Wednesday, March 5, 2014

I Want To Complain about 'Experts'

My refrigerator started giving me trouble.  No, it wasn't the Iris Smart Switch I installed in the power, it was that the darn thing started to get warm.  I opened the door and the little thermometer I have inside said it was 55 F inside.  It usually runs under 45, so something was up.  I checked all the obvious things, the compressor was going, the fan on the condenser coil was running; I couldn't see anything obvious.

Once again, a little bit about the refrigerator:  It's a refrigerator (only) that I've had for some years and it has given me trouble before; I even had to have the evaporator coil replaced.  I got this thing because I wanted it to be the last refrigerator I'd ever buy.  To meet that I got the very top of the line GE Monogram model ZIRS36 in stainless steel (ZIRS36NMRH).  It's a really, really old design that doesn't even have a frost free option.  That's because it has no freezer inside and just doesn't form frost.

Basically, the power comes in, goes to the temperature control, then to a temperature sensor on the evaporator coil (to prevent freezing up) and then to the compressor.  There's three fans: one on the top to cool the condenser and condenser coil, one inside to circulate air from the evaporator coil to the rest of the fridge, and one on the bottom to evaporate any water that drains out of the evaporator.  Then the lights are all that's left.  Not much to go bad, and not much to troubleshoot when it has problems.

However, I couldn't find anything wrong with any of those things, so I went to the web and found this discussion on one of those 'Ask an Expert' sites <link>; basically, the expert said the correct thing first, then corrected himself to the wrong thing.  This fridge is a middle level cooling system.  It doesn't cool below freezing anywhere inside except the actual surface of the evaporator coil.  It maintains a temperature of about 38 degrees and doesn't need a defrost timer or defrost heater at all.  The customer in the discussion tells the expert this, but that doesn't keep the expert from getting confused and messing it up.  I chuckled a little bit and then found this discussion <link>;  once again, the expert changes his mind midstream and messes it up.

The last link is especially interesting because a couple of other repairmen get into it and try to straighten things out.  By the very bottom of the discussion, the actual possible problems finally show up.

So, what was wrong with mine?  The door needed to be adjusted.  Yep, the door has sagged a little bit over the years and was far enough down that it didn't close a switch at the top that turns on the fan for the evaporator.  See, if the fan isn't on, the evaporator goes into freezing range and the temperature sensor I mentioned above, shuts off the compressor to prevent ice forming and breaking the evaporator coil.  I drug out the tools and modified the top hinge to be adjustable and reset the door.  Problem solved.

The reason I had to modify the hinge was because GE made provisions for raising and lowering the door, but not tilting it.  They even avoid the subject in their installation manual (yes, I read it) like a door will never, ever skew a little bit.  The experts out there will tell me that I should adjust the fridge to assure that it's square because that can cause the same problem; I did that first with a nice level, framing square, and all.  Nope, the door actually needed to be adjusted.

But the point of this is that after I found the two discussions listed above, I found several others where the expert just wouldn't listen to the customer, assumed he knew everything, and screwed it up.

I'll never, ever ask a question on one of those sites.

But, there were a few good things that came out of this fiasco.  I moved the Smart Switch back to the fridge (I had it on the freezer for a few days), and took a look at the power usage during the problem:

Notice the small spikes?  It seems the compressor was turning on for a very short period, then shutting off for a very long period.  This was because the evaporator coil got too cold (no airflow) and the thermal protection kicked in and shut the compressor off.  This is very different from the graph I blogged about earlier <link>.  Another thing good about this was that I improved the performance of the appliance:

Now, the compressor is on longer, but off longer as well.  I turned the temperature control down and allowed it to stabilize at 38 F and all seems to be well.  Of course, something else can crop up and cause problems, but it looks like I fixed it.

Edit:  It's been a little over a day since I fixed the door on the fridge and I thought someone out there might be interested in the result.  Yes I fixed it, and I made out like a bandit on this:

Ignoring the couple of bumps in the middle of the chart, notice how it has settled down to a regular rythm?  It's on for about 15 minutes and off for around an hour and a half.  The huge spike in the middle is when I had the door open and the compressor kicked on at the same time; 300 W for the lights and around 400 W for the spike of the compressor starting.  The other bump right next to it was where I finally finished up assembling the fridge.  I put the drawers back in that I had take out to check things and also the temperature controller cover.  

Net, over time I'll get a feel for the usage of the fridge and a simple check every once in a while will tell me if it's working OK, or if it needs some attention.  It would be cool to completely automate the operation of this device with a little computer and radio combination, but not now, I want to take a really close look at the freezer setting nearby.  Then I'll take a look at the chest freezer I have out in the garage.  These appliance have been blamed by many people for using too much power, but my experience is the exact opposite.  The pool is my biggest electrical usage followed by the water heater.  Those I have under control with load balancing to off-peak periods and solar assistance.  Next is the two A/C units I have;  if I left them to run on their own, they would far exceed everything else, but I control when they can run also to minimize their impact on my wallet.

So, you folk that are looking at one of those multi-hundred dollar fancy thermostats to control the temperature in your house, think again.  You won't get nearly as much information from them as I do with my set up, and you won't be able to control it as well.  Sure, you'll have to actually learn something instead of buying the hype they try to sell you, but what's wrong with that?

Smart grid my butt, smart house is the solution.


  1. Great post. Being able to have the instrumentation to identify what "normal" looks like is key. But you can't really buy that off the shelf today and have to build your own.

    I appreciated your XBee and other documentation. I recently came across an interesting project called TheThingSystem. It's all open source and is basically a controller for "things". I'm starting to work with them to hook in some XBee devices. I hope you don't mind, but I referred the project leads to your site and suggested they might want to contact you. It seems right up your alley.


    1. No problem. I got a note from them and it was the first time I noticed them. It actually sounds like a really cool project, but I'm on, like, page three of their documentation, and I know exactly zero about nodejs.

      Guess I have some work to do.

    2. Likewise! But I'm going to dive in after Spring Break and see what I can do.

  2. Have you considered hard-wiring around the relay in the Smart Switch to essentially take it out of the circuit? If not, does it look like the device could be opened without destroying it? I really like the price for an outlet power monitor, but not so much if I accidentally have it switch off.

    Also thanks for sharing all that you do. You are a great writer as well as a technical resource. I often find myself here looking for ideas, to grab a little code, or just be entertained.


    1. I was concerned about turning it off at first. Actually, I watched it like a hawk on other things for a few days to see what would happen. Then I hooked it up in the garage to a light and proceeded to turn the breakers off, transmit tons of garbage over the XBee channel I was using and so forth. The little device just ignored all of it.

      They store the state of the switch in something non-volatile and restore it as soon as the power comes on. It doesn't accept traffic that isn't encrypted, so random data can't turn it off. There is the possibility of an internal component failure, like the relay itself frying that can't be over come no matter how well they put it together.

      So, at a future time, I'll be posting what it looks like internally and how to bypass the relay. I'm just heavy into the spring stuff we all have to do right now. Fixing the roof, changing the oil in the vehicles, pruning the plants for summer, getting my dog a refresher course in avoiding snakes ... you know the stuff we all have to deal with.

      Oh, and trying to figure out how I'm going to pay my taxes this year.