Waeco fridge maintains different temps at 120 AC and 12 volt

Spyderweb

Spurred by a thread from @YYZRC, I did some research into my galley fridge that doesn’t maintain temp very well when on hook.  I believe the model is 1110. Thermometer is set to 7, “full on”.  At dock, overnight, plugged into shore power, fridge goes down to around 30-35.  Freezer down to -4- +1.  Out on the water for a day, with cabin temps rising to 79-82, fridge will rise to 46-53, and freezer to 30-35.  2 house batteries are on 3rd year, but by end of day on water, voltage at meter does not go below 12.2, and measured directly at batteries, 12.4.  

Testing the door door seals with a dollar bill, it slides out pretty easily anywhere on the door.  So I suspect seals are not great.  

My thought is that with the battteries staying within a safe range (12.2) the fridge is getting full power and batteries is not the cause of fall of.  

I’m sitting at the dock this afternoon  on shore power and despite the cabin being 79 degrees, the fridge is maintaining at 33 degrees (certainly colder than I need).  So despite weak seals, fridge is able to maintain temp in a warm cabin.

Out on the water we open the fridge some, but not very often with just the 2 of us.  I can understand a little drop due to that.  Open it less on shore.

I don’t believe this is typical for fridge boats as we checked my daughters Bayliner (my former boat) with 1 year older house battery and her temp was the same on the water at end of day as it was in the morning at the dock.  And thermostat is not even set to full.

Does AC power make the compressor run inherently more efficient to account for this? (I wouldn’t think so based on daughters boat).

What  would account for my differences and is there something I can do?

YYZRC

I’m still not happy with mine so I’m following along!

Handymans342

You would have to ask the compressor manufacturer about the 2 different voltages. I suspect that it runs better on 120. I bet the compressor runs slower on 12 volts. How old is this unit? Compressors run inherently worse with age

Spyderweb

Likely original on this 2008 boat.

Handymans342

It’s a 12 volt compressor so when 120 v AC goes thru the board it probably puts out 14 or so. 

raybo3

@Spyderweb next time your on shore power shut off the 120vac breaker so the fridge runs on the battery but keep the battery charger on. See if that makes a difference. If the charger keeps up then it sounds like it could be a battery problem. 

Spyderweb

@Handymans342 so if I understand, it’s running on the 12 volt compressor, but in 1 case it’s maybe 12.2-12.6 volts.  In the other case closer to 14 volts.  Hence the 14 volts will help the compressor keep up with the heat of the day better?

Spyderweb

@raybo3 So with fridge breaker off, hence running off battery, but with the battery charger on, compressor is getting 13-14 volts , and I would expect fridge to be about as cold as running on 120 overnight at the dock?  

Ian

Silly question but is the fridge actually running when on battery? Do you hear it kicking in?

Handymans342

When the fridge goes up in temp that’s the time to measure voltage. 

Spyderweb

@icoultha the fridge is pretty quiet, so I don’t think about it a lot on the water, but whenever I check to see if it’s running, it seems it is ALWAYS running.  At the dock, i’ll notice it occasionally off.

Spyderweb

@Handymans342 as the fridge goes up during the day, and it seems to be always running, the battery at the panel meter will generally not go below 12.2.  And several checks in the past with a reading directly on the batteries show the meter reads 0.2 lower than direct.

raybo3

Yes that is what I am thinking 

YYZRC

I was told by a Dometic repair guy that you need to measure the voltage at the fridge at the moment the compressor kicks on. 

I’ve been tracking the 24 hour min/max fridge temps for a couple of weeks now. Both of my original Waeco units swing between 8 and 12 degrees Celsius in any 24 hour period without being opened. The range is what concerns me. 

Handymans342

YYZRC said:

I was told by a Dometic repair guy that you need to measure the voltage at the fridge at the moment the compressor kicks on. 

I’ve been tracking the 24 hour min/max fridge temps for a couple of weeks now. Both of my original Waeco units swing between 8 and 12 degrees Celsius in any 24 hour period without being opened. The range is what concerns me. 

Both of you guys fridges probably have bad thermostats

YYZRC

My thermostat in the cabin fridge is new. Replaced at start of season. 

Handymans342

YYZRC said:

My thermostat in the cabin fridge is new. Replaced at start of season. 

Do you still have the box it came in? You should be able to calibrate it

YYZRC

I don’t recall any instructions being with it. I usually save that stuff or take a photo of it for reference. 

Handymans342

https://www.instructables.com/id/Calibrate-Fridge-Freezer-Thermostat/

Spyderweb

Tried @raybo3 experiment last night.  Despite fridge being 33 yesterday morning, and freezer -2, by end of the day on the water fridge was 53 and freezer maybe in 30’s.  Back at the the dock in the evening I left fridge on, but did not turn on fridge breaker.  So fridge should be runnning on house batteries, same as on water.   Cabin was 80.  Battery charger was on.  Whenever I checked, volt meter on panel was reading somewhere around 13.4 (?).  Within a couple of hours I noticed fridge was back in the forties.  This morning fridge was 33, freezer -4.  

YYZRC

Your experience is exactly the same as mine. I’ve decided these fridges just take forever to recover after being opened. 

Spyderweb

@YYZRC did you say you put in new gaskets?

YYZRC

No I didn’t. I don’t think there is anything wrong with them. I cleaned them and the fridge surface where they mate. 

Handymans342

Spyderweb said:

Tried @raybo3 experiment last night.  Despite fridge being 33 yesterday morning, and freezer -2, by end of the day on the water fridge was 53 and freezer maybe in 30’s.  Back at the the dock in the evening I left fridge on, but did not turn on fridge breaker.  So fridge should be runnning on house batteries, same as on water.   Cabin was 80.  Battery charger was on.  Whenever I checked, volt meter on panel was reading somewhere around 13.4 (?).  Within a couple of hours I noticed fridge was back in the forties.  This morning fridge was 33, freezer -4.  

What was the DC voltage when it was 50 inside? Was the compressor running. You don’t answer these questions

YYZRC

My voltage after a day on the hook is 12.2-12.4 as per the analog panel gauge and the compressor runs constantly. 

@Spyderweb I think part of the issue for us is the dark hull absorbing heat and the inability of the fridge to dissipate that heat - some of the Four Winns guys with dark hulls added computer fans to the fridge compartment to pull the hot air out. The problem with that is you can’t wire them to the fridge condenser fan as it senses the additional draw and errors out. Once I have solar I won’t mind a couple small fans running all day. 

My uneducated assumption that the dark hull issue combined with Handy’s assertion that the compressor becomes less efficient as it ages = crappy performance. I no longer believe it’s a DC vs AC issue. I think that it’s an ambient temp + old compressor + door open issue. At night on the hook my fridge will recover because it’s not being opened and the hull is not warm from the sun. 

I will replace my cockpit fridge over the winter and I will keep messing with the cabin fridge. I will pull the thermostat out and see if it can be adjusted as per Handy’s comments above. 

Spyderweb

Handymans342 said:

Spyderweb said:

Tried @raybo3 experiment last night.  Despite fridge being 33 yesterday morning, and freezer -2, by end of the day on the water fridge was 53 and freezer maybe in 30’s.  Back at the the dock in the evening I left fridge on, but did not turn on fridge breaker.  So fridge should be runnning on house batteries, same as on water.   Cabin was 80.  Battery charger was on.  Whenever I checked, volt meter on panel was reading somewhere around 13.4 (?).  Within a couple of hours I noticed fridge was back in the forties.  This morning fridge was 33, freezer -4.  

What was the DC voltage when it was 50 inside? Was the compressor running. You don’t answer these questions

When it was 50 inside (end of day on the hook) voltage on meter in electrical panel was 12.2.  In the past checking directly on house batteries I always get a reading 0.2 higher than at panel.  I’ve always thought 12.2 was still safe for battery and I’m assuming i’m not taking it below 12.4  Every time I checked fridge I hear a hum, so I assume that’s the compressor running.  So again i’m assuming voltage no lower than 12.2 with compressor running.

Spyderweb

@YYZRC I also wondered about the dark hull.  We did spend 1 day at the dock this week, but it was mostly cloudy and fridge maintained in 30’s, similar to night.  That’s also on shore power.  I’m pretty sure it gets real warm in those cavities because sometimes when I turn on the cockpit sink, very warm water comes out initially.  Need to spend a warm sunny day at dock and monitor temp.  But who wants to spend a warm sunny day at dock?  Would have to be a very windy day.

i think the fact that you recover on the hook is very telling.  Seems battery is not the issue, and like you say, old compressors that can’t keep up with the daytime temps, and loss of cold from door openings.

YYZRC

Yes it gets super hot in there. Just pull out the garbage bin and stick your hand in!

Handymans342

That could be the problem. Any way you can put a small fan behind and blow it right in the condenser coil

YYZRC

The condenser coil already has a fan mounted to it but I think circulating the air in the void would certainly help the existing fan.

Spyderweb

YYZRC said:

The condenser coil already has a fan mounted to it but I think circulating the air in the void would certainly help the existing fan.

I’m wondering.  That cavity is all below the rub rail, hence dark hull sides.  Assuming heat rises, would the top of the cavity be warmer than the bottom?  If the coil is in bottom of fridge, would that be making the warm air mix with the cooler bottom air and make this worse?  (I don’t know where the coil is)