Friga-Bohn melted fan guards

Hi guys,

This is something I have come across a few times before, but there has always been an explanation for.. Not so in this case though it seems.
I have been to a low temp coldstore with two Friga-Bohn LUC (ceiling mount) coolers - type with plastic fan guards. The two coolers operate seperately on their own refrigeration and electrical systems including the defrost control, which in both cases is via a small Lae or similar (no logo on the front panel). Because the store is within another freezer store, and therefore never gets any warm moist air entering, the defrost periods are minimaL, being set for just 5 minutes every 8 hours.

All 5 of the fan guards on both coolers have melted towards the top. There is no evidence of a failed controller as it would be too much of a coincidence for them both to have the same problem at the same time. There is no scorching of the roof immediately above the guards, there is no frost or condensation on any of the roof surfaces. Has anyone else come across this please?

not seen that one but is it not possible to press the defrost button and stand inside to see whats happening ?

We had this years ago i thought it had been sorted, the Muc suffers from the same thing.

We disconnect the top row of heaters and let the defrost heaters from below do all of the defrost.

We do this on all FG blowers no more burn't fan covers.

Regards
Lrac

Quote:

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Originally Posted by fridge doctor

Hi guys,


All 5 of the fan guards on both coolers have melted towards the top. There is no evidence of a failed controller as it would be too much of a coincidence for them both to have the same problem at the same time. There is no scorching of the roof immediately above the guards, there is no frost or condensation on any of the roof surfaces. Has anyone else come across this please?

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I have seen this before and have caused it myself on one occasion:o.
It is either a defrost heater issue or in my case someone has brazed inside the evap and did not think about the heat affecting the guards:D

First I would look to the heaters, being how it is on both evaps if not the heaters make sure there is not an over enthusistic maintenance guy helping the defrost with a blowtorch of some sort:)
It happens;)

taz.

all the time cant understand why they put so many heaters in their evap,even had the type with plastic fan blabes melt

fridge doctor,

Hi,we have encountered also that problem.Basically the reason is failure of the defrost heater to terminate either by time or by temperature.

I am not very familiar with Lae controller, but check on the defrost termination temperature cut off, defrost time in minutes.Check also the sensor location inside the evaporator coil, it has to be fixed in the coil itself may be by mistake it is not properly strapped..you can relocate that sensor somewhere in the middle of the coil.Is your evaporator sensor and room sensor have not interchanged?

Five minutes of defrosting will not harm the evaporator fan guard.During defrosting hot air will come toward the ceiling and will melt the fan guard if defrosting do not terminate.Overheating of heaters will also shorten its lifespan and will be damaged early.

I hope this will help...

Yes thanks to you all guys, points taken and duly noted, however I can definitely rule out the over zealous brazing or maintenance guy as it is an owner occupier situation and he is pretty switched on to the problem. The controllers (nestor greg 220 - and many thanks for your PM) are not actually LAE only similar, and unfortunately they have no name on them whatsoever, which makes things a bit difficult in terms of accessing the parameters.

Friga Bohn (Heatcraft Europe) are on holiday !! and so I go a reply from some caretaker bod who clearly knows next to 0 on the tech side. I have to produce a report to the client in the next 2/3 days because he is witholding payment from the installation Co. I want to be fair to everyone in this situation, I dont think it is right that the installer should be blamed, but Friga Bohn are not responding ?? Difficult.

fridge doctor,

you can try to temporarily replaced the controller with the one you are familiar with.
most of the controller have the same operation, i can say try eliwell, for me its very good controller and you can have some trial.sensors will not be the issue since you can program the sensor type in the controller either NTC or PTC without changing the existing sensors,if you are able to do that then check all the parameters for defrosting because you need to do the setting yourself depending on your usage of the room chiller or freezer.

is the fan guard completely burnt or you can still rotate the guard and see if ok as long as it will not hit the fan blade. you can run the unit and do manual defrost and observe the status. you can even monitor the evap coil temp during defrost.

You should check that the fans are not operating during defrost. Maybe there is a fan peripherical heater kit (mounted behind the front plate) that should also only be connected during defrost