time forget to turn off the inverter and destroy it when coming back into the dock.

Sailmc 03-25-2005 06:06 AM

Inverters and AC Transfer switch
Don''t really know what an AC transfer switch is. I''ve had two Heart Interface inverters and they run fully automatically. Really all you do is turn them on or off and no harm done if you forget except for maybe some dead batteries.

GordMay 03-25-2005 09:10 AM

Inverters and AC Transfer switch
If you have another source of AC (in addition to the Inverter), such as Shore Power or/and a Generator, you need a Transfer Switch - either Internal or External to the Inverter. This could be as simple as:
(2) 2-Pole main Breakers with a Lockout Slide, which requires that (1) Breaker be Off prior to turning the other on.
(Ie: Blue Sea Systems #4125 on Pacer page 4 - )

ABYC A- (Inverters):
If an inverter, and any other source(s) of AC can supply a branch circuit or receptacle, then the transfer from one power source circuit to another shall be made by a means that opens one source circuit before closing the alternate source circuit, preventing arc-over or feedback between sources.

Email me, if you need FAXED diagrams.

Gord May

WHOOSH 03-27-2005 06:41 AM

Inverters and AC Transfer switch
Hi, Paul - hope the season''s changing quickly for and you get to leave work early every day.<g>

I think there are two kinds of issues raised by your question. Most of today''s larger inverters have a built-in AC sense circuit, which allows one to leave the inverter (or inverter side of the inverter/charger)energized for instant AC use, should shore power (or generator power) be interrupted. E.g. on our Freedom 10, I can unplug the shore power cord and there won''t be a nanosecond''s blip on anything pulling AC...not that this is a good practice.

However, there is a second issue which has to do with what you power from your AC panel; I think this is partly what you are concerned with. You can either feed your incoming AC line VIA the inverter and then on to the AC Panel, or you can feed it first to a transfer switch. The reason you would choose to do the latter is that you may have some AC systems on the AC but your inverter can''t handle...and so these systems have to be wired to accept shore power but not inverter power. This is the more idiot proof choice...sort of. The wiring becomes much more complicated and one can also argue that keeping wiring simple precludes problems, too.

FWIW we chose to keep it simple and power the panel VIA the inverter. Normally when on shore power, the inverter sense circuit is kept off; if we lose AC power then we just momentarily lose power until I troubleshoot why. Since our boat is relatively simple and we have no AC generator, we only have two systems that the inverter would choke on: hot water heater and HVAC. Our Freedom inverter, like all the rest, has circuit protection and, provided it works, the inverter pops a breaker if it''s called on to do too much. Since I depend on breakers for lots of other things, it seemed reasonable to me to count on one in this case, as well.

I found the Freedom installation manual to discuss both these options; I haven''t regretted the choice we made.


GordMay 03-27-2005 07:35 AM

Inverters and AC Transfer switch
Heart Interface (Xantrex) “Freedom-Combi” Inverter/Charger Manual:
Gord May

GordMay 03-27-2005 07:46 AM

Inverters and AC Transfer switch
Xantrex “ProSine” Inverter Manual:

aphil138 03-28-2005 03:26 PM

Inverters and AC Transfer switch
Your right Jack, trying to keep it simple is a chore. Of course I can come up with circuits to wire the inverter to just the outlets, trying to troubleshoot it later maybe somewhat more difficult. Using the transfer switch through the main AC breaker IS simple. Just need to add some protection like you suggested to "Pop" when you try to use the inverter to heat 10 gallons of water!.

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