Fridges

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colvic

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Having had two 12/24v compressor type fridges fail within four years, I am looking for a more reliable or cheaper alternative. I have seen a model that works from 12vDC or 220vAC and has a heater instead of the compressor. Does anyone know if this type of cooling system gets the fridge as cool as a compressor type?


Many thanks


Phil
 
Guess you are talking about absorption types and tend to be the standard for caravans and motorhomes. They work OK but are far less efficient than compressor types and generally won’t cool to as low temperatures. Being inefficient, they need several amp’s from a dc supply (better on main’s 240 V) so OK whilst engine running but need to run them from gas (normally have this option) if not as soon flatten battery. I’m surprised to hear of your problems with the compressor types (work on same principle as domestic fridges), guess it might have just been bad luck. Was it the same fault both times?
 
Have used the 'heater type' for many years. They can be fairly efficient but also fiddely. They do use a fair amount of electricity, ( but so does the compressor type)you can switch to gas but you must ensure that the fumes are vented outside the boat.
I am ripping out my old 'heater' type and replacing with a small cheap compressor type (£90 from Argos!) I will run this from shore power and possibly for short periods via an inverter when the engine is running.
The compressor type is I feel much more reliable.
 
Yes it was the same fault. When working the fridge was excellent and the ice box allowed us to freeze fresh meat etc.. However, after initial problems with excessive consumption due to the interior light switch not working and generating a lot of heat with the bulb on all the time, the compressor then stopped working.

This was diagnosed, eventually, as the control box which in turn was eventually confirmed by the technical dept. at Waeco as a type of inverter that makes the compressor think it's getting a 240v supply when it is only 12vDC, the 24vDC being dropped to 12v across a simple resistor.

Priced at the best part of £200 and "sorry sir, we don't export to Europe" we eventually bought another fridge in Spain. Went for the next size down as the previous one took a lot of filling, even with cans, and that lasted only 14 months before the control box on that one failed.

Almost £1k poorer and no working fridge. May just be bad luck, but I may well go with the new Dometic range at about half the price and ice making facilities.

Phil
 
As I said to the same question on the other board, I don't think an absorbtion fridge is a good choice on a boat, with limited electric power. Their efficiency is way less than a compressor type. Lond time ago we had one of those and running it on battries wasn't really feasible unless you motored a lot. It also worked on propane, but you had to stop it if you healed to boat too much. Really nothing I would consider today.

Sorry, and slightly surpriced about your problems with the WAECO fridges. They do use the Danfoss BD35F compressor, which I have three of and had no trouble other than the need to modify the 24V cut-out voltage.

The control box is usually quite robust as it is all semi conductor technology, however it could be that excessive temperature might damage it. A combination of setting the box to max RPM of the compressor and very high ambient temperature might be a reason.

The box also has a few shut-off criteria, like when the motor doesn't reach the right RPM and some other and it has a way to attach a simple LED and by it's type flashing tells you what the box thinks the problem is.

Very detailed specifications for that can be found at:

<A target="_blank" HREF=http://www.taniwani.de>http://www.taniwani.de
 
I'd strongly advise against the absorption refrigerator, it is virtually useless in really hot climates and uses x5 - x8 the power of a reasonably well-designed compressor unit, besides making everything uncomfortably hot

To have had two compressor units go down in 4 years suggests, in the words of Lady Bracknell "to lose one could be deemed misfortune, two lose two demonstrates extreme carelessness...".

The original Freon 12 filled ASU unit I had lasted 10 years and was only replaced because an overfull bilge of seawater shorted out the cooling fan.
It's replacement cracked an inlet pipe and lost all the propellant, but now works better than it ever did before. (Though getting it re-filled involved endless trips with it balanced on a bike from Gijon to just outside Oviedo).

If your compressor unit is a Grundfoss (and all the well-known makers use them) you should get 15 years of really hard work out of them.

I spend about 8/12 months on my boat in much warmer summer temperatures than in the UK.

Try Anders @ Thermoprodukter AB, Box 715, Kalmar, 391 27 Sweden tel 0046 480 15080 e-mail anders@isotherm.com. He talked me through fine-tuning my unit after I'd mended and filled it and is a straight talking techie.
Both the best european marine refrigeration plant manufacturers are in Sweden - your alternative is the States - or if you have pots of money Penguin Engineering Ltd, 01705 465607 (dialcode now changed) who are probably the best marine refrigeration engineers in the S.

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Peltier plate?

By 'heater' type do you mean a Peltier Plate type?

I've had a boat unit for about 10 years though it is only in the last four or so that portable fridges using the system have been widely available.

Peltier plate refrigerators are highly reliable, because the system has no moving parts. But it is not a very efficient. Ours is about 4 cuft and needs a steady 4 amp supply (at 12v) to cool from around 20C to about 6C - cool beer in an English summer. In the Caribbean, with temperatures of 28C+, it was simply unable to cope.

It has 3in of insulation. It needs a cool air supply drawn up from the bilge which in turn needs a fan which wears out periodically. I have heard from others that a water-cooled version is much more efficient, but this requires seacocks, pump etc and detracts from the simplicity.

Portable versions are typically no more than ¼ cu ft. So I'm currently halving the capacity of mine, adding extra insulation.



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Fault sounds like it’s the invertor/power unit technology rather than the fridge and hence makes sense that if using a 230 volt ac fridge, use a separate invertor.
Regarding the refrigerant freon 12 (R12) comment from Charles. It is now a banned substance but many of the modern refrigerants now used in compressors are at least as good. I agree too that if you are unable to dissipate the heat from an absortion type, don’t go for it. The same applies to Peltier plate types, very simple but inefficient and hence lots of waste heat to dissipate (also virtually useless in the summer unless water cooled). I’d stick with the compressor type BUT with a separate, quality, invertor.


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Apparently their is a synthetic R12 replacement called I think R12X. I was told of this after I'd binned the non working fridge off the Draco which was designed to fit the hole and replaced it with an Isotherm!

Jim
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Boats of the big charter companies are mostly equipped with engine-driven compressors and holding plates. This is by far the most reliable system, especially on charter boats where hirers always fiddle with everything, mostly breaking whatever they touch. Running the engine for about half an hour morning and evening is enough to keep the beer cool. This suits charter operations very well, but possibly not so ideal for cruising, especially in Europe where mains electricity is free in marinas. In this case a 12 volt Danfoss compressor unit either engine alternator or battery + charger driven is probably the best choice. Water cooled version works better in high ambient temperatures but needs a small circulating pump and inlet/outlet connections.

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Some of the synthetic replacements are not necessarily “drop in” and often need at least different compressor oil and maybe even different expansion device (valve or capillary) and have different refrigeration characteristics. Not used (or heard of) R12X so can’t comment further but suggest not necessarily relevant when purchasing a new fridge as would have been taken care of, but may be of interest to anyone who still has an R12 based unit.

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Told to me by our BT service engineer, I'd not heard of it either but sounded interesting.

Jim
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Further to the inverter bit, I've run a small domestic off an inverter before and it was ok. Have managed to source a 50ltr. 220v fridge with ice box from Macro in Barcelona for about £85 that the info claims is "soft start". Made by LG, what isn't these days, it is overall slightly smaller than the Waeco and still has a Danfoss compressor though larger ones didn't. At only a sixth of the cost it will be interesting to see how long it or the 400watt inverter lasts.

Phil

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Just checked Danfos web site for 12v dc motor driven compressors (as I may be interested in one if available) but none found. Have you got a model number and are they really 12V dc or do they have a built in invertor?

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My guess is the inverter will go first.

Mind you, at that price you really can't do too badly.

Using modern refrigerants, it appears you are more likely to get leaks than with Freon so your unit might need topping up - usually a simple thing to get done in a large city like Barcelona.

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Danfoss

They are the BD35F and the BD50F. Both are either 12 or 24 volts, the unit senses which is being supplied. They don't run via an inverter. PM me your e-mail address and I'll send you the brochure in 8 different languages.

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Re: Danfoss

Hi

I honestly think that this type has the "inverter" built into the control box; its not very large about the size of a packet of cigs. It is 12v with a step down resistor.
The compressor works fine, but these control boxes are the items that kept failing and the man in the workshop in the UK said they were "like an inverter and fool the compressor into thinking 22ov ac is being supplied. The replacement cost was over a third the price of the fridge, and as we only spend about four weeks a year at anchor our batteries will cope with the seperate inverter and domestiv fridge; works out at almost three fridges & inverters for the same size Waeco 12v fridge.


Phil

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Re: Danfoss

All the info I can find on these units says they are 12/24 volts DC. Several companies offer a 220/240 volt adapter, which seems odd if the motor is AC already. Are you sure that the box you are referring to isn't the electronics that changes 12 - 24 volts? As far as I can see this is a switching device and a few resistors. Some refrigerator builders extend this principle a little, providing higher motor speed when the engine is charging but reverting to slower when on batteries. My limited knowledge of electronics suggests that this requires a DC motor.

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