-20 deg freezer

[tonyhavcr]

Hi this box has 4 - 5 ton compressors
where I need help is when the unit comes out of defrost it is so cold that the defrost tem / fan delay will not switch over to delay the fans from starting so the water will freeze back on the coil not on the fan shroud and fan blade. I have the bulb in the coil top center and I tried to replace the control I need to find a control the will keep the fans off till 10 deg most defrost term is @ 45 deg thanks

[smpsmp45]

I think you have to chenge the defrost setting . We check the suction temp & decide on the time for the defrost.

[Grizzly]

Hi this box has 4 - 5 ton compressors
where I need help is when the unit comes out of defrost it is so cold that the defrost tem / fan delay will not switch over to delay the fans from starting so the water will freeze back on the coil not on the fan shroud and fan blade. I have the bulb in the coil top center and I tried to replace the control I need to find a control the will keep the fans off till 10 deg most defrost term is @ 45 deg thanks

Hi Tony.
Just a quick reply.
It sounds as if you have tried a lot of options so my suggestion may be useless?
Have you tried lowering the defrost sensor slightly?

I must admit your last comment has me confused?
surely there are lots of options or have I missed something?
Cheers Grizzly

[tony--1]

tony
is there a drip down delay on this system? after defrost ?

[Brian_UK]

Change the controller to one where the sensor is wired to an outside-of-box control - this way there are no mechanical switches inside.

[powell]

Ranco makes an adjustable 3 wire fan delay/defrost termination switch.

part # F25-107

I too, am confused by your last comment.

[US Iceman]

The return bends on the evaporator will freeze first, not the fins. If the air temperature is cold enough it could be possible for this to simply bypass the fan delay and contribute to the problems.

[tonyhavcr]

Thanks for the help : (you have to change the defrost setting) all 4 units have different defrost times.

(I must admit your last comment has me confused?
surely there are lots of options or have I missed something?
Cheers Grizzly ) The defrost heaters are started by the time I have 4 defrost @ 45 mins they terminate by time or temp you want it to terminate by temp shorter defrosts for 1 this around 45deg.

(is there a drip down delay on this system) No
tony---1 there is no drip down delay but I did add a time delay to the evaporator fans and set it for 3 sec
that will let the water freeze to the coil to see if adding one would help it didn't work.

( Ranco makes an adjustable 3 wire fan delay/defrost termination switch.) Thank you powell but ranco 3 wire fan delay/defrost termination switch bulb must be mounted vertical not horizontal I have the bulb horizontally in the coil.

I will check on the job and get back with more info

[powell]

Thank you powell but ranco 3 wire fan delay/defrost termination switch bulb must be mounted vertical not horizontal I have the bulb horizontally in the coil.

tony,

The bulb was redesigned. The revised design isn't position sensitive and the word "TOP" has been removed from the bulb.

powell

[tonyhavcr]

(Tony,

The bulb was redesigned. The revised design isn't position sensitive and the word "TOP" has been removed from the bulb.

powell )

thanks powell this shows how far behind we are in ma. us when I got one from my suppler last week all they had was the old type :rolleyes:

I went to the job found the evaporator fans froze to the shroud again.
The evaporator was froze @ the top 3" down no more and was 4 to 5" thick.
I did find this be for when I changed the control
defrosted all the ice and tested all the heater and amped them all heaters look good .
The bulb is is the middle of this ice.
This is a 502 system 20 yrs old but works well the fan delay I have is a danfoss the doors are 20' in front of
coil I do have air curtains. One other unit does the same the evap @ the top 3" but it stop in the middle of the coil so I got ice coil ice but this one is working fine and water does not come off the coil.