Re: New Thread on A54 fridge pumps (ATTN: OLIVER Vela Nautica)



According to Frigoboat, the pump selected should move at least 6 liters/min. A 24-volt pump rated at 12 liters/min. running half speed on 12 volts will pump about 6 liters/min.

I am not the electrical expert that Dean Gillis is, but I will try to answer your question. In this schematic, the relay has a 12-volt coil that activates an internal switch. The switch could switch either 12 volts or 24 volts. In the schematic, you will note that only the positive is switched. Dean, feel free to edit or correct.

That relay in the schematic is a very ordinary "Bosch style" normally open 4 pin relay which uses 2 pins (85 & 86) to activate the coil, meaning when 12 volt positive is connected to 85 and 12 volt negative is connected to 86, a switch is closed between 2 pins (30 & 87). There are 2 types of 4 pin relay available; normally open or normally closed. A normally open relay will switch power ON for a circuit when the coil is activated. A normally closed relay will switch power OFF for a circuit when the coil is activated. You want a normally open relay for this project. To further confuse, there are 5 pin relays which allow either normally open or normally closed depending on whether you use 87 (normally open) or the fifth pin 87a (normally closed).

CW Bill Rouse Amel Owners Yacht School
Address: 720 Winnie, Galveston Island, Texas 77550 
View My Training Calendar

On Thu, Jul 9, 2020 at 4:27 PM Porter McRoberts via <> wrote:
Bill in your schematic,
The relays are 12VDC control and 24VDC load circuit, easy to put a 2-3 amp fuse on the load circuit.
I've searched for this relay and find it quite difficult to find the definitive solution.  Commonly the reverse is found.
I’d like to build a control board for the pumps.
Might you have a source, or nomenclature that would reveal this hidden gem on the web for me?

A second question:  running a 24v pump at 12v, surely spares the pump, but will it affect the pump volume, as the 1.5+ GPH is quite important, yes?

Always appreciated,

S/V IBIS A54-152

On Jul 3, 2020, at 3:30 PM, CW Bill Rouse <brouse@...> wrote:


I wish I was on your 54 with you because I have a burning question about all of this. and I have a recommendation for you.

My burning question:
If you see the schematic in my previous post in this thread, you will notice the schematic from a Frigoboat manual. The source of the voltage output from the E51385 blue box to the water pump originates in this schematic with each of the Danfoss Compressor Controllers at the F terminal. In fact, the two wires for each fridge unit come directly from the Danfoss to the E51385. The Frigoboat manual clearly states, regardless of the voltage of the fridge the output on the two F terminals is 12 volts. BTW, the Danfoss operates on 12 or 24 volts, but always outputs 12 volts to Terminal F. Have you checked the output voltage on each of the Danfoss on terminal F and the terminal next to it? I do not see any other way that the E51385 blue box can output 24 volts and if there is 24 volts on the Danfoss fan terminals, I suspect something is wrong with the Danfoss.

My recommendation:
Why don't you do this eliminating the E51385 and eliminate the limitation on amps on the Danfoss terminal F, and run a 24-volt pump??:
<Relays to control water pump.jpg>
CW Bill Rouse Amel Owners Yacht School
Address: 720 Winnie, Galveston Island, Texas 77550 
View My Training Calendar

On Fri, Jul 3, 2020 at 2:02 PM Jamie Wendell <mysticshadow54@...> wrote:
OK, my "final" update on the Flojet pump and Frigoboat E51385  interface. I cannot explain it, but the interface is definitely out-putting 24 volts to the pump at all times.
Maybe my interface is malfunctioning, so I installed a solid-state relay and a DC converter to step the voltage down to 12 volts. I used a 24-volt relay in place of the E
51385 pump connection and then feed the converter and pump via the live 24-volt terminal box in the engine room. The relay simply engages the pump when the compressors call for it.

A bit more complicated than I would like but the pump runs perfectly now and obviously I no longer get the pump overload signals at the interface. The higher capacity pump may draw more power, but it really cools down the 3 refrigerator units fast.

My next task is to get the brushless motor working to replace the Flojet motor. I will drive it directly via the 24-volt terminal block and eliminate the DC converter.

Until then I am "over and out" regarding this perplexing issue with the E
51385. I really appreciate all the suggestions and assistance, but will report once I have the brushless motor controller operational. That will be the gold standard.

Phantom, A54 #44

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