Run AC Watermaker off Inverter?

[Maerin]

Typically, the VMT remote panel will start the boost pump (low pressure seawater feed pump) first. If it proves flow, then the HP pump will kick in. Using the remote precludes changing the backpressure, there's no facility to accomplish that from the remote panel. The typical use is in repeatable conditions so there's not a need to adjust the pressure every run. The remote is a convenience item.

The HP pump is probably a 3 cylinder, 1-1/2 HP pump with a centrifugal start switch and capacitor, 115/230 field convertable. I'm not sure how a soft start kit can be adapted to that configuration, you'll need to get the input from a motor expert for that. The pressure can indeed be set to bypass to startup, so the HP pump is starting with minimal load. It takes a couple of seconds to build backpressure even if the bypass valve is closed, so I'm not sure just how much difference that will make in inrush/start current. You'll just have to experiment and draw conclusions from real time factors. I'm also in the group that thinks a handoff from genset to inverter is possible.

My system is configured with an auto/off/manual switch that runs the HP pump, it bypasses a lockout that is triggered from the sensor unit that reads the TDS PPM content of the product water to shut down the pump if the TDS climbs over the setpoint (550 PPM). Point being, I can switch that bypass into "Auto" while the pump's running, it interrupts power to the pump for a split second, and the pump stays running. This is probably the same pump used in the STW600. My NF450 is just a basic (No Frills) version with a smaller membrane and no automated controls, although mine's wired 240V. So I'm out of the running for an inverter handoff.

I often wish I COULD run it underway, it'd be very convenient to arrive with a full tank of water. No genset running at anchor to make water. I'm with you 100% on that objective.


Good Luck!

 

[eheffa]

Thanks. Yes this is a great community resource.

 

[ksanders]

Today I arrived at my boat, and started up the watermaker. The pressure needed to get 40GPM was a bit over 600, and my TDS ended up at a bit over 100.

I use my watermaker pretty much every day. In harbors, in bays, in the open ocean.

The pressure adjustment valve is just a needle valve limiting brine water through the membranes. The position of the needle valve is different EVERY time.

Again, if you want to get the most out of your watermaker, in terms of produced water, and lifespan, you NEED to adjust the pressure EVERY time.

It’s EASY... close the needle valve slowly, watching both your produced water, AND your pressure. Stop when the pressure reaches your operating max (generally 800 PSI), OR when your flow reaches your membranes rated output.

That is the HAZARD of the self contained units. This can often only be done from the unit itself.

I have a modular watermaker, for a reason. I installed the control panel in a cabinet in the salon so that I do not have to go anywhere to run it properly.

 

[eheffa]

Today I arrived at my boat, and started up the watermaker. The pressure needed to get 40GPM was a bit over 600, and my TDS ended up at a bit over 100.

I use my watermaker pretty much every day. In harbors, in bays, in the open ocean.

The pressure adjustment valve is just a needle valve limiting brine water through the membranes. The position of the needle valve is different EVERY time.

Again, if you want to get the most out of your watermaker, in terms of produced water, and lifespan, you NEED to adjust the pressure EVERY time.

It’s EASY... close the needle valve slowly, watching both your produced water, AND your pressure. Stop when the pressure reaches your operating max (generally 800 PSI), OR when your flow reaches your membranes rated output.

That is the HAZARD of the self contained units. This can often only be done from the unit itself.

I have a modular watermaker, for a reason. I installed the control panel in a cabinet in the salon so that I do not have to go anywhere to run it properly.

Thanks Kevin,

I was intending to get the CruiseRO system but we got this used Village Marine unit for a very good price instead.

I had hoped to run the unit from the remote but I have fairly ready access to the main unit by simply opening the lazarette hatch and reaching in, so using the front panel every time I start the unit is a viable option. So far, it's been pretty consistent in running at the specified 800 PSI & not needed much adjustment from run to run.

I will be back to the boat on the weekend and will give it a whirl.

-evan

 

[eheffa]

Typically, the VMT remote panel will start the boost pump (low pressure seawater feed pump) first. If it proves flow, then the HP pump will kick in. Using the remote precludes changing the backpressure, there's no facility to accomplish that from the remote panel. The typical use is in repeatable conditions so there's not a need to adjust the pressure every run. The remote is a convenience item.

The HP pump is probably a 3 cylinder, 1-1/2 HP pump with a centrifugal start switch and capacitor, 115/230 field convertable. I'm not sure how a soft start kit can be adapted to that configuration, you'll need to get the input from a motor expert for that. The pressure can indeed be set to bypass to startup, so the HP pump is starting with minimal load. It takes a couple of seconds to build backpressure even if the bypass valve is closed, so I'm not sure just how much difference that will make in inrush/start current. You'll just have to experiment and draw conclusions from real time factors. I'm also in the group that thinks a handoff from genset to inverter is possible.

My system is configured with an auto/off/manual switch that runs the HP pump, it bypasses a lockout that is triggered from the sensor unit that reads the TDS PPM content of the product water to shut down the pump if the TDS climbs over the setpoint (550 PPM). Point being, I can switch that bypass into "Auto" while the pump's running, it interrupts power to the pump for a split second, and the pump stays running. This is probably the same pump used in the STW600. My NF450 is just a basic (No Frills) version with a smaller membrane and no automated controls, although mine's wired 240V. So I'm out of the running for an inverter handoff.

I often wish I COULD run it underway, it'd be very convenient to arrive with a full tank of water. No genset running at anchor to make water. I'm with you 100% on that objective.


Good Luck!

Thanks for your thoughtful post.

I do have ready access to the main unit so can play with the load on the HP pump.

It sound like our systems are a little different in how they deal with the high saline output. The VM runs the HP pump continuously and simply dumps the product water until the TDS value drops below the adjustable threshold for acceptability. Once the acceptable threshold is achieved (~ < 500 ppm) a solenoid valve will trip and the product goes to the "tank". (I actually have this line with 3 way valve to bypass into the sink until I choose to direct it to the FW tank).

In any case, if having the bypass valve on the unit open minimizes the startup load on the HP pump, that may well be the answer to my problem. I would prefer not to get into the hassle and expense of wiring an easy start or soft start capacitor into the system if this simpler solution will suffice.

As a backup plan, if running the generator to start up and handing over to the inverter with the inverter in UPS mode does the trick, I could live with that too.

It's nice to know that others see the virtue in not having to run the generator to make water. It would be quite wonderful to have a full water tank at the end of the day's run just using the alternator and inverter output.

-evan

 

[cafesport]

I have a one of these units setup to run off 240 from the generators or shore power and I have a similar unit set up to run off of one of our inverters. On startup the unit can demand over 6kw and that’s with the hp bypass set for zero pressure. As has already been mentioned you want to avoid pounding your membranes with high pressure on startup, so you should always close down by relieving the vessel pressure then shut off the hp pump then the lip pump. Another thing is you should not be running anywhere near 800 psi in those waters. Take a look at the temperature compensation factors and adjust your product flow to match the water temp that the panel sensor indicates. Also note that salinity probes will drift and loose their accuracy over time. Install a sampling t on the output and confirm the readings. Handheld sensors need fresh batteries and regular testing and calibration as well. Trust but verify what you are drinking.

 

[eheffa]

I have a one of these units setup to run off 240 from the generators or shore power and I have a similar unit set up to run off of one of our inverters. On startup the unit can demand over 6kw and that’s with the hp bypass set for zero pressure. As has already been mentioned you want to avoid pounding your membranes with high pressure on startup, so you should always close down by relieving the vessel pressure then shut off the hp pump then the lip pump. Another thing is you should not be running anywhere near 800 psi in those waters. Take a look at the temperature compensation factors and adjust your product flow to match the water temp that the panel sensor indicates. Also note that salinity probes will drift and loose their accuracy over time. Install a sampling t on the output and confirm the readings. Handheld sensors need fresh batteries and regular testing and calibration as well. Trust but verify what you are drinking.

Hi cafesport,

I have yet to try starting the HP pump with the bypass valve engaged. Even with that maneuver I recognize that the startup surge/draw may still be more than the inverter can handle.

Interestingly, the VM manual states that after starting the unit the first time, one can then start using the remote panel thereafter without needing to use the bypass valve. I'm not sure how that could be a good practice if indeed the system is subject to shock when you start it up with the HP pump in high pressure mode....?

The manual also states that one should dial back the pressure when output exceeds the nominal maximum as in very warm water or brackish water. We don't see especially warm water here but do get into some inlets with large rivers diluting out the seawater. I have kept an eye on this but have not yet seen product outputs that warranted dialling back the pressure.

Thanks for the suggestions.

-evan

 

[eheffa]

Testing Update (it's complicated)

So, I got out to the boat after work last night.

I had to re-wire the the watermake (WM) back to be on the Inverter supply of the breaker panel. (I had previously moved the WM breaker to be supplied by shore power / generator only as running the WM and bulk charging at the same time with the generator running was tripping the overload on the inverter.)

I switched the Inverter to UPS mode.

1. Attempting to start the WM powered by the inverter alone with the bypass valve open (full house bank batteries and the main engine running) did NOT work. The WM chattered the HP pump as in a brown-out condition for about 10 secs and quit. The Inverter did not actually trip out in overload as before but it was not able to provide the needed current to get the WM up and running.

"OK, I think to myself, let's go to Plan B and start the WM on Shore power, then switch to Inverter Power."

2. Shore Power Startup and Handover

Here's where it got interesting and more disappointing...

When wired to the Inverter circuit, even with shore power on (or generator power), attempting to start the WM HP pump failed due to this same brown out chattering effect. I had to turn off the Inverter's UPS mode inverting function or turn off inverting altogether and turn off its charging function to get a clean start for the WM.

Once the WM was truly up and running in RO mode on shore / generator power, I had to then turn on the inverter in UPS mode. I could then switch the shore power and hand over to inverter only and the WM would keep going. It would occasionally (~1 out of 3 attempts?) drop the ball and the WM would simply quit when attempting this handover.

I have to experiment a little more with all this but it looks like the inverter is interfering with the startup of the WM when on shore power unless the Inverter is totally disengaged. It CAN actually run the WM using the the shore power start and handoff routine; but, the multiple steps involved and the fragility of the power supply to do this is concerning. I'm not sure that this will be a viable routine way to run the WM.

-evan

 

[twistedtree]

Two things come to mind to check, with no assurance either will help....

Check the wire gauge and connections through the whole path from gen to WM with particular focus on that around the inverter. You could have power loss due to too small wiring and or poor connections that are preventing the WM from starting.

Check the start capacitor on the WM pump motor.

 

[eheffa]

Hmmm.

It starts up cleanly when on the Shore power only bus. ( I have 12 AWG wiring to supply the WM with AC power. All the same connectors just screwed to different bus.)

I don’t know how to evaluate the start up capacitors.

I’m thinking I will bail & just run off the generator unless starts can be reliable & trouble free.

 

[DavidM]

If you can't start the WM from shore power but through the inverter's transfer switch then you likely have a problem with wiring- why is it 12 gauge, it is usually 10 gauge or you have burned contacts in the transfer switch.

Put a voltmeter (AC of course) on the incoming/supply side connection to the inverter and try again starting the WM on shore power transferred through the inverter. Note what happens to the voltage. Then do the same thing but measure the load side of the inverter. A big drop during the first test is wire, a big drop on the second test is contacts.

The problem could also be in the wiring from the inverter to the WM, so measure the voltage at the WM when you try to start it.

It has to be one of these three that won't let the WM start on shore power transferred through the inverter.

David

 

[eheffa]

If you can't start the WM from shore power but through the inverter's transfer switch then you likely have a problem with wiring- why is it 12 gauge, it is usually 10 gauge or you have burned contacts in the transfer switch.

Put a voltmeter (AC of course) on the incoming/supply side connection to the inverter and try again starting the WM on shore power transferred through the inverter. Note what happens to the voltage. Then do the same thing but measure the load side of the inverter. A big drop during the first test is wire, a big drop on the second test is contacts.

The problem could also be in the wiring from the inverter to the WM, so measure the voltage at the WM when you try to start it.

It has to be one of these three that won't let the WM start on shore power transferred through the inverter.

David

Hi David,

I was mistaken.

The AC wire from breaker panel to WM is 10 AWG
but you are right, it may well be the supply side from the Inverter to panel. (I’ve been blaming the Inverter assuming it’s the problem rather than a wiring issue. )

I did not change that wiring when I replaced the factory installed Xantrex Inverter.

I will do more diagnostics.

-evan

 

[Southx10]

Watermaker

12 amps of 115 volts AC from an inverter will cost you 144 amps of 12 vdc each hour it is making water. You better have a big battery bank and a way of replacing all those amps.
You will be better off running your genset and make water, make hot water, charge a smaller battery bank. You can keep throwing money at it and make it work but you already have the gender. Do the math. Math doesn't lie.

 

[rgano]

OK, Evan, I have read every post here, and as always (well almost always), I learned a bit and thought how wonderfully helpful to you all here have tried to be. I can help a little bit in regard to soft starting microprocessors, but it is hard to imagine you getting away with running the various 12 VDC demands for long underway periods while simultaneously supplying a huge amount to the WM via an inverter. Seems like eventually you will likely be draining the batt banks and straining the alternator (maybe a cooling air hose to it?).

In regard to the soft starting issue, it would seem simple and cheap to start with the earlier suggestion of the bigger capacitor, but an actual ramp-up soft start requires a microprocessor like the two I have on my boat for my two ac units. Yes, they are expensive, but I discovered that Micro-Air sells their soft starter circuit board separately at a greatly discounted rate. I went that route and bought a plastic box to put each board in and ran my own wires to the push-on attachment points on the boards and thence to the proper place on the ac unit. I found the people at Micro-Air extremely helpful, and I would suggest calling them to see if their unit might be applicable to your WM pump.

When the water here is cooler than mid-summer 90F, my 3.5 KW generator will run the 13.5 KBtu and 10 KBtu air conditioners simultaneously, and you never hear the gen taking the load. Unfortunately in the mid-summer the load on the little Kubota one-lung diesel when running both ac units causes it to overheat and shut down after a few minutes, no fault of the soft starters.

 

[eheffa]

12 amps of 115 volts AC from an inverter will cost you 144 amps of 12 vdc each hour it is making water. You better have a big battery bank and a way of replacing all those amps.
You will be better off running your genset and make water, make hot water, charge a smaller battery bank. You can keep throwing money at it and make it work but you already have the gender. Do the math. Math doesn't lie.

Hi,

Yes, I have done the math & thought that my 160 Amp alternator would be up to the task of supplying the WM needs while we were underway. ( I was assuming that I would only run the WM once the 660 Ah house bank was recharged... )

But you make a good point in that this is still a significant 12V draw that will stress both the alternator & inverter; not to mention the WM if voltages are fluctuating.

I have a 9 KW Onan generator that works well & can easily handle the extra load so maybe this is a fruitless exercise. It uses about 2 L /hr diesel at half load.

I am now thinking that I will chalk this up to a good learning experience and resign myself to running the WM off the generator.

Thank you everyone for your very helpful & constructive input.

-evan

 

[eheffa]

OK, Evan, I have read every post here, and as always (well almost always), I learned a bit and thought how wonderfully helpful to you all here have tried to be. I can help a little bit in regard to soft starting microprocessors, but it is hard to imagine you getting away with running the various 12 VDC demands for long underway periods while simultaneously supplying a huge amount to the WM via an inverter. Seems like eventually you will likely be draining the batt banks and straining the alternator (maybe a cooling air hose to it?).

In regard to the soft starting issue, it would seem simple and cheap to start with the earlier suggestion of the bigger capacitor, but an actual ramp-up soft start requires a microprocessor like the two I have on my boat for my two ac units. Yes, they are expensive, but I discovered that Micro-Air sells their soft starter circuit board separately at a greatly discounted rate. I went that route and bought a plastic box to put each board in and ran my own wires to the push-on attachment points on the boards and thence to the proper place on the ac unit. I found the people at Micro-Air extremely helpful, and I would suggest calling them to see if their unit might be applicable to your WM pump.

When the water here is cooler than mid-summer 90F, my 3.5 KW generator will run the 13.5 KBtu and 10 KBtu air conditioners simultaneously, and you never hear the gen taking the load. Unfortunately in the mid-summer the load on the little Kubota one-lung diesel when running both ac units causes it to overheat and shut down after a few minutes, no fault of the soft starters.

Thank you rgano.

Yes, this has been a very helpful discussion.

As I just posted, I think I will take the easy out & just run the WM off the generator.

My Firefly Batteries like a higher current charging source anyways, so running our 9KW Onan to charge and make water will not be a terrible option by any means. On days when we have a long 8 hour run it seemed to me that running off the main engine would have been much better; in reality though, it has become far too complex.

I am bailing out on running off the Inverter.

- evan

 

[OldDan1943]

No one runs a 12vt WM?

 

[DavidM]

Evan:


I do respect your decision to forego the inverter driving the water maker concept.


But do check the voltages I spoke of in an earlier post. You don't have to do it with the WM, any large 10-15 amp AC load like a heater or hair dryer will cause enough voltage drop in the AC wiring to be able to check. If you have more than a couple of volts drop at any one spot with that load and particularly at the load's terminals vs the incoming power, then with the inrush current of the inverter that will go up 5-10 times and cause the problems you are experiencing.


Finding any bad connections or undersized wiring now will help avoid future disasters whether you use the inverter for the WM or not.


David

 

[motion30]

No one runs a 12vt WM?

I do. Why my water maker was initially AC with a 1 horsepower motor I traded that for 1 horsepower DC motor and also change the feed pump to 12 volt. It uses a maximum of 80 amps 12 volt making about 40 gallons an hour. I have a large solar array that can cover that on the sunny days

 

[eheffa]

Evan:


I do respect your decision to forego the inverter driving the water maker concept.


But do check the voltages I spoke of in an earlier post. You don't have to do it with the WM, any large 10-15 amp AC load like a heater or hair dryer will cause enough voltage drop in the AC wiring to be able to check. If you have more than a couple of volts drop at any one spot with that load and particularly at the load's terminals vs the incoming power, then with the inrush current of the inverter that will go up 5-10 times and cause the problems you are experiencing.


Finding any bad connections or undersized wiring now will help avoid future disasters whether you use the inverter for the WM or not.


David

Hi David,

I appreciate your good advice and suggestions.

I routinely monitor the AC voltage on the main panel when running on the inverter. (One reason I replaced the Xantrex inverter / charger was that it was starting to push the AC voltages up to 130+ VAC. )

The new Magnum inverter / charger is handling all other loads without any discernible voltage aberrations. For example, the microwave will draw 120 DC amps from the inverter without any voltage change at all. Similarly a hairdryer on high does not budge the AC voltage from the inverter - it's rock solid.

When the watermaker is wired directly to the Generator / Shore power bus, startup of the watermaker is consistently clean and flawless. I do not see any voltage drops.

When the WM is wired to the AC Inverter serviced bus, it will start up cleanly some times but at other times, it will fail with a brownout chattering and flickering lights at the watermaker. I noted that the panel voltage values would flicker and disappear while it is doing the flickering. The 25A breaker does not trip but the WM gives up after about 10 secs. I am not seeing a High output alarm on the inverter. I could apply a multimeter to various parts of the circuit to investigate further but I think I recognize that I am not likely to improve on this and further testing carries a risk of damaging the watermaker or inverter.

The inverter is wired on the AC supply side and to the main breaker panel with the OEM Nordic Tug factory installed cable which looks to be good quality 8 AWG wire. The battery cables from the house bank supplying the Inverter are 2/0 and a fairly short run. I have no trouble charging from the Magnum at 120 A.

I suppose that I could investigate further to see where the problem is but I'm betting that somehow the startup draw for the WM HP pump is more than the inverter can handle even when acting as a passive conduit. I do not see any other examples where the inverter is not working to its proper specs.

Looking at all this and reanalyzing the situation, it appears that the WM would be stressing the inverter and alternator, i.e. the DC side, close to its capacity. This is closer to its limits than I would like, whereas our 9 KW generator (max ~ 75A AC output) has no trouble and plenty of reserve supplying the necessary power for charging and making water and any other AC house demands. (We rarely use our Air conditioning when at anchor.)

In 15C water temperature, I'm seeing 17 GPH output from the WM. When being less than frugal, we would typically use about 80 gal of fresh water a week (our fresh water tank is ~144 USG), so that works out to be ~ 4.5 - 5 hours of watermarking a week. If we are at anchor and not underway we would typically run the generator 2 hours a day to top up the battery bank or ~10 - 14 hours a week. Assuming we are in anchorage locations that are clean enough, we would have more than adequate generator time for water production.

It's when we are underway making longer passages, that it seems redundant to run the generator in addition to the main engine, as we would normally let the main engine top up our batteries with excess power capacity going unused. We would not bother running the generator on those days. This was my main reason for wanting the inverter to be able to supply the power for the WM... BUT The logistics and expense of adding soft start etc. and still risking overtaxing the DC system has me thinking that it isn't worth it.

So, in the end, after a lot of discussion and testing, I do not think I see a cost effective or viable way to run the WM off the inverter.

Thank you everyone for your suggestions and input.

It's very much appreciated.

-evan

 

[OldDan1943]

I do. Why my water maker was initially AC with a 1 horsepower motor I traded that for 1 horsepower DC motor and also change the feed pump to 12 volt. It uses a maximum of 80 amps 12 volt making about 40 gallons an hour. I have a large solar array that can cover that on the sunny days

I was beginning to sound like an orphan because I have a DC WM.

 

[DavidM]

Evan:

Humor me and when you get a chance do this simple test:

When running a decent load- 15 amps AC to a circuit that is supplied by the inverter, but with shore power or genset power supplying that load, do the following:

Set a multimeter to a low AC voltage band, 50V or lower. Hook one lead to the incoming power at the main panel before it feeds the inverter/transfer switch. Then measure the voltage at these three points- at the supply AC terminals to the inverter, at the load terminals of the inverter and at the device itself or if that isn't easy then at the sub breaker that feeds it.

You will be hooking up both sides of your meter to the black wire but at different locations and will be reading voltage drop directly. You will not have to read two voltages and subtract the difference. The low range and just measuring the drop will make it easy to see voltage drop.

Like I said before a total voltage drop with 2 volts at 15 amps will result in 10 volts at 75 amps inrush current and that may be enough to produce the brownout symptoms you are seeing.

Then if you see a noticeable voltage drop look at where it is happening: supply wiring, transfer switch contacts or load wiring and see if you can find what is causing it. Also a 2 volt drop at 120V AC will produce quite a bit of heat if it is at a connection so look for hot spots as well. It probably won't be noticeable if it is spread over several feet of wiring though.


I truly believe that the symptoms you have described are indicative of a bad connection or marginal wire size on the AC circuits and have nothing to do with the inverter producing power itself.

David

 

[OldDan1943]

Evan:

I truly believe that the symptoms you have described are indicative of a bad connection or marginal wire size on the AC circuits and have nothing to do with the inverter producing power itself.

David

If the wire size is marginal, increasing the gauge will also verify the connections are sound and tight. SMILE

 

[eheffa]

Evan:

Humor me and when you get a chance do this simple test:

When running a decent load- 15 amps AC to a circuit that is supplied by the inverter, but with shore power or genset power supplying that load, do the following:

Set a multimeter to a low AC voltage band, 50V or lower. Hook one lead to the incoming power at the main panel before it feeds the inverter/transfer switch. Then measure the voltage at these three points- at the supply AC terminals to the inverter, at the load terminals of the inverter and at the device itself or if that isn't easy then at the sub breaker that feeds it.

You will be hooking up both sides of your meter to the black wire but at different locations and will be reading voltage drop directly. You will not have to read two voltages and subtract the difference. The low range and just measuring the drop will make it easy to see voltage drop.

Like I said before a total voltage drop with 2 volts at 15 amps will result in 10 volts at 75 amps inrush current and that may be enough to produce the brownout symptoms you are seeing.

Then if you see a noticeable voltage drop look at where it is happening: supply wiring, transfer switch contacts or load wiring and see if you can find what is causing it. Also a 2 volt drop at 120V AC will produce quite a bit of heat if it is at a connection so look for hot spots as well. It probably won't be noticeable if it is spread over several feet of wiring though.


I truly believe that the symptoms you have described are indicative of a bad connection or marginal wire size on the AC circuits and have nothing to do with the inverter producing power itself.

David

Thank you David.

I appreciate the advice. I understand the rationale. It would be good to verify the source of this brownout condition. I will try to do that sometime in the near future and report back here.

I have to pack up for a weekend boat trip. :-D

Cheers

 

[sunchaser]

Evan
When you have a chance describe your vessel, water demands and tankage.

 

[eheffa]

Evan
When you have a chance describe your vessel, water demands and tankage.

Hi,

We met in Prince Rupert last year.

We have a 2006 Nordic Tug 37. "Tugaway"

144 USG water tank.

Village Marine STW600 watermaker nominally capable of 25 GPH at 25C water temp.

at 15C we see ~ 17-18 GPH production.

We used to be more frugal without a watermaker but now can be a little more liberal with our water usage. We probably use ~ 80 USG per week.

-evan

 

[sunchaser]

Hi,

We met in Prince Rupert last year.

We have a 2006 Nordic Tug 37. "Tugaway"

144 USG water tank.

Village Marine STW600 watermaker nominally capable of 25 GPH at 25C water temp.

at 15C we see ~ 17-18 GPH production.

We used to be more frugal without a watermaker but now can be a little more liberal with our water usage. We probably use ~ 80 USG per week.

-evan

Evan
Remember you and Jane (?) well. Nice boat, smart people and you live near Sidney as I recall. BC above Port McNeil is indeed fresh water short. Easy to see your wanting to get the water maker right. We’ll keep an eye out for you.

 

[BDofMSP]

Ok I'll bite. Perhaps a stupid question (and a thread derail) but why all the concern about running the gen to run the watermaker? I mean, isn't that why we HAVE generators? So that we can have AC when we need it? I completely understand not wanting to run it in a quiet anchorage, but I'm missing something about why I shouldn't want to run it underway.

 

[Transaxial]

No one runs a 12vt WM?

What kind of capacity WM do you have? I came across a Spectra product the other day that makes 8 gal/hr on 10 Amps and 12 V. It can run all day if it has to just on solar or from the main engine generator.

 

[Transaxial]

Hi,

We met in Prince Rupert last year.

We have a 2006 Nordic Tug 37. "Tugaway"

144 USG water tank.

Village Marine STW600 watermaker nominally capable of 25 GPH at 25C water temp.

at 15C we see ~ 17-18 GPH production.

We used to be more frugal without a watermaker but now can be a little more liberal with our water usage. We probably use ~ 80 USG per week.

-evan

I know you already have your STW600 and had your heart set on running it from the inverter. I just went through a project reconfiguring an old boat with an old school electronics guy and he was very down on the use of inverters because of the inefficiencies in converting power and when you do the math, most boats do not have nearly enough batteries to do what we think we want to do. And stay over 50% charge to not kill the life of the batteries. So good choice to not run your WM from the inverter. One thought I had regarding the starting of the high pressure pump, would it work to just install a T in the pressure line with an extra ball valve that you could open for starting and then slowly close it to bring it up to pressure? Vent the leaked water wherever is handy.

My main thought for you is to use a smaller DC WM that only draws 10 amps at 12 Volts and is rated at 8 gal/hr. If you do your 8 hr cruise you could fill your 144 gal water tank from the main engine charging system and also have your battery bank charged at the end of the day. With that low of a draw you could make water daily from solar power and not run any engine. I found these Spectra WMs online and the Ventura 200T is the one the specs are for. List is $6,795. They have smaller ones too, about 4 g/hr for $4,000ish. Does anyone else have any experience with these DC units? Maybe OLD DAN will chime in!

Just a note on why your 1 1/2 HP single phase motor will not start easily is these single phase motors, specially on 120 volts, have a current in rush of at least 7-8 times full load running amps. Specs on a Baldor 1 1/2 HP 1800 rpm capacitor start motor are full load running amps 6.2 amps at 230 V, 12.4 amps at 115V which is what you had from the inverter, and 7.7 times full load amps at start. So now you have 12.4 A x 7.7 = 95 amps trying to supply power down a #10 or #8 wire so your voltage drop is very bad. Take into account the hundreds of feet of wire in the marina supply system that is rated for a 30 amp service and you have a severe overload and low voltage which spikes the amps even higher by Ohm's law. I wondered if your WM was possibly belt driven maybe you could have changed pulleys to slow it down, use a smaller motor, like 3/4 HP, that came more in line with the supply of power you have?