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Giannis
17-12-2007, 09:42 PM
Many controllers have a parameter named FST
Fan Stop temperature this parameter stops the
fan if the temperature in evaporator coil is over
the FST setting .

My question is how importan is this , i understand that is better to start the fans when the evaporator
has low temperature and stop fans when is hot but
i am worry about the ice. Maybe you get ice when you are waiting FST Temperarure.

Do you use this parameter ? It is important ?

Regards,

Brian_UK
17-12-2007, 10:03 PM
Are you using this in a cold room or a freezer?

Some controllers use a 'drip time' to hold the fan OFF after a defrost which could be similar to your FST.

The FST could be set to a temperature that prevents moisture carryover which woould be around the pipe freeze temperature, some ice/frost will always be developed but not a major covering.

Giannis
17-12-2007, 10:06 PM
Are you using this in a cold room or a freezer?

Some controllers use a 'drip time' to hold the fan OFF after a defrost which could be similar to your FST.

The FST could be set to a temperature that prevents moisture carryover which woould be around the pipe freeze temperature, some ice/frost will always be developed but not a major covering.

Hi,

Iam using this to cold rooms

chillin out
17-12-2007, 10:23 PM
It should only be used with a heated assisted defrost system.
Other than that it is up to you / the client whether it get used or not.

Chillin:):)

Grizzly
18-12-2007, 01:26 AM
My understanding is that it is form of safety setting.
Whereas if the defrost termination stat dosn't work.
(quite common on smaller evaps. ) Many of these stats fail and then are linked out, rather than replaced.
Also it is not uncommon for the defrost contactor to weld itself shut.
Therefore my advise would be.
If FST is available as an option use it!
Yes it is important, as if the coil temperature rises above this temperature. At least the fans will stop and this will minamise the heat being blown around the chamber.
Grizzlyhttp://www.refrigeration-engineer.com/forums/images/icons/icon14.gif

hendry
18-12-2007, 02:12 AM
we've done on-line recording of cold room parameters with Yokogawa paperless recorder.

we found
1] drip time
2] FST
3] defrost stop temperature
are very useful parameters.

Good settings ... save our clients a lot! esp. when the defrost is by electric heater.

hendry
18-12-2007, 02:46 AM
Hendry.
Surely all of the above settings are parameters within the controller and therefore the user already has access to that information. Or yet again am I missing the point?
Grizzlyhttp://www.refrigeration-engineer.com/forums/images/icons/icon4.gif

no .. [i'd to be careful in my words again!]

"same cold design & system apply to 2 different locations od similar ambient will not seemingly have same parameters."

... just because the human is diferent; they operate differently; the plant has its life then, they also operate differently ...

i believe you must experient with 2 exact model of compressor operates in same plant but has different problems totally.

that's my opinion. after all, we have not found easier way out to set these parameters. we are more to efficient plant ...

hendry
18-12-2007, 05:36 AM
Hendry
I'M Sorry but your posts must make sence to you.
I just can't understand what you are actually saying.
More importantly If I can't understand ( English is my native toungue). How many others can.
I'M sure you have a wealth of experiance to offer.
But unless you can word the posts differantly all you are going to do. Is confuse and sometimes even offend.
Grizzly

thanks.
no worry because i'm not like others easily feel insulted.

yes, my mother tongue is NOT english.

but, i'm improving day by day.

some engineers are better with words than real engineering works; i'll never ignore that.

i shall improve my words / statements. thanks.

Chicharronne
18-12-2007, 02:08 PM
I think the guy's english is good. anyone else try to communicate with others in their native tongue? you might want to concentrate on your communication skills. por ejemplo, "your a good engineer" his What is a good engineer? you confused me.

refrigeration that uses the 3 wire defrost termination/fan delay switch use them to keep the fan from running until the evap gets colder. keeps liquid from flooding back to the compressor and keeps the fan from blowing hot air.
On freezer, usually the switch goes bad, then it stays in defrost the entire time and the area around the evap starts to sweat. then the fans come right on, with the txv wide open, blowing the hot air.

Grizzly
18-12-2007, 05:09 PM
Chicharronne and Hendry
It has been pointed out that my posts were rude to you guys for that I appologise.
Grizzly

Chicharronne
18-12-2007, 05:34 PM
I accept, but he probably doesn't understand. I wish we could all help him.

Chich.xxx

Giannis
18-12-2007, 07:16 PM
I Have to explain again,
becouse my english are not very good ..

The controller has a parameter named FST (fan stop temperature) parameter .

For example :
We use 2 temperature probes NTC ,the first is inside the room and the other in the evaporators coil.
So if i set FST= 0C then the fans will start when the evaporators probe measure teperature < 0C
The fans are programmed to work together with the solenoid valve and the defros is electrical. The FST is not a defrost parameter.
Protects the room when you have problem in all of your copressors and you cant make refrigeration (so no low temperature in evaporator) dont start the fans whitout cold evaporator.

Is this important ? Is dangerous for ice (becaouse of delay of fans until evaprator is cold)?

i hope i try :)

Giannis

Brian_UK
18-12-2007, 11:34 PM
Giannis

As you say, if the compressor fail for any reason then the FST will protect the product.

The amount of 'ice' that may form on the coil should be minimal because you should not set the FST too low.

If however your fans are connected in line with the solenoid valve then FST could not be used, an unlikely set-up I know.

hendry
19-12-2007, 09:53 AM
I accept, but he probably doesn't understand. I wish we could all help him.

Chich.xxx

thanks ...


Chicharronne and Hendry
It has been pointed out that my posts were rude to you guys for that I appologise.
Grizzly

You've done nothing wrong to me. No apology is necessary.

on the other hand, i should thank you for pointing out the way i write is misleading.

anyway, once a senior told me that the purpose/s of a discussion is to collect idea/s [i means useful ones] disregards of how the statement is made.

thank you both of you. i'll be better person ...

chillyblue
22-12-2007, 01:27 PM
Hi all

FST, can be dangerous, use with caution, i've seen many freezers set with a fan stop temperature of upto 0degC and ice compressors solid, the problem is as follows

1 most controllers have a diff for the FST this works below the FST setting, so if you set it at 0degC with a diff of 5K the fans won't start until the temperature is -5degC this seems fine but when the fans are not operating the expansion device is massivly oversized and liquid flood back is a big threat.

use with caution
or make sure you set it at a temperature where your superheat does not drop to low even after the fans have started.
alternatively use the drip down timer

Cheers CB

Giannis
22-12-2007, 04:11 PM
Hi all

FST, can be dangerous,..

use with caution ..

Cheers CB

Thank you Chillyblue .

So is usefull only if the copressors are out of order to stop the fan inside the room ,and not warm the room.

Plank!
23-12-2007, 01:40 PM
Thank you Chillyblue .

So is usefull only if the copressors are out of order to stop the fan inside the room ,and not warm the room.

Thats about right.
Mostly i work on industrial systems so i don't see many of these units, however I would look at setting the FST about 10c or more above normal room temp.
Less than that could prevent the system pulling the store temp down after defrost.
FST should be considered a back up to protect the store from extended defrosts or other mechanical faults.

Steve