LG GM5148AERV refrigerant circuit - purpose of solenoid valve?

[Norfolkchris]

I am trying to understand possible reasons for no cooling in this model. You will see from my previous post that I am already getting the compressor replaced. However there seems to be a real lack of experienced and knowledgeable refirgeration engineers over here in the UK.  I am considering the possibility that the failure could be in the solenoid valve in the circuit. My engineer does not seem willing to consider this and is unable to explain to me its exact purpose in this model.

I have read several posts referring to a three way valve of which the purpose is to direct refrigerant to either or both of separate evaporators in the freezer and refrigerator compartments. I understand this concept and what the valve would be doing in that case.

In my model there is only a single evaporator in the freezer section and cooling to the upper fridge section is regulated by a flapper  which controls the cooled air circulation between the two sections. The solenoid valve in this case is obviously not 3 way as there are only two pipes going to it. It must just therefore serve an open or closed function. So my question is what is the purpose of such a valve in this application and could it fail and cause a loss of cooling? I have tried to trace the pipework but it just disappears into the insulation so the exact circuit cannot be worked out.

I would be grateful if someone could explain the purpose of this valve and, even better if possible, provide a link to a diagram of a typical circuit that uses this configuration.

Thanks Chris

[Rhubarb Tau]

This is just an educated guess, since your model doesn't come up on the US LG site (possibly a UK-only model, or possibly a character missing?)

That style of valve is typically used as a switching valve, with 3 or more refrigerant lines running to it as you pointed out. A true solenoid valve would only have 2 wires going to the coil, and only have 2 operating states, fully open and fully closed. The coil on your valve looks more like a stepper motor (typ. 5 or 6 wires running to it), and is used to precisely control the position of the valve element. I would guess that this valve is being used as an "Electrically-operated expansion valve (EXV or EEV) to provide a variable restriction, to separate the high-pressure and low-pressure sides of the refrigeration system.

[Norfolkchris]

Rhubarb Tau

Thanks very much for your reply. The model number is correct but it probably is UK only. Could you explain to me a little further the function of such a valve in a typical fridge freezer circuit and whether it has a failure mode that would prevent cooling? When power is switched on it vibrates for a few seconds as if it is initialising or self testing.

I have added a couple more photos which show that, as you suggest, it has six wires running to it and two refrigerant lines.  I've also added a  diagram which shows what pipework is visible. The four lines at the top disappear into the foam and can't be easily traced.

I have managed to download a service manual for this model but now I look at it the electrical schematic is completely different to what I have - fat lot of use that is. It does though show 6 wires running to something just labelled "valve". There is a completely different schematic inside the PCB cover plate which appears to be correct though.  In similar schematics I have seen something labelled as "Energy Valve" which I suspect is the same thing.

I'm just trying to gain a bit of insight into how the circuit on this model is supposed to work as it's clear that my engineer is going to do little more than replace parts. As a retired oil field engineer I need to understand the system to have any hope of getting it fixed. The guy LG sent round initially just turned it on and listened to it then told me that it might have a leak or a blockage and that it was unrepairable with no attempt at diagnosis at all. I think they just don't want to pay for a compressor under their 10 year warranty scheme.

 

 

 

 

 

 

 

[Rhubarb Tau]

32 minutes ago, Norfolkchris said:

Could you explain to me a little further the function of such a valve in a typical fridge

Google EEV or EXV expansion valve. A typical fridge doesn't have one; it's unusual to see on a domestic refrigerator, used almost exclusively on larger (HVAC) systems. Most fridges use a length of small diameter capillary tubing to create the same pressure drop to allow the refrigerant to boil.

 

43 minutes ago, Norfolkchris said:

...it's clear that my engineer is going to do little more than replace parts.

 

On 7/8/2020 at 6:00 AM, Norfolkchris said:

I am already getting the compressor replaced

Even if your tech doesn't inspire much confidence, it's pretty likely that he'll solve the issue. If you want to learn more about domestic refrigeration out of curiosity, go for it. The failure rate on some LG Compressors, though, is such that even if he doesn't understand exactly how to analyze the failure, it'll probably be running and cooling when he's done. 

[Norfolkchris]

4 minutes ago, Rhubarb Tau said:

The failure rate on some LG Compressors, though, is such that even if he doesn't understand exactly how to analyze the failure, it'll probably be running and cooling when he's done. 

That's what I'm hoping. My next battle will be to claim the compressor cost from LG under 10 year warranty.

I'm going off to google now.

[Terry Carmen]

3 hours ago, Norfolkchris said:

The guy LG sent round initially just turned it on and listened to it then told me that it might have a leak or a blockage and that it was unrepairable with no attempt at diagnosis at all. I think they just don't want to pay for a compressor under their 10 year warranty scheme.

They're happy to give you a compressor. The compressor is cheap. However doing a good job on the installation is going to be much more than the machine is worth.

 

 

[Vance R]

In the US the linear compressor are dying by the ton due to higher pressure of r134.. The linear compressor was supposed to be design for r600a pressures.  Your valve looks very similar to the 3-way stepper valve used here in the US. Think LG is using it as a variable opening valve to control refrigerant flow. Would you post picture of wiring diagram.  Your guy is probably going off of experience with model instead of doing troubleshooting. He is probably just going to replace the usual parts for this failure.

[ECtoFix]

https://www.classaction.org/lg-refrigerator-linear-compressor-failure-lawsuits

[Norfolkchris]

11 hours ago, Vance R said:

In the US the linear compressor are dying by the ton due to higher pressure of r134.. The linear compressor was supposed to be design for r600a pressures.  Your valve looks very similar to the 3-way stepper valve used here in the US. Think LG is using it as a variable opening valve to control refrigerant flow. Would you post picture of wiring diagram.  Your guy is probably going off of experience with model instead of doing troubleshooting. He is probably just going to replace the usual parts for this failure.

I was aware of the failures in the US which is why I thought it worthwhile to persist in trying to get mine replaced. This one uses R600a so maybe I have a different problem of course. What are the typical symptoms of the failure in the US? My compressor was still running but no/minimal cooling.

This is the schematic from the inside of the PCB cover plate. No point posting the one from the service manual I downloaded as it appears to be for a completely different model. Suspect some kind of mix up when producing english language versions.

 

[Slav]

1 hour ago, Norfolkchris said:

What are the typical symptoms of the failure in the US?

In the US, linear compressors running on R134a typically fail the same way as yours... running but not compressing.The reed valve inside the compressor usually cracks or breaks after a few years of running. The debris may travel into the High Side and clog the system, which requires cleaning, and sometimes replacing most parts of the Sealed System.

[Norfolkchris]

Well I amused myself over the weekend by cutting open the old compressor to see if I could see any sign of problems. Unfortunately to my relatively untrained eye it all looked good which makes me think that my replacement compressor tomorrow is not going to solve the problem.

I was particularly looking for any signs of damage to the inlet or discharge valves. Here are some pics if anyone is interested to see waht they look like inside an LG linear compressor:

 

 

 

No signs of any damage at all.

If anyone is interested in pics of any more of this I'm happy to upload.

I'm still interested to know exactly how the sealed circuit in this model is configured. If anyone can completed my previous hand drawn sketch and fill in how the 4 free ends of pipe are connected that would be very interesting.

Thanks

 

 

 

[Vance R]

The first picture has the updated exhaust valve and tapered spring. Not sure it the intake valve is the thicker design.  Just wondering about the piston to cylinder clearance?

Looked at the exhaust valve enlarged, wear pattern is off-center. The previous design the valve would get off center and wear then leak. New design was supposed to fix that issue.

Edited July 12, 2020 by Vance R
Added exhaust valve info.

[Vance R]

Red is yoder loop or hot gas pass.

Light blue is capillary tube

darker blue is evaporator and suction line 

[Norfolkchris]

1 hour ago, Vance R said:

The first picture has the updated exhaust valve and tapered spring. Not sure it the intake valve is the thicker design.  Just wondering about the piston to cylinder clearance?

Looked at the exhaust valve enlarged, wear pattern is off-center. The previous design the valve would get off center and wear then leak. New design was supposed to fix that issue.

Kind of surprised to hear that this is an updated version as the fridge was bought in 2014. Intake valve is 0.150mm thick. Not sure if that is new or old.

I have no way to judge the clearance but it seems to me to be extremely close fitting. Quite hard to hold it staright enough to withdraw it.

See what you mean the wear is slightly off centre but it still looks like it was sealing to me.

[Norfolkchris]

1 hour ago, Vance R said:

Red is yoder loop or hot gas pass.

Light blue is capillary tube

darker blue is evaporator and suction line.

Thanks you. That makes sense. Why does the red line need to go back up inside the insulation. Seems like it could go directly from condenser to drier inside the machinery space?

1 hour ago, Vance R said:

 

[Vance R]

When i enlarged your picture you can see the wear pattern on the disc. Agree it looks like it is sealing, but is slight off - center.  The original design for r134 compressor used a round puck with a straight spring.

The yoder loop is for warming the freezer door gasket area to prevent condensation and mold.

[LearningTech]

 To anyone seeing this in the future.  The valve is for energy purposes. Thr fridge expends enerygy to fill the condenser and that full of liquid refrigerant, and when the unit is satisfied  and shuts off without a valve that  stored energy jsut pittles our into the evaporator and is not used to its full extent. This valve simply holds the refrigerant in the high side, and with it, when the unit calls for cooling and turns on the compressor it  does not have to wait to build up a pressure it just opens the valve and unti imeadiatly begins cooling.  Marginal energy use differince IMO, but is needed on some units to meet erquirements