Re: [Amel] Isolated or non Isolated DC to DC Convertor

David Pawley

Traditionally DC circuits have always had a issue with inductive reactance, it becomes apparent when you see a huge spark leaping across contacts, often where there are coils such as relays you will often see a diode that is there to sustain the reactive field (lessen the contact damage). Do not underestimate its power. So powerful is it that in early days of radio the first use of it was made to send a wireless signal as it has a radio wave component. Recently I rewired a old neco autopilot, the aching of the relays would send you blind for a few minutes. Its not the only type of interference, switch mode power supplies may send ripples down the DC power supply. On a boat, it would surely interfere with the radio, either on the power supply or intereference like lightening except more powerful. I do not know if a tuner placed near the autopilot would also have issues. I'd say Amel had it right years ago to have isolated power supply. If you must not have isolated power supplies make sure the ferrites are in place and be prepared to turn off the Autopilot.
Waverider not only boatless, but I may not know what I'm talking about.

On 21 December 2013 00:41, Anne and John Hollamby <annejohnholl@...> wrote:

Alphatronix make an isolated version of their 24/12 volt Powerverter  and sell a large number of them for use in fuel bowsers etc presumably to reduce the risk of sparks and also,I imagine to reduce the amount of interference from things being switched on and off elsewhere in the wiring circuit.
                            Regards,  Anne and John, Bali Hai,  SM 319,  Malta
From: Mark Erdos
Sent: Friday, December 20, 2013 12:15 PM
Subject: RE: [Amel] Isolated or non Isolated DC to DC Convertor


I would be concerned that since the SSB must connect to a ground plate the use of a non-isolated DC-DC convertor could compromise the ships system (by connecting you entire ships ground to the same plate). This would most certainly cause electrolysis. Per the instructions of the iCom M802 it states the base unit must be connect to the same ground as the antenna. This is where I fear you would create a problem. It would be best to ensure the negative circuit is closed and not compromised at any point in the SSB connection.

Best regards,


SM2K #275

From: amelyachtowners@... [mailto:amelyachtowners@...] On Behalf Of terencesingh@...
Sent: Thursday, December 19, 2013 6:12 PM
To: amelyachtowners@...
Subject: Re: [Amel] Isolated or non Isolated DC to DC Convertor


I have given this thread much thought and also done some reading since opening up this topic for discussion.

I understand that our beloved boats were designed to have the negative side of the DC circuitry for any accessory home run to the negative side of the battery bank. I understand this and accept this.

I believe it is common practice in ABYC conforming boats to have the negative side of the battery bank tied to the engine block which the feed an Accessory negative bus. The negative side of all accessories on board are then tied to the negative accessory bus. I understand this and also accept this. Different concept.

Here is my question that I need help with.

If I use a Newmar  32-12-50 (24 to 12VDC to DC convertor 50 Amps) as a DC to DC convertor which is non isolated with the input  feed directly from the ships 24VDC battery bank, and the output feeding a 12VDC distribution panel and each branch circuit from that distribution panel powering the various accessories on the ship with a direct positive and negative home run from the distribution panel, am I compromising the Amel DC circuit design?

If the answer is no, does this hold true for a SSB installation?

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