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Old 07-09-2014, 10:01   #16
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Thanks Ex-Calif and SaiFastTri... I did google "low voltage disconnect." Lots of options that would accomplish the goal. And thanks Ex-Calif for the specific Blue Seas product suggestion. I think I'll just go with that.

I tried to preempt the fridge debate a little with my original comment.... "assuming leaving the fridge on is important." I recognize that there are a number of different views on this subject and I appreciate where everyone is coming from. There is always a balance between cost and convenience. It's different for everyone, and for us, I'd prefer to keep the fridge on if possible. But as Ex-Calif said, if the voltage drops too low, and given the choice, I'd rather ditch the contents of the fridge and save the batteries. That's all.
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Old 07-09-2014, 10:18   #17
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re: Using a Combiner for the Fridge

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Originally Posted by Ex-Calif View Post

OP may have other reasons for leaving the fridge on. Condiments for sandwiches perhaps, milk, cheese, cold cuts.

The answer is, yes. There are any number of ways to automatically shed DC loads on the battery bank.

What if he wasn't plugged into shore power and was meeting his fridge needs with solar 90% of the time and in case of 4 days of overcast he wanted to protect his $1,000 battery bank vs. $12 bucks worth of mustard, mayo and cheese.
Dan, I did give him a solution: solar, while others chimed in with good ideas about LV cutoffs, great ideas. As I mentioned, I have been having this discussion for the past 16 years with many of our C34 skippers. Unless the electrical system on the dock can be guaranteed to "come back" after failure, having "Condiments for sandwiches perhaps, milk, cheese, cold cuts" is the SUREST way to cure the OP from ever leaving his fridge on.

Ever have to clean a fridge after the power goes off on Sunday night right after you leave, it's been 90F all week, and you don't get back til Friday night?

It's a bloody MESS, it stinks and his wife will have HIM clean it up!

That is the reason for my post based on my experience. The ONLY skipper who convinced me it works for him has his home and office 500 feet away from his boat, has lunch on the boat and can, daily, check that things are OK.

IMHO, a cold beer when he gets to the boat is not a good reason to deplete a finite resource: not the electricity eco-issue, but rather the fact that marine fridge systems are NOT like fridges in your house which are built to work 24/7 for years and years; boat fridges just have a limited service life, and last longer if they're off when not really needed.
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Old 07-09-2014, 10:25   #18
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re: Using a Combiner for the Fridge

Although dock power is available to me I'm so anal about electrolosis that I prefer to run on my own batteries. That is the reason I suggested a solar panel. I think Stu Jackson is also a bit queasy about electrolosis too, which is why he had similar suggestions.
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Old 07-09-2014, 10:31   #19
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re: Using a Combiner for the Fridge

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I think Stu Jackson is also a bit queasy about electrolosis too, which is why he had similar suggestions.
Not so much, but I really don't know, because I am a proponent of NOT leaving your boat plugged and live when you're not there. It's also a good reason, but not my primary one. My primary issue is that I don't want my boat to burn up because I was too lazy to stop for a cold beer. Indeed, sometimes I GASP! bring warm beer to the boat and have to wait GASP! a whole 15 minutes for it to get cold when I stick it into the evaporator once I turn the fridge on.

And we have very reliable electrical on our dock. With unreliable electrical on the dock, it's simply a problem waiting to rear its ugly head.

What's your entire boat worth to you? A cold beer...

As for the solar issue Dan mentioned with shading, folks on moorings (i.e., not docks) have been running their fridges 24/7 unattended with properly sized solar systems for years. It can and does work if designed properly. They do, it's just that I wouldn't.

But, look, everyone has different priorities. I'm simply stating MY opinion with my reasons.

Your boat, your choice.
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Old 07-09-2014, 10:47   #20
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re: Using a Combiner for the Fridge

I was in a flaky marina that had off and on (mostly on) service, I used a little transformer that I wired to my fridge and when the power went off, only the fridge was plugged into it as I have solar that covers everything in the summer but sometimes not the fridge in the winter here in the PNW, which is really the PNE.................. you could do this and then move the power to your whole boat to charge up the batteries on the weekends.....
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Old 07-09-2014, 13:22   #21
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re: Using a Combiner for the Fridge

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Not so much, but I really don't know, because I am a proponent of NOT leaving your boat plugged and live when you're not there.
Stu, I don't hook up to dock water for the same reason. All you need is one wrong hose in your boat to let go and you'll be on the bottom before you can say Jackie Robinson...
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Old 07-09-2014, 15:28   #22
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re: Using a Combiner for the Fridge

Old school, put a relay with contactor in the DC line and with an AC coil. Yours drinks may get warm but batteries will last.
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Old 07-09-2014, 16:26   #23
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re: Using a Combiner for the Fridge

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Dan, I did give him a solution: solar, while others chimed in with good ideas about LV cutoffs, great ideas. As I mentioned, I have been having this discussion for the past 16 years with many of our C34 skippers. Unless the electrical system on the dock can be guaranteed to "come back" after failure, having "Condiments for sandwiches perhaps, milk, cheese, cold cuts" is the SUREST way to cure the OP from ever leaving his fridge on.

.
Sorry Stu - Maybe I am a bit sensitive. It seems more and more threads around here go immediately into thread drift when people are asking for simple solutions.

You've got the OP thinking about solar I am sure but even with solar a low voltage cutoff would be prudent to protect the batteries.

So add $1,000 worth of solar to run a fridge to $89 bucks for an isolator.

Solar will keep the beer cold but it still won't isolate the batteries.
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Old 07-09-2014, 16:33   #24
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re: Using a Combiner for the Fridge

Well put!
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Old 07-09-2014, 16:38   #25
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re: Using a Combiner for the Fridge

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Sorry Stu - Maybe I am a bit sensitive....

Solar will keep the beer cold but it still won't isolate the batteries.

Thanks, Dan, much appreciated.

Yes, you're right, but the one thing we don't know is how bad his electrical dock system is. IF it goes out for more than a short time, then he still ends up with low batteries (but NOT dead, at least) and warm beer anyway.

I'm just givin' him some options, see my earlier posts.

His boat, his choice.
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Old 07-09-2014, 17:08   #26
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re: Using a Combiner for the Fridge

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Thanks, Dan, much appreciated.

Yes, you're right, but the one thing we don't know is how bad his electrical dock system is. IF it goes out for more than a short time, then he still ends up with low batteries (but NOT dead, at least) and warm beer anyway.

I'm just givin' him some options, see my earlier posts.

His boat, his choice.
And a stinky fridge to clean - LOL...

You points were not lost on me.



In regards to the water - I am wondering if a high flow valve at the shore hookup is a good idea. Sure one can get a spill when unattended but how about when sleeping?

It would be a crappy morning to wake up to 3 inches of water in the salon - LOL...
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Old 11-09-2014, 16:42   #27
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re: Using a Combiner for the Fridge

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And a stinky fridge to clean - LOL...

You points were not lost on me.



In regards to the water - I am wondering if a high flow valve at the shore hookup is a good idea. Sure one can get a spill when unattended but how about when sleeping?

It would be a crappy morning to wake up to 3 inches of water in the salon - LOL...
Apology for extended "off-topic" but worth mentioning, my solution to water safety was one of those garden water valves where you set how many gallons (not minutes) to run and it then shuts off. I set it on 100 gallons each day and that is the maximum that can come aboard to sink you if unattended.
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Old 11-09-2014, 17:47   #28
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re: Using a Combiner for the Fridge

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Originally Posted by Ex-Calif View Post
Sorry Stu - Maybe I am a bit sensitive. It seems more and more threads around here go immediately into thread drift when people are asking for simple solutions.

You've got the OP thinking about solar I am sure but even with solar a low voltage cutoff would be prudent to protect the batteries.

So add $1,000 worth of solar to run a fridge to $89 bucks for an isolator.

Solar will keep the beer cold but it still won't isolate the batteries.
There are a lot of solar controllers that isolate the loads if the batteries get low. You can tell which ones, they have connections for solar panels, batteries and a set of connections for load. Even that $100 controller does that, and allows you to set the LV disconnect setpoint.
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Old 11-09-2014, 18:01   #29
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Re: Using a Combiner for the Fridge

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Apology for extended "off-topic" but worth mentioning, my solution to water safety was one of those garden water valves where you set how many gallons (not minutes) to run and it then shuts off. I set it on 100 gallons each day and that is the maximum that can come aboard to sink you if unattended.
Great idea!
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Old 12-09-2014, 10:18   #30
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Re: Using a Combiner for the Fridge

Acr wouldn't work. You need 12v on both sides for it to engage.
Get a dual power fridge. It should be running off ac at the dock with DC breaker off. turn dc breaker on when leave dock.
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