Marine Refrigeration Question

[Atom Ant 0]

Here is your man/woman for Isotherm. I can vouch for them.

 

http://www.fridgetech.co.nz/

[Guest]

Email sent. Thanks

[SanFran 12]

So where is the best place to get solar chargers?

[mattm 98]

Greg at fridgetech is the man, unless you want someone to install it, then best to get it from the tradie himself, the price will be the same, and the tradesman will be happier about doing it..... As for solar, 80 watts is the amount you need to compensate for a fridge. BUT, that is 80 watt of quality panel. There are soo many cheap panels on the market, they may be rated at 80 watt, but you will only see it at lunch time on the equator, with the sun any lower (ie NZ) the output falls a lot. A quality panel will give you a good % of its rating from 9am until 6pm in summer, and even on cloudy days. Id go for Suntec or Rewa (manufacturer for BP solar panels) as being good for output. The suntec's proably have a better frame, its stronger and flexes less. an 80/85/90 watt suntech should cost around $250. two smaller ones might be better if you are short on space.

[Murky 1]

Great thread guys, really informative and interesting.

 

Royale, if you end up doing a changeover to electric, you could post photos of the various stages - it could be [nearly] as big as the Timberwolf thread.

[too_tall 15]

You could get the existing system pressure tested with some N2 to make sure there are no leaks, and get the compressor bench tested ( not hard, nor expensive ) to make sure its working.

 

I am not a huge fan of _having_ to run the engine to chill down a reefer, but I also have seen small DC systems not exactly performing as they should... If our system is at ambient temperature, as soon as we get onto the boat we turn it on. By the time we have cast off, got out of the marina and are in a suitable position to turn the engine off, we have got ours down to around 2 degrees in the fridge section, and the freezer will be around -10. ( It is a hold over system - nothing really happens for the first 10 minutes then it happens rapidly! ). If we are just wanting to keep some drinks and milk chilled, this is all that is required until the following morning.

 

This will keep the system at a fairly constant temp until at least 12 hours later.

 

If your without a 240v feed, and want to use a 12v low power system, do you really want to rely on your solar to keep the fridge from killing your batteries during an extended period of rain/heavily overcast days? Its hardly as if you can ask a 12v low power system to pull down from ambient temps even a smallish fridge for an evening sail/race enough to cool some beverages....

[Island Time 1,235]

I'd look at the ozefridge. Better compressor, water cooled option, lower power consumption than Isoterm. Intelligent engineer who will ask you the right questions and size the unitcorrectly. Comes from Ausy, have to install yourself though - although that's easy - presgassed, simple instructions. http://www.ozefridge.com.au/

Hope whatever you select works well..

[Grinna 2]

Mattm, you have a PM.

[marinheiro 352]

780, who are you getting advice from, seem to be alot of telephone no's being thrown around? I paid $500 for a new condensor a few years back, cannot see them having tripled in price. Suggest if you want to get some good info on refitting the compressor system, talk to Bill Penny at Coolquip. Remember these compressor units are virutally identical to those on cars, the biggest problem on boats is lack of use, shaft seal dries out allowing the gas to escape. I am with Matt, best option ideally is both compressor & electric (if you already have a compressor unit), you could find all electric for a freezer requires as much engine running to charge the batteries as you need to run the compressor, solar panels notwithstanding.

By the way, the Ozefridge unit is running Danfos compressors, same as Isotherm, they come in sizes BD3,5, 5.0 and 8.0.

If you went Isotherm, Greg's father Des does installations (he did mine) as do a few other guys

[Island Time 1,235]

Sorry, you are right The BE80 is in fact a danfoss, bd80

 

A.COMPRESSOR. The Ozefridge BE80 compressor has 25% greater capacity than the BD50 and 50% greater than the BD35.....

From their website

 

BUT the real secret is the water cooling - FRESH water!

 

look here;

http://www.ozefridge.com.au/?page_id=24

 

Matt

[Island Time 1,235]

The efficency gains are really the water cooling;

 

Water has a higher thermal conductivity than air - it can move heat faster than air can. Water also has a higher specific heat capacity. It can absorb more heat before it starts to feel hot....

 

And, air cooling systems degrade faster as ambient temps rise...

 

Matt

[too_tall 15]

The efficency gains are really the water cooling;

 

Water has a higher thermal conductivity than air - it can move heat faster than air can. Water also has a higher specific heat capacity. It can absorb more heat before it starts to feel hot....

 

And, air cooling systems degrade faster as ambient temps rise...

 

Matt

 

 

Seconded.

 

To raise the temp of water one degree, per litre, you need to put in 4184 joules of energy. Lots. To raise air that amount, for 1 litre ( at normal sea level atmospheric pressures ) you need .12 joules of energy. Not very much.