Electrical troubleshooting – phase 1
As you may have read, our refrigerator’s evaporator plate met with an untimely demise and we were forced to replace it back when we were in Puerto Rico. Since we did that, I’ve never been 100% sure just how well it has been working.
Our friend Jeff had long ago suggested that we install a thermometer inside the fridge to act as an “early warning sign” in case something was amiss. The absolute reading that the meter shows isn’t all that important but the relative readings day to day are. Prior to swapping the evaporators we had readings around 4.x degrees C. Now, the lowest we have seen is 6.x and it’s often as high as 9 to 12 degrees C (the fridge does work much better when it is full of food). So, the fridge is definitely working, and it can even make some nice ice cubes, but how well it’s working is the question.
One thing I haven’t been sure about is the percentage of time the compressor has been running each day, or the duty cycle. What typically (should!) happens is the compressor turns on, sucks the heat out of the box and then shuts off. When the temperature rises enough, it repeats the cycle. The refrigerator is our number one power draw, as it is for most other cruisers who have fridges (some opt not to), so this is pretty important. After discussing this subject with our friend Jeff the other day, who is also experiencing his own set of refrigerator woes, I decided to run the numbers to calculate the duty cycle. Here is how to do it showing our actual numbers from one particular night:
Sleep: 9:15 PM (I know, boring!)
Wake: 5:45 AM (What was I thinking?)
Total Sleep: 8.5hr
Starting AH consumed: 42.1 (as determined from our Link battery monitor)
Ending AH consumed: 96.5
Total AH consumed: 96.5 – 42.1 = 54.4
Fridge Draw: 5.8A (Also determined from our Link battery monitor. Watch the current draw when the fridge is both on and off and record the difference.)
8.5 hours x 5.8 amps = 49.3 amp/hours
First we can deduce from this that the compressor is not turning off at all. In addition to that, there is another 5.1 amps being used during the night (54.4 – 49.3).
We know that our anchor light draws 0.1 amps. I have also found that if I have only the main electrical system turned on with nothing else running, there is a 0.5 amp draw showing on the meter. This could be to run the analog meters and/or the little lights that illuminate the panel. I’m not yet sure.
0.5 amps (panel?) + 0.1 amps (light) = 0.6 amps.
0.6 amps x 8.5 hours = 5.1 amp hours
5.1A + 49.3A = 54.4A – That is all of it. BUT, it also means there is some stuff to fix.
The fridge is running 100% of the time which is obviously NOT SO GOOD! We have been exploring both getting the fridge running properly and getting rid of that mystery current draw. The 0.5 amps might not seem like a big deal but if it is running 24/7, that equals 12 amp hours which is significant. More to come.
Roger’s Ramshackle Bar on Hog Island, right in front of where we are anchored.
A folding mast? Um, not intentionally. I wonder what the story is behind this one.
Since we don’t plan to be doing any big passages in the next few days, we removed the jack lines and tethers from the boat. The tethers were washed, the carabiners were lubed and the whole kit was stored inside. This left our dock lines free for the time being so Rebecca set to work to braid them into another “dance” rope.
Here is a cool photo of Rebecca from the Georgetown Variety Show using a rope like the one above. We received this photo from our friend Don Engler.
I hope you figure out whats wrong, if anything.
The reason I wanted to comment is to note the stark contrast contained in your post! As I read and scroll down I am confronted with an ever increasing maze of equations, amps, celsius and numbers whose sum all equal stress!
But then suddenly, BANG! I am thrown onshore at none other than the most idyllic beach bar setting I could ever imagine. And of course as I scroll down farther there are the very soothing images of Rebecca 🙂
If blog posts could be judged on the same criteria that art is, I would say that you just won first prize!
LOL. Thanks Jim. 🙂
Your comment about power draw (fridge on ZTC) is related to outside cooling (ambient temperature). If you cool with water and the water temp rises you have a condition very similer to variation. As we know variation changes with location. Since you cannot blame altitude you can only blame humidity or outside temperture rise unless you have propane fuelled refrigeration. The same can happen when you have a compressor hidden in the hull or cabinet. Outside air temp vs inside a cabinet. Check water inlets or do a flush for best flow if water cooled. Critters will live in a water cooled system. Check for dust bunnies on an air coolied unit or lack of air flow due to storage of items. eg air intakes to that space. All of these things will affect cooling percentages. I deal with small bar fridges every day. Most stop working for two reasons. Someone damaged the cold plate or they cannot breath. Amp draw goes way up causing more heat less cooling. Be sure if you have a fan cooled unit to check the fans RPM to ensure proper air delivery over the cooling coils. Also look at any bent cooling fins. Most calculations result in a 60- 70% efficiency rating for refrigerated units. A 2-5 degree temperature rise can change efficiencies by 5-10%. If you can make ice it’s working well. I hope this helps.
Hi Brian
It is an air cooled compressor with an evaporator plate. Definitely the ambient temperature is higher, but should it be running 100% of the time? Our friends on a similar boat with a similar unit have about a 50/50 run time.
There are no dust bunnies as I just checked and the compressor has decent airflow (as good as it has ever had).
Thanks for your input!
Please can you clarify what you mean by ‘jack line’ and ‘tethers’ as I often see these terms and they are not the same usage as I am accustomed too. Thanks.
Mike
“Jacklines” are run bow to stern on a boat. To prevent MOBs (Man overboard), the crew is then secured to the vessel via the “tether” which attaches one one end to your harness and on the other end to the jacklines.
See this post:
http://sail-delmarva.blogspot.com/2009/10/climbing-gear-for-sailors-or-jacklines.html
Fine, that’s familiar thanks. It is just that terminology varies. Cheers. Mike.
You’re welcome.
Have you had any trouble with the jackline interfering with the jib sheets?
No, not at all, either with the self tacking jib or the traditionally-sheeted genoa.
Looking at some of your older pictures of ZTC it looks like you have two jacklines. Port and Starboard. I was just running one and it went around the mast then to the forward beam. Your set up looks better. What type of knot do you use at the cabin top handrail? How long are your jacklines? Are they tight enough to keep you inside the lifelines with a 6′ tether?
Just finished reading ‘An Embarrassment of Mangoes’.
It was a great book. Have a blast in Grenada.
Hi John
The jacklines are just docklines (idea stolen from Drew). They are attached to the forward cross beam with a larks head (through the eye) and then secured reasonably tightly to the cabin top rail with a clove hitch (of sorts) and a whole bunch of half hitches. These knots allow me to get the tension that I want which is tight-ish but nowhere near piano-string tight. The tethers are long enough to allow me to get to the port side of the mast when clipped to the starboard jackline and vice versa. With that said, no, I do not think it would keep me on the boat, nor will it allow me to coast back to the transom. I do think that Rebecca and I are strong enough to get ourselves back on board though (untested) which perhaps, not everyone could do.
We also love the book. We just told our friend about it this morning and she wants to borrow it. If we run into Anne again we’ll tell her that you thought it was great:)
With all that said, I think the system will work, even if it isn’t perfect.
If you fear refrigerator problems, can you vacuum-bag things? This helps to keep them a long time without freezing. Many things also stay fresher this way.
Of course you need the sealer and a supply of bags or tube film. And it uses some power, though only briefly. They are often described as a ‘cruisers friend’. Good for safe food and also good for storing things so they don’t get wet etc, eg computer spares and other sensitive things.
Mike
Unlike many cruisers, we never really had a problem with our fridge. And even now, I can’t say that it is a huge problem, although it is using a lot of power. Too much I think.
The vacuum bag thing is a good idea. We actually just purchased some frozen vacuum packed meet yesterday from the local butcher. We don’t have one of those systems but have contemplated getting one on several occasions.
Hi Mike! You might want to try checking the placement of your thermal pickup for the thermostat. Make sure it is not being blocked by items in the fridge (keeping it from getting a proper sampling of air temp) or completely covered in ice (one would think covered in ice would shut it down, but this can be the same as a pickup outside the fridge). From following your posts, inless your plate met with it’s demise due to a puncture, it may have blown due to water particles “IN” the lines (nortoriously happens during fridge installation on boats) that eventually setteled in a bad spot and expanded when frozen and broke the plate (all guesses since I’m not there to troubleshoot). The water particles can cause a host of problems, such as flow obstruction and so on – causing the unit to runnaway. Was the system brought into a full vacuum during the plate replacement? Sounds like if there are no ventilation problems with your compressor stage, then your thermostatic control (or something having an effect on it) is to blame. By the current draw, I already knew you did not have a water cooled system, and by the stats it’s probably a Norcold or Dometic? And yes, I have over 30 years Master level experience with this stuff… It just gets a little difficult doing it remote control… If we were on schedule, we could pull up beside you and have a look. Depending on how laong you are cruising this leg, we’ll probably cross paths just after the hurricane season lets up. Good travels!
Hi Chase
Thanks for the info. I hope we do meet up! We plan to be in the Grenada area until November and then will likely start moving a bit more northward.
The fridge is an Adler Barbour. The compressor did die due to a puncture. I just replaced the thermostat with the brand new one that came with the new evaporator on the chance that it was the issue. Replacing it did not solve the problem. I checked the pickup for the thermostat again yesterday to ensure that I had it installed properly. It is not covered by ice. This also didn’t seem to fix the issue. The compressor still runs non stop.
I can only assume that the guy who charged the system knew what he was doing. He did vacuum the system but how well it was done, I don’t know.
Mike,
Just as a check, while you can hear the compressor running turn the thermostat to a higher temp until the compressor shuts off or not.
This will show whether the relay contacts are welded together or not and preventing the compressor from shutting down.
Bill Kelleher
ps I hope I worded that correctly as it is the middle of the night. LOL
Sorry Bill, I’m not sure what you mean exactly.
Tried several times to post reply but keep getting “Forbidden” error message…
Not sure why Chase. Please try again or alternatively, email us directly: zero to cruising ATT gmail DOTT com
Part one – Hi Mike! Forgot about the Adler Barbour (of I guess I put it out of my mind – lots of problems with those on Catalinas for some reason) – it’s about the same design class as the Norcold, but uses more power (less efficient). Waeco is a Connecticut company, and I’m not sure their stats were designed so well for tropical climates. Up north, where they tested the units, the conditions are much different than down here. Thetford (Norcold – a big company) has testing in the Miami area and Dometic is Pompano Beach (just north of Miami) – both of those designed well for tropical environments. Bill’s comment below is about the cooling knob for controlling the cycles and fridge temp. In a normal system, you can turn down the cooling knob (sets the unit to a higher temp – his reference), and once the setting matches the temp range the thermostat is looking for, then the thermostat SHOULD turn off the compressor, IF the relay has not welded it’s own contacts in the on (or closed) position.
I’m hoping the system saves email addresses? Send me an email and I’ll get you the important part of the data the system won’t let me post . . .
Email to you . . .
Thanks Chase.
Hi Mike . All the guy`s I work with who do cooling repairs want to know if your repair guy installed an inline dryer . Looks like a fuel filter . This would pick up any moisture or oil from the repair. Most of us think you may have a very small blockage ,causing the unit to run harder . Most cooling units will still work Ok but don`t last as long given they run harder to do the job. Some of the guy`s think maybe it`s from the amount of beer you are drinking to many trips to the fridge.
Hmmm… I don’t know, we’re pretty quick retrieving the beer.
I don’t know about the other things but we may be forced to hire a pro to come look at it.