Re: [Amel] Re: Dessalinator model D50 50 l/h
Derick Gates SM2K #400 Brava
toggle quoted messageShow quoted text
Thanks for the great explanation of a simple timed fresh water flush system for the Dessalator membranes. In sending for the timer using your link, I note that it refers to a 24 Volt AC timer. Can I safely assume that you meant to refer to a 24 Volt DC timer? Here is the corresponding 24 Volt DC link that I found:
Same price, same functionality, I believe.
Amel SM #400
Currently on the hard at Bailey's Boatyard in Antigua
As of January 4th, 2013, Sapphire Beach Marina, St. Thomas USVI
---In amelyachtowners@..., <no_reply@...> wrote:
Regarding the timer flush system that I hooked up: I purchased one of these
I hope that link will post. If not, just google "24 volt fish feeder timer" or something like that and you will come across some 24 volt 7 day timers. The one mentioned above was about $35.00 US. This one was rated at 16 amps and had an internal battery backup. Since I wasn't exactly sure of the current draw of the fresh water pump on my boat I hooked the output of the timer to a 28 volt relay that was rated at a much higher amperage. I don't have the specification of the relay, but it was about $15.00 US at the local chandlery and its contacts were rated at 50 amps or something like that. So the timer controls the relay, that regulates power to the fresh water pump. At any rate, in the area behind the 24 volt breaker panel is a terminal block with a cover for 24 volt power. I wired the timer to this source, I then cut the wire from the breaker for the fresh water pump and wired it through the contacts of the relay. The control coil of the relay is controlled by 24 volt power from the control contacts of the timer (ganged relays). (I will try and post a schematic of this wiring in the Dessalator photos folder). The timer has a switch for "On" or "Timer" mode. When aboard the boat, we place that switch in the ON position and the fresh water pump operates as normal with the pressure switch on the pump functioning as usual. When we leave the boat, we make sure the water tank is full, switch the flush valve on the water maker low pressure pump to the flush position, and set the timer to the TIMER mode. We program the timer to flush for 5 minutes every other or every third day. 5 minutes of flush every third day will use about 500 to 700 liters of fresh water in 6 months. Your results may vary and you should actually time and measure how much flush water will pass through your system by collecting and measuring how much water comes out the thru hull fitting on the port side of the hull. At the programmed time, the timer contacts close sending 24 volts to the relay coil. This causes the relay coil to actuate and the relay contacts close, sending 24 volt power to the fresh water pump, The pump actuates for 5 minutes, sending fresh water thru the water maker system (flushes the low pressure pump, the series of filters, the high pressure pump, the membranes and the plumbing of the control panel). It has worked for 5 years without fail. I have a small portable solar panel that I leave out when off the boat to trickle charge the batteries and this has always kept up with the energy needs of the brief run cycles of the pump.
My only concern was having to leave the main 24 volt power switches on the battery bank in the on position when I leave the boat. I do make sure that every other breaker on the boat is turned off, including (1) the breakers in the engine room, (2) forward cabin, (3) beneath the nav station, (4) in the hanging locker by the nav station, and (5) above the overhead of the quarter berth, (6) all the 24 volt panel breakers except the bilge pump and fresh water pump. A potential failure mode would be if the timer or ganged-relay failed in the "on" position. In that case the pump would actuate until the water tanks were empty and them might continue to run until pump failure or battery depletion. I have toyed with installing some sort of "run-on" sensor that would time out the system and turn it off if the pump ran too long. I just haven't gotten around to that yet.
To flush with the water maker on or off is an interesting discussion. I have always flushed with the water maker off except when I am flushing the entire sea-chest/manifold system when leaving the boat. In that case I put the hose from shore water source in to the sea-chest and turn the water maker on. I have yet to find a source of water strong enough to keep up with the water maker's need for water. I have to cycle the water maker on and off to prevent it from sucking air from the sea chest. I can see why flushing with the system running would give more through-put of flush water and thus do a more thorough flush, but having the high pressure pump cavitate with air is supposedly damaging to that pump. Perhaps you can keep up with the feed water needs of the lower capacity water maker using shore water to flush but I cannot.
Nice chatting with you Jonas. I will post an alert when I post the schematic of the timer modification in the photo's section.
Amel SM #335
Sint Maartin Dutch West Indies
--- In amelyachtowners@..., Ann-Sofie Svanberg <kanalmamman@...> wrote: