Author Topic: Cool blue technautics problem  (Read 6360 times)

Colin Wright

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Cool blue technautics problem
« on: January 14, 2014, 10:37:05 am »
Hi Richard and everyone, I hope you can help.
Quote
We have a Technautics cool blue with the danfoss BD-35 compressor and large 2.5 inch holding plate to run our 8cu ft fridge box (6" insulation)

The holding plate has a tev valve on it which is possibly the cause of our problems.

What happens is that occasionally the compressor will not work properly,  and either draw a lot of power when this happens, or occasionally throw up a three flash error code (high differential pressure) and shut down.

When the system shuts down we have icing all the way to the compressor on the return line. (This hints at a stuck open tev?)

A little history of our system,  it was recharged with aircon r134a which had a lot of pag oil and leakstop in it. (All we had available at time). This was then all vacuumed out and pure R-134a replaced in by a fridge engineer.

He had trouble getting the 24 ounces of gas in (his own bottle was low) and we still had bubbles in the sight glass (air? )

I've since added more pure r-134a in the system to remove bubbles as per instructions.

However we are still having intermittent problems and are desperate to get this fixed otherwise we'll have to scrap it and buy something else that works!


My questions are: with the symptoms of high power consumption (occasionally); poor cooling; overpressure differential; and frozen return line
1. Is the system simply overcharged?
2. Is there air in the system with ice then sticking open the tev valve?
3. Is the tev valve broken on the holding plate?
4. Could the plate be blocked with oil/leakstop
5. Would the leakstop break the tev?

Finally our plan is to have the system vacuumed down (again!) And refilled with clean r134a,  then test run it. After that we have to consider replacing the valve or scrapping the system.  What would you do?

Many thanks
Colin and Nichola
Yacht Emerald
Portugal

Richard

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Re: Cool blue technautics problem
« Reply #1 on: January 16, 2014, 12:02:45 pm »
System was recharged with 134a that had PAG oil in it and dye instead of POE oil. There are some PAG oils that claim to be compatible with POE, but I warn against mixing. them. Occasionally high amperage and 3 LED overload flashes. After overloaded compressor stops and frost will show up on line back to compressor.

YOUR questions are: with the symptoms of high power consumption (occasionally); poor cooling; overpressure differential; and frozen return line:

1. Is the system simply overcharged?

Could be as simple as too much refrigerant. What do you see happening in sight glass? When seen first when system is turned on? and again when  there is some frost on plate? And when plate is covered with frost?

2. Is there air in the system with ice then sticking open the txv valve?

Pressure high on low side of TXV and a warm temperature sense control tube will increases amperage and refrigerant flow by opening valve wider. A wide open TXV valve or air can cause frost on return line only when compressor is running so it is unlikely valve is stuck open. Air mixed in refrigerant could cause frost on return line while compressor has run long enough to start freezing plate and it is still running.

3. Is the txv valve broken on the holding plate?

I do not think valve itself is the problem but it may be its small inlet screen that is restricting flow.

4. Could the plate be blocked with oil/leakstop?

It does indicate there is intermitted refrigerant flow blockage somewhere in this system.


5. Would the leak stop break the tev?

I do not think TXV is broken. Sludge from mixing PAG oil with POE oil and the presents of stop leak and possible moist air can affect refrigerant flow.

RECOMMENDATION:

a.   Report answers to Sight glass Questions. If you have pressure gauge reading list them at each time glass is checked.
b.   Remove small amount of refrigerant so that when refrigeration is first started with a warm holding plate there are small bubbles still present in sight glass after 15 minutes of running time and glass is clear when plate is covered with frost.
After the above information is evaluated then in order to resolve the problem it may be necessary to:
Remove refrigerant.
Add to liquid line an oversized filter/dryer.
Remove fine screen from inlet side of TXV and clean or replace it.
Dehydrate system keeping it warm for 4 hours evacuating with a good refrigerant two stage vacuum pump. The dye and sludge can not be evacuated so it will later be confined to new over sized filter preventing future blockages..

Colin Wright

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Re: Cool blue technautics problem
« Reply #2 on: January 17, 2014, 10:03:53 am »
Hi Richard, thanks for replying. You've given us some hope that perhaps we can fix this system.

 I've let some gas back out and am currently running the compressor and making notes which will hopefully help the diagnosis. Unfortunately I do not have access to a set of pressure gauges to be able to supply that info. This is the best I can come up with are the following observations:

1. At switch on: box temp 54f; plate no frost; compressor cold; sight glass small bubbles.

2. 15mins running: box temp 51f;plate slight sweating with no frost; compressor luke warm to touch; sight glass no bubbles.

3. 30 mins running: box temp 49f; condensation on plate; compressor warm to touch; frost starting to form on return line; sight glass clear,  no bubbles.

4. 1 hour running: box temp 47f; condensation on plate and some frost on return line top of plate; compressor cooler to touch,  with frost heavier on return at compressor; sight glass bubbles again.

5. 2hours running: box temp 46f; condensation frozen on plate and heavier frost on return line in box; compressor same as above at 1hr but thicker frost at compressor end of return line. Same amount of bubbles in sight glass.

6. 3hours running: box temp 45f; ice on plate and return line in box; compressor still cool, and ice on return line; bubbles still in sight glass

I'll keep the box running for 24 hrs to see how cold it gets.

I have a suspicion that the last fridge engineer may have pumped air in by mistake while trying to increase pressure in his almost empty refrigeration gas tank using the vacuum pump in reverse but not sure about that, as I wasn't watching that closely. He certainly left in a hurry shortly afterwards! We didn't get the chance to call him back as we had to take a weather window south.

Are there any more tests I can try or should I get the receiver drier fitted to liquid line,  or risk just having the system well vacuumed and recharged? I guess that is the decision we face.  Do the above observations help narrow our choice down?

As always Richard, many thanks for your help and expertise.
Kind Regards
Colin

Richard

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Re: Cool blue technautics problem
« Reply #3 on: January 17, 2014, 08:09:58 pm »
 Do you have a way to read amperage of unit after there is frost on return line?

Do you think service tech may have messed with TXV adjustment?

Is the temperature sensing tube bulb clamped so it is firm against return line.

Frost on return line outside refrigerator indicates energy is being wasted.
 
The last non destructive test I can think of is to confuse the TXV by temporally placing an insulating blanket around temperature sensing bulb and the line where it is attached. Using a moisture resistant piece of insulating foam held on with tie wraps better joining bulb to line will cool thermostat bulb further and cause TXV to reduce refrigerant Superheat back into plate’s evaporator coil where it belongs.

Colin Wright

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Re: Cool blue technautics problem
« Reply #4 on: January 22, 2014, 10:37:59 am »
Hi Richard, thanks for getting back to me.

I know for sure that the Txv valve hasn't been adjusted but wondering if that perhaps it has vibrated open a little over the years or if that is even possible!?

I've found one fault with the plate.  When I reinstalled it I'd moved the return line by accident getting the plate in and it was just touching the liquid line aeroquip connection fitting and fooling the txv bulb and flooding back to the compressor.
I separated them and insulated the bulb and return line and the system appeared to work normally.

The box temperature after 12hrs running got to 32f then didn't reduce any further. (Much colder than we would use)

With the compressor running at this point it was drawing approx 8.5 amps and had iced up with bubbles in the sight glass.

To measure this I had to turn the compressor off (to see the drop in amps on the battery monitor). I tried to switch it on again straight away and got the three flash differential pressure warning and the compressor wouldn't start until the system warmed up a little again.

I then let the box warm up to 49f to run a normal cooling cycle (we usually run the box 43f to 49f when cruising).

However the plate was frozen hard still in the box. The system ran normally for about an hour (compressor getting warm drawing about 3.5amps) then locked up again this time only at 48f box temp drawing 8.5 amps.

Therefore I know the system works from warm on first cycle, then once locked it stays locked until plate completely unfreezes.

I haven't been able to do the txv bulb test due to the position of the plate in the box as I would have to take the plate off to get to the bulb,  but it is held tightly against the suction (return) piping by a metal band.

I guess the decision is what to do next. I'm checking with a local commercial fridge company to see if they can supply and fit a liquid line filter drier (like the Sporlan Catch-All C-30 series) and clean the Txv valve pre filters for me.

I'm at a loss to know for sure what is happening.

1. Is the valve broken: not sure because it works to freeze plate first time?

2. Is there too much gas? Not sure as there were bubbles when whole system warm and idle for few days,  but no bubbles at 49f when plate frozen.

3. Is there moisture in system, possible because valve sticking when plate frozen?

4. Is there too much oil/leakstop from the old aircon gas which gradually locks compressor. Not sure if that is even possible.

5. Once the compressor has locked up does the system need to warm up completely to re-equalise the pressures in the high and low sides? Not sure if this is the case.

6. Has valve moved over the years?  Should I close it down half a turn to see if this frees compressor up?

7. Would you expect a fridge system to lock up if running it down to freezing, or is this a sign of a fault. Again I don't know if you would expect system to lock or just keep cooling box until heatload is matched?

I've just restarted compressor again at box temp of 48f (about an hour after lock up) and it is working, compressor hot, box dropped to 47f. Will update you on progress as to whether it locks again.

Many thanks for your help
Kind Regards
Colin

Richard

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Re: Cool blue technautics problem
« Reply #5 on: February 03, 2014, 08:50:46 am »
After compressor ran 12 hrs and amperage was at 8.5 amps there is a refrigerant problem.

When tried to restart high pressure shut down, again refrigerant flow problem plate was frozen solid.


System later worked OK for one hour then amperage went back to 8.5 amps, indication again of blockage.

Question 3
If there is moisture freezing TXV  best test is when flow stops and amperage increases place a hot wet dish rag on valve . When ice melts wet rag will freeze to valve then amps will drop in several seconds, then rag will fall free. As long as compressor is running this valve freeze up will continue to repeat keeping plate temp at around 33 degrees F.


The condition you report is most likely Moisture in refrigerant or Contaminated refrigerant. I would suspect moisture that is almost impossible to remove from a holding plate system containing POE (Ester Oil.)
Moisture removal would be drawing system down to 300 micron of vacuum while maintaining complete system near 100 degrees F for at least 4 hours. Then before adding correct refrigerant install a new oversized filter dryer and a new receiver/dryer.


Colin Wright

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Re: Cool blue technautics problem
« Reply #6 on: February 06, 2014, 02:43:02 pm »
Hi Richard, the system has been vacuumed, (but not sure how long, or to what strength of vacuum).

We have had a new txv installed.

The last thing we can do is get a liquid line filter/drier put in but i'm not sure if that is worthwhile without replacing the receiver /drier and getting it deep vacuumed.

I'm also wondering if maybe a controller fault or lack of compression could do the same thing?

Many thanks for all your help and advice.
thank you
Colin

Richard

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Re: Cool blue technautics problem
« Reply #7 on: February 12, 2014, 09:50:55 am »
Before you changed the TXV did you confirm that moisture was not the problem? If it was moisture then you must assume it is sludge induced by contamination of leak sealant, wrong oil and a very small amount of moisture in refrigerant. Changing receiver/dryer and installing an oversize filter/dryer in liquid line to evaporator along with a super dehydration vacuum is all I can think of.

Colin Wright

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Re: Cool blue technautics problem
« Reply #8 on: April 13, 2014, 05:49:52 am »
Hi Richard, thanks for all your help to date. Our cool blue fridge system has been working 'ok' (cooling a little slowly on the cycle) down to a box temp of about 36/37 deg f . If left running it will get the box down to about 31f overnight.

I followed your suggestion of a large filter drier in the liquid line which seemed to do the trick. The system was vacuumed and regassed and as worked ok
for approximately a month, cycling at 4.5amps and cooling in about 6 hours.


However it has now started playing up again, running at 8.5 amps, only cooling the box to 44f (with no increase in ambient outside temp). Even after running constantly for 36hours, with the compressor very hot to the touch and no loss of gas, the plate has condensation but no frost,  and condensation on the return line, but no frost.


I'm  wondering if maybe a controller fault could do this?

If not then maybe the compressor is leaking at the pistons and locking up?

We are not sure what else to try,  other than putting it in the bin and buying an air cooled evaporator plate system from frigoboat or similar which will at least work.

Can you think of anything else we could try?

Many thanks again for all your help and advice.
thank you
Colin

mayball

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Re: Cool blue technautics problem
« Reply #9 on: April 13, 2014, 01:00:46 pm »
Colin,

I don't know if this applies if your boat is in Portugal, but here in Puerto Vallarta, Mexico, if you fill a Cool Blue system to a no bubble sight glass, it is overcharged. I think the reason for this is that the filter/dryer/receiver is too small to contain all of the liquid refrigerant when the expansion valve pinches back. The units down here run fine with bubbles in the sight glass.
Don

Richard

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Re: Cool blue technautics problem
« Reply #10 on: April 13, 2014, 01:57:45 pm »

As I understand it system ran good for a month and no one tampered with refrigerant so refrigerant charge is correct.

Amperage at 4.5 or higher would indicate compressor is good.

Loss of cooling and amperage of  8.5 would indicate a flow restriction or poor condenser cooling.

Condensation on plate instead of frost can indicate moisture freezing in expansion valve or restriction somewhere in system.

Replacing evaporator is not likely a solution.

Conclusions:

Are you positive condenser cooling is very good?

A restriction normally shows up by a temperature change at the point where restriction. This is why frost forms only at and after expansion valve. If there was a substance moving through system for a month and collected at new filter the filter and line after would be cooler than line from condenser to filter. If restriction is somewhere else look for temperature change spot.

I know you think you vacuumed moisture from system but it takes extensive low vacuum to get all moisture out. A simple test can confirm if moisture in valve is the problem. When amperage is high and only condensate is on plate place a hot wet rage on expansion valve. This hot rage will temperately melt an ice restriction causing a mass of refrigerant to flow through valve and rag will freeze tight to valve. When moisture (ICE) blocks flow again rage will flow free.
There is always a chance that contamance from PAG oil and Dye could be causing sludge stuck somewhere other than filter. To increase flow for a while warm up system including holding plate an then turn system on again. With luck blockage will move into new filter.

If problem is not moisture in valve or filter does not feel cold did you check inlet screen at inlet of expansion valve when system was opened up?

 
 

Colin Wright

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Re: Cool blue technautics problem
« Reply #11 on: May 16, 2014, 04:26:58 am »
Hi Richard, thanks for all your help to date.

Our fridge saga on Emerald continues. I tried the hot water test you suggested several times on the expansion valve with a rag as you described, but it  made no difference at all to either the valve or power consumption of the compressor (still running flat out at 10amps) so I think it is not a moisture problem.

The only thing I can think to do now is to replace the receiver drier that has the sight glass in it at the compressor end, run new copper for the liquid and return lines, and dismantle all the aeroquip fittings to check or replace them. 
I am wondering if one of these 're-sealable' aeroquip fittings is blocked/broken or has o-ring damage, so as the pressure increases during the cooling cycle, it is closing up/failing. I really can't think of anything else it might be. I guess if that doesn't fix it it must be the compressor?

Can you think of anything else we could try? We also changed out the valve as well so there is no screen block.

Many thanks again for all your help and advice.
thank you
Colin

Richard

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Re: Cool blue technautics problem
« Reply #12 on: May 16, 2014, 06:12:34 am »
It still sounds like the mixture of PAG and POE oil combined with stop leak and possible moisture having developed sludge. The only thing you can do now is replace Receiver/filter/dryer unit.  If compressor can still operate with a 10 amp load then compressor is not your problem.

There are normally only three points in that system where refrigerant flow can be blocked inlet screen at expansion valve, the valve’s orifice and filter/dryer. It may take more than one filter/dryer change to remove the contaminates.

Are you you sure that you have not overcharged system also?