Adding 507a to 404a-any problems?

[TJ D]

Originally Posted by Richard Kollmann

The tech will not have much success checking pressure if he can not get the compressor to run. It would help to know the compressor model and module part model. Most of Seafrost small compressor systems have adjustable low pressure regulators has anyone tampered with this valve's adjustment?

It is important to know at what point of time does this compressor start rejection problem begin, First start up or after thermostat cycled unit off and tried to restart again. Off cycle time is also important to allow low pressure regulator to bleed down high pressure. Hopefully the off cycle is at least five minutes as this type flow control is not always internally equalized.

Richard, it's running now. It alarmed for about 2 hours (the box temp started at 10f, rose to about 22f when it finally started), we've been letting it run all day to see where things get on pressure/temp.



The unit's a bdxpx-the module is the 101n390. I think the compressor's a bd80, but I might be wrong. Remember that we put in a new module with no change in alarm status.



The start rejection doesn't really seem to have any particular time that it decides to rear it's head. It's done it with box temps of 10 degrees, and with box temps of 50 degrees.



The compressor is not short cycling. Off time between cycles is at least 45 minutes.


Once the thing starts, it's fine.



The expansion valve has been adjusted-this was necessary when we put in the 404 system (it replaced a 134 unit.) SF specifies 15psi, it's currently running 14.2psi with a temp of -30c per gauge.



The tech is supposed to be back in an hour or so to do a final check. He doesn't know why the compressor's so hard to start. It's running, temps and pressures appear correct, so he's happy.


I'm not-we've gotten nowhere closer to solving this alarm problem. After he's done, I'm going to inspect the wiring very closely and see if I can find something there-The tech was pretty quick with the multitester, so I'll look at that part of the picture more closely.

[Richard Kollmann]

You have to understand the compressor and module are unaware of temperature and pressures. The module monitors starting amperage, fan amperage, module temperature and voltage. The thermostat runs compressor when thermostat tell it to based on evaporator plate or box temperature.

Did Cleave at Seafrost authorize this conversion to 404a refrigerant?

Are you saying when power is reapplied after compressor is stopped by thermostat that attempts to restart are more than ten minutes are less than five minutes this is important. This unit is not a simple capillary tube or expansion valve system. The module does not know what is happening so its internal electronic timer will try to restart compressor triggering LED code every 20 to 40 seconds. I am concerned the time between compressor stopping and the signal to restart is too short.

I do not have a Danfoss engineering data sheet on 101n390 module but you should do as Pete recommends in disconnecting thermostat wires from module and replacing them with a jumper. This jumper gives you control over compressor cycling times buy turning power off and on to this system. Many of the new systems use electronic thermostats that permit the off on differential to be set holding off restart till pressures equalize.

[TJ D]

Originally Posted by Richard Kollmann

You have to understand the compressor and module are unaware of temperature and pressures. The module monitors starting amperage, fan amperage, module temperature and voltage. The thermostat runs compressor when thermostat tell it to based on evaporator plate or box temperature.

Did Cleave at Seafrost authorize this conversion to 404a refrigerant?

Are you saying when power is reapplied after compressor is stopped by thermostat that attempts to restart are more than ten minutes are less than five minutes this is important. This unit is not a simple capillary tube or expansion valve system. The module does not know what is happening so its internal electronic timer will try to restart compressor triggering LED code every 20 to 40 seconds. I am concerned the time between compressor stopping and the signal to restart is too short.

I do not have a Danfoss engineering data sheet on 101n390 module but you should do as Pete recommends in disconnecting thermostat wires from module and replacing them with a jumper. This jumper gives you control over compressor cycling times buy turning power off and on to this system. Many of the new systems use electronic thermostats that permit the off on differential to be set holding off restart till pressures equalize.

Richard-
First, this is a brand new system. Our 134a system failed (the same 3 flash warning--hmmmmm....), and I was never happy with it, so I simply purchased the 404a bdxpx unit. Thermostat and evaporator plates were re-used, as they are just a couple of years old. All was done through Seafrost-all good there.



We are using our old Glacier Bay thermostats. I have plenty of control over the operation, and I'm very sure that there is at least 30 minutes from the time the compressor turns off when temp is reached until the thermostat calls for another cycle. It's not a matter of a few minutes, that's for sure.



Of course, when it's in an alarm condition-it attempts restarts a couple times a minute, as you say.



If I keep the SF freezer, I'll probably get their multi-speed thermostat. It has a soft start function, and that would probably be a good solution to this.



I hope I answered your question.

[Richard Kollmann]

I believe with the thermostat and its its possible speed control bypassed compressor will run at minimum soft start speed all the time.

Can you clear up the question of refrigerant control TXV, Cap Tube or Seafrost pressure regulator.

[TJ D]

It's the seafrost pressure regulator-the brass hex valve that's sited just before the evaporator.


We just dropped the evaporator pressure from 14psi to 9, and achieved 5 degrees colder; -35c at the gauges. Maybe having this valve open a little more will also reduce startup amperage?

[OzePete]

Originally Posted by OzePete

TJ, From what you have described and specially that you have replaced the module and confirmed that the DC power supply is not dropping off at start up we can assume that the module is not the problem and the supply voltage is adequate.

REFRIGERANT: If the system is over charged to the point of restricting start ability, there would be frosting on the suction line when running and as the evaporator temperature lowers. (If it is a capillary system). If no suction line frosting occurs when the plates are very cold then it is not overcharged.

Another possibility gas wise is if the refrigeration unit is located much lower than the freezer cabinet and in a relatively cooler position.
Also check by feel the temperature of the compressor after it has completed a long run period. It should be quite warm, not cool / cold. (Refrigerant will migrate and condense into liquid inside the compressor during off periods if the compressor is relatively cold when off. This will hydraulically restrict motor startup which relates to what you report.)

Cheers OzePete

With the added info since this earlier post, this is a refrigerant issue. I would further suggest that liquid slugging in the compressor on start up as highlighted above, could be the culprit, or the system is not 'balancing out' during off cycle and is trying to start under load.

1: What is the temperature feel of the compressor after it finishes a cooling cycle? And when it is attempting to start does it get slightly colder?

If the compressor is cool / cold at the end of a run cycle, try warming it before it attempts to start. (Warm the base) Warming will boil off any liquid refrigerant migrating to the compressor sump. Even a small amount of liquid in the compressor sump can easily stall the compressor as they are not designed to pump liquid!

2: What were the gauge readings prior to start up? Did the pressures 'balance out' ?
If there is a large difference between the suction and discharge pressures, the compress or will fail to start. Specially important with 404a

Cheers OzePete

[Valmika]

Originally Posted by TJ D

Well, we installed a new module, and we are still getting the motor start failure error. So, it's apparently not the module.


I can't imagine that I've got an overcharge situation happening, as we never added any gas, and the new unit was shipped with the correct charge.



I can't see any connection between temperature and when the compressor will and won't start, it just seems to try and try and then eventually it does kick on and work fine.



I really wonder what the heck is happening here.

Watch Rich's video (twice)

https://www.youtube.com/watch?v=r9FoE1uHzy8

[Scrimshaw4]

Have you checked the brushes on the compressor motor? Also my Seafrost system will throw it's breaker if either the compartment the compressor is in gets too hot as well as if the raw water flow is diminished / blocked. Just some thoughts.

[OzePete]

Hi TJ,
Your b..... freezer is preventing my sleeping!

I am now totally convinced that your system is not 'balancing out' its pressures during the off cycle.. as in point 2 of my previous post.

To explain.... When a compressor runs there is a vast difference between the suction and discharge pressures. When it stops these pressures balance out so that there is little or no pressure on the piston upon the next start up and so away it goes and again builds pressure to refrigerate.

I notice your system has a Crank case regulator on the evaporator. Upon compressor stopping the suction pressure rises a little but that causes this device to close off totally preventing refrigerant pressures in the compressor from balancing thus causing it to fail start up.

Suggest gauges be connected and note pressures while running, then switch off and you will notice that the pressures will come somewhat together but not balance out sufficiently to allow the motor to start. Usually a difference of 75PSI or more will prevent start up.

Now I'm back to bed!

Cheers OzePete

[TJ D]

Originally Posted by Scrimshaw4

Have you checked the brushes on the compressor motor? Also my Seafrost system will throw it's breaker if either the compartment the compressor is in gets too hot as well as if the raw water flow is diminished / blocked. Just some thoughts.

Thanks-the unit is brand new, about 45 days in service. I'm sure the brushes are fine. We've got water on and everything opened up-it's as cool as it'll ever get here in the med at the unit.

[TJ D]

Originally Posted by OzePete

Hi TJ,
Your b..... freezer is preventing my sleeping!

I am now totally convinced that your system is not 'balancing out' its pressures during the off cycle.. as in point 2 of my previous post.

To explain.... When a compressor runs there is a vast difference between the suction and discharge pressures. When it stops these pressures balance out so that there is little or no pressure on the piston upon the next start up and so away it goes and again builds pressure to refrigerate.

I notice your system has a Crank case regulator on the evaporator. Upon compressor stopping the suction pressure rises a little but that causes this device to close off totally preventing refrigerant pressures in the compressor from balancing thus causing it to fail start up.

Suggest gauges be connected and note pressures while running, then switch off and you will notice that the pressures will come somewhat together but not balance out sufficiently to allow the motor to start. Usually a difference of 75PSI or more will prevent start up.

Now I'm back to bed!

Cheers OzePete

Good one-sorry to be keeping you up.



We ran it all day, then shut it off, setting a 20 degree (f) rise as the set point for re-start. This took about an hour. I got the error a couple of times, then it did start.



We only have the blue hose connected right now, it spiked up to about 30psi when stopped.



I will connect the red hose, note pressures, then shut it down and then connect the red hose and see what the differential is.



If you're still up in 10 minutes-I'll have the answer!

Thanks, mate.

[TJ D]

Ok, running is 6.5 psi/233 psi.



I'll wait a little while and see how close the 2 get. It isn't changing very fast on initial shut-down. I imagine that's normal.

[TJ D]

Originally Posted by OzePete

With the added info since this earlier post, this is a refrigerant issue. I would further suggest that liquid slugging in the compressor on start up as highlighted above, could be the culprit, or the system is not 'balancing out' during off cycle and is trying to start under load.

1: What is the temperature feel of the compressor after it finishes a cooling cycle? And when it is attempting to start does it get slightly colder?

If the compressor is cool / cold at the end of a run cycle, try warming it before it attempts to start. (Warm the base) Warming will boil off any liquid refrigerant migrating to the compressor sump. Even a small amount of liquid in the compressor sump can easily stall the compressor as they are not designed to pump liquid!

2: What were the gauge readings prior to start up? Did the pressures 'balance out' ?
If there is a large difference between the suction and discharge pressures, the compress or will fail to start. Specially important with 404a

Cheers OzePete

Pete, I just shut it down, and the compressor was hot to the touch. It had been running for about 50 minutes. It's running just fine once it gets going.


Still waiting for a while to see where the pressure differential ends up. How long should this take?

[TJ D]

Originally Posted by Valmika

Watch Rich's video (twice)

Thanks, some good layman-understandable info there.

[TJ D]

And, after 50 minutes of being powered off, the pressures read 41 and 190 between the 2 sides. I take it this is getting to the root of the problem.



Now, the question is what to do about it.



Cleave's on vacation for a couple weeks so I can't get anything out of him-I'm guessing based on Pete's comment about the expansion valve that this thing may be unsuitable for the higher pressures of 404?