Marine refridgeration.

[Guest]

I have a engine driven compressor type of fridge. It has stopped cooling and it seems as if it no longer has enough gas. It probably needs a service, regas, pressure test, new dryer, etc. Any recommendations who to use and possible costs?

[PaulR 3]

Bill Penny 027-494-6731

[Island Time 1,214]

Does it have a sight glass? If so, before starting the fridge, the sight glass should be empty. When started, it should fill, and stay full. If the level drops and or it has lots of bubbles after a few minutes running, it is low on gas, and needs servicing.

[Guest]

Does it have a sight glass? If so, before starting the fridge, the sight glass should be empty. When started, it should fill, and stay full. If the level drops and or it has lots of bubbles after a few minutes running, it is low on gas, and needs servicing.

 

Yes, I think that is what it does. I thought it was full before starting and that a few bubbles came into the glass after starting. Now it gets some bubbles and then looks as if the sight glass empties completely shortly after starting.

 

It has been working well, I've run it every couple of weeks in winter to keep the seals from cracking, etc.

 

 

After a bit of time on Google…………should I repair ($$$$$$) or replace with a Waeco, etc (More $$$$$$$ but new equipment/technology).

[Bogan 8]

I was contemplating taking mine out. Called the guy at Ocean Air to talk about decommissioning.

 

His tone (total disgust) at the prospect of removing a working system convinced me to rethink. In his view, you would be crazy to switch away from the engine driven freezer.

 

Hasn't been able to run over winter though (no working engine) so it'll be interesting to see what condition it's in when we finally hook it up this week.

[wheels 543]

Engine driven are fast and powerful. But only cool when the engine is running ofcourse. Electric means you have to have battery capacity to run it and that still means having to run the engine to recharge at sometime. Personally, if it is just a re-gas, I would go ahead. If it was a new compressor unit, then maybe consider a swap.

[too_tall 15]

My experience has been that should your house battery bank be substantial, and your charging systems up to the task, a water cooled, 12v system is the best. In most situations, they will draw about 6 - 10ah off the bank per day as long as you are sensible about not opening the fridge/freezer up too often. They can be left on indefinitely - so every time you get on board your beers are cold, and being sea water cooled, they retain efficiency in summer. Engine driven requires more careful management

[PaulR 3]

With an engine driven system you know it's working within a few minutes. It works with engine on and when you stop the engine, the compressor stops. Simple. You have control! No waiting, wondering.

 

With electric you have to wait 30+ minutes to see if it gets cold and then it works quietly until the thermostat cuts out or the voltage falls when it's electic black box master magic controller quietly stops and you don't find out until the next day, by which time it's to late, and it's all spoilt.

 

Ideally having both would be great.

 

Having been in a position on an ocean race when the engine stopped dead, we ate really well for 3 days. Steaks 3 times a day, and seconds as well. Then OFF was overboard and diets compulsory for the rest of the voyage.

 

I have pondered somehow linking the refrigerator compressor to a collapseable bicycle and pedalling (as they do in gyms these days)was another possibility but the cold beer the cyclist needed was never guaranteed. Perhaps the 4th or 5th cyclist might get lucky but it's still a perhaps

 

Using smaller (Mini, Micro) compressor(s) linked to the winch(es) or pedestal grinders. So that whenever the winch was turned, the compressor(s) gave the fridge/freezer that little tickle up.

 

Perhaps somehow getting the engine flywheel going by hand so the compressor also worked could be another possibility, or having a flywheel on the compressor that could be driven by a winch handle perhaps.

 

But then I'm knot an engineer and can't work out the energy requirements gains and losses involved. The winch handle approach seemed good as one immediately had power and grunt right from the start.

 

However having faced the disaster of having to throw overboard frozen meals that have melted and gone off big time, allows one to ponder methods that may work in emergencies and survival conditions.

 

I think the energy used in pealing an orange is greater than the subsequent energy consumed, unless the orange has carefully been injected with rum via syringe, gentle rolling to massage the orange and brak the pith boundary layer but knot disturbing the segments, before pealing. After the 6th or 7th orange, maths calculations always fail.

 

On one boat 47ft we built with a variable pitch propeller, we could get the shaft to spin easily when at 7+ knots and this would charge both batteries and/or freezer. Worked very well.

 

Solar power and wind generators can help with electric problems.

 

Wanted an engineer who knows this sort of stuff

 

BTW FWIW, going south or north far enough to get CLEAN WHITE ice is a myth, because it melts before you get back to the Equator, even with a full boat load.

[wheels 543]

I have pondered somehow linking the refrigerator compressor to a collapseable bicycle and pedalling (as they do in gyms these days)was another possibility but the cold beer the cyclist needed was never guaranteed. Perhaps the 4th or 5th cyclist might get lucky but it's still a perhaps :thumbdown: :thumbdown:

This could be perpetual; motion in reverse cycle.

Seeing as it takes several Hp to run one, I think you would be constantly downing cold refreshments to enable the continual peddling to cool the liquid refreshments so you could enjoy the cooling effect while peddling, cooling the liquid refreshments....see, a continual cycle so you can continue to cycle.

[PaulR 3]

I always disliked cycling, especially the uphill bits.

[Fusion 0]

A couple of tricks with 12 v electric refrigeration:

 

The fridge is like a battery. fill it up with cold, then keep topping it up with cold.

 

Good batteries are a must as is good battery management.

I have an override set up so when the engine is running the 12V fridge compressor runs.

I have 2 thermostats that work in 2 ranges so if you motor for too long you don't freeze everything. I has the advantage of pulling the fridge/freezer down an extra 4 degrees at the same time as charging the batteries and extends the time before the compressor has to kick in again. I have also seen a smart solar charger that ports extra current directly to the fridge compressor so once the batteries are fully charged the power goes to the fridge.

[Island Time 1,214]

If the sight glass empties, the unit needs topping up with gas. It should start empty, fill quickly on startup, and then remain full. If it is empty, partially full, or there are bubbles going through it (after a few mins running), in needs recharging.

 

Engine driven units are powerfull, freeze down systems WAY fast compared to electric, but they do not maintain constant freezer temp due to the fact that they only run when the engine is on.

 

Electric systems are great for maintaining the temps. You can keep icecream!! Icecream is a real freezer test as it requires a max temp of -15 c.

 

Both is what we have. Compltely seperate systems, with their own freezer tanks. The Engine one gets it down to temp, and the electric one keeps it there. Ours is a OZE fridge, cooled with fresh water, which it then returns to the water tank. It draws 4.5 amps when running, and runs about 30% of the time. It has an ecomomy mode that switches it on if the voltage is over 13v - ie there is a charging source, be it solar, wind, engine, whatever. We have a very large fridge and freezer - about 275 ltrs each. Yes we can keep icecream!

 

The engine driven unit seems to slowly leak gas, and, in constant use (we live aboard), I have to top it up with gas once or twice a year...

its all good

[Guest]

Thanks for all the above. Looks like I should stick with the engine driven compressor. It used to work very well - too well some times as the beer was frozen solid.

[Bogan 8]

That's been my problem. Frozen bottles of beer = small piles of frozen glass.

 

Suggestion has been to freeze bottles of water and use these in a separate bin to cool down the drinks.

[wheels 543]

If you use Saltwater, you can get even colder ice for cooling down the beers or for bring the temp down in a fridge/freezer. It takes a little longer to initially freeze.

[Guest]

a well engineered open drive system will give you the biggest bang for your buck without question,output is roughly 3/4>1 1/2 hp, similar performing 240VAC compressors will draw in the vicinity of 6 or so amps and the 12/24VDC units are very fractional

Problems with.

1/ stagnation

not running the unit on at least a fortnightly basis will in time lead to the shaft seal drying out which has the effect of gluing the carbon and steel faces of the seal together causing the seal to spin on either the shaft or the body depending on compressor type therefore chewing out the rubber

2/over running the unit

this has the effect of taking the refrigerant out of its operating parameter and causing the low side of the system to run in a vacuum, the longer you run it the deeper the vacuum, which leads to complications with regard to the shaft seal which is intended to be operated at a postive pressure, when running in a vacuum 4 things can and do occur

 

a the shaftseal will suck in moisture laden air to the system which will in time cause a freezeup of the expansion valve...that frustrating "sometimes it works"syndrome"over a period of time this moisture ingress can and does scour and mark the shaft meaning no matter how many times the seal is changed it will always leak!!!

 

b as the vacuum deepens in the low side the poor old compressor has little to nothing in the way of return gas which it relys upon for cooling therefore they get hotter and hotter squeek sieze etc etc

 

c as the compressor has nothing coming in with regard to return gas and it's still trying to put out it will eventually empty itself of oil into the evaporator and condensor......squeek seize etc etc

 

d with the abolition of CFC's most refrigerants are blends which are near or non azeotropic( they dont completely mix) these days (with the exception of R134A which just doesnt deliver in open drive systems) and it is becoming apparent that a situation occurs called fractionation which is the separating of the various components in the blend much like a tequila sunrise, performance goes out the window when this occurs and I did have a couple of charter boats where every 2 years or so I'd pull the gas, shake and mix it up the put it back in working fine

 

What to do??

every refrigeration unit regardless of type needs a thermostat, wired with a relay into the ignition so when the engine goes the fridge goes, and when the engine stops so does the refrigeration, the thermostat can be a simple one like the ranco VC1 varifix or a danfoss UT72 right through to the electronic Carel units type is not that important, function is, The probe for the thermostat should sit approx midway up the evaporator and measure EVAPORATOR temperature, most all open drive systems are what is known as "holdover"units which means they have brine tanks to store energy and cut down the number of times you need to run to keep things cold, as a brine tank has 2 sides( ie an inner and outer) it is not necessary to put the actual probe inside the typical kiwi fridge cabinet it can be placed against the outer skin on the foam/ insulation side, generally there will be an adjacent cabinet/ cupboard to drill a hole about 100mm later filled with selleys mousehole foam to access this and voila there you have it....... a fridge that'll do what it pleases when it needs to and the big plus......... quick set of the thermostat and that freezer becomes a fridge and the days of klutzing out with frozen piss after a race are a thing of the past, oh and if you have a fridge and freezer the thermostat always goes on the freezer (or larger freezer in multiple chiller setups)

Having served an apprenticeship soley on these systems in the 80's and having spend 22 odd years in my own business making beer and air cold on the water the above is related to fact not fiction so quit with the hour morning and night malarkey (refrigeration effect is actually better doing 20 mins on, 20 off then 20 mins on again as opposed to 1 full hours running) and get that thermostat fitted

[Guest]

in relation to the above, the method of wiring of the thermostat pertains in this instance to open drive systems

[Bogan 8]

great stuff.

 

I was wondering how to add a thermostat.

 

Now just hoping the compressor seals aren't stuffed after 4 months not running.

[Kestrahl 6]

Interesting thread,

 

Our compressor one doesn't seem to be working now, I can see the clutch engage and the compressor spin.. But there is no drop in rev's or extra load on the motor like there used to be when you switched it on..... Any ideas?

[B00B00 310]

This is a great thread.

 

I have a similar problem with my compressor driven system on the marauder. It has a leak and only lasts about 2-3weeks before slowly failing. I have regassed it twice in the last year.after the first time we checked for leaks and tightened all the fittings. I'm pretty sure the seals in the compressor are stuffed as it wasn't used or conected for about 5 years before I got it going.

Once gassed up it runs mint and will freeze everything in 15min but just slowly becomes less efficient.

Anyone know a friendly expert who can sort this for me? I have the gas ( its the drop in alternative but I have both available) and need the seals replaced on my sankyo SD-508 gold label compressor( I have the manual for it), a new dryer and then a gas up. The boat is on g pier westhaven.

I have a family friend who can do it but he is getting harder and harder to nail down these days and I just want it fixed.

Can do contras on sail repairs too!