View Full Version : ePTC question

David Heaf
23-03-2017, 10:10 PM
The background to this is in the closed thread http://www.refrigeration-engineer.com/forums/showthread.php?43825-ePTC-question-103N0050&highlight=ePTC

In 2014 our Bosch fridge-freezer with a Danfoss NLX8.8KK compressor and a ePTC 103N0050 with run capacitor failed. The same problem occured again some days ago. I took out the ePTC and measured its resistance. It was open circuit, but should be 25 ohms. I put it back on the compressor. As with the previous incident I turned off the fridge-freezer and left it overnight. The following day I switched it on, and after a some delay it started normally and has been holding temperature normally ever since.

Can a Danfoss NLX8.8KK compressor start and run normally with a defunct ePTC?

Glenn Moore
24-03-2017, 01:17 AM
The ePTC starter has a standard PTC pill inside like a standard PTC starter, but also has a triac and an electronic timer circuit inside. The standard PTC start device uses a couple of watts power when the compressor is running purely to keep itself warm thereby keeping the start winding out of circuit. With the ePTC with the triac and timer circuit the triac cuts out the current loss when the compressor is running, which allows the PTC to cool down allowing its resistance to drop ready for the next start sequence and the timer allows for restart within a few seconds.
The standard PTC needs an off cycle time of about a minute to allow the PTC to cool down sufficiently for the compressor to be able to start correctly. I.e. If you turn the compressor on then off and then on again the compressor would trip on its internal klixon as the start winding would be kept off by the PTC and the compressor would not be able to rotate.until the PTC has cooled down and allowed its resistance to drop sufficiently for the start winding to energise.
So in theory if the ePTC shows open circuit the compressor will not start, but it may be locked out for some reason via The triac timer circuit which may be sus.
Try a standard PTC in its place it won't break the bank

David Heaf
26-03-2017, 11:28 AM
Try a standard PTC in its place it won't break the bank

Thanks Glenn. In the previous thread over two years ago you suggested "103N0011 or if you have a run capacitor fitted use the relay code no 103N0016". Are these still the best alternatives for the Danfoss NLX8.8KK compressor? (There is indeed a run capoacitor fitted.)

Glenn Moore
27-03-2017, 07:57 PM
Hi David
Yes I don't know of any other changes.
Like all cheap electronic devices there only as good as the factory who build them. Just to save a couple of watts just causes more problems with poor quality devices, Simple is always best
Regards Glenn