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Talylawdi
29-03-2016, 01:14 AM
Hi All

Wanted to debate best location for defrost control probe on a standard cold/freezer room evaporator with defrost heater elements. Side of coil fixed to pipe turns or poked into fins in face of coil. See probe in different location alot on my travels.

cadwaladr
29-03-2016, 02:02 AM
If there are no spare holes in the evap I put them in the fins trying to get them in the center of the coil but close to the top away from the heater element,depending on use of cooler freezer or chiller the termination temperature in my experience is around twelve to fourteen centigrade and the max time out thirty minutes,but sometimes you have to hone defrost cycles for door openings warm loading.

Talylawdi
29-03-2016, 11:08 PM
Hi Cadwaladr

Thanks for your input. I've done the same myself, keeping away from element heat is some times difficult though. Is there a ntc/ptc probe availible with some sort of spring retaining clip that would fix to copper pipe turns on side of evap, like the old termination stat's used to?

cadwaladr
30-03-2016, 12:10 AM
I usually stick it in the fins,and then close the fins with long nose pliers,putting it on the return bends not me,when I say opposite to the tev I mean the back or front depending where the fans are opposite the fans where you see all the fins.

CONROD
30-03-2016, 10:18 PM
In the past I've put a 100mm length of 3/8 pipe into the fins, with the sensor inserted into the pipe, to give a more stable temp reading. Generally favour the evaporator coil side from which the heaters enter the coil.

Sandro Baptista
31-03-2016, 06:00 PM
Guys, my opinion:

I would check first the coil of the aircooler after the end of the defrost cycle seeing where the last ice tends to remain and then would put on that location the defrost sensor...that is the location more difficult to defrost so the defrost cycle should stop only when that ice is all defrosted.

airtrackinc
01-04-2016, 04:57 AM
Do not put a sensor on the return bends of an evaporator. The best sensor placement is where the most frost accumulates. This is usually close to the refrigerant inlet area of the evaporator.

Sandro Baptista
01-04-2016, 10:42 AM
Do not put a sensor on the return bends of an evaporator. The best sensor placement is where the most frost accumulates. This is usually close to the refrigerant inlet area of the evaporator.
Yes, that's right! shall be putted where more frost acummulates. However in that areas of the evaporator the electrical defrost coils can be in greater quantity so I would test where the final defrost remains during the defrost cycle and would put in that place the sensor to guarantee all frost is vanished before the defrost cycle be interrupted by the sensor signal.

Glenn Moore
01-04-2016, 01:14 PM
Hi Sandro your answer is the correct one . Failure to fit the defrost termination sensor in the correct position, and set defrost times and termination conditions correctly can lead to poor expansion valve superheat control and can also lead to the "ice ball syndrome" where the partially melted " ice tubes" refreeze around the evaporator tubes and then crush them causing leaks

123-steve909
10-04-2016, 04:42 PM
Hi Sandro your answer is the correct one . Failure to fit the defrost termination sensor in the correct position, and set defrost times and termination conditions correctly can lead to poor expansion valve superheat control and can also lead to the "ice ball syndrome" where the partially melted " ice tubes" refreeze around the evaporator tubes and then crush them causing leaks


Agree with Glenn Moore on this and have seen the ice balls that he is talking about when working for manuacturers on two separate occasions

off subject slightly but could poster glenn moore be a guy I met around 2000-2003 and he was working for danfoss at the time?

Glenn Moore
10-04-2016, 11:19 PM
Hi Steve
Yes that's me where did we meet ?
Best regards Glenn