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Salona

How cold should the refrigerator get?

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My fridge runs, but it doesn’t seem to get very cold (only to 45 degrees f) and I’m not sure if there is something wrong with it or if the unit is just undersized.

Some background. 
When I first got the boat, it stopped getting cold entirely. So I am not sure if it ever worked properly.  (I am the second owner, boat is 3 yrs old.). So we just hooked up a recharge kit, added r134a refrigerant to about 10psi, and it gets cold again!  But only to about 45deg f. I am wondering if I need to charge it to higher psi, or maybe pull a vacuum first to remove any air/moisture in the system?

On a previous boat, it seemed like the fridge got much colder and would even frost over at the cool plate. But maybe my expectations are off. This unit draws about 4.5-5 amps while running, but when the compressor kicks on, it can also give me a low voltage alarm.

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The amount of refrigerant is an exact thing. Not “about 10psi”. Evaporator should get frosty no matter what. Even if insulation is crappy. Depends if you have an expansion valve or capillary setup. Probably need an expert or book.

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What El Boracho said - overcharging and undercharging can lead to not getting cold enough, and how to determine the right amount of charge varies depending on the unit.  Find the manual for it and see what it says to do.  If you expose the interior of the system to atmosphere (like replacing a valve) you will probably need to put a vacuum pump on it and evacuate it before recharging.  If it's charged correctly you should be able to get the cold plate / evaporator to frost up.  We've had mixed results with fridge techs - some have been great and willing to read the documentation on the system and actually fixed problems, some have just tried to cram more refrigerant into one without any real thought.

Finding either a fridge guy familiar with your system / model or the manual or ideally both is a must.

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Beers are best just above freezing, any warmer is hot.

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When its running normally, the coolant is at about 7psi. If that makes any difference.

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Does it cycle on and off? Have you checked the thermostat?

[Edit] How much current does it draw when running? My bad, I see it's drawing 4 amps. If that doesn't change while it is running then it suggests to me that it has a charge and the compressor is not stalled.

Does it have a trouble light and do you have it hooked up? Are you getting an error code?

Any hints about the brand and type?

I think it's not a great idea to dump 134a into it without some specific reason to believe it will help. If you must, I suggest you avoid any that have extra ingredients in them. You local auto parts store will likely have a collection of r134a adulterated with magic stuff.

 

 

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42 minutes ago, Salona said:

There is cold plate/radiator with a fan, That is frosting up.

If there's frost at the condenser, you have only to determine whether there's any frost further back on the coolant tubes.

Too much coolant will exhibit frosting all the way back to the compressor. 

As it's likely got too little R134a, you'll need to slowly bump up the coolant level, wait an hour, check for frosting further back from the condenser, etc..

Again-

http://kollmannmarine.com

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Refrigerators are a very common appliance and virtually every home has at least one. 
most communities have not just one but multiple companies and individual servicemen who install, maintain, repair, and replace refrigerators. 
Have you ever heard of Google?? 

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3 hours ago, Gouvernail said:

Have you ever heard of Google?? 

Thanks for that very helpful advice, /s... always one in every crowd right...

5 hours ago, weightless said:

Does it have a trouble light and do you have it hooked up? Are you getting an error code?

Any hints about the brand and type?

The compressor is a Danfoss BD35F. Everything works and runs, and temp was set to max cool.

No trouble lights came on, using an LED connected to the controller, which makes me think that around 40-45  deg is just as cool this fridge will get, in terms of internal temps. 

I think I was just spoiled with the much smaller icebox on the Beneteau, the compressor only had to cool a much smaller area.

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my danfoss-based, air-cooled  frigoboat system gets cold enough to freeze tonic water. you may have an insulation problem, instead of a compressor problem.

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What is the volume of your icebox and the size of the evaporator plate?

If you had to add r134a there is probably a leak somewhere in the system (3 years is too fast to loose it) and that means you need to fix the leak, vacuum it all out, and charge it back up.  I had a slow leak on my boat's system that made it stop working well about a year after installation, the first sign was the compressor was running a lot more often, and the second sign was the evaporator stopped freezing.  I found one of the couplings had a tiny spec of dust on it, so I cleaned those, recharged, and it's been great for the last 4 years.

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1 hour ago, Salona said:

The compressor is a Danfoss BD35F. Everything works and runs, and temp was set to max cool.

My boat has one bd35F system for the fridge and a second one for the freezer. All things being equal (obviously not in your case) you should be able to get the box well below 40-45 degrees if you want to. FWIW, IMO, etc, 40 degrees isn't a bad temperature for a fridge.

[wild_ass_speculation_mode = "bigly"]

The old mechanical thermostats came setup for either freezer or fridge use. If you have a fridge version it and it's just a bit buggered it might be that it is regulating the temp to 40-45 degrees at its coldest setting. If the system is cycling, drawing a reasonable amount of power and is getting cool I'd check the thermostat. The switch can go bad -- eg. get full of condensation and rot; get out of adjustment; the sense tube can get out of place or messed up, etc. [/bloviation]

Good luck!

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17 hours ago, Gouvernail said:

Refrigerators are a very common appliance and virtually every home has at least one. 
most communities have not just one but multiple companies and individual servicemen who install, maintain, repair, and replace refrigerators. 
Have you ever heard of Google?? 

This is not great advice because many of them don't have experience with the systems on boats.  You can over charge a boat system quite quickly.  The link provided by Justaguy is good advice. 

 

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What kind of recharge kit did you use, if you bought it at an auto parts store you have pretty much wrecked it.

Automotive ac systems use different oils, and they do not play well with the POE in your system.

And absolutely do NOT use any type of leak stop in the refrigeration circuit.

You need to leak check the system with dry nitrogen, then once you eliminate that, you need to install an 032 filter drier in the liquid line then evacuate at 85 degrees or higher for at least 12 hours.

Then recharge it with r134a from a 30 lb cylinder.

The total charge is measured in grams....very small amounts are actually used, I think the last one I did held 4.5 oz.

My advice is to call a tech and pay to do it right the first time.

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A few thoughts on this:

My BD35  draws 3.5 to 4 amps (and can get below 32F) , so your 4.5 to 5 amps seems a little high.

If the unit was low on refrigerant, it would pull low amps. .

The low voltage alarm is possibly due to a dirty/loose connection somewhere in the power supply.

I would suspect a faulty thermostat.

Rather than the expensive Danfos thermostat, the Inkbird digital unit available on Amazon is a great alternative at $15 

I used this model

https://www.amazon.com/gp/product/B019I3YCFS/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

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35 minutes ago, Pilott said:

My BD35  draws 3.5 to 4 amps (and can get below 32F) , so your 4.5 to 5 amps seems a little high.

If the unit was low on refrigerant, it would pull low amps. 

These things likely draw more current as the voltage drops. Yeah, check all the connectons. "It's always the connections."

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41 minutes ago, El Boracho said:

These things likely draw more current as the voltage drops. Yeah, check all the connectons. "It's always the connections."

They do. They also have a low voltage cut out which might be an issue but should show an error on the LED if it is installed and working properly.

I'm thinking that more specifics about how the system is behaving might make speculations on the problem a bit less random.

FWIW, the thermostat is easy to test. I don't recall the voltages on the circuit so be careful. The thermostat can be shunted out at the switch inside the box or at the controller. Short the connections, leave the box shut for a while and see if it keeps getting cold. If the thermostat is working but can't be set cold enough it can be adjusted (there's a set screw) or, as a short term hack, by moving the sensor to a warmer part of the plate.

Okay, googled it. Here's some official looking stuff.

http://files.danfoss.com/TechnicalInfo/Dila/06/bd_compressors_04-2007_pk100c802.pdf

image.png.fd03239d79ec934e332a0e2524564b5d.png

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Just had a thought: another thing that can cause high amps & no cooling is air/ moisture contamination of the refrigerant

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8 hours ago, Pilott said:

Just had a thought: another thing that can cause high amps & no cooling is air/ moisture contamination of the refrigerant

This is correct, and it is for this reason that we really try and get those who are not trained in HVAC and especially these types of systems to NOT try and "just add a little to it"

The site linked above to Richard Kollman is a great place to start.

The non-condensables introduced by incorrect procedures occupy space in the condenser and stay there, thus decreasing capacity and eventually they acidify the oils, which in turn eats the coatings on the windings. 

Heat kills compressors.

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FWIW, standard refrigerator temperature is 4°C for food safety.  Or 39°F, 312°K, etc.    

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45 minutes ago, toddster said:

FWIW, standard refrigerator temperature is 4°C for food safety.  Or 39°F, 312°K, etc.    

The OP reported ~40-45F and 45F. That might be overly warm but when and how he sampled the air temp is a mystery and could matter. I suspect the OP has a system that regulates the air temperate indirectly and with quite of lot of hysteresis. FWIW, as I read the OP's reports I'm not sure there is a problem with the system. I think it'd be interesting to know if the compressor runs continuously and at what speed. I wouldn't mess around with the refrigerant or even put gauges on it without knowing a bit more about the details of operation.

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Is it air cooled? If so have you cleaned the cooling fins of dust and cat / human hair?

Is it water cooled? Is the sea water pump pumping lots? Is the strainer clear? Is the thru hull free of lots of barnacles?

On 6/2/2020 at 8:31 AM, Salona said:

when the compressor kicks on, it can also give me a low voltage alarm.

Check the wiring!

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Thank you everyone this very helpful. To the question of temperature sampling, I used a an IR non-contact thermometer. It sounds like I will need to monitor temps and current/rpms over a longer period, before determining if there’s really anything wrong with this or not.  I will follow up here after this weekend.

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I would follow Coolerkings advice above.  It's very easy to mess one of these up and they are not that forgiving.  It sounds like a combination of non condensables and incorrect charge, but who knows.  I would call a tech, does not have to be marine someone who works on small resturant chillers cool displays, ice makers etc.  Have them evacuate, pressure test with nitrogen, if needed flush pull a vacuum and recharge.  If the unit has service valves on it all of this will be fairly quick and easy.  If you are in the boondocks or remotely cruising then yes pursue further advice for trouble shooting, but start with someone like Richard Kollman he is great and usually is fielding a huge volume of free advice.

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