Refrigeration on a CD31?

[Dean Abramson]

If anyone has installed a refrigeration system on a CD31, I'd love to hear your thoughts.

I think I would prefer an engine-driven system like Sea Frost. But my initial thought is that there is not enough room in the engine compartment for the Sea Frost compressor. ???

My understanding is that the Dometic or Isotherm type would require a large battery bank, or significant solar or wind help; so I doubt I'd want to go down that road.

Any feedback would be greatly appreciated.

Thanks.

[jen1722terry]

We added a cooler 3 years ago. We live aboard full time all summer and the ice runs were getting old. We love the cooler. If you are mostly a weekend and vacation sailor, you may want to just super-insulate the ice box and just use block ice.

We installed the smallest NovaKool compressor and it works fine. We did super-insulate the ice box with lots of foam, drilling holes every 8 inches or so and pumping the stuff in with cans. The cold plate is integral with the small freezer compartment.

The fridge was not all that expensive, less than a boat dollar with all parts. We did the install ourselves. Not rocket science.

The unit runs off our house bank and is not really a significant draw, with all the insulation. Most days it runs about 15 minutes every few hours. Less at night. We try to keep the box pretty full to store the cool. Part of this efficiency is the fact that top-loader ice boxes lose very little cool air each time you open the lid.

Our house bank is two Grp. 31 Odyssey AGM batteries, 92 ah each. We also have a relatively small solar panel (130 watts). We have to run the engine every few days to top up the batteries, but that would have to be done whether we had the NovaKool or not. We are planning on a larger solar panel (300-350 watts) to keep the AGM batteries topped without running the engine or using the portable charger to periodically desulfate the batteries.
You could probably get by with smaller batteries if you conserve power other ways we mention. We choose the expensive AGMs for low maintenance, as we have access issue due to back problems. Regular deep cycle golf cart batteries would be cheaper and less of a charging worry.

The compressor has it's own fan and is mounted in the starboard cockpit locker, on top of the fridge compartment. We installed a 60 sq. inch vent on the bulkhead just aft of the ice box to provide more air to the compressor. It runs fine.

We also installed a thin plywood wall on the port and aft sides of the compressor to protect it from shifting gear.
This wall is mostly large holes drilled in it to improve air flow.

The prior owner had moved the batteries to a custom rack under the cockpit sole. The extra required ventilation is supplied by two large solar vents with hoses leading to the batteries.

Wiring was very simple. We installed a 20-amp Blue Sea breaker on our breaker panel.

Our engine alternator is 65 amps.

You're right about the tight engine compartment, one of the reasons we installed a new engine last year with easier-to-reach service points and more compact size.

Anything else you can think of, pm us.

Jenn and Terry

[Dean Abramson]

Thanks so much, Jenn and Terry. That's very useful info.

We take a month-long cruise each summer. Sometimes the need to be where ice is available is like the tail wagging the dog. I've thought, if I am motoring three hours to get to Iceville, then why am I not just sitting here in this beautiful cove running my engine for an hour or two to make some coolness?

We also use AGMs, and I really like them, but ours are just Grp. 27s, I think.

I am in the early stages of research. There is a lot about this I don't really understand.

I do have some questions. I will PM you for sure, once I organize my thoughts. But just for now: I am confused about where the new vent for the compressor is. Does it vent to outdoors, or into the cabin? I can't envision where it is.

Much obliged. Its great to hear from a CD 31 crew who has actually done this!!

[Capt Hook]

I have a CD-31 that was set up for extensive cruising by the previous owner. Unfortunately I have not been able to take advantage of all its equipment.

The boat has a Frigoboat (I think that's correct spelling) refrigeration system. The cooling coil is mounted in the original icebox which he sprayed foam insulatin around as best he could get access to. The compressor is mounted in the cabinet under the galley sink. The house bank, which is mounted under the cabin sole has accommodated up to four Group 29 batteries. I only have two Group 27s installed. He also had two large solar panels mounted on a structure he had built on the stern. The panels can rotate so they can be pointed toward the sun. I can't take credit for any of this.

He says that he went to the Dry Tortugas and didn't have to run the engine to charge the batteries. I would think that even if you had to run the engine to charge the batteries that would be preferable to having to run the engine to run a refrigeration compressor.

[Dean Abramson]

Thanks, Capt Hook.

Running the engine to charge batteries, or to cool the fridge? It seems like it would come down to how much time one needs to get the job done. I haven't gotten a handle on that yet. I've gotten differing opinions; but then everyone's situation and needs are different.

[Capt Hook]

I think you have more flexibility running off battery bank. Compressor will run when it needs to and you can run engine when it’s convenient.
I would think with an engine driven compressor you’d have to run the engine on some sort of schedule.

[fmueller]

Dean,

I just completed an extensive refit of my CD27 Jerezana. I put in a cleaver Isotherm compressor/plate unit which uses a coil in the starboard scupper thru hull as the heat dissipating device. I got this one:

https://www.defender.com/product.jsp?pa ... 3&id=58806

notice the coil/thru hull fitting - saves having to have a fan/air cooling coil and is much more efficient for that reason. Any cooling system that uses water to dissipate heat is usually more efficient.

I cleared off the batteries (2 grp 27 Trojan AGMs) from the shelf in my stbd locker (I put the batteries under the cabin sole) and put the compressor right there just aft of the ice box in the 27. I also got a Wabasto cabin heater and put it on that shelf as well. I'll try to post some pictures. Any way the ice box is now a fridge and it certainly works. It's a smart unit and when it senses over 13 volts (ie shore power or alternator) it will turn on full and draw about 6 amps. Less than 13 volts (ie battery) and it draws about 3 amps.

I have no idea how it would be long term cruising, but it works a treat day sailing, plus a few overnights around Narragansett Bay since my boat is on a slip w. shore power I think it is about as low a current draw as can be found. its also nearly silent.
So far it seems to run about 10 min an hour (but this is just a casual observation at this point) ... that works out to about 24 amp hours a day. Boy that's pretty hard to believe, and I'll try to figure that out more closely ... but that would mean a 100 watt solar panel (8.3 amps/hour, full tilt) and a couple of grp. 27 batteries might keep up with it pretty well on the hook. 200 wats of solar no problem.

here is a watts to volts to amps calculator:

https://www.supercircuits.com/resources ... -converter

cheers

Fred

[Boyd]

In a previous life I had a CD30 mkII which had an Adler Barbor refrigeration unit. It would completely flatten two group 31 batteries over night.

I went thru the typical routine of insulating the box using squirt foam and rebuilting the lid adding gaskets where there were none before. I also installed a Frigoboat keel cooled unit. Also plug the drain at the bottom. I found I never needed it anyway. A sponge works just fine and the drain is a huge loser of cold.

At the same time I swapped out the house bank with 4 Trojan 6 volt golf cart batteries. No changes were made to the charging system. I kept the stock alternator.

This reduced my fridge load to a point where I could pretty much go for days without concerns about depleting the house bank. I accidentally left the fridge on when I had to leave the boat in Key West for 10 days tied to a dock, but without shore power. The fridge was still cold and the house bank was at about 25%. I was impressed.

Two weeks in the Bahamas and no energy shortage at all with this system.

If your going to put in refrigeration and be away from shore power for longer than say .. 2 days, I would increase the house bank to 400 am hr and add a second charging source, say solar or wind. Its a real pain to run the engine just to charge the batteries. Typically I move every 2 to 3 days, but its still a pain.

Now I have a Catamaran and have a custom air source upright refrigerator, built by the boat manufacturer, that uses an average of 2.5 amps per hour. This system has the typical Danfoss compressor and an air cooled condenser. I currently have 4 - 100amp solar panels on top of the dodger which usually keep up with all loads when at anchor. I run a 60-70 amp hour deficit from all loads, which is usually made up by the panels by noon the next day. My system is not 100% efficient as the boom shades at least one or two of the panels unless I move it accordingly. I have 300 amp hours of conventional grp 27 deep cycle batteries and rarely run them below 80% state of discharge.

One key is to have ALL Led lights and reduce other loads to a minimum. The TV is a big load. The fridge is by far the 800# Gorilla when it comes to energy use.

A common solution is to carry a Honda 2000i on board. It will charge the batteries in a pinch.

Keep in mind that I dont tie up to Marina's at all when out cruising.

Boyd
s/v Cat-a-Tonic
Prout 34
Fort Lauderdale, Fl

[wikakaru]

I have cruised extensively with both engine-driven and 12 volt refrigeration systems, both of which were made by Sea Frost. Hands down I would choose the 12 volt system over engine driven. Here's why:

* With an engine-driven compressor you only have refrigeration if you run the engine. With a 12 volt system you can provide the power with the engine via the alternator, from solar/wind, or from shore power via a battery charger if you are in a marina. The flexibility is so beneficial that it far outweighs any advantages in efficiency you might gain by having the compressor directly driven from the engine. Along the same lines, with an engine driven system the engine will be a single point of failure in your refrigeration system. If you have an engine problem that lasts for more than a day you will also lose all of your refrigerated food.

* The temperature of the fridge is more even with the 12 volt system. With the engine driven system the box gets super cold when the holding plate is pulled down to temperature, then gradually warms until the next time the engine is run.

* The holding plate for an engine driven system is larger than on a 12 volt system, so if space in your fridge is limited, it will be even smaller with an engine driven system vs 12 volt.

* Mounting the compressor on the engine is a fiddly bit of custom engineering. Finding a place on the engine to mount the compressor, having a custom bracket built, adding the extra power takeoff to the engine, getting the belts aligned properly, and keeping it tensioned properly as the belts stretch and wear is difficult, even for professionals. (Ask me how I know...)

* If you ever want to stay aboard while the boat is hauled out (we were full-time live-aboards, so this was an issue for us) with an engine-driven compressor you can't have refrigeration unless the boat is sitting in the water. If your 12 volt system is air cooled or air cooled with a water cooled assist, you can still have refrigeration when you are hauled out. Life "on the hard" is difficult enough, adding living without refrigeration to the list just makes it that much harder. Even if you don't want to stay aboard while hauled out, it might be nice not to have to get rid of all your food just because you want your bottom painted.

* You have to remember to turn on the fridge compressor when you are motoring. (Ours had a twisty timer dial, similar to what you see in some bathroom exhaust fans that shuts itself off after a period of time.) If you forget to turn it on, you don't have refrigeration. More than once we spent a day motoring down the ICW, got to the anchorage, and realized we had forgotten to turn on the fridge compressor and had to sit and listen to another hour of the engine charging the fridge at anchor. Maybe you won't be as forgetful as I am, but it certainly can happen.

The caveat about 12 volt refrigeration is that you MUST have an electrical system that can handle it--large enough batteries, alternator, wiring, breakers, solar/wind, plus proper monitoring instruments. If you don't approach a 12 volt refrigeration installation with a full 12 volt electrical system perspective you will likely be disappointed. Ideally you want to be able to run all your loads, including the fridge, for 48 hours and only draw your batteries down to 50% of their total capacity. There is a good thread here (http://www.cruisersforum.com/forums/f14 ... 56604.html) where people post their fridge energy consumption. Depending on where and when you cruise and how well insulated your fridge is, I agree with a previous poster that you might need something like 400 amp-hours of battery capacity just to handle your refrigeration loads. Add your normal house loads to that.

So my suggestion would be, if your current 12 volt system is not adequate to handling refrigeration loads and your budget can't handle a 12 volt system upgrade along with the refrigeration upgrade, go for the engine driven compressor (understanding the compromises), otherwise, go for a good 12 volt refrigeration system along with a robust 12 volt electrical system.

Good luck to you!