inverter Whirlpool Refrigerator Dual Evaporator WRF989SDAM00

[rogs]

Hi: 

Whirlpool Refrigerator Dual Evaporator WRF989SDAM00

I have been trying to get this working properly for a while now. Initially I determined a leak, found the leak on the RC evaporator and repaired it. Held 100 PSI nitrogen for a couple days, vacuum, and recharged with R134a 5.5 oz. Now it does this: On warm startup the refrigerator section cools down as it is supposed to as I understand. This unit cools one evaporator at a time. So the RC goes down to around 36.3F or so on my K-type thermometer at the RC fan output. That seems normal enough because the front panel setting is 37F. So then it goes to cool the freezer section. I see the freezer temp coming down on my second Ktype thermometer lead at the FC evaporator outlet, but does not ever get the freezer section cold enough. Front panel setting is 0F for the freezer. It goes down alright into the 40F and under area. But not lower. My suction pressure was a little too high seems to me. Would not go below 18 to 20 PSIG. I removed some refrigerant gas so it is drawing down to 6 to 10 PSIG now. But that is not the solution. It seems to me the compressor is just not drawing down enough to reduce the suction pressure to near 0 PSIG where it needs to be. So here's my question for now. What is the DC voltage into the compressor start inverter supposed to be doing during all this? The 120VAC into the compressor start inverter is solid. The 3-6 VDC into the inverter just stays at 3.4xx all the time, no matter what. Shouldn't this be varying to increase the compressor speed and therefore draw the suction pressure lower? What am I thinking wrong or missing here? I got this for nothing and as a project but would really like to troubleshoot it correctly. Thanks for any ideas/experience.

[AccApp]

Should be a tech sheet hidden behind the lower front grill and that should give you steps to put into diagnostic mode. In diagnostic mode it will open the refrigerant valve to each evaporator and run the compressor at full speed. That will tell you if the compressor is efficient enough to cool the freezer down and if the charge is correct. How did you measure in the 5.5oz?

[rogs]

45 minutes ago, AccApp said:

Should be a tech sheet hidden behind the lower front grill and that should give you steps to put into diagnostic mode. In diagnostic mode it will open the refrigerant valve to each evaporator and run the compressor at full speed. That will tell you if the compressor is efficient enough to cool the freezer down and if the charge is correct. How did you measure in the 5.5oz?

Yea OK. That is diagnostic test 4. https://www.dropbox.com/s/5xnjc7sk8rp1muf/Whirlpool WRF989SDAM03 tech sheet.pdf?dl=0 I am still a bit confused with that because it does not draw down the suction side low enough in the freezer mode. (I will do it again to verify) But I could not convince myself that the compressor was being told to run full out since I question the 3.4 VDC going into the Compressor start inverter. But maybe I should just realize the fact that  the compressor suction valve are damaged and try changing the compressor.  To measure the 5.5 oz I use a dial a charge but not scaled to r134a. But it is very good because I also set the dial charge on a digital scale to verify. And then draw the hoses down with the suction side. I connect through a valve depressor service valve connection at the compressor to minimal loss. Thanks for your response.

[AccApp]

Part of test 5 is to go to max compressor speed, what is the voltage at that point?

[rogs]

I am not at the machine right now but it is the current project in my garage. I will do that Test 5 again tonight after work. I have done it and here is what I remember it does. The 3-6 VDC stays at 3.4xx VDC no matter what. However I do hear the compressor ramping up and down and do see varying suction pressure lowering during and on ramp up. No variation in the 3.4 VDC. But again not low enough suction with the full charge. Only draw down to 16-20 PSIG or so. I can also see current draw increase.{.6A-.8A low end /1.6A-1.8A high end} Current meter is on the bench outlet the refrigerator plugs into. I could not convince myself that during this test only one evaporator was open at 3 way valve. Or any. Or both. If both then the suction pressure would probably not be able to draw down, only testing the compressor speed ramping. So this has a big hole in my logic. If the compressor is truly ramping, can hear it, and the 3-6 VDC is not varying, what's up? The 3-6 VDC is used to control the compressor 3 phase speed? Thanks for your good questions. I will verify these procedures this evening to see I can get things to make sense. Again though I am not convinced that I really should be seeing the 3- 6 VDC varying with compressor ramping. I think so. Not sure.

[rogs]

Refrigerator off all day -- restart:
Verifying Test 5 readings:
Compressor Min speed: Refrigerator Current Draw .4 A -- Compressor inverter 3.430 VDC -- Compressor service port 28 PSIG 
Compressor Max speed: Refrigerator Current Draw 1.4 A -- Compressor inverter 3.430 VDC -- Compressor service port 13 PSIG

https://www.dropbox.com/s/ga4nsneu7zmf5ki/Whirlpool WRF989SDAM00 VDC Meter.jpg?dl=0

Tech sheet says I should have -11 DEG F {about 1.8 PSIG} when in freezer and 15 DEG F {about 15 PSIG} when in refrigerator. Compressor inefficient? Still over charged somehow? How does the 3.4 VDC to compressor inverter work?

Thanks for any attention/experience here.

[Rhubarb Tau]

The DC signal to the inverter is a variable frequency; lower frequencies correspond to lower compressor speeds. 150 Hz is full speed, 54 Hz. is minimum speed, with 5 intermediate speeds 16 Hz apart. I did some bench testing on the Embraco inverter; it seems to accept infinite frequencies between the min and max, but those seem to be the frequencies that Whirlpool implemented.

 

I've done a handful of system jobs on these dual evap Whirlpool units, but I've never developed a feel for their normal pressures; they always seem higher than I expect, but they cool fine.

 

What does the frost pattern look like in the freezer? Do the compressor and FZ evap fan continue running after the unit bottoms out at 40*F?

[rogs]

1 hour ago, Rhubarb Tau said:

The DC signal to the inverter is a variable frequency; lower frequencies correspond to lower compressor speeds. 150 Hz is full speed, 54 Hz. is minimum speed, with 5 intermediate speeds 16 Hz apart. I did some bench testing on the Embraco inverter; it seems to accept infinite frequencies between the min and max, but those seem to be the frequencies that Whirlpool implemented.

 

I've done a handful of system jobs on these dual evap Whirlpool units, but I've never developed a feel for their normal pressures; they always seem higher than I expect, but they cool fine.

 

What does the frost pattern look like in the freezer? Do the compressor and FZ evap fan continue running after the unit bottoms out at 40*F?

The DC signal to the inverter. So is it a square wave varying in frequency from the motherboard? If you know, besides an oscilloscope, what is a meter that I could see those frequency changes on that signal wire pair as the compressor ramps up and down? 

Yea those pressures are usually higher, that's why I am stumbling with this troubleshooting. I would like to know when the compressor is running full on. Maybe with monitoring the frequency as you are explaining I could be more close to knowing what to expected for pressures when the cooling is weak. Just monitoring VDC shows the motherboard is talking but not telling me what % of full capacity compressor is at. So yea freezer is not getting low enough. I am trying to troubleshoot - motherboard not interpreting to drive compressor more or compressor weak and inefficient. The freezer thermistor just checks out good or close as I can see with the information on the spec sheet. RC thermistor also.

I will try to get a picture and/or a description of the frost pattern in the freezer.  I really don't know what it is but I restarted it now and will get a look with the panel pulled back. It was not freezing up when I ran it for a full day or so a while back. From what I could peek into the slots. Yes on the fans. The freezer fan runs all the time and so does the refrigerator fan. So when the refrigerator temp is coming down and the freezer is not, the freezer fan is running. Also once the refrigerator gets to around 37-40 or so and then when it switches to the freezer coming down in temp(the refrigerator fan still runs and drifts up in temp). Again I am monitoring those temps with a dual K type meter. T1 at the refrigerator evaporator fan output and T2 at the freezer evaporator fan output. Front panel does not show actual temps only the set temps, unless I am missing how to read that up there. 

 

Thanks.

[AccApp]

Even if it were to be slightly overcharged the freezer should get down to freezing temps. With the current it’s drawing it sounds like it’s getting to full speed. I think you have an inefficient compressor. 

The only way to view the frequency sent by the control board to the inverter would be with an oscilloscope.

[scgms1]

18 hours ago, rogs said:

The DC signal to the inverter. So is it a square wave varying in frequency from the motherboard? If you know, besides an oscilloscope, what is a meter that I could see those frequency changes on that signal wire pair as the compressor ramps up and down? 

 

DC voltage is always going to be 0 Hz, unless we're talking about Pulse Width Modulation - PWM, or logic circuits. This will be a square wave. I'm thinking you're not measuring the correct circuit if voltage stays at 3.4 V, but the current to the compressor changes. If this control circuit is DC then it would be using PWM to vary the ON/OFF time to change the compressor speed. You will see a corresponding DC V change based on how long the circuit is on versus how long it is off. If it is 0 - 5 V and they want the compressor to run at 10%, the off/low 0V might 90% and the on/high 5 V 10%, you'll see about .5 V on the DMM.

With a different DMM you won't see the actual signal like with a DSO/scope, but you can measure frequency, duty cycle, or pulse width. Your particular meter will only measure AC frequency, but another Fluke, or other DMM will do what you're asking. Either way, if your leads are on the compressor control circuit you would see a change in voltage with the meter you have.

[scgms1]

19 hours ago, rogs said:

 If you know, besides an oscilloscope, what is a meter that I could see those frequency changes on that signal wire pair as the compressor ramps up and down? 

 

My Fluke 87 & 88 will, and I'm sure many others. If you need a scope, I can recommend Picoscope. They have 2 channel scopes starting at $139. You supply the laptop. https://www.picotech.com/products/oscilloscope

[rogs]

OK I have come across a way to see the motherboard controlling signal to the compressor inverter. My Fluke Model 116 has a feature to watch frequency in numeric form. So for instance when I hook the meter to 120 VAC and press the yellow mode button it reads a number for the frequency(60 HZ) on the screen. It was incorrect to expect the signal from the motherboard to change in VDC level or VAC level. So when using diagnostic Test 5 to ramp up and down the compressor speed I now set my meter to VAC then pressed the yellow mode button to see frequency and there it is. I can see the frequency change on the signal from the motherboard to the compressor inverter. So now I have verified that the motherboard is doing it's job and more likely the compressor at full speed is not efficient enough in suction to lower the evaporator pressure properly. At least I am more sure that the motherboard is good. I did not want to change the compressor only to find the motherboard was not driving the compressor with enough signal. I made a video( kind of crude) and shot it up to YouTube to show this process I described here. I am also including a link to Youtube to show using a multi-meter to check the frequency. Many have this mode we just have not used it. But it is really fine multi-meter mode for troubleshooting this refrigerator signal IMHO.

 

[rogs]

15 hours ago, scgms1 said:

My Fluke 87 & 88 will, and I'm sure many others. If you need a scope, I can recommend Picoscope. They have 2 channel scopes starting at $139. You supply the laptop. https://www.picotech.com/products/oscilloscope

Thanks for the link. Those might have some uses for me.

[scgms1]

22 minutes ago, rogs said:

Thanks for the link. Those might have some uses for me.

This would be interesting to see a scope capture on the signals used for the compressor control. There's more to the circuit with VDC remaining the same. I guess I only think I have an understanding of electronics. There's much I have to learn.

 

[rogs]

That is a very nice explanation in the video. Yea so many concepts in the electronics world.

For the Whirlpool VDC I had up to now read about the compressor control utilizing 110 VAC and 3-6 VDC. So I checked if they were present and not concerned much about what I assumed would a varying VDC level. But In this case I wanted to see the VDC level changing to qualify the motherboard. Well it just did not happen. Embraco is not vague about it I just could not find a detail explanation about the compressor control. They make two types of control grey boxes for the vari-speed compressor. One they call the "frequency" and the other is termed "Drop-In". As shown here:

http://refrigerationclub.com/pt-br/wp-content/uploads/sites/3/2017/08/Manual-de-troca-de-inversores-compressor-Embraco-Fullmotion.pdf

Well the frequency one makes good sense to me now. Just so happens I just now have an other smaller single door Whirlpool refrigerator in my garage right now with the Drop-In type grey box compressor controller on a vari-speed 3 phase compressor. The Drop-In is meant to drop in to replace a old style compressor that had start winding & a current relay. The compressor and current relay(all start components) are replaced with the vari-speed compressor and Drop-In version of the grey box controller. The vari-speed compressor with the Drop-In grey box controller just takes 2 wires of 110 VAC at one connection and another connection of one side of 110 VAC from the thermostat closure(No motherboard board anywhere in it.). With those two inputs it supplies the 230 Volt 3 Phase signal to the vari-speed compressor.

So back to the confusion about the frequency type. Even the Tech Sheet for this Whirlpool WRL989SDAM00 I am working on states the Inverter as 3-6 VDC and 120VAC. See the upper left side of this spec sheet:

https://www.dropbox.com/s/5xnjc7sk8rp1muf/Whirlpool WRF989SDAM03 tech sheet.pdf?dl=0

Well I know better now I suppose. Until the next surprise---enjoy. Thanks for your input here. It definitely helps me along on the right direction.

 

 

[Rhubarb Tau]

I haven't scoped the control signal, but I don't think it's anything too exotic. I was able to get an Embraco frequency-controlled inverter to vary compressor speed from min to max with a square wave from a function generator.

As far as VDC vs. Hz., keep in mind that the duty cycle (% on time / off time) isn't necessarily changing; in fact it probably isn't, just the frequency. You could probe a pulsating 5VDC signal, and as long as it's 50% duty cycle, a DMM will display it as 2.5VDC whether it's 100 Hz or 500 Hz.

FWIW, I've also seen Embraco make mention of a serial data controlled VCC compressor, though I've never seen one in the wild. http://www.embraco.com/desktopmodules/catalogo/arquivos/04014.pdf

 

[Rhubarb Tau]

I don't know if you guys will find this super useful, but this is part of a an explainer video I put together (but never finished) on measuring stepper motor drive signals. There's a segment in it where I show how frequency, duty cycle and DC offset affect how a pulsing DC signal will be displayed on a DMM. If you can ignore the subtle cat drawings and Martin Shkreli digs, it does contain a couple scope / meter shots that might be helpful.

 

[rogs]

9 hours ago, Rhubarb Tau said:

I haven't scoped the control signal, but I don't think it's anything too exotic. I was able to get an Embraco frequency-controlled inverter to vary compressor speed from min to max with a square wave from a function generator.

As far as VDC vs. Hz., keep in mind that the duty cycle (% on time / off time) isn't necessarily changing; in fact it probably isn't, just the frequency. You could probe a pulsating 5VDC signal, and as long as it's 50% duty cycle, a DMM will display it as 2.5VDC whether it's 100 Hz or 500 Hz.

FWIW, I've also seen Embraco make mention of a serial data controlled VCC compressor, though I've never seen one in the wild. http://www.embraco.com/desktopmodules/catalogo/arquivos/04014.pdf

 

I think I can scope that control signal while I am into this as a project anyway. If I can/do I will discuss it & try to shoot some video.

Yea I see what you are saying about the VDC vs Hz. The duty cycle is probably close to 50% and not varying. I had not known/thought about that as you described it here.

Your video on Viagra(sp) of DC measurement is VERY HELPFUL. That will be useful as more variations of these types of compressor controllers show up in the 'wild'.

Thanks for the Embraco link to the serial port option. "Serial communication port for control, monitoring and remote diagnosis;"

 

[rogs]

Here is a short video with a scope on the control signal from the Whirlpool WRF989DSAM00 refrigerator motherboard to the frequency grey box controller on the Embraco vari-speed compressor VEGZ-7H.

 

[TurtleRock]

Before You repaired the evaporator did you put it in service mode and go to step 4 to make sure the 3 way valve was in the open position if not then it is possible that system was still holding charge.

[rogs]

5 minutes ago, TurtleRock said:

Before You repaired the evaporator did you put it in service mode and go to step 4 to make sure the 3 way valve was in the open position if not then it is possible that system was still holding charge.

5 minutes ago, TurtleRock said:

Before You repaired the evaporator did you put it in service mode and go to step 4 to make sure the 3 way valve was in the open position if not then it is possible that system was still holding charge.

No I did not but I learned and understand about that better now. However when I let the nitrogen leak test charge off I fixed the evaporator leak & changed the liquid line filter. So no charge would be trapped in the condenser or the other evaporator then correct?

[rogs]

Found a new compressor with inverter & liquid line filter on E bay for $165.00 with freight included. Bought it, just installed this morning. Used original inverter so I now have a new spare. Looks good. I will run it for several days and shutdown/restart a couple of times over the next days to be sure. Interesting to me: Initial suction pressures can be around ~0 to +3 PSI, or ~10 PSI - makes sense as to when it is cooling the freezer or refrigerator. Drive signal spent some time at 150 HZ(max speed) on initial pull downs. Now that the boxes are at temp(freezer around 3 to -5 F, refrigerator 37-44 F or so) compressor mostly runs about 60-65 HZ drive signal, sometimes I did see it at 100 HZ drive signal (.6 to .7 amps-Refrigerator total amps). But the suction pressure is at ~0 to +3 PSI even when compressor is 60-65 HZ or so. It does shut off completely at times then pressure equalizes. Ambient temp 50 to 65 F. FWIW.

[AccApp]

Might be fun to do an autopsy on the old compressor just so you can see what exactly failed.