Scotsman Frimont MAR126 flaker

[NewmanRef]

Good evening gents,

I do not usually go near ice machines as I simply don't have the experience, however the above machine is on one of our contract customers sites and so I have been asked to work on it...

I originally found it with no gas. Nice and easy I though. Found and repaired leak, new drier, good vacuum, weighed in factory charge. Next found bin stat failed and holding system out. Nice and easy I thought...New stat fitted and away she goes.

Next problem is that ice only forms halfway along the drum with the last half only producing slush. This can be improved by opening the AXV but this results in liquid flooding back to compressor. After lots of to and fro on the adjustment screw of the valve find a happy medium whereby 80% of the drum forms ice with no liquid flood back. This the best I can get out of it. Water pressure is fine, unit level and even water distribution of the drum. Anyway although only 80%:capacity customer very pleased even if I'm not totally satisfied and machine running without fault for last 2 to 3 weeks.

UNTIL today. Called back as unit has stopped working. Find cut out on drum rotation fault and drum jammed stuck with solid ice. Switch off and clear all ice. Start system and within 30 seconds thick solid ice has formed on first half of the drum and jammed drum again. Repeat this a few times and same problem after 30 seconds each time. I didn't get much time to spend on this today as the same site had more pressing issues but I am due to go back tomorrow currently feeling pretty clueless as to what might be the cause???

ANY ideas, advice or manuals for this machine would be HUGELY appreciated

Many thanks in advance
Rob

[marco59]

Hi Rob
here you can download some service manuals of Scotsman MAR series
http://www.scotsman-ice.it/documentation.asp
in step 1 select "service manual MAR series" in step 2 you can select the language
Hope this help
P.S. I am going to post some technical question regarding rotating evaporator flake ice machine...
I am tryin to fix / optimize one of them for a friend of mine
Regards
Marco,Italy

[NewmanRef]

Thanks very much indeed Marco. I will start studying these manuals! Best regards Rob

[marco59]

Hi Rob,
if you will be back on site could you take a look at the brand/model of the AXV fitted on that flaker?
and if it is internally or externally compensate
Is it water or air cooled?
Thanks
Regards
Marco

[NewmanRef]

Hi Marco,

The AXV is stamped 'H' and is model AMVX-00002, It is factory set to regulate at 3 Bar and is externally equalised.

The condenser is air cooled. The fans are controlled on a mechanical pressure switch and currently set to cut in at 250psi, Out at 220psi

After downloading the manual I am going to return to site today. I have read that the minimum water temp into the machine should be 5degC. I suspect that it could be colder than 5DegC with current ambient temperature here. Hopefully I am on to something....

Thanks again for your help.
Rob

[marco59]

Hi Rob
thanks for reply,the AXV is same brand of mine machine,just mind that the pressure of 3 Bar is absolute not gauge.
I discovered it using the Honeywell selection software (AMV valve are Honeywell).
One tip...after setting the valve or add-remove charge wait a longer time than usual to stabilization.
The refrigeration circuit is very basically,it is critically charged (no liquid receiver),if electrical controls and mechanical are
OK very few things could be wrong.
Regards
Marco

[NewmanRef]

Marco,

The manual has proved very useful! It mentions some fibre keys in the gearbox which protect the gearbox if the drum freezes solid. On inspection these keys were completely sheared off. So every time the drum meets some resistance (ice against the blade) it stops rotating and trips on the drum magnet switch.

I have ordered some new keys but obviously now need to work out why the drum froze solid in the first place... I think it may just be low air/ water temperature which caused this. When I was there I measured the room temperature at 7degC and the manual says not to run the machine at lower than 5degC. I suspect the room temp does get below 5 in lower ambient.

I assume at too low of air temp the ice just freezes too hard to the drum.

Have to wait 2 weeks for the new fibre keys now but will update on here when I get it going again.

Thanks Rob

[marco59]

Hi Rob,
glad that the manual was been useful and you founded the problem...
I really do not think that the low temp of water would be a big issue at least if the flaker has a brine doser.
Most of subcooled ice makers will benefit of a very little salt added to water,the right concentration is very low,between 200 to 500 ppm.
Without it the ice could be too "hard" to be scraped off the drum.
Sometimes the vendor's machine have the brine dispencer/doser as option.
If you want take a look to have an idea about it go here:
http://www.scotsman-ice.it/sitedocs/EVE%20Split%20Manual07-2006UK1.pdf
pages 30 and 31. It is referred at a static evaporator type but it can be used on every machine and,believe me,
it helps a lot.
The evaporator load doesn't change a lot from winter to summer,most of the cooling power is used to "make" ice,
the cooling power to bring the water to 0C is arond 10% of total and even less to subccol the ice.
The machine has a condenser temp. controller moreover the AXV capacity is NOT inlet pressure sensitive but as the system is critically charged I would check again for right charge and/or AXV setting in warmer climate as the manual says that the charge qty is approssimate
Mind also that there is a suction/liquid heat exchanger in MAR126 so less superheat more subcooling.
P.S.
I believe that with new keys all will be good...it could be possible that they was already weakned by a previous bad event
when it was low on refrigerant charge.