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Old 09-08-2020, 18:58   #1
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Debugging Refer issues

Ok, so my head is spinning (A good IPA no doubt is an additional factor) after reading a whole slew of fridge threads.

I've finished off rebuilding my fridge and started to work on the Super Cold Machine that cools it.

The fridge is a 6.5 CU ft unit that is split between a freezer side and a fridge side. Basically 2 cu ft and 4 cu ft with 2" of XPS between them. The box has either 6" of XPS or 3" of cryocell on all sides. The lids are not fully leak proof yet (gotta add some seals). The box has an inner fiber glass box do not leaks there.

The CU-200 super cold machine (not using water cooling) was working OK in the old box with Bad, bad 45 year old insulation. The evaporator is a large horizontal unit that has been mounted vertical. When reconnecting the evaporator to the compressor there was a few drops of oil present at the joints. In addition when first started up the evaporator had frost on about 50% of the evaporator.

It appears that the "cooling" capacity has gone down over the last month or so. I've had it off for a week then turned it on today. It started out drawing about 5 amps and then within about an hour dropped to 2.5 amps. Frost was observed on the evaporator on the lower 10% and tended to only be frosting near the capillary tube. Not much cooling wa observed.

Prior to this point I was seeing the compressor running 100% and the box was running at about 33F. The divider between the freezer and fridge is not sealed. The total air gap on the divider >>might<< be equal to a 3" diameter hole.

Not being an expert - I am guessing that I have a leak somewhere. Putting a tissue under the compressor to evaporator connectors did not show any oil. The route for the lines is convoluted at best.

So, I guess that I should try to do a pressure check. I've read to fill the system to 200 psi with N2 and go to town with soapy water. Actually I have atank of 92% N2, 8% H2 that I might try, that or argon. Some of the run is out of reach so just monitoring the pressure for a few hours could do the trick.

Once that is done (and any leak repaired) I'm thinking the nest step is it pull a vacuum on the system and recharge. My vacuum pump will not go down quite enough but I could leave it on for days.

Anyway, Sage advise is welcome on this journey.
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Old 09-08-2020, 19:28   #2
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Re: Debugging Refer issues

Sounds like it leaked a bit while you had the connections taken apart?
They don't need to lose much to not cool effectively.
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Old 09-08-2020, 19:39   #3
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Re: Debugging Refer issues

That would be nice if I only had to add some freon to get the amperage up to (what>?) 5 amps.

I suppose that first attempt would be to get some gauges and add charge to the system.
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Old 09-08-2020, 20:15   #4
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Re: Debugging Refer issues

It's possible that if the system had positive pressure in both sides when you reconnected it then yes, you could add the correct refrigerant to top it back up to correct levels.
Make absolutely sure you have nothing but pure refrigerant in the hoses when you attach to the low side access port.
I'd advise you to first read Richard Kollmann's info at his website with regards to troubleshooting these systems.
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Old 12-08-2020, 12:00   #5
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Re: Debugging Refer issues

I'm fairly certain that the system had and still has positive pressure on both sides. I do get some cooling last time I turned it on.

I do need to order Richards book. Looks like we just send a check now-days.

I'm gathering "supplies" at them moment. There are a few questions that I have.

- On a Danfoss BD50 what thread dia/pitch is used for the low and hi side ports?
- I have a set of gauges that use quick connects. I think that there is an adapter for the quick connect to DB50 ports. What part number or source for them is there?

My current plan is to turn the fridge on today and let it run for a few days. Then get a look at the frost coverage and if there is any frost on the lines.

Then I'm thinking that I can use some 134a to pressurize the system to whatever pressure is in the canister (50 psi?) and do both soap and water and see how long it keeps its pressure.

From there I either repair the leak and/or top off the refrigerant (per Richards website) as indicated. I am doubting that I have too much as that the system ran for ages without problems. Problems only showing up after rebuilding the box and thus disconnecting the compressor from the evaporator. I'll also check the end caps on the service ports too.

Which adapters to use is the main question of this post. As always, sage advise is always welcome.
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Old 12-08-2020, 21:39   #6
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Re: Debugging Refer issues

I found that the r12 to r134 adapter kits at my local autozone would fit for the suction side.

When screwing the adapter into the service port I noted that there was some pressure in the system. This indicates that the system was not fully empty (and potentially contaminated). Plus in prior testing it was able to cool the lowest 1" of the evaporator.

After purging the low side lines and connecting them up I was able to see a vacuum on the gauge as the compressor was started. That did not sound good. So, I opened the R134A tank a few seconds at a time and measured pressure in between.

I stopped filling the system when the pressure got to 8 psi. The current draw was around 5 amps. By this time 20 minutes had gone by so I bagged it for the evening.

The evaporator was by then making nice gurgling sounds and was rapidly cooling. I'll leave the unit running overnight and check it sometime tomorrow.

As a guess I ended up putting 3 oz of R134A into the system. That is based on the frostline on the R134A canister.

To me it appears that that the coolant leaked out quite rapidly. Perhaps over 3 weeks. It may be that the connectors were not quite tight enough. I had tightened them after the initial (re) connection. Also, the tubing run is somewhat convoluted and a bend may have opened a small leak.

In anycase I'll run the system for a few days and see if the frost on the evaporator covers less and less of the surface. If so then time to look for a leak with soap and water.

If no leak then I'll shut it off and let it come back to "room" temp and from there see what suction side pressure I've got along with the percentage of frosting. That will let me know if I need more or less R134A.

Does anyone have one of Richard's books that I can borrow? I understand that new are not available.
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Old 13-08-2020, 13:30   #7
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Re: Debugging Refer issues

Quote:
Originally Posted by evm1024 View Post
I found that the r12 to r134 adapter kits at my local autozone would fit for the suction side.

When screwing the adapter into the service port I noted that there was some pressure in the system. This indicates that the system was not fully empty (and potentially contaminated). Plus in prior testing it was able to cool the lowest 1" of the evaporator.

After purging the low side lines and connecting them up I was able to see a vacuum on the gauge as the compressor was started. That did not sound good. So, I opened the R134A tank a few seconds at a time and measured pressure in between.

I stopped filling the system when the pressure got to 8 psi. The current draw was around 5 amps. By this time 20 minutes had gone by so I bagged it for the evening.

The evaporator was by then making nice gurgling sounds and was rapidly cooling. I'll leave the unit running overnight and check it sometime tomorrow.

As a guess I ended up putting 3 oz of R134A into the system. That is based on the frostline on the R134A canister.

To me it appears that that the coolant leaked out quite rapidly. Perhaps over 3 weeks. It may be that the connectors were not quite tight enough. I had tightened them after the initial (re) connection. Also, the tubing run is somewhat convoluted and a bend may have opened a small leak.

In anycase I'll run the system for a few days and see if the frost on the evaporator covers less and less of the surface. If so then time to look for a leak with soap and water.

If no leak then I'll shut it off and let it come back to "room" temp and from there see what suction side pressure I've got along with the percentage of frosting. That will let me know if I need more or less R134A.

Does anyone have one of Richard's books that I can borrow? I understand that new are not available.
Kollmann Marine
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Old 13-08-2020, 13:37   #8
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Re: Debugging Refer issues

Quote:
Originally Posted by Richard Kollmann View Post
Thank you Richard. I have those and have been studying them.

Right now the system is cooling and cycling. This morning the frost level was at about 70%. I put another small bit of R134A into the system.

For me the key appears to be if there is a leak. If no leak then perhaps some fine tuning of refrigerant is in order (frost line and current draw).

If a leak then find it and fix it.

Regards

PS any more books available or not needed any more?
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Old 13-08-2020, 15:47   #9
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Re: Debugging Refer issues

Quote:
Originally Posted by evm1024 View Post
Thank you Richard. I have those and have been studying them.

Right now the system is cooling and cycling. This morning the frost level was at about 70%. I put another small bit of R134A into the system.

For me the key appears to be if there is a leak. If no leak then perhaps some fine tuning of refrigerant is in order (frost line and current draw).

If a leak then find it and fix it.

Regards

PS any more books available or not needed any more?
Technical Books are outdated after four years so I stopped printer from producing them.

Now that you have established a known frost area around evaporator you need to determine if leak is in high pressure or low pressure side of system by leaving system cycling on thermostat control for one or two days. With frost on evaporator low pressure will remains very low so now record frost cover percentage on evaporator. Complete the same test with compressor not running, if leak rate is faster you will confirm leak is in low pressure side of system which includes the complete area of evaporator.
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Old 13-08-2020, 15:54   #10
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Re: Debugging Refer issues

Quote:
Originally Posted by Richard Kollmann View Post
Technical Books are outdated after four years so I stopped printer from producing them.

Now that you have established a known frost area around evaporator you need to determine if leak is in high pressure or low pressure side of system by leaving system cycling on thermostat control for one or two days. With frost on evaporator low pressure will remains very low so now record frost cover percentage on evaporator. Complete the same test with compressor not running, if leak rate is faster you will confirm leak is in low pressure side of system which includes the complete area of evaporator.
That makes sense and sounds like a good plan.

I understand 4 years out of date - but I do like to read...
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Old 13-08-2020, 17:03   #11
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Re: Debugging Refer issues

Did you evacuate the system after you reinstalled it prior to recharging? I would bet you didn't. Now you have air in the system. You have to get that out as well as find the leak.
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Old 13-08-2020, 17:28   #12
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Re: Debugging Refer issues

This system has quick disconnect fittings that tend to leak a very small amount when disassembled.
The OP stated that he had positive pressure when reconnecting the line set, so we can be reasonably sure that the charge, while not correct due to the leak, was enough to keep the refrigerant circuit free of non-condensables.
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Old 13-08-2020, 18:19   #13
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Re: Debugging Refer issues

Quote:
Originally Posted by Coolerking View Post
This system has quick disconnect fittings that tend to leak a very small amount when disassembled.
The OP stated that he had positive pressure when reconnecting the line set, so we can be reasonably sure that the charge, while not correct due to the leak, was enough to keep the refrigerant circuit free of non-condensables.
Yes, this is correct. Thanks for that.

...
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Old 18-08-2020, 11:22   #14
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Re: Debugging Refer issues

After recharging the system I've been running it to see if we would have a decrease in the frost line. I've not been to the boat in a few days so I've not been able to check the frost line (to see if we have a leak) yet.

But I do have a graph of the current draw so we can get an idea of the duty cycle. It looks to be running about 30% to 45% with the peak temps in the boat reaching 100F at times.

Typical draw is between 4.5 amps and 5.5 amps.

The box has R30 on all sides - 6" XPS on 4 sides and 3.5" or so of Aspen AeroGel on 2. IR testing shown that the sides are pretty much running "room" temp withing 0.5 degrees.

I was expecting to see a change in the duty cycle (increasing on time) based on the thought that there was a leak. However, it may be that the reconnect of the coolant lines leaked. I recall that I did re-tighten them early on. I may have under tightened them and later corrected it.

Checking the frostline for change and then letting it sit (turned off) for a week then starting it and looking at the frostline on restart will tell the tale.
(Per Richards suggestion)
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Old 20-08-2020, 12:50   #15
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Re: Debugging Refer issues

I did get to the boat and have discovered that the frost line has not changed. The evaporator is vertical and the frost line remains somewhere on the second refrigerant passage from the top.

The system has been running for almost 6 days and is consuming 45 AH / day. Perhaps a little bit less because of other minor loads that I have turned on now and again. Still 45 ah/d is a good number.

This is turning into a battery load test. I am only running on the house bank and have delivered 270 AH. The bank (LiFePO4) is sitting at 13.06 volts no-load with my Victron BMV-712 indicating a 64% SOC. Of course I doubt the SOC number because doing the math would indicate that he bank capacity was 750 AH. The sticker AH for the bank is 700 AH and then have been running less than that... Of course I have been trying to recover capacity but that was another thread.

I'll like take the bank down to 3 VPC then shut the fridge off and let it come to room temp for a week or so then restart it and see if the frost line is at the same place. The idea there is to see if there is a leak on the suction side that is being masked by the somewhat low pressure there during operation.

But it is looking good. If I had to guess I would say that the quick connects leaked during the time that the compressor and evaporator were disconnected and possibly for the day or so that they were connected before re-tightening.

I could also presume that the system was undercharged at initial startup.

At the end of testing (presuming no leak) I think that I will charge the system a little bit more to bring the frost line up into the top passage. Just a few seconds more refrigerant. Another option is to slight over fill it until the frost line is on the suction tube outside the box. Then decrease the refrigerant until the frostline retreats into the box.

Next update will be when the battery is around 10% SOC.
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