New Fermentation Chamber: True GDM-26 Refrigerator Cooler

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dermotstratton

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Just picked up a refurbished True GDM-26 refrigerator cooler for my new fermentation chamber. I was going to try and build a box, but decided this was a perfect fit for my conical and would save me a lot of time.

Has anyone else used one of these before?

Trying to figure out how I am going to feed in the temperature probe and heater power cord. Was thinking I might drill through the side, but not sure if there is a better way? The drain plug won't work because I need it to collect condendate.

Looking forward to making a lager sometime soon!

ferm chamber.jpg
 
I would think that you can go through the sides or rear without any problem, but that vertical sheet metal cover panel on the back wall I'm pretty sure is where the refrigerant lines go up to the evaporator. There may be some wiring there as well, but it's easy to remove to check.
 
So, there is not enough room to run it through the same hole as the light inside the chamber. It's integrated into the door very well with no extra room for another cord.

I am worried about hitting electrical wires or refrigerant lines. I'm almost positive that the side walls are just insulation inside aluminum panels, but would hate to learn the hard way. I'm hoping to find out if someone has already attempted this.

Thanks!
 
I've worked on this model & that's why I said in the earlier post that the cover on the rear inside is where the lines are - including the evaporator drain. If you don't want to pull the cover, try giving TRUE tech support a call. They don't publish much tech info on their website like other manufacturers do, but they will answer specific questions via their support staff. http://www.truemfg.com/ContactUs_en.aspx Good luck!
 
I love mine!
I just run the temp probe thru the door. The rubber seals around it pretty well. and no holes to drill
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I have a GDM-10 in use as a fermentation chamber. I ran the probe wire thru the same hole that the wiring harness passes thru in the floor. In mine, the wiring harness was behind a cover in the corner and the refrigerant lines were in the opposite corner. It appears that your unit has a cover in the center. I carefully worked a screwdriver up thru the putty that seals the hole. I punched a hole with a grommet to protect the probe wire as it exited the cover. You can learn a lot by checking out the cooler from the bottom rear. It is common to have a wiring diagram behind the lower front panel.

I removed and bypassed the existing thermostat and wired in a STC-1000 controller mounted in the lower front panel. Using the existing wires, a heater module was installed into the upper area between the evaporator fan and the evaporator core. The thermostat plate was replaced with a duplex receptacle having independent auxilary heat and always ON options.

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To the left can be seen my GDM-12 in use as a corny cooler. I drilled two holes in the side for CO2 for the kegs. As long as you know where the refrigerant lines are running, you can punch a hole just about anywhere but that stainless floor might be a little tougher.

BTW, Layne, we're almost neighbors. I'm close to Springfield.
 
I am picking a refurbished GDM26 this week. Friend of a friend that just refurbished it and it has a new compressor (one year warranty) for $500. :rockin:

Mine will be used for a kegerator/wine rack/soda rack etc. Taps out the side which works best in my garage where I need it to be.
 
Are you sure you can drill through sides without hitting any lines?
The refrigerant lines, as well as the wiring harness, in the TRUE GDM units are usually run behind a removable cover in the interior. This is done for ease of maintenance and repair.

BTW, the compressor module on these units usually has a standard 120V plug attached, which makes it very simple to add a controller that bypasses the existing thermostat. An added bonus is that it doesn't impact the light or evaporator fan, which should always be running for best operation.
 
I've got a used GDM-12 (with awesome 7-Up livery, haha) that's running the compressor regardless of the number I set on the thermostat. Probably a bad thermo? I pulled it and it's just two wires and a coil of wire that I assume senses the temperature. How hard is it to replace this with a better thermostat or temperature control? And how expensive? Thanks.
 
I've got a used GDM-12 (with awesome 7-Up livery, haha) that's running the compressor regardless of the number I set on the thermostat. Probably a bad thermo? I pulled it and it's just two wires and a coil of wire that I assume senses the temperature. How hard is it to replace this with a better thermostat or temperature control? And how expensive? Thanks.
Are you using this as a refrigerator? Is it getting cold quickly when the compressor is running or does it take a long time to cool items in it? Do you have it on an external controller?

If you are using the unit as a refrigerator, I would strongly suggest using the correct/compatible thermostat. Stock, these units use what is called a constant cut-in control. The probe actually monitors the temperature of the evaporator core. The probe, at the end of the coil of tubing, should be inside a tube that runs into the side of the evaporator. A kink in the tubing can disable the thermostat. The compressor runs until the evaporator reaches a temperature (well below freezing) set by the thermostat knob and then cuts off the compressor. The temperature of the evaporator is then allowed to rise well above freezing to a fixed cut-in temperature for consistent defrost purposes. Then the cycle repeats.

My GDM-12 had its thermostat replaced at some point with the incorrect one. After a thorough investigation, I installed a Ranco A12-701 constant cut-in thermostat and it has run perfect ever since. $40 on ebay Ranco A12-701, $50 at pexsupply.com Ranco A12-701

If you are using it as a fermenter, the thermostat wires can be jumpered together and an external controller like the STC-1000 can be installed for operation at higher temperatures.
 
I'm just using it as a fridge right now to store bottles of beer. It's completely stock. It gets cold quickly, too cold. Can't keep it above freezing as a matter of fact! The compressor never turns off. That's why I suspect a faulty thermostat since whatever setting I select, from 1 to 9, results in it running forever and too cold.
 
I'm just using it as a fridge right now to store bottles of beer. It's completely stock. It gets cold quickly, too cold. Can't keep it above freezing as a matter of fact! The compressor never turns off. That's why I suspect a faulty thermostat since whatever setting I select, from 1 to 9, results in it running forever and too cold.
I would agree on the thermostat diagnosis, but I'm no expert. I assume both the upper and lower fans are functional?

I do strongly recommend using the correct thermostat. It's not that hard to replace. The upper front panel, where the light is mounted, is removable. It's a tight fit but I was able to remove the old thermostat and install the new one with very little trouble. I seem to recall there was a section of tubing elbow that helped thread the probe into the side of the evaporator.
 
Both upper and lower fans are going - I'll go with your recommendations to replace it with a new stock thermostat.

The compressor also needs some new rubber feet - it sounds like marbles rattling around in there at the bottom which I have read can indicate it's in need of new mounting bushings to firmly and quietly mount it to the frame.
 
My GDM-12 had its thermostat replaced at some point with the incorrect one. After a thorough investigation, I installed a Ranco A12-701 constant cut-in thermostat and it has run perfect ever since. $40 on ebay Ranco A12-701, $50 at pexsupply.com Ranco A12-701

The one in there now that I just removed is this one: 25T65 800368 - wonder now if I should just get a new one of these or go with your Ranco suggestion. Or go with a high-altitude version since I'm at 5,000 feet... Ugh.

A side note - the probe lead was sealed into the copper pipe with some black bubble gum type stuff - any idea where I can get more when I install the new probe to get a good seal?
 
Thanks - looks like this is pretty much the same stuff. Non-hardening sealant dough good in extreme temps.

Any advice on the thermostat I should order?
 
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Well, new thermostat and permagum and it's still running 24/7 and even on "1" it's below freezing. Darn. What the heck else could it be?
 
Well, new thermostat and permagum and it's still running 24/7 and even on "1" it's below freezing. Darn. What the heck else could it be?

Is the temp probe in the right spot? Some have them in front of the coil others mount on the back side. It' could also be in perishable mode which should pull down in the low 30's If you press the snowflake button and "PAS" is shown on the screen it will no go into stand by mode to let the temp rise.:D
 
The temp probe fits into a copper tube that goes into the chiller. It's a dial, not an LCD screen on my model. Simple twist from 0 to 9 to set the temperature. 0 turns it off, and anything else just runs 24/7 and goes below freezing.

Sigh. My wife is not happy my bottles are in the regular fridge :) This need to get sorted.
 
EDIT: I just reread your post and you state that turning the thermostat all the way to 0 turns the compressor off? If that's the case then the non-bold post below really doesn't apply but I'll leave it. This bit of information tells me that the thermostat is controlling the compressor, just not the desired/expected way.

Did the thermostat have more than two connection points? Were you careful not to kink the tubing between the probe and thermostat when installing it? The probe, tubing and thermostat operate on temperature induced pressure changes within the sealed system. Any kinks will disable its function. Snapshots?

I assume you are measuring "freezing" by actually having a container of water freeze, and not just measuring the temperature of the air blowing out of the evaporator, down the rear of the unit, because that air will often measure below freezing.

Another thought. Can you post a snapshot of the interior label? Can't imagine since it's labeled 7up but are you sure this isn't a GDM-12F? Or maybe it was converted to an F model.


Ok. Let's back up a little and I'll throw out a few thoughts. It's entirely possible that someone has rewired the unit to bypass the thermostat.

Remove the front bottom grill and validate that the compressor assembly is plugged into the electrical box built into the cooler, behind the front grill. If it is, flip the toggle switch and make sure the entire unit shuts down, upper and lower sections.

Unplug the compressor assembly from the electrical box and flip the toggle switch back ON. The upper fan and lights should be enabled. Take a few snapshots while you're in there.

Can you read a basic schematic? If yes, then unplug the unit from the wall outlet and open up the electrical box behind the grill and check it against this schematic. The components on the schematic are divided between the electrical box and the upper section of the unit. In particular the, evaporator fan, temperature controller, light switch, and lamp are in the upper section. The ballast is usually mounted behind the electrical box. Pay attention to the pink wires. There should be two entering/leaving the electrical box. One should be tied to the HOT/black buss. The other pink wire should be connected to the compressor outlet. They should not be connected to one another within the electrical box.


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First let me thank you for your time, it's appreciated.

turning the thermostat all the way to 0 turns the compressor off? If that's the case then the non-bold post below really doesn't apply but I'll leave it. This bit of information tells me that the thermostat is controlling the compressor, just not the desired/expected way.
Exactly - it seems the thermostat is working as I have replaced it and it's functioning exactly the same.

Did the thermostat have more than two connection points? Were you careful not to kink the tubing between the probe and thermostat when installing it?
No - just two points. I was very careful not to kink it, nor was the original one I removed kinked.

Can't imagine since it's labeled 7up but are you sure this isn't a GDM-12F? Or maybe it was converted to an F model.
It's the standard GDM-12.

I assume you are measuring "freezing" by actually having a container of water freeze, and not just measuring the temperature of the air blowing out of the evaporator, down the rear of the unit, because that air will often measure below freezing.
Okay here's the thing - I have been using three different measuring devices to determine that it's below freezing. One, there's an OEM hanging mercury thermometer installed in it near the rear top of the unit, it always reads in the 20's. Two, I put a digital probe thermometer inside, dangling it exactly in the middle of the middle rack, not touching anything, and it goes down to about 28 degrees and always reads "low" which indicated below that temp. Third, I have been using an infrared thermometer to sample the temperature all over the inside. Always well below freezing.

BUT - after your post I put a bottle of water inside, and after 48 hours it has not frozen. It's just very cold (even on "1"), but not frozen. Not even frosty. So ... I guess it's sort of working correctly. I put my energy monitor on it and it's going to cost me nearly $500 / year in electricity to use this fridge (at $0.15/kwh)!!! It's averaging 350 watts / 3 amps over 48 hours of use. I do hear the compressor cycling on and off, but it's running most of the time, I'd say 80%+.

Does that seem reasonable? If it is I might have to sell the fridge and just get something else. A household fridge would use 8-12% of that annually. I just feel like something's wrong with this guy using that much juice. Please share your opinion if you don't mind.
 
I ran through my spec sheets and these units IF running 404a refrigerant are set for 33-38allowing for multiple door openings. This is through a TXV to keep this as MINIMUM temp. I think that you will need to use a different controller (TXV's are adjustable but only by a tech who has worked with them) I recommend that you look into a stc-1000 or ranco for your control. True units will use more power then a residential type fridge as the evaporator fan runs 24/7 and the units are designed to run more frequently.
 
The unit is designed to have the evaporator output air below freezing, when the compressor is on. Because they are designed for commercial use and frequent door opening/air exchanges, these units are designed to constantly run through a cooling and defrost cycle.

This is how the cooling/defrost cycle works: Cooling - The compressor starts and the evaporator starts chilling. When the evaporator reaches a particular temperature below freezing, set by the thermostat, it cuts off. Defrost - The evaporator temperature then slowly rises to a specific temperature, usually in the low 40's, and the thermostat cuts in and the cycle begins again. The ON/OFF duty cycle basically regulates the liquid temperatures.

Try using the fridge to actually store a decent amount of items. This "cold" sink may make a positive difference. Simply running it to cool the interior air over and over is not a good test of its functionality or even its average power consumption. In addition, don't judge anything on air temperature. Measure the liquid temperature and adjust the thermostat to get the liquid temperatures where you want them.
 
You may well be 100% right but I can't spend this much on electricity to keep beer bottles cold :) I am going to sell it, and I bought a small fridge at Costco that uses about $30/year in go-juice and will fit 5 gallons in bottles.

Thanks to everyone for the help and advice.
 
......I put my energy monitor on it and it's going to cost me nearly $500 / year in electricity to use this fridge (at $0.15/kwh)!!! It's averaging 350 watts / 3 amps over 48 hours of use. I do hear the compressor cycling on and off, but it's running most of the time, I'd say 80%+.....
I'm not completely sure of the calculations you have made. Is this it basically? 350x24 = 8.4KWH/day @$0.15/KWH would result in $459/year ?

The compressor is rated at 115VAC/4.4A which is about 500watts when running and the evaporator fan is rated at 9watts which runs all the time. Therefore, during your monitoring the compressor consumed 340watts on average, so it ran about 68% of the time, 340/500.

The manufacturer claims energy consumption of 2.08KWH per day, or an average of 86watts continuous. This represents about a 17% run time and would be about $115 per year at $0.15/KWH. Of course that figure is best case test results.

Still, I'm not sure why your measurements would be so different from the manufacturers. Either the unit is not operating correctly or an unloaded unit consumes 3-4 times the energy of a perfectly operating/filled unit.
 
I'm not completely sure of the calculations you have made. Is this it basically? 350x24 = 8.4KWH/day @$0.15/KWH would result in $459/year ?
I have a power meter that calculates the cost per year for me. I left it running for more than 48 hours (after it had been on for a few days, too, so it wasn't just some initial startup running or anthing) and that's where I got the numbers.

Still, I'm not sure why your measurements would be so different from the manufacturers. Either the unit is not operating correctly or an unloaded unit consumes 3-4 times the energy of a perfectly operating/filled unit.
I don't think a freezer empty would use more electricity anyhow - more airflow means it should run more efficiently and theoretically cost less.
 
I have a power meter that calculates the cost per year for me. I left it running for more than 48 hours (after it had been on for a few days, too, so it wasn't just some initial startup running or anthing) and that's where I got the numbers......
But the cooler was empty, correct?

......I don't think a freezer empty would use more electricity anyhow - more airflow means it should run more efficiently and theoretically cost less.
I disagree. A refrigerator or freezer is designed to operate with a load. I don't think it's about airflow, but a measure of the resistance to heat conduction/loss, thermal resistivity might be a way to describe it, of the items in the unit. Air would have very poor thermal resistivity while the solids or liquids being refrigerated have higher thermal resistivity. The items in the unit function as cold sinks that resist the absorption of heat. Once they are at the target temperature, it takes little energy to keep them there. But then again, maybe I'm wrong.
 
But the cooler was empty, correct?

I disagree. A refrigerator or freezer is designed to operate with a load. I don't think it's about airflow, but a measure of the resistance to heat conduction/loss, thermal resistivity might be a way to describe it, of the items in the unit. Air would have very poor thermal resistivity while the solids or liquids being refrigerated have higher thermal resistivity. The items in the unit function as cold sinks that resist the absorption of heat. Once they are at the target temperature, it takes little energy to keep them there. But then again, maybe I'm wrong.

Yes, they are designed to run WITH a thermal mass factor other wise they lose a lot opening/closing and quite a bit during defrost.
 
I removed and bypassed the existing thermostat and wired in a STC-1000 controller mounted in the lower front panel. Using the existing wires, a heater module was installed into the upper area between the evaporator fan and the evaporator core. The thermostat plate was replaced with a duplex receptacle having independent auxilary heat and always ON options.

Hi Raouliii, you've provided the best information I could find so far on True cooler conversions. I am knee deep in a conversion of a model GDM-41. I am using a Love dual output controller which I'll mount close to where you mounted it. I cut the connection between the pink and black wires leading to the compressor outlet and spliced in three new pink wires on one (pink) end and a black wire on the other (black) end. I also spliced in a white/neutral wire for the controller and the neutral wire of an extension cord (to be used to plug in a heater). I made all these connections inside the existing box. The three pink, one black, and one neutral wires all exit the box (along with the neutral end of the cord) and will be connected to the controller along with the hot end of the cord. I used the drain line for the extension cord and the probe wires.

I did not attempt to put the heater up above in the fan/condenser box as you did, but I have to assume the "existing wires" you used were the pink wires to and from the thermostat which was bypassed. I bypassed the thermostat using a pink connector with solderless crimp connectors so that I didn't have to cut the existing pink wires in case I wanted to restore the cooler to normal operations.

The heater I plan to use can run as low as 150 watts (has a fan as well) but I'm afraid it still may be a bit of overkill. I'm hoping I can program the Love Controller to either heat or cool, but not switch back and forth risking burning out the compressor. If not I'll likely add a kill switch for the compressor that I can access externally. The heater can be simply unplugged when in cooling mode.

If you happen to see this post, let me know if you can see any issues with my build. I'll likely be firing it up later today.

Best Regards
Joe

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