brema vm900 ice machine

[paul_h]

I got stuck with this machine yesterday. It's a two plate cube machine that's not dispensing the ice and making a huge block in between them.
It's a prehistoric machine, no cleaning mode, no sump drain (that I could see). All controls are done by mechanical thermostats, a contactor and a timer.
Someone else changed the compressor, but couldn't get it working so hand balled the job to us.
First problem is the back plate makes a thicker block of ice than the front and it doesn't drop off in time. The front evap is where the coil sensor is for harvest, and that ice sheet drops, but the back one doesn't. I've set the timer for a longer period, but it didn't seem to help much. It's hard to set it up without knowing all the controls and functions.

The second problem is ice production doesn't stop. From what I can work out, there's a magnetic sensor on the horizontal ice flap. If the flap stays open after harvesting ice because the bin is full and the ice doesn't clear the flap, ice production should stop. I can't see how it works as the flap is stainless steel, but I've drawn a dead end here. I've been to the local distributor of the machines, and they know nothing about it. They called the national dealer and asked them, apparently it's called a "closeness switch" :cool:
The newer models don't have this flap switch, they just use a bin thermostat so the local distributor has no other info or parts .
Has anyone seen one of this older machines with these switches, know how they work, or have settings and manuals for one of these older ones?

[Electrocoolman]

Paul,
With regard to the plates....are they connected in 'series' on the refrigeration circuit. Is there an undercharge of refrigerant? How is the harvest achieved....hot gas defrost?
Have you ensured the plates are clear of scale....I've known scale prevent an ice block from slding off, which then continues to get thicker and thicker.

With regard to this 'closeness' switch.....I would suggest that it either a Reed switch which requires a magnet to operate it, or a proximity switch which senses the presence of metal in its sensing zone (ie does not require a magnet).

The first is the simplest...as used on door sensors for burglar alarm systems. Normally 1.5" long rectangular in shape with a couple of mounting holes, with a similar shaped magnet. Can you see where a magnet might have been attached to the flap and has dropped off? Contacts (low current only) normally close in presence of magnet, though you might be able to get reverse sense operating units.

The other type .... a proximity detector requires a power supply feed and usually are cylindrical with an external threaded body so that they can be adjusted. One end is the sensing end, the other end has cable in and also they usually have an LED to indicate operation....much more complex and expensive.

Suspect magnet has dropped off the door.

ECM

[paul_h]

I gave it a good descale with cleaner and situation not improved, that was the first thing I'd thought I'd try when I went there friday. Not knowing anything about the machine at all I didn't want to play with any settings before trying just cleaning it.
The switch this has sounds like the proximity switch, it fits your description exactly. Didn't see a LED though, as far as price, maunfacturer quoted $300 for a new "closeness switch"
I need data on the system though, I have no schematic, wiring diagram, or setting of anything though. This system has a mechanical timer, electronic delay timer, hot gas harvesting, one contacter and three mechanical thermostats. I don't even know where this" closeness switch" fits into the circuit.

[setrad7791]

Hi there! The door curtain switch is just operated via a magnet mounted on the curtain... just dis-connect it and test for continuity, it should open and close circuit as you open and close the door curtain, if it does you may want to check for a faulty relay/contactor. As for the ice production.....? I have had trouble with some older machines losing their evap transfer due to the piping on rear of the plate dislodging. May want to check that and also the refrigerant charge as mentioned.

[paul_h]

Hi there! The door curtain switch is just operated via a magnet mounted on the curtain... just dis-connect it and test for continuity, it should open and close circuit as you open and close the door curtain, if it does you may want to check for a faulty relay/contactor. As for the ice production.....? I have had trouble with some older machines losing their evap transfer due to the piping on rear of the plate dislodging. May want to check that and also the refrigerant charge as mentioned.
It's not that type. Thats the ice machines I am familiar with, with plastic curtains hanging from rods and magnetic sensors on the curtains.
This one is different, a big 400KG/day machine with seperate maker/ice bin.
Dual plate, each fed off it's own capillary, pump sprays water between them.
Had another look today, fault occurs after the first cycle as the rear plate does not dislodge ice. The defrost cycle goes for 5 min, the machine is slightly tilted forward.
1697


But also noticed the plate seems slightly bent.
So maybe the evap tubing doesn't contact the plate very well at the bottom/middle part, so it's not getting enough heat from the hot gas defrost. It's bowed outwards so that the middle is closer to the front of the machine than the edges.
1698


edit: I'm leaning more to that now, as I remember there was heaps of ice behind the bent plate, so the coils are icing up and maybe getting some frost build up from the air rather than working on the plate. That may explain poor defrosting, though wouldn't explain the massive blocks of ice in front of the coil that it ends up making if poor plate contact is the cause.

[fri11j]

who did you contact for information??
not actrol i hope?

contact icemaster in victoria 03 9455 2300

the VM series is still a current model and they should be able to give you a copy of the service manual..

im not familiar with the VM series but brema machines are generally crap machines and suffer badly in moderate ambients above 30c and water inlet higher than 15..
if its like any of the other bremas..this is the basics..

ice harvest is activated by a thermostat that is on the plate.. once the plate temperature is reached, the thermostat will close and activates a countdown timer which is about 10-15 mins
im sure that harvest is terminated by time (timer) or curtain switch (proximity switch)

If compressor has been changed, then i would be starting with basics and recover refrigerant & re-charge and weigh it in, as most boneheads never check the charge weight on a capilliary system and generally over/under charge, which may explain why one plate is getting ice..
also, check your TD on condensor because you might find condensor is blocked and refrigerant is flashing ( hence why you are getting one cold plate..

is each plate individually metered by cappiliary??

[paul_h]

Actrol is who I got info from.
Anyway, It does look like poor plate to coil contact is to blame. Looks like a most of the welds joining the evap coil to the plate have cracked, meaning the hot gas defrost doesn't warm the plate up fast enough to defrost the ice off.

Neither plate had any problem making ice, it;s just the rear ones doesn't drop the ice, so after 3-4 cycles it's a massive block spanning the space between the plates.

Each plate is fed by it's own capillary.
VM is a current model, but this older one is the only one that has a proximity switch, newer machines (according to actrol) use a bin thermostat to stop ice production.

So anyway, I've ordered a new rear plate and a proximity switch.