Run AC Watermaker off Inverter?

[eheffa]

Thanks Lepke.

It sounds like you have a well worked out power scheme.

Our boat is smaller (Nordic Tug 37) but some of the same principles apply.

I’m optimistic that we can find some solution to our problem. It wouldn’t be the end of the world to have to run the generator but on our sea days it makes sense to exploit the already existent capacity of the engine / alternator.

 

[Maerin]

Perhaps a bit of a kludge, and not sure if the inverter transfer relay will be happy with the amount of current, but since the watermaker runs continuously once it starts, can you start it up on the genset then switch the genset off, allowing the inverter transfer switch to take over. The dip in voltage might not be long enough that the motor will slow enough to pull in the start windings and keep running. You could also unload the back pressure valve so the HP pump is running at a low load. Once the pump is running, and provided the inverter can make the transfer quickly enough, it should be able to power the water maker since it won't be cycling. Again, not ideal, but it might work. I believe the transfer relays are rated at 50A, but I'd talk to Magnum to see what they recommend. I'm with you on utilizing that power under way, but only if it can be accomplished without consequences to the equipment.

 

[eheffa]

Perhaps a bit of a kludge, and not sure if the inverter transfer relay will be happy with the amount of current, but since the watermaker runs continuously once it starts, can you start it up on the genset then switch the genset off, allowing the inverter transfer switch to take over. The dip in voltage might not be long enough that the motor will slow enough to pull in the start windings and keep running. You could also unload the back pressure valve so the HP pump is running at a low load. Once the pump is running, and provided the inverter can make the transfer quickly enough, it should be able to power the water maker since it won't be cycling. Again, not ideal, but it might work. I believe the transfer relays are rated at 50A, but I'd talk to Magnum to see what they recommend. I'm with you on utilizing that power under way, but only if it can be accomplished without consequences to the equipment.

Hi Steve,

I've tried that maneuver several times: Run Generator, switch on Watermaker with High pressure pump running at normal workload and then switch out the Generator. The Magnum either trips out with over current alarm light or the watermaker quits due to the brief loss of power.

In theory the Magnum should have more than enough capacity to run this WM, except for the potential start up surge (it is rated for 70A surge for 1 msec and 40A surge for 10 msec.) I can't measure the HP startup current but it is presumably exceeding these parameters.

I plan to try dialling down the pressure output to as low as possible and then slowly bringing it up to 800 PSI as another maneuver but this means grovelling down in the lazarette every time we start up the watermaker...

-evan

 

[Lepke]

Figure out what your power draw will be. Most modern alternators will make more than enough amps to keep ahead of the draw. Optionally you can add an external voltage regulator to better control the charge settings.

My boat came with a 12v, 2200 watt inverter. I use GM CS-144 alts (140 amp) for 12 volts and (as I remember) at full inverter AC power each alternator was putting out about 75 amps. The same output on the 48v inverter uses about 20 amps each, depending on the charge voltage. A big reason why I went to 48V.

 

[eheffa]

Figure out what your power draw will be. Most modern alternators will make more than enough amps to keep ahead of the draw. Optionally you can add an external voltage regulator to better control the charge settings.

My boat came with a 12v, 2200 watt inverter. I use GM CS-144 alts (140 amp) for 12 volts and (as I remember) at full inverter AC power each alternator was putting out about 75 amps. The same output on the 48v inverter uses about 20 amps each, depending on the charge voltage. A big reason why I went to 48V.

I do have an external regulator for the alternator. (A Balmar unit that I don't really like as the programming is a PIA; but that is a separate issue I think.)

I believe that the alternator is capable of providing the DC power. The wiring is up to spec. It's the inverter that isn't handling the startup current on the AC side.

-evan

 

[syjos]

I appreciate the discussion points made above.

I have tried the start with the generator & switch to inverter only trick & with the brief lapse in power, the watermaker either quits or the inverter trips out over the surge...

Are you using the inverters automatic transfer function or switching manually?

There should not be a brief lapse in power with the inverters automatic transfer function. It should be a seamless, uninterrupted transfer.

 

[eheffa]

Are you using the inverters automatic transfer function or switching manually?

There should not be a brief lapse in power with the inverters automatic transfer function. It should be a seamless, uninterrupted transfer.

Good question.

I see re-reading the manual that I can set the inverter to be in UPS mode so that it has less than 16 msec transfer to invert mode when switching off the generator. This might just allow the start on gennie and switch to inverter trick.

-evan

 

[DavidM]

Are you using the inverters automatic transfer function or switching manually?

There should not be a brief lapse in power with the inverters automatic transfer function. It should be a seamless, uninterrupted transfer.

No!!! It takes a high end inverter like the Victron which will synchronize the AC inverter waveform with the shorepower waveform before switching. Most inverters don’t do this, so there is a momentary pause when it switches.

David

 

[motion30]

the only other draw I had was the supply pump which I change to an DC diaphragm pump at midday my solar covers the amperage. I am producing 40 gallons per hour

 

[eheffa]

No!!! It takes a high end inverter like the Victron which will synchronize the AC inverter waveform with the shorepower waveform before switching. Most inverters don’t do this, so there is a momentary pause when it switches.

David

This Magnum Inverter/charger is no slouch either.

It seems that when I was trying the startup with generator & switch to inverter idea, I did not have the inverter set to 'UPS mode'. There was a noticeable moment when all AC power was lost and the Watermaker either quit or the brief lapse in AC power and resultant power surge tripped the overload on the inverter. In UPS mode it takes less than 16 msec to switch over to inverter AC mode. (By my math, that is less than a single sine wave cycle at 60Hz. I'm guessing that the Watermaker won't be too fussed to miss one cycle of the AC wave...)

I will try that next and report back.

If the problem could be solved by simply starting with the gennie and switching over to inverter supplied by the main engine alternator, I would be happy.

-evan

 

[DavidM]

I'll bet the inverter keeps the pump running in UPS mode if you first start it with the generator. UPS mode synchronizes the wave form.

David

 

[eheffa]

I'll bet the inverter keeps the pump running in UPS mode if you first start it with the generator. UPS mode synchronizes the wave form.

David

Thanks David.

I am optimistic with fingers crossed.

It never hurts to read the manual either.

I will report back here after testing.


- Evan

 

[sunchaser]

Possibly there is an issue with the used water maker or initial wiring setup.. What are the major loads on your inverter while cruising? If any big ones have you tried turning them off before powering up the water maker?

 

[eheffa]

Possibly there is an issue with the used water maker or initial wiring setup.. What are the major loads on your inverter while cruising? If any big ones have you tried turning them off before powering up the water maker?

Hi,

No other loads when attempting to get this to work.

I'm quite sure the wiring is correct as it runs just fine off the generator or shore power. The inverter runs other loads without issue including the microwave which, when in active heating mode, actually draws more power than the watermaker.

i'm hoping that having the Inverter in UPS mode, I can get the watermaker started under generator power and then switch the generator feed off to hand over to the inverter. It will be a few days before I can test this out but I could live with this arrangement...

-evan

 

[motion30]

something doesn't seem right here. I have a magnum 2000 watt inverter and it has no trouble running their microwave at well over 100 amps. I regularly use a coffee maker IU's is 105 amps, and a hot water heater which uses 87 amps .. seems to me your inverter is not producing its rated power

 

[FF]

Plan B might be a belted water pump simply run off the main engine?

 

[twistedtree]

With the faster transfer from gen to inverter, I think you have a good shot at getting it to work the way you want.

 

[C lectric]

something doesn't seem right here. I have a magnum 2000 watt inverter and it has no trouble running their microwave at well over 100 amps. I regularly use a coffee maker IU's is 105 amps, and a hot water heater which uses 87 amps .. seems to me your inverter is not producing its rated power

Many motors can draw 4 or 5 times their running current when starting.
If the inverter has enough surge capacity AND If the motor starts UNLOADED from any back pressure and quickly maybe the inverter could handle it.

Once the motor starts the inverter can most likely handle the water maker.

Microwaves, coffee makers, HWT. and such DO NOT have that high inrush current of this motor. Yes, electronics can have some inrush but not like a motor in most cases.

He should try the the inverter UPS mode and the handoff from the generator.
ALso he should seriously consider some of the other things mentioned such as the hard start cap. which in reality is just a larger capacity capacitor, or a soft start module, or finding out if the high pressure kick in can be delayed even just a few seconds. It sounds like it is already delayed, it just needs more of a delay.
Try the cheapest first:
--THe inverter UPS handoff since you already have it.
--Then the hardstart cap.

THe last two will take a bit of research:
-- If the high pressure is already on a delay then it is most likely on a relay of sorts which may be adjustable OR replaceable by one with more of a delay possible. If not that way maybe a cascade if the delay is off the control board. Then an adjustable delay relay could be powered from the board output. Once the delay relay is energized set it for 2-3 second delay then allowing the high pressure to kick in. If this is the route chosen then try adjusting the delay for the minimum needed to reliably start the motor and then kick in the high pressure. It may mean some trials.
-- The last would be, at least to me, the soft start control for the motor. But I half suspect that unless the high pressure kick in is also timed later there could still be a problem.

I don't know since I don't have one of these units or an inverter of any size to operate something like this so these are just my musings..


EHEFFA Is the motor a capacitor start type or not? Copy the nameplate info about voltage, current, HP also and post it. Also post a photo of the motor if possible. It all may help. Without that info we are flying blind to a degree.

 

[ksanders]

I think first off that running the watermaker from the inverter is just fine.

My watermaker currently runs just off the generator, but I have a switch already installed and am going to put a feed back to my inverter panel so that I can choose sources.

The why part is simple. There are times when I’m under way that I just want to make some water and do not want to have to start the generator, just for that load.

It also provides a backup source for water in case the generator is not working. I love redundancy!

As to the OP’s issue I think a post above that many missed says it all.

If the pressure valve on the watermaker is set to 800 psi, then the high pressure pump is starting under load. I would be willing to bet that if you dropped the pressure back to zero or near zero the pump would be able to start up just fine.

 

[C lectric]

As to the OP’s issue I think a post above that many missed says it all.

If the pressure valve on the watermaker is set to 800 psi, then the high pressure pump is starting under load. I would be willing to bet that if you dropped the pressure back to zero or near zero the pump would be able to start up just fine.

END QUOTE:

RIght on.

It may be possible to install a control valve and timer, back to that, that will dump the water untill the motor is fully running and then close to pressurize the system for operation or some similar arrangement. Likely only need a second or two.

 

[ksanders]

Regarding watermaker pressure valves and membrane pressure...

People seem to think that on a watermaker the pressure valve is a “set and forget” kind of thing.

Nothing could be further from the truth.

You should be checking your watermaker membrane pressure, and adjusting the valve every time you run the watermaker. If you do not do that you are either getting less than rated water output, or overpressuring your membranes.

The pressure required to get rated production varies based on water salinity. That salinity varies greatly based on a lot of factors, including recent rainfall.

For example the other day I was anchor’d in a large bay with a nice big stream emptying into it. I was able to produce my rated 40 GPH of water at less than 600 PSI and the water came out at less than 50 PPM.

The next day I was underway in the open ocean and barely got 40GPM at 800 PSI, and the flow was 140 PPM.

Huge differences!

The point is that there is no reason to startup a watermaker under load. Just back off the pressure as part of your shutdown process, and build pressure as part of your startup process.

Then you can be assured that you are getting the most out of your watermaker.

 

[eheffa]

Many motors can draw 4 or 5 times their running current when starting.
If the inverter has enough surge capacity AND If the motor starts UNLOADED from any back pressure and quickly maybe the inverter could handle it.

Once the motor starts the inverter can most likely handle the water maker.

Microwaves, coffee makers, HWT. and such DO NOT have that high inrush current of this motor. Yes, electronics can have some inrush but not like a motor in most cases.

He should try the the inverter UPS mode and the handoff from the generator.
ALso he should seriously consider some of the other things mentioned such as the hard start cap. which in reality is just a larger capacity capacitor, or a soft start module, or finding out if the high pressure kick in can be delayed even just a few seconds. It sounds like it is already delayed, it just needs more of a delay.
Try the cheapest first:
--THe inverter UPS handoff since you already have it.
--Then the hardstart cap.

THe last two will take a bit of research:
-- If the high pressure is already on a delay then it is most likely on a relay of sorts which may be adjustable OR replaceable by one with more of a delay possible. If not that way maybe a cascade if the delay is off the control board. Then an adjustable delay relay could be powered from the board output. Once the delay relay is energized set it for 2-3 second delay then allowing the high pressure to kick in. If this is the route chosen then try adjusting the delay for the minimum needed to reliably start the motor and then kick in the high pressure. It may mean some trials.
-- The last would be, at least to me, the soft start control for the motor. But I half suspect that unless the high pressure kick in is also timed later there could still be a problem.

I don't know since I don't have one of these units or an inverter of any size to operate something like this so these are just my musings..


EHEFFA Is the motor a capacitor start type or not? Copy the nameplate info about voltage, current, HP also and post it. Also post a photo of the motor if possible. It all may help. Without that info we are flying blind to a degree.

Thanks for all these suggestions.

The Watermaker is a pretty standard circa 2007 Village Marine Stowaway 600 (25 GPH) unit. I don't think is has any sort of capacitor start component.

I do have the ability to start the watermaker with the Bypass valve on so that the HP pump is not at full output when it starts.

I have a few options to try...

Thanks,

-evan

 

[eheffa]

I think first off that running the watermaker from the inverter is just fine.

My watermaker currently runs just off the generator, but I have a switch already installed and am going to put a feed back to my inverter panel so that I can choose sources.

The why part is simple. There are times when I’m under way that I just want to make some water and do not want to have to start the generator, just for that load.

It also provides a backup source for water in case the generator is not working. I love redundancy!

As to the OP’s issue I think a post above that many missed says it all.

If the pressure valve on the watermaker is set to 800 psi, then the high pressure pump is starting under load. I would be willing to bet that if you dropped the pressure back to zero or near zero the pump would be able to start up just fine.

I feel a little sheepish in realizing that there are two ways to start the watermaker and I never actually tried the second method - duh!.

One is using the remote panel, which starts the HP pump up in full load @ 800 PSI. The other way is to go to the WM unit itself and have the bypass valve "engaged" so that the HP pump is not under load and then gradually turn the valve to load the HP pump to 800 PSI. That would be the obviously better method & I totally missed that.

 

[eheffa]

Regarding watermaker pressure valves and membrane pressure...

People seem to think that on a watermaker the pressure valve is a “set and forget” kind of thing.

Nothing could be further from the truth.

You should be checking your watermaker membrane pressure, and adjusting the valve every time you run the watermaker. If you do not do that you are either getting less than rated water output, or overpressuring your membranes.

The pressure required to get rated production varies based on water salinity. That salinity varies greatly based on a lot of factors, including recent rainfall.

For example the other day I was anchor’d in a large bay with a nice big stream emptying into it. I was able to produce my rated 40 GPH of water at less than 600 PSI and the water came out at less than 50 PPM.

The next day I was underway in the open ocean and barely got 40GPM at 800 PSI, and the flow was 140 PPM.

Huge differences!

The point is that there is no reason to startup a watermaker under load. Just back off the pressure as part of your shutdown process, and build pressure as part of your startup process.

Then you can be assured that you are getting the most out of your watermaker.

Thanks - Yes. I have been monitoring all these functions but got into the default of activating the Watermaker with the remote panel and totally missed the opportunity to start up at the unit itself and use the Bypass valve to reduce the startup load. I will try this and report back.

The high river flow inlets with brackish water allow for much better production and I have used the pressure regulator to keep the flow and pressures in spec but missed the obvious clue here.

-evan

 

[eheffa]

As to the OP’s issue I think a post above that many missed says it all.

If the pressure valve on the watermaker is set to 800 psi, then the high pressure pump is starting under load. I would be willing to bet that if you dropped the pressure back to zero or near zero the pump would be able to start up just fine.

END QUOTE:

RIght on.

It may be possible to install a control valve and timer, back to that, that will dump the water untill the motor is fully running and then close to pressurize the system for operation or some similar arrangement. Likely only need a second or two.

Thanks. I think that all the functions are probably already in place. Missed opportunity... duh!

 

[eheffa]

something doesn't seem right here. I have a magnum 2000 watt inverter and it has no trouble running their microwave at well over 100 amps. I regularly use a coffee maker IU's is 105 amps, and a hot water heater which uses 87 amps .. seems to me your inverter is not producing its rated power

It's all about the start-up surge I think. As I said above, I can run the microwave without difficulty. The microwave draws more power than the Watermaker does in its steady state.

 

[Russell Clifton]

While reading my owners manual and related part manufactures literature, I read that the water maker should not be started under high pressure as the shock load to the membranes can damage them. The manual says: "During start-up, a gradual change from a standstill to operating state is recommended. Feed pressure should be increased gradually over a 30-60 second time frame." This is Dow Chemical guidelines.

So now I start the water maker down in the engine room instead of from the pilot house, a little more trouble but those membranes are expensive. Anyone else doing this?

 

[eheffa]

While reading my owners manual and related part manufactures literature, I read that the water maker should not be started under high pressure as the shock load to the membranes can damage them. The manual says: "During start-up, a gradual change from a standstill to operating state is recommended. Feed pressure should be increased gradually over a 30-60 second time frame." This is Dow Chemical guidelines.

So now I start the water maker down in the engine room instead of from the pilot house, a little more trouble but those membranes are expensive. Anyone else doing this?

Yes. I read that too. (Reviewing the manual); but, it also says one can start from the remote panel as an alternative. This is what I had been doing and probably one reason the start up surge is too high...

-evan

 

[Russell Clifton]

I hope you find a solution as I too would like to not run the generator while under way just to make water. But I will need to rewire the water maker as it is now being supplied by a circuit breaker that is not powered by the inverter, just shore power or the generator.

 

[dhays]

I feel a little sheepish in realizing that there are two ways to start the watermaker and I never actually tried the second method - duh!.

One is using the remote panel, which starts the HP pump up in full load @ 800 PSI. The other way is to go to the WM unit itself and have the bypass valve "engaged" so that the HP pump is not under load and then gradually turn the valve to load the HP pump to 800 PSI. That would be the obviously better method & I totally missed that.

Don’t feel sheepish. I don’t have a watermaker and didn’t realize they could be started with a low pressure load. You just installed a watermaker yourself. As with anything, there is a learning curve. One of the reasons I appreciate TF so much is there is so much I don’t know!