Understanding my genset alternator

I'm trying to figure out what good my genset alternator is other than to charge up the battery connected to it. My genset has a battery whose only purpose is to start the genset and can't be used for anything else.

Does the genset alternator is a typical installation provide charging capability to the house banks? Again the genset battery is not in anyway connected to the house bank.

My guess is that the genset alternator only supplies a charge to the battery connected to it. What a waste. So has anyone upgraded their genset alternator and wired it in such a way as to charge up the house bank.

I'm thinking that if I had a 200 amp alternator on the genset, I could charge the house banks much quicker that the currently installed 30 amp 3 bank battery charger.

Comments please.

My problem is I have a power hungry refrig that the battery charger is not capable of providing enough of a charge to recharge the batteries in a reasonable amount of time when on the hook.

*

What you have is common I believe.* The idea being that the Gen-Set battery always gets a full charge no matter what happens to the house and or start.

I think the problem is that the Gen Set engine will not be able to drive your Generator plant and a 200 Amp Alternator.* It takes a lot of HP to drive a 200 Amp Alt.* Not to mention the*double belts and pulleys that will be needed.

Change the fridge to something that is more economical on battery usage (the most expensive, maybe), add batteries to house bank to increase the size (which will be the least expensive)*or add a 200 Amp Alternator to your main*engine with external*Three Stage*regulation.* But keep in mind wet batteries can only accept half of their rating as a charge rate per hour, so they recharge slower than Gels that take up to 70% or so and AGM's that will take*a 100% charge rate.* So what this means is a 400 Amp wet battery*system at*half charge, down to 200 Amps, will be able to take only a max of*100 Amps no matter how big the alternator is so it will take two hours + to recharge them but an AGM battery system*of the same size would be able to take 200 Amps per hour and be charged*about an hour + or so if the alternator was a 200 Amp alternator.

To change your batteries to AGM is probably the most expensive but then again if taken care of they will last seven or more years and they have minimal maintenance requirements.* But to take full advantage of them you will need to do the alternator at the same time or change the house charger to a larger size to do the job in a shorter time.

Nothing that money can't fix.

Thanks JD.

My refrig is a Norcold DE 461 which has on the label on the inside of the unit a tag that states: 1.3 Amp at 120 volts which I believe translates to 13 amps at 12 volts. I'm assuming this amp draw is when the compressor is running so in the So FL summers I estimate it runs 75 % of the time thus using almost 10 amps per hour. If I want to limit charging to 2 times daily then 10 amps times 12 hours is 120 amps that just the refrig uses and must be replaced. Adding in additional electrical components I estimate 150 amps every 12 hours.

My current battery charger is a 30 amp 3 bank unit. I have 2 house banks consisting of 2 AGM 105 AH batteries on each bank for a total of 210 AH per bank or 420 total. The 3rd bank only charges the genset battery, a 92 AH AGM, and can't be paralleled.

My 30 amp 3 bank battery charger will probably only charge at the rate of 20 amps per hour due to line loss and in-efficiency thus requiring the genset to run 7.5 hours to produce the 150 amps used. That's 15 hours per day and of course un-acceptable. Even moving up to a 50 amp charger won't help much. If I get 35 amps out of it then I'm still looking at running the genny 4.2 hours every 12 hours.

That's why I was thinking of getting a bigger alternator for the genny.

Suggestions??

timjet wrote:
Thanks JD.

My refrig is a Norcold DE 461 which has on the label on the inside of the unit a tag that states: 1.3 Amp at 120 volts which I believe translates to 13 amps at 12 volts. I'm assuming this amp draw is when the compressor is running so in the So FL summers I estimate it runs 75 % of the time thus using almost 10 amps per hour. If I want to limit charging to 2 times daily then 10 amps times 12 hours is 120 amps that just the refrig uses and must be replaced. Adding in additional electrical components I estimate 150 amps every 12 hours.

My current battery charger is a 30 amp 3 bank unit. I have 2 house banks consisting of 2 AGM 105 AH batteries on each bank for a total of 210 AH per bank or 420 total. The 3rd bank only charges the genset battery, a 92 AH AGM, and can't be paralleled.

My 30 amp 3 bank battery charger will probably only charge at the rate of 20 amps per hour due to line loss and in-efficiency thus requiring the genset to run 7.5 hours to produce the 150 amps used. That's 15 hours per day and of course un-acceptable. Even moving up to a 50 amp charger won't help much. If I get 35 amps out of it then I'm still looking at running the genny 4.2 hours every 12 hours.

That's why I was thinking of getting a bigger alternator for the genny.

Suggestions??

Click to expand...

*Simple

Get a bigger charger, or even upgrade to a inver/charger combo.

We have a Xantrex 3kw inverter/charger that has a 150 amp charger.

You program it with the type and size of your house bank and it determines the correct charge rate based on that.

*

Cost is about a boating unit.

It's pretty simple...if you use electricity...you have to produce it and/or store it.

If you use A LOT...you have to generate*A LOT*or store A LOT.* I know I'm insulting a lot of smart people with that one!!!

Increase your battery bank and the ability to charge it...or run your genny a lot.

I don't know why people are against running their genny a lot...most die from under use.

Considering how loud and what some people talk about or what music they listen to...running their genny is the least of their noise worries*

Thanks guy's.

One thing I don't understand about battery chargers is if one bank of a 3 bank charger needs charging is the charge rate still the same even if all 3 banks need charging.

Example, over night I deplete bank one but bank two and three are still at full charge. I start the jenny and turn on my 30 amp 3 bank charger. Will the charger charge bank one at a rate of 30 amp per hour, not including line loss and ineffeciencies?

Next Example; I deplete bank one and bank two. Bank 3 is reserved for genny starting and I start the genset and turn on the battery charger. In this case does the charger charge both bank 1 and bank 2 at a rate of 30 amp per hour?

timjet wrote:
Thanks guy's.

One thing I don't understand about battery chargers is if one bank of a 3 bank charger needs charging is the charge rate still the same even if all 3 banks need charging.

Example, over night I deplete bank one but bank two and three are still at full charge. I start the jenny and turn on my 30 amp 3 bank charger. Will the charger charge bank one at a rate of 30 amp per hour, not including line loss and ineffeciencies?

Next Example; I deplete bank one and bank two. Bank 3 is reserved for genny starting and I start the genset and turn on the battery charger. In this case does the charger charge both bank 1 and bank 2 at a rate of 30 amp per hour?

Click to expand...

*depends on the charger..some will put out so much and it can all go to 1,2 ,3 or 4 banks.* have to read the fine print

timjet wrote:
Thanks guy's.

One thing I don't understand about battery chargers is if one bank of a 3 bank charger needs charging is the charge rate still the same even if all 3 banks need charging.

Example, over night I deplete bank one but bank two and three are still at full charge. I start the jenny and turn on my 30 amp 3 bank charger. Will the charger charge bank one at a rate of 30 amp per hour, not including line loss and ineffeciencies?

Next Example; I deplete bank one and bank two. Bank 3 is reserved for genny starting and I start the genset and turn on the battery charger. In this case does the charger charge both bank 1 and bank 2 at a rate of 30 amp per hour?

Click to expand...

*I agree with Scott.* You are probably getting 11 amps per bank.* So why not combine the two house banks into one large house bank and then use only bank one on the charger directly to the house bank B+.* If you think the wire is under gauge fix it.* #8 should be able to make almost any run or go to #6.* Then get a 150 Amp alternator for the engine and take it through it's external three stage regulator directly to the + post on your house bank.* Install an Echo charger for the start battery or two if you want to charge the Gen set battery as well.**

When plugged in and*on the charger it will take a little longer than seven hours to recharge the house bank.* But on the hook you won't have to run the engine but about 1.2 hours every other day to do the same thing.* One more thing about the battery bank.* The B+ comes off of the positive post on first**battery in the string and the B- come off of the negative post of*last battery in the line.* Thus the loads are even in the battery pack.

You might try improving your fridge by installing a muffin fan to circulate the air in the locker that the fridge is built into.* I did this on mine and it made a 9-10* difference inside of the unit.

You keep mentioning a bigger alternator for the gen set.* I really don't think that is possible or at least one that would do what you want. Spend the money on a larger altornator for the engine and you will be way better off.*

Tim

You may have read my posts on this subject in the past.

Norcold AC/DC fridges require lots and lots of electricity. If it comes out of your batteries, you have to put it back. There are several solutions, all of which are helpful.

1 - change the fridge to DC only. That may seem expensive at first, but reduces the demand for amps while on DC from the 13 you have calculated, 75% of the time, to (with the Danfoss DC unit I got) 2.7 amps. That will reduce your need for 2 and 3 as follows:

2 - change the charger to an inverter/charger with at least 100 amps charge, This will also get rid of your ferro-resonant charger, if you still have one, and get you a 3 stage charging program, that you should have anyway. Using a 4kw or larger genset and only getting 30 amps to the batteries is so totally inefficient.* Think about how many hours of gen time it will take to put back just what the fridge is using.* You have to get rid of that dinosaur. OR, no , make this AND, as you have to change your charger:

3 - add a larger alternator, either on the genset or the main engine. On the genset, you may find that your engine is rated to drive the generator only, so be careful what you add. a big alternator will need extra horsepower. If you don't have any extra, that could be a bad idea. On the main engine, you shouldn't notice the extra load. You will definitely need this alternator to be feeding through a smart regulator, ie, 3 stage, so as to properly charge the batteries.* When you put in the inverter.charger you will get an Echo charger that will keep the start batteries up too, reducing the load on the tiny genset alternator.* You would be putting the start batteries on the new alternator and its new smart regulator, and on the new charger, anyway.

Over the years I have done 1,2 and 3. 1 - getting rid of the AC/DC power hog, made the most significant difference. I was able to reduce the weight of batteries that I carry, from a pair of 8Ds and a pair of 4Ds, all for house supply, to a 4 pack of Golf Cart 6v batteries. That setup is more than ample, where the old setup was woefully inadequate to try to keep the ice cream from melting. Oh, and my present power consumption includes a DC freezer that we added at the same time as converting the Norcold to DC.

I now find that using the genset to charge at 100 amps is efficient enough to keep everything going, with an hour of gen charge in the morning, when the shower needs hot water, and again in the evening, when hot water is needed for dishes, and the microwave needs to be exercised.


-- Edited by koliver on Saturday 25th of February 2012 10:01:46 PM

I'm thinking that if I had a 200 amp alternator on the genset, I could charge the house banks much quicker that the currently installed 30 amp 3 bank battery charger.

A different noisemaker with a 200A DC output and AGM batterys would allow keeping the current power hog, an inverter could run the TV.

A better fridge , Sun Frost could lower the amp draw .

Or simply use a mechanical refrigeration compressor of the noisemaker or main engine , run 2 hours every 3'rd day , with a well insulated box.

WE do just that with a custom top loasding reefer.

Finally the simplest , install a propane fridge/freeze and refill a 20# bottle every month.

*

OK, Ive nixed the idea of putting a bigger alternator on the genny.

I've got a couple of considerations to take into account. As much as I would like to install a propane system, (by far the cheapest solution), my Carver ACMY is just not setup to do that. I know it could be done but I think it would reduce its appeal in an eventual re-sale. Plus propane can and has killed, I'm just not comfortable having propane running constantly throughout the boat.

My twin '98 Cummins diesels are due for a front end alignment, according to the guru's on boat diesel. Meaning everything on the front of the engine that spins, idler pulley, alternator, and supporting stuff should be replaced. So with this in mind I think upgrading the current 100 amp alternator to a 200 amp on both engines will solve most of my charging issues. When I do this front end work, probably this summer, Ill reread Keiths post on how to hook this up. An hour engine run time twice a day will put back everything I use. Thats like being back on my sailboat!

It's obvious that my current 30 amp 3 bank battery charger is inadequate in my current configuration. But if I upgrade my engine alternators it may not need to play a significant role. Additionally during the summers when we run the air conditioner at night, the charger will be able to put back a significant amount of the 150 amps we're drawing.

The Norcold refrig is the real culprit in all this. It is original on my '98 boat so I don't expect it to last much longer. Keith you mention youre refrig setup is using 2.3 amps per hour, a significant drop in what Im using. When my unit goes, Ill look into something like that.

JD, you mention combining the house banks. Perhaps the way Ive been managing my electrical use is not efficient. Currently when on the hook, I select Batt 1 or Batt 2 but not both. If my current 30 amp 3 bank charger is only putting out 10 amps per bank then if I only need to charge one bank because thats what I used then only 10 amps is going to that bank. The other bank was not used and should be nearly full. However if I select Both banks, the same amount of power is used, however when I start the genny and turn on the battery charger, it will put out 10 amps to both Batt Bank 1 and 10 amps to Batt Bank 2, charging the batteries twice as fast as if Id only used one Battery Bank. Is this correct??

If I use both battery banks when on the hook as mentioned above, I would either need to carry a pair of jumper cables or add a Battery Switch to enable me to connect Battery bank 3 (jenny start battery) to the other banks in the event I drew too much power from the batteries overnight and am unable to start the main engines. Is my thinking correct here??

In summary it appears the cheapest solution is to upgrade the engine alternators. Especially since they need replacing anyway. Then when the Norcold goes, replacing it with a more efficient unit should solve my charging issues. In the mean time Ill look into installing a muffin fan as JD mentioned. JD, do you have any source for this? Additionally Ive heard putting a small AA cell battery operated fan inside the refrig could help.

timjet wrote:*Timjet wrote:

Click to expand...

"So with this in mind I think upgrading the current 100 amp alternator to a 200 amp on both engines will solve most of my charging issues."

Why waste the money on two.* One 200 Amp*and leave the other one like it is. Then you have a spare.

"If I use both battery banks when on the hook as mentioned above, I would either need to carry a pair of jumper cables or add a Battery Switch to enable me to connect Battery bank 3 (jenny start battery) to the other banks in the event I drew too much power from the batteries overnight and am unable to start the main engines. Is my thinking correct here??"

So does this mean one bank is the start batteries and the other the house?* If that is true then leave the one as the start and install two more batteries*for the house.* It you have all the same as house then hook the four B+ positive posts*together and the four B- negative posts together.* Remember that the B+ is from the battery at one end and the B- is from the battery at the other end.* No additional switches needed.*

Now run the charger wire from bank one*directly to the B+ (disconnect the other two charging*banks from the system)*and the wire off of your new 200 Amp alternator to it's three stage regulator and directly to the B+ on your house bank.* This will give you 30 Amps from your charger and 200 Amps from your new alternator when you are running your engine.* Remember directly to the B+ not to the battery switch where the factory runs them to so many times.* Then an Echo charger will take care of your start bank and a second to take care of the Gen Set battery.

"JD, you mention combining the house banks. Perhaps the way Ive been managing my electrical use is not efficient. Currently when on the hook, I select Batt 1 or Batt 2 but not both. If my current 30 amp 3 bank charger is only putting out 10 amps per bank then if I only need to charge one bank because thats what I used then only 10 amps is going to that bank. The other bank was not used and should be nearly full. However if I select Both banks, the same amount of power is used, however when I start the genny and turn on the battery charger, it will put out 10 amps to both Batt Bank 1 and 10 amps to Batt Bank 2, charging the batteries twice as fast as if Id only used one Battery Bank. Is this correct??"

Not quite but the thinking is close.* Lets put the gear up and go around. The charger you have probably puts out a total of 30 Amps.* So it will put 30 to one bank or 15 to two or 10 to three.* The problem is you don't know for sure how it is going to split up the current.* But it probably will put out all it is worth to one bank only so lets say 30 Amps at bank one.* Now as far as the batteries go.* You have two buckets full of Amps.* Bucket one and Bucket two.* 210 amps per bucket.* You never want to draw down both buckets at the same time.*That's how you will get to the point of not staring your engines when you need to.*So Either live with a house of 210*and 105 available amps or double the one bucket to 420 and then you have 210 available Amps (which I suggest above).* Add the big alt to your one engine and always start it first that way you have 200 Amps available instantaneously.*

So to sum up.* Add one 200 Amp alt and three stage regulator wired directly to the house bank, add two house batteries to the house bank (wire as described above), leave the other bank as it is for starts only, add an Echo charger to keep the start batteries up to full capacity, add second Echo charger to keep Gen Set battery charged, hook present charger (as described above)*or a new charger directly to your house battery B+.

So now if you increase your house to 420 Amps and have a 200 Amp Alt you can replenish your house once every other day by running your engine for a little over an hour.* If you just stick to the two house batteries you have your 200 Amp alt will do the job every day for a little over a half hour run time on one of your engines.

Have you checked to see of your fridge is or is not a 12V compressor?* If it is then why run it on 120V* when under way or on the hook?* Pull it out and look at the back of it.* The panel on the compressor may have a couple of terminals that are marked 12V+ & -.* If so then you can wire it to run on 12V.

"Ill look into installing a muffin fan as JD mentioned. JD, do you have any source for this? Additionally Ive heard putting a small AA cell battery operated fan inside the refrig could help."

You can get then at any computer store.* They are 12V and that's what keeps your computer from frying eggs.



-- Edited by JD on Sunday 26th of February 2012 12:37:50 PM


-- Edited by JD on Sunday 26th of February 2012 12:41:45 PM

timjet wrote:
Thanks guy's.

One thing I don't understand about battery chargers is if one bank of a 3 bank charger needs charging is the charge rate still the same even if all 3 banks need charging.

Example, over night I deplete bank one but bank two and three are still at full charge. I start the jenny and turn on my 30 amp 3 bank charger. Will the charger charge bank one at a rate of 30 amp per hour, not including line loss and ineffeciencies?

Next Example; I deplete bank one and bank two. Bank 3 is reserved for genny starting and I start the genset and turn on the battery charger. In this case does the charger charge both bank 1 and bank 2 at a rate of 30 amp per hour?

Click to expand...

*First, I'd suggest a battery monitor to be able to onitor the current bank state and charging rate.* With one, you'll always know how much electricity you have and how much is coming in/out.

My ProMariner 30A 3 bank is connected to 2 banks distributes the 30A across both banks as needed.* If only one bank is low, it gets nearly 30A.* If both are in need of a charge, the 30A gets shared between the 2 based on need.* As one tops off, the extra charge goes to the other bank.

Sounds like your genset battery is a deep cycle rather than a starting battery.*

Another alternative to the 200A alternator is:

1.Add a Balmar (or similar) 100A alternator with the smart regulator.* The advantage here is you can run this with a single 1/2 inch belt so you don't need twin belts and the high cost of new pulleys (assuming the current genset belt is 1/2").*

and

2. Add a Blue Seas Automatic Charging Relay (ACR) between the genset battery and the house bank.* Another ACR can be added between your 2 house banks to provide charging to the second bank after the first reaches charge.

With this setup, as long as your alternator wire is large enough, your existing wiring remains the same except for the addition of the ACR(s).* As the genset batt approaches a full charge, the ACR closes sharing the alternator output with the 1st house bank.* As that house bank approaches full charge, the 2nd ACR closes sharing the current with the 2nd house bank.* When the charging stops, the ACRs open isolating each bank from the other so no loads are shared between the banks.*

I'm left wondering why you have 2 separate but identical house banks.* Weight distribution?* Maybe that's the way the boat came to you, but I think fewer but larger banks simplifies the system and reduces wiring.*

Your house banks combined allow you 210AH to consume (50% of the 420AH).* That can go pretty fast.* When it's time to replace them, it might be a good time to consider increasing the size and configuration to gain storage capacity and simplify the system.*

timjet wrote:
I'm trying to figure out what good my genset alternator is other than to charge up the battery connected to it. My genset has a battery whose only purpose is to start the genset and can't be used for anything else.

Click to expand...

Just about every boat will have a different setup.* Our old 7.5k generator does not have an alternator per se.* instead it has a sort of resistor or rheostat--- it's a round metal cyinder--- on which thre is an adjustable contact that can be slid up or down to adust the charging power going to the generator's dedicated 4D battery.

When the genertor is shut off and the main engines are running, the generator's battery is charged by the alternators on the engines as are the house and start battery banks.

When nothing is running and the boat is on ground power, one of the Heart Freedom 25 inverter/charger's two echo chargers charges the generator's battery.

When the generator is running and the Freedom 25's charger is turned on, both the house and start battery banks are recieving chargeing current.* So I'm not sure what tapping off the generator's alternator--- if it had one--- would accomplish.* If you're running the generator, you can power the boat's charger, which should take care of the boat's batteries.* And if you have an inverter, too, or an inverter/charger the generator should power any AC equipment on the boat (hot water heater, ec.).* So what would you want the generator alternator power for other than charging up the generator's dedicated battery?


-- Edited by Marin on Sunday 26th of February 2012 06:34:16 PM

Tim

The culprit is undoubtedly the Norcold 120v fridge. Waste no time. Get rid of it!

Then talk to us about how to set up your systems, without the extreme power consumption to mess you up.

Change the alternator on one engine.
But also change the charger to , a three stage type, one that will do the job and the generator can run it. To me it does not make sense to run the main just to charge the batteries when you have a genny that can do the job and it is intended to do that.

The large engine mounted alternator on the main will look after recharge when you are running. Secondly, unless you also install a three stage alternator regulator along with that large alternator you will not get nearly the benefit or improvement you are looking for.

Make one big house bank out of all the house batteries rather than two small ones and you will actually gain some capacity /operating time over using the house batteries as two separate banks.

Change the fridge to reduce the load.

timjet wrote:

My current battery charger is a 30 amp 3 bank unit.

Click to expand...

It seems to me that your boat is WAY undercharged, so to speak.* The Heart Freedom 25 inverter/charger we have, for example, puts out 130 amps at 12vdc from the charger side.

When we're at anchor or on a mooring for more than a day we will run the generator (7.5kw) for an hour in the morning every other day or so.* Our boat is not over-batteried by any means.* In addition to the 4D generator-only batter the boat had just two 8Ds, one for house and one for start altough in reality their funtions could be switched with the battery selector.

Last year we replaced the two 8Ds with six 6vdc golf cart batteries connected in pairs. So we've doubled our house battery capacity and the start battery capacity is still the same as a single 8D.

We have a going-on-15-year-old Norcold AC/DC refrigerator and it is not very efficient at all as Keith has pointed out earlier.* But it's there and it still works as advertised although we have already selected a replacement if or when it should die.

With its poor insulation and inefficient cooling system it runs as much as it's not running.* But when we run our generator every other day having not run the main engines in the meantime, it takes the Freedom 25 about an hour to put a full charge back into all the batteries on the boat while at the same time the AC output of the generator is heating hot water for showers and washing dishes and stuff.

So if you think you have to run your generator 7 hours or so just to let your charger bring your batteries up to charge, it sounds to me like a major part of your solution is to replace that too-small charger with something up to the task.

Not that the other ideas presented earlier are not worth pursuing.* But it seems to me that a fundamental component of your problem is an undersized battery charger.

"upgrading the current 100 amp alternator to a 200 amp on both engines will solve most of my charging issues."

ALL engine Mfg. have a limit to the HP or KW that can be pulled from the front of their engines.

Opposing loading of the belts will help, but there IS a limit which must be observed.

Simply ideling a propulsion engine will cause under loading and an earlier death.

The best solution so far is scraping the Norcold, for a modern efficient off grid reefer , not boat or RV.

koliver wrote:
Tim

The culprit is undoubtedly the Norcold 120v fridge. Waste no time. Get rid of it!

Then talk to us about how to set up your systems, without the extreme power consumption to mess you up.

Click to expand...

*what's your suggested replacement?

OK, thanks guys. I've got to study all this. There is a lot to consider. I'm not going to replace the refrig just yet. I need to upgrade the alternators. It has been suggested by the Cummins guru on boat diesel that I replace them with a 200 amp model. This guy knows what he is talking about so no worries about overloading the engine or belts. Since I need to replace both alternators it makes sense to replace both with 200 amp units. The cost saving using a smaller amp unit is not enough to justify putting in a smaller unit. His suggestion to replace the alternators has nothing to do with my electrical system. He says they are worn out and need replacing due to age.

FF does have a point about underloading the engine. Being able to produce 400 amps from the engine won't take long to charge up the batteries. I know I won't get that much, but you get the idea. The way we use our boat is condusive to doing it this way. We won't spend more than a couple of nights on the hook at any one place, so the engines will get a good work out going from anchorage to anchorage.

I'm headed down to the boat this morning, but will return to ask more questions later tonight. \

Thanks guys for all the info.

Also what refrig unit do you suggest.

My current unit is an AC/DC unit. Have no idea if the compressor is AC or DC, but the label on the inside listed the amp draw as 1.3 amp at 120 volts AC. So perhaps it's a AC compressor converted to DC when necessary.

I'm not defending my current refrig unit and would like to replace it, but the boat bucs are building up. Weaver leaver, deck delamination fix, and new alternators are starting to add up. Just replaced my stbd riser in December for 3.5 bucs.



-- Edited by timjet on Monday 27th of February 2012 07:05:13 AM



-- Edited by timjet on Monday 27th of February 2012 07:08:34 AM


-- Edited by timjet on Monday 27th of February 2012 07:12:30 AM

You say your fridge is a Norcold.

The compressor is actually driven by a 20VAC motor. There will be a box somewhere on the back of the fridge which contains a relay, a transformer, several transistors and capacitors.. When on 120VAC supply the relay operates and isolates the 12VDC supply from operation and connects the 120VAC to the transformer. When you plug the fridge into a 120VAC outlet you will hear the click. The transformer drops the 120VAC down to 20VAC and away it goes.

On 12VDC , 120VAC not available, the relay is not actuated and the 12VDC goes through the transistors, which due to the caps. and a connection to the transformer are used as an oscillator [becomes an inverter] to produce a 60HZ ~12VAC which is fed to some other taps on the transformer which steps the voltage up to the 20VAC the motor requires.

It is no where near as efficient a setup as the Danfoss systems which have been around for over 20 years. Compared to the Danfoss compressors it is a power hog. They were reliable and long lasting if checked once in a while.

One of the things I found is an adjustable resistor in the box which is used to adjust the HZ. It does need to be adjusted periodically as the frequency falls off which results in a huge increase in inefficiency as the motor runs slower. You may find if you check this out that your ffridge has fallen of frequency and an adjustment will be worthwhile untill such time as you can or want to replace it. Don't be tempted to increase the HZ above 60 to 61.

Most mfgrs. use the Danfoss now due to the efficiency improvements over the older systems.

Several mfgrs make direct replacements for the Norcolds, box size for box size. Nova Cool is one. I still have my old Norcold and when $$ permit I will replace it as I have already picked out the unit I want .

I have the same concern with my fridge and I thought about a solution that may be interesting for you as well. I'm thinking about getting one of those 120v power bank you can get for your home and hook it up exclusively on the fridge when I am at anchor. I figure it will be able to power the fridge for an entire weekend with the bigger model (less than $200). Easy to install and to charge when I get back at the dock. Just a thought.

-- Edited by Fotoman on Monday 27th of February 2012 08:51:57 PM

I hear ya' Tim! This isn't the kind of news I want to hear either. I just replaced my Norcold with... wait for it... another Norcold about two years ago. At $1600, I can't at all justify replacing it any time soon. Fast forward to today and I am now replacing my charging system. The last news I needed to hear is that my refrigerator is now a major DC hog on my boat. Well, at least I'll know to look for it. In the past, just out of paranoia, I will turn the fridge off before bed when we are at anchor.

The fridge and ice maker are the culprits. *However, the convenience is just too good to do without. *When we go to the Bahamas, we lift the arm on the ice maker and turn it into a freezer for extra food. *When that's emptied, we put the ice container back in and use it for that. *

I gave up fighting being too miserly on power consumption long ago. *LED lighting helps, but with music, TV, hot water, lighting and cooking producing enough power is a trade off I am glad to do. *1.5 hrs of generator time morning and evening takes care of it all. *If anchoring out for a week that's 21 hrs on the gen. *Not too bad.**Beats staying in marinas.

timjet wrote:

Also what refrig unit do you suggest.

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When we thought our Norcold was failing we conducted a pretty thorough search for a replacement with these requrements--- it had to fit the same space in the galley counter closely enough that only minor shimming/trim work would be necessary, it had to be AC/DC and connect to the same leads going to the Norcold.* It had to be a refrigerator/freezer, and it had to have a Danfoss compressor.

In the end, the hands down winner for us was a stainless steel Isotherm.* Our refrigerator is an under-counter unit, not as big or tall as yours.* But Isotherm makes a variety of refrigerator/freezers.

Actually, the Isotherm units we really like are their drawer-type refrigerator/freezers.* Unfortunately, the size that would fit our space would actually reduce our refrigerator/freezer volume from what we have now.* The Isotherm front door model we selected increases it even though it fits the same space.

Naturally, as soon as the Norcold realized its head was on the chopping block it "fixed" itself and has been running as flawlessly (and inefficiently) for the last three years as it did when it was new almost 15 years ago.* One factor in the longevity of the unit might be that from the day we took delivery of the boat in 1998 the refrigerator has never been turned off.* So it's been running 24/7/365 for almost 14 years now.*

A piece of advice we were given when we bought the boat by a person with a lot of credibility in this regard is never replace anything on a boat's that's working properly and doing the job you want it to do.* Electronics, toilets, anything.* So we have given the Norcold a stay of execution until such day as it truly does die.* At that point, we will go with whatever current stainless Isotherm model meets our rerquirements.


-- Edited by Marin on Tuesday 28th of February 2012 02:15:39 AM

Scott:

Danfoss compressor.
either a complete new fridge, that uses the DF unit, or a DF replacement for the guts of the Norcold.

In Vancouver, North Shore Refigeration, where "Freddy Freezer" will make the swap for a reasonable price.

What is the thing that makes a Danfoss compressor better?

Moonstruck wrote:
*When we go to the Bahamas, we lift the arm on the ice maker and turn it into a freezer for extra food.

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I do the same thing. I've talked with guys who have ice makers who have never thought of doing this.

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Don:

There may be someone here who can give you the technical niceties. That is not me.

I can tell you the results: 10.5 amp DC draw from the old Norcold AC/DC unit when running DC, compared to the 2.7 amp DC draw of a Danfoss. That makes it better.

That reduction to 25% consumption allows a similar reduction in charging capacity, batteries for storage, genset size, or conversely, allows more days on the hook between plug in days, or allows the addition of freezer capacity.

I credit Norcold AC/DC elimination with the following:

1; healthy batteries

2; fewer batteries: my boat now runs happily with only 4 Golfcart 6v in one house bank. I used to have 2 house banks, a pair of 8D, and a pair of 4D, which were never enough

3; we carry a 12v freezer (another Danfoss unit) which allows fewer trips to the grocers on long trips and allows fishing to occur.

4; more days continuously away from a plug-in to shore power. One summer holiday recently we unplugged when we headed towards Desolation Sound, and didn't plug in again until returning 21 days later. With the old fridge, we had to stay within range of a plug-in, as there was no way we could keep up with the draw while on the hook. Neither us or our neighbours could handle the running of our genset for the hours needed to keep our batteries up, so we were constantly in danger of wrecking them with too much discharge. The alternative of charging from the main engine only works if the group we are cruising with all want to move, and the move is far enough to get a decent charge.

Don, none of this matters if your cruising style is dock to dock and you always have a ready shore power supply. In that event, keep your Norcold.

What is the thing that makes a Danfoss compressor better?

Without writing a book , the basic improvement is the units ability to operate slower and slower ,using smaller electric pulses from your batt set.

The fridge folks would love it if owners were knowledgible enough to understand a high eficency modern fridge should run 24/7 at a very minor draw .

A dumb compressor that does not monitor run time , just a thermostat is always a power hog.

From the SSCA cruising board, this comment,

Your Boat Refrigerator's Future

Postby Richard Kollmann » Sun Jun 13, 2010 2:11 pm
The pleasure boat refrigeration industry today is following marine industry down the drain. We have seen refrigerator companies like Grunert, Crosby, Adler Barbour, WAECO acquired by Demitic. Gleaser Bay has stop production of their boat refrigeration products. Northern Lights, a manufacturer of marine generator sets has acquired Ft. Lauderdale-based Rich Beers Marine. What seems to be missing in this new market are the experienced people that provided technical after market support in the past. The technical approach to small boat refrigeration today is the same as when you buy a toaster, if it does not work after a short warranty it is expendable so they advise you to buy a new one. The most resent loss to small boat refrigeration support is the announcement from Rparts.com that they will discontinue operations of Refrigeration Parts Solution Effective June 30, 2010.

If someone tells you to buy new 12 volt refrigeration because compressor will not run do not believe them. If your compressor runs but there is no cooling then solution is difficult and generally requires technical help. If compressor fails to run then anyone with basic technical knowledge can find and correct a failure to run of a Danfoss compressor. If your refrigeration unit is over 10 years old and has a Danfoss BD 2 or BD2.5 or BD3 compressor then it has the older discontinued electronic 4 pin module.
Troubleshooting Danfoss compressors with 4 pin modules will consists of the following steps:

1. All of these compressors have a 4 pin module connector and their modules contain an external fuse. If this fuse is blown there are two reasons why either power wires to module are reversed or module has an internal failure.

2. Check to see that there is actually power at the refrigerator control module.

3. Place jumper wire across thermostat terminals on electronic module, Compressor still does not run go next step.

4. Disconnect black fan wire from electronic module, Compressor runs, replace fan. Compressor still does not run after fan ground wire is disconnected, go to next step.

5. Run correct size and correct polarity jumper wires direct from a fully charged battery in order to bypass all boatâs wiring. Volt meter readings are of no value when looking for voltage spikes. Compressor still does not run electronic module needs to be removed and tested on another unit. If there are no other units available to test your module on I will test all 12 volt Danfoss control modules free except BD80 compressor modules. Email me for shipping address and details.

Small 12/24 volt boat refrigeration using Danfoss compressors manufactured after 1996 will have a BD 35 or BD 50 variable speed compressor with a troubleshooting computer chip built into their control module. This circuit makes them easier to find troubled area if compressor fails to run. If your unit does not have this $2 LED install one, as it could save you a lot of money later. Without the LED on these new units troubleshooting will be the same as earlier 4 pin Danfoss BD compressors.

If installed trouble shooting LED will only flash if electronic module sees a compressor problem. In each case problems of compressorâs failures to run are identified by Counting number of flashes of LED:
⢠No LED flashes would indicate either thermostat is open or no power to module.
⢠One LED flash and a 4 second pause indicates a boat wiring electrical resistance problem or low batteries. Because of modules sensitive to milliseconds of a voltage spick they cannot be detected by a voltmeter. Solution is to bypass boatâs wiring till problem is located.
⢠Two LED flashes indicates fan over current cutout. If fan circuit on these variable speed compressors exceeds ½ amp compressor start up will be aborted. This condition can be confirmed by disconnecting Black fan wire at module if fan runs replace fan.
⢠Three LED flashes indicate excessive torque is required to start compressor. This is commonly caused by turning compressor off and back on too quickly or too much refrigerant or poor condenser cooling. Most people jump to the conclusion that there is a mechanical rotor lock up inside compressor and this is a mistake on Danfoss BD compressors.
⢠Four LED flashes indicate compressor motor not reaching sustained controlling speed above 1,850 rpm quick enough.

If someone has tampered with refrigerant by connecting gauges to a system letting air in or adding too much refrigerant can cause either a Three or Four LED flashing signal. On water cooled Danfoss condenser systems three and four LED signals are common when seawater gets into refrigerant circuit.

If you have sources for refrigeration fair priced parts and technical assistance email them to me and I will list them on my web site. I found a source for 4 pin modules at a fraction of the price currently being asked and have been advised that refrigeration parts outlets like United Refrigeration can special order the newer Danfoss modules or compressors at a fair price.

Richard Kollmann