Evap motor no come on

[Apprentice]

Bear with me here, I'm no refrigerator tech. I do ok with furnaces & a little a/c, but am lost of refrgerators and had my friend ask to help fix his...I'm ok with a multi tester but am unfamilier with ref. circuts and controls.

What I'm working on is a Traulsen M# GLT232NUT, double door commercial freezer.

The initial complaint was that its not defrosting and that they were told that the defrost timer is bad. When I put power to it, the evaporator motor would not run while wired into the circut, but would when jumped straight to power. I found a paragon defrost timer, manually cycled it and nothing. The contacts were fried and since they'd already been told it weas bad, I replaced it with identical guts. It didnt make a difference. I found two freeze stat looking things on the evap coil and checked continuity while using a lighter and a glass of ice water to change temps. The red one would close on drop and open on rise, so is ok. The yellow one was totally open and not cycle. I think I figured out that the red one brings on the defrost element on drop and the yellow one shuts the element off on rise. Since the yellow one was open, I replaced it, and powered it up to see what happen. After an hour it was getting cold in there, but the evap motor never did come on. I figured since it runs direct but not in the circut that it was good and must cycle with a sensor or something and since it was off for weeks it would cycle on eventually?? (It was late). Well no more cooling the next day. It was frosted but not a block of ice, and the evap motor still wont run.

There's a terminal strip spagetti factory, no wiring diagram, and I dont know what cycles the evap fan, or is it supposed to run constantly? Cycle with the compressor? I'm get a little confused with parrallel circuts, series circuts I'm ok with. Cycling the timer wont bring it on (I set 4 pegs at 6 hr intervals as on the original one and wiring went back exact) What am I looking for???

It seems to me that the evap motor almost have to cycle with compressor, they have to have airflow to get cooling, but am unfamilier with this type of equipment, and am lacking the exact sequence of operation to be able to pin it down, not to mention some greyness with these circuts. (and it has a 'defogger' switch on front, that dont seem to do anything and I've no clue what its for.) What am I looking for here? Please help!!

TIA.

[Gary]

The defrost timer starts the defrost and shuts off the fan.

A sensor on the coil closes a circuit and trips a mechanism in the timer when the coil is defrosted, ending the defrost cycle.

When the coil drops below freezing temperature, the coil sensor closes another circuit, allowing the fan to run.

This "fan/termination switch" is generally a three wire single pole double throw control. The second (two wire) sensor is likely a high limit in series with the defrost heaters.

Another strategy would be to use 2 two wire switches. One of these would open when the coil is defrosted, disabling the heaters. The timer would then continue until the defrost time period is ended. Then the compressor would start. When the coil is below freezing, the second switch enables the fan.

In addition, there may be a door switch which would prevent the fan from running if the door is open.

These circuits are described in great detail in lessons 10 and 11 in my ACR Trouble Shooting book. :D

[mrchatts]

Sorry I haven’t worked on that type of fridge before but the paragon defrost timer is quite common, well it used to be before electronic timers tuck over.

I think there are two types of paragon timers, one with internal solenoid for defrost termination and one without. One klixon (two freeze stat looking things) would be for the fan and the other to terminate defrost

The klixon that makes on fall of temperature would control the fan and the live should come from the refrigeration output of the timer or the fan delay live output (if fitted) through the make on fall klixon to the evaporator fan motor.
When the evaporator is cold enough the fan should operate when in refrigeration mode.

The other klixon that makes on rise of temperature would send power to X on the defrost clock, (Note. X may need live or neutral to operate be careful don’t short your solenoid) energising the termination solenoid and switching the points over to refrigeration. If the defrost timer hasn’t got defrost termination solenoid, then the klixon that terminates defrost would be break on rise of temperature stopping power to the heater and the clock will timeout switching back over to refrigeration

Be careful not to mix up the live and neutral and cause a short in the klixon or timer. Some paragon timers switch neutrals.

Hope this helps because it started to confuse me

[Peter_1]

Have you checked the motor itself :D

[Apprentice]

I went back over today and voila', it was at -8 F and chugging right along.
<When the coil drops below freezing temperature, the coil sensor closes another circuit, allowing the fan to run.>

The "defrost termination" (or what I thought was) switch must actually be a type of fan delay as gary suggested, which waits until the coil is below freezing to trip the fan. I guess I didn't wait long enough to see it cycle on! I'm used to a/c, and if there's compressor action, there better be evap fan action also. One of the little ideosyncracies of refrigeration, I suppose.

I spent some time with it getting familier and checking temps etc., and from what you guys are saying, I surmise that when I manually cycled the defrost timer trying to get the fan to come on that I was manually sending it into defrost which cuts the fan, so no wonder it wouldn't come on! And the yellow sensor wouldn't trigger the fan b/c the coil was still too hot. (correct?) and the red sensor must be a defrost terminator, being a 2nd way (?) to end defrost, one being the timer, and one for if the coil rises above a certain temp.? Correct?

The good/bad news is, he's up & running, I muddled my way through it, and now, he's convinced that I'm some kind of crack reffer man and says only I will touch it in the future!

So, can you guys suggest a good ref troubleshooting / reference book that I could get to brush up and learn more with. I don't think I need a textbook that greys everything up with a bunch of theory. I think I need a book that cuts out the theories and addresses practical diagnosis & troubleshooting for the most common controls, flowcharts, setpoints...that sort of thing.

Thanks!

[Gary]

I just happen to have the very book you are describing.

http://www.techmethod.com

When you get there, click on "Products", then click on "Books". The book you are looking for is "ACR Trouble Shooting". It was written by a veteran (35+ years) hands-on service tech (me). It covers everything from high temp systems to cascade freezers, and none of it is theory.

[angryk]

Hello apprentice. Gary's books are what you are looking for.

[Apprentice]

Sounds like just what I need.
His pepsi cooler (Different machine) only makes it down to 60 deg F now and I'm supposed to fix it next week. It was going off on IOL so I chemically cleaned the 1/2" of fur off the coil. Its not going off on IOL anymore but wont get down past 60 still. I doubt its low on charge or it'd probably be empty from the leak, no frosting either. Kind of points to the T-stat I think. There's not much to this unit and doesn't look very old.

(think you can get me a book by morning? LOL)

Now those stats on those coolers, kind of like an electric water heater stat in that I could check continuity while manually cycleing the switch, but thats not going to let me know if it works automatically. Is there a more definitive way to test them?

(I want the book but might be a couple weeks to squirrel away the 90 bucks. Priorities ya know!)

[angryk]

I doubt it's the t/stat. Those coolers usually have a constant cut in t/stat which constantly cuts in at a set temp. Usually between 37* to 41*. They are coil sensing, so they usually cut out around 20*(that's the adjustable part). Unless your compressor and condenser fan are shutting off at 60*, it's not the t/stat. If both your coils are free from restriction, your going to have to check the charge. You may have to braze on a low side access. Use a pair of pinch off vise grips and pinch shut the low side process tube on the compressor. Cut off the brazed end, install an 1/8" access fitting and braze(make sure you remove the shraeder core). Round out the pinch with your flaring block. It's either low on charge, has an ineficient compressor or if it' r134a you very well may have a cap tube restriction. By the way if it's a pepsi cooler, pepsi owns it and maintains it, unless it's one of those that they forgot the cutomer has.

[Apprentice]

Restriction eh? Maybe some varnish from the compressor windings.

I'm going to take a good close look at that compressor. The IOL should've saved the compressor I would think. Maybe the IOL is weak from it cycling it so much. Thanks for the input. It is r12 btw.

[angryk]

If it's R12, it's not going to be any newer than 1993. Probably inefficient.

[Apprentice]

I mentioned to him that pepsi may own it and he called them to see if they'd fix it for free and they replaced it for him with a new unit and hauled off the other one. From what he said they had forgotten about it but he's all online now.

The other unit I put the defrost timer on was at -15 and doing fine.:cool:

[RogGoetsch]

Originally posted by Apprentice

What I'm working on is a Traulsen M# GLT232NUT, double door commercial freezer.

(and it has a 'defogger' switch on front, that dont seem to do anything and I've no clue what its for.) What am I looking for here? Please help!!

TIA.

The switch on the front controls the door frame heater. When the customer complains his doors are freezing shut or dripping water on the floor, his switch is off and the environment too humid.

GLT2-32-NUT's use two two-wire sensors, one to cycle the fan (yellow) as you now know, and the second (red) should make on rise of temp to terminate defrost through the paragon defrost termination solenoid, also as described in this thread. On many units you may find this has been changed to a hi-limit and wired in series with the heaters, because they are very common in domestic units, and the previous tech had one on his truck, I suppose.

The defrost timer setting is a failsafe and should be set for a slightly longer time than should be necessary in wet weather. (I once serviced a unit whose termination sensor had failed in the open position and was cycling on the clock alone. I was called when the clock failed in the defrost position! The customer had pulled the plug when he smelled something burning. The plastic fan blades had melted like Dali clocks!)

Traulsens also use a small SPST contactor (mounted under the temp control in that "spaghetti" box) to start the compressor. You will often find them gone and the compressor wired through the temp control directly. The contactors are expensive from Traulsen but cheap at a local electronics store, just make sure they are rated for the compressor current.

As mentioned before, Traulsen coolers, like most commercial coolers, use a coil-sensing t'stat with a fixed cut-in to allow for coil defrosting. It is also common to find an air-sensing t'stat installed instead. (They cost less.) This is a very bad idea. If someone leaves the door ajar for a time the coil becomes a solid block of frost and can't recover.

I stock a control (Ranco A12-1560) with a long capillary without a bulb. Ranco also sells a small tool that allows you to wrap the end of the capillary into the smallest possible diameter without kinking to form a bulb-shape for good coil insertion. I usually find them just folded and inserted between the fins, which also seems to work.

The more I think about this, the more I realize how very many things there are to learn about every unit out there. I admire Gary for putting together a course to help educate techs.

One last thing about Traulsens: the SS louver strips have a fat edge and a skinny edge in back. The fat edge goes Down under the plastic clips on the sides FIRST, then you lift the louver up to engage the top, skinny edge. I'm sorry, but I see so many with broken clips and louvers falling off because they don't quite fit with the fat edge up unless you jam them on, breaking the clips. Thanks for letting me get that off my chest!

Rog

[Apprentice]

Sounds like you know these units very well. You hit the nail on the head about everything even the contactor being gone out of the box and the compressor wired through the temp control. I had eventually got literature from traulsen on this unit and am now fairly comfortable with it. I also realize that one of the condensor fans was scabbed in and plugs in direct to a 115V outlet and the other one cycles with the compressor. I thought it weird when I saw that at first but figured that it was probably supposed to be that way, being unfamilier with freezers in the first place. The guy did a good job of making it not obviously a scab by the way he ran the wiring. I appreciate your input on this.

I still got to order that book from him soon.