View Full Version : ePTC question / 103N0050

29-09-2014, 10:18 AM
I have a faulty Danfoss ePTC Part 103N0050 - does anyone know if there is a suitable replacement / alternative PTC as I'm struggling to find this particular one.

Fitted to a NLX10KK compressor.

Thanks - David.

Glenn Moore
29-09-2014, 12:14 PM
You could use the standard relay 103N0011 or if you have a run capacitor fitted use the relay code no 103N0016

The ePTC is an energy efficient relay which saves 2 watts of energy when the compressor is running as against the standard relay. The e relay has a timer circuit with a triac switch to turn off the PTC device once the compressor has started ,as against the standard relay which uses a small trickle power flow just to keep the PTC device warm (keeping the Start Winding out of circuit)
So the e relay has an energy saving and also a quick reset advantage over the standard relay , but the start PTC is identical in both

09-10-2014, 08:21 PM
I have a shelf and boxes full of them


David Heaf
11-10-2014, 07:20 PM
My Bosch Fridge-Freezer has this particular ePTC. Two nights ago we had a violent electrical storm accompanied by several transient power cuts. The following morning the temperature control panel showed a red warning light. All the other lights were normal. The freezer had warmed to -5C, the fridge to +10C. The compressor was hot and a quiet hum coming from it. Could the ePTC have been affected either by the power outages or by any spikes on the mains? If so, is there a way to test it other than by substitution? Where can I get a replacement quickly? I'm in West Wales.

Glenn Moore
11-10-2014, 09:47 PM
Hi David
It is very possible that the relay has gone faulty, as there are small electronic components inside the device which if damaged could prevent the start winding being energised and the compressor to run.
It is not easy to test the relay but you should immediately disconnect the freezer from the power supply, as leaving it connected could cause the motor winding to overheat and burn itselfout.
You can get these relays from the previous poster teemyob or from a wholesaler Dean & Wood or Climate Centre or even a local fridge contractor
Whenever you have power cuts it is advisable to turn your fridges and freezers OFF at the socket and turn them ON when the power is restored as you can get allsorts of voltages in the line during a power out which can damage the compressor start winding. I get many repairs of freezers after a power cut . Ps Remember to turn them back On as soon as the power is restored

David Heaf
12-10-2014, 08:35 AM
...you should immediately disconnect the freezer from the power supply, as leaving it connected could cause the motor winding to overheat and burn itself out.

Thanks for your detailed response. I wish I'd known about this forum two days ago. The compressor was hot after the storm. I switched off for 8 hours until it had cooledagain and switched back on. It started to get warm again but with no refrigeration and there was a hum from it suggesting the winding is might be still OK. I'm inclined to try ePST substitution.

Glenn Moore
12-10-2014, 11:43 AM
Hi David
In the compressor there are 2 windings , Start and RUN . Both are in circuit at start up and after about a second the start winding drops out, controlled by the relay. After a few seconds the relay resets itself ready for a new start as required. If the relay is suspect it may not reset and therefore the Start winding will never be ready to Start the compressor. The Start winding is only in circuit for less than a second to give the compressor a slight kick to get it spinning. The compressor being hot and humming may be the motor RUN winding being enerised but not spinning. You can measure the compressor windings with an ohmeter. Un plug the unit from the mains then pull the relay off the compressor , there are 3 pins that the relay are simply pushed on to. If you take an ohmeter reading across the pins , 2 pins at a time and measure the resistance it will tell you if the motor is still OK.
If you give send the details of the compressor model I can tell you what the resistances should be
Br Glenn

13-10-2014, 09:22 AM
If you have motor-capacitor around 4-8 F or have 'tropical' kit (ie. motor capacitor...) for used compressor (go to danfoss site and locate data sheet for you used compressor and look for value of F for capacitor in 'tropical kit'... most case 4-8 F motor capacitor is safe value for testing but you need check with data sheet if you can leave capacitor connected for continue, long time running use) and connect between R and S winding (mostly of PTC-unit have spare connection outside for possible to connect to 'tropical kit')

- compressor should starting witch more torque with capacitor than using PTC or ePTC and working PTC is almost not necessary if you have running capacitor on recommended value.

if not started even if capacitor mounted and only humming - compressor is broken...

With 'tropical' running capacitor - compressor can start witch full pressure on high pressure side in most case and is why capacitor in 'tropical' kit used to handle situation as small and short break or brown out on power line come very often and be sure compressor starting up quick again with PTC still hot and not conduct current (ie PTC-start is complete useless in this situation).

And last - running capacitor give many time better power factor on compressor under running condition and reduce starting current to almost half of current compare to using PTc/ePTc starting methode...

ie. important fact if you want starting and running on smaller sinus shaped UPS/converter from battery, but in this case need modify or remove starting device so PTC not working at all in start moment and use running capacitor as 'tropical kit' value on capacitor connected between R and S connection on compressor...

But... (in case modification for lower starting current for feed from UPS/converter)

Danfoss compressor have klixon safe protector embedded inside compressor in many ears and possible to remove starting device complete and mount mains to R and C and mount running capacitor between R and S for both starting and continue running without any relay or PTC starting device

BUT - dont try this on compressor from other manufacture if not be sure is klixon inside starting device (not mounted inside compressor in most case) placed right and pressed to compressor surface and working after you take PTC out of order inside starting device - is only protector device from make compressor to fire bomb if compressor not starting in some reason.

David Heaf
15-10-2014, 06:21 PM
if not started even if capacitor mounted and only humming - compressor is broken...

Thanks for your detailed suggestions. But my issue has taken a very unexpected turn. When we discovered the fridge-freezer failure, the compressor had a just audible hum coming from it, and the compressor housing was too hot to leave my hand in contact with it.

But a neighbour's friend familiar with refrigeration agreed to come an look at it. He unplugged the ePTC and then plugged it back in. On power-up the compressor started! The appliance is behaving perfectly normally now.

David Heaf
15-10-2014, 06:45 PM
If you give send the details of the compressor model I can tell you what the resistances should be

I've only just spotted your post. Thanks Glenn. This would useful for future reference if it is not too much trouble, but sadly the thaw water pipe seems to have been misaligned and some of the compressor's model number is now erased. All I can discern now is NLX 8.8K and the bottom of the next character. Other numbers on the label are 105H and 6874.

I've added a short aluminium chute below the thaw water pipe to ensure it drips into the catch-tray for evaporation.

15-10-2014, 08:39 PM
you have all information you need for searching on Danfoss :-)



if compressor starting after removing and mount back ePTC - look for lose connection, burned pins and socket for pin inside ePTC etc. electrical error

have compressor running capacitor ?? (look pdf-data sheet above so you have idea what for component to look after)

Glenn Moore
15-10-2014, 09:34 PM
Hi David
For your info the resistance of the Main Winding is 26.2 Ohms , the Start winding is 48.7 Ohm

When you pull the relay off the compressor it will expose 3 pins . 2 at the top and 1 at the bottom . The top left pin to the bottom pin is the Main winding, and the top right pin to the bottom pin is the Start winding. Across the 2 top pins is the total of the Main & Start windings ie 26.2 + 48.7 = 74.9 Ohms approx at 25 Deg C Kr Glenn

David Heaf
17-10-2014, 09:02 PM
Thanks Glen and xxargs. I've filed all that away on my PC for future reference should this glitch happen again. Hopefully when the compressor winding was powered but not started and the pot warmed up, the windings were not somehow reduced in their lifespan. Anyway, the applieance has now been on test for several days and seems like it always was. We'd claimed for the damage by lightning and the insurer's cheque has arrived. Now we've got the stricken appliance going again, we'll be returning the cheque!

David Heaf
09-11-2014, 11:24 AM
the appliance has now been on test for several days and seems like it always was.

It's been OK for 3 weeks now but we monitored the freezer temperature and found an anomaly. It is -23C even though the control panel setting says -18C. (This is a Bosch KGU36005GB/03 dual evaporator A-rated fridge-freezer with 263 litres net capacity new in 2006.) So I put an electricity meter on it for a week. The consumption result came to 390 kWh per year. It cycles on/off and the fridge compartment is close to the set temperature. We had never checked the freezer temperature before the aforementioned electrical storm affected the ePTC, so do not know if it had always been running cooler than it should be.
Interestingly, the new similar sized unit we had bought in error also ran below -20C when set on -18C.
Two questions: 1) Does anyone here have access to the original kWh/year test result for this appliance? 2) Would 390 kWh/year for this A-rated 263 litre unit seem excessive?
Current A+ rated fridge-freezers around the same capacity use around 285 kWh.