Hello You have a problem that requires people with experience in searching for electrical failures, it is not very likely that you can find it easily. The case you describe is very possible that you have the neutral to ground , because what you say the thermal are unipolar and do not cut the neutral, it is the most difficult case to find. I will give you a guide of how to look for failures, tell me that you do not understand Search for earth leakage in residential facilities The following is for 220v single-phase rush voltage, for 220v three-phase rush there are extra considerations to keep in mind that I will already mention. The necessary elements to look for an electrical leakage to ground can be a differential circuit breaker connecting it to the circuit that you believe is responsible (for not having it in the main panel); you can also with an Insulation Resistance Meter (megometers), but it is not usual in the guild at least in most of Argentina (if in Spain or Europe it is easy to buy them, here they practically do not exist for such use); or having a lot of experience, in the old style through a 5w lamp in series with the installation (this system was used when it was not possible to "see" the leak in the meter and the differentials did not exist), with multimeters or other elements High impedance is not sought. If the leak is large, its existence can be identified by watching the meter rotate. The electrification zone of walls and pipes does not indicate the location of the leak, in fact it may be in a rush of the house or of a neighbor; the electrification zone which indicates that it is a zone of good conduction, be it metal or moisture in the wall. The capacitive pager, the one that turns on “the tip or head” is ideal to identify the electrification zones (not leaks). Fundamental search concept For fault searches you must have experience in home electricity, it is searched methodically and systematically; it is not necessary to disarm by disarming. [/B] Basically, branches should be separated until practically a few mouths are reached that can be responsible for the leak. [b] Some considerations If the differential circuit breaker exists in the house, and this “jumps”, we must verify with the test button that it works well, for this we section all the “downstream” circuits, to have double thermal no difficulty, or disconnect the cables of the differential circuit breaker output and we tested it. The test with the differential button is sufficient to be considered in good condition. If it is not placed, it is necessary to place it provisionally to look for the leak, then advise our client to make it definitive. The leaks can be in the live or much more difficult to find in the neutral: they can also be intermittent, which makes them a serious problem for the time necessary for their location. - Before wanting to do any test, we must disconnect all non-fixed connection artifacts. If the leak persists, we continue. There are a number of steps, which if followed should lead us to find the problem in a couple of hours. - First we tested the differential circuit breaker as I mentioned. (When in doubt we change the differential for a reliable one). - We determine in which circuit the leak is, if you have bipolar, it will not present many problems to know; of having simple thermal and if sectioning continue the problem, it is because the leak is in the neutral. At this time, we test a resource that sometimes saves us search time, we open all the ignition keys (that are turned off) all the luminaires and turn the installation wires (inverted) after the cutting key and before differential, you may hook, if you do, first we test with the simple thermal, which will guide us the sector, then turning on luminaire by luminaire and the fault may appear. WE MUST NEVER LEAVE AN INVESTED INSTALLATION, BECAUSE WE MASK THE FAILURE AND IT IS DANGEROUS If everything stays the same, we replace the cables as before. - If we find the circuit with failure, we replace the rest to know which area is the one that has the problem, then we cut for the search. So far we have only delimited the fault sector, or directly we have the whole house without tension, to go now if to the search, we must look for the distribution box of the area with problems where the rooms are divided. Once this is done, part of the distribution in THE DISTRIBUTION BOXES that are in that circuit begins to separate; for this we can start from the furthest part of the house, from the middle part or the one closest to the board. The distribution boxes can be 10 x 10 cm boxes, or octagonal boxes on the wall, it may also be that an installation is distributed through the central boxes on the ceiling, in those boxes the branches of the same branch are branched or derived circuit. let's see this example ... in a distribution box of one of the three rooms that have a problem, we check how many line cables there are, then we separate them all (four live, four neutral in the air); we go and lift the thermal, ... if it jumps the same, it means that everything after the splices is fine (we leave everything like this and look for a PREVIOUS registration box and repeat the process); if it does not jump, with a pager we identify the living and neutral that are active, and we begin to connect a couple of lines until it jumps; When I jump, we know it's from there and the rest is not. The process of separation of lines, connection and disconnection is repeated as we proceed in the area that originates the fault, in the branch that is well we leave it connected It must be methodical until it is oriented in which branch the tripping of the cut-off occurs, do not disassemble by disarming, do not disassemble exits, sockets, lights, unless there is a very strong reason (humidity, exterior lights, etc); you must go disconnecting circuits in the junction boxes of each room, and see that it covers To the aforementioned there are exceptions, in rainy weather begin by checking external luminaires and power lines. Caution with three phase In the case of three-phase installations of single-phase circuits of different phases with neutral in common, if we disconnect the neutral, the installation is between phases and we will burn something, and surely sooner rather than later this will happen, we will disconnect the neutral and SOME SECTOR WILL REMAIN BETWEEN 380V, so we must temporarily convert the three-phase installation to single-phase until we find the problem, then normalize. It is possible that each circuit with its neutral does not intersect with another phase in the same pipe, but just in case ... Using this form, the entire sector is systematically reviewed WITHOUT DISARMING A KEY, when we reach the point where there is no problem. more leads, check if the key or apply has contacts with the box, wet spider webs or the cable of that piece is stripped. This job requires experience and patience, you learn little by little and you have to be VERY CAREFUL when working with tension. When we connect and disconnect many times, it is not uncommon for us to get confused and touch the conductors with the connected voltage believing that we had cut it. Diagram that exemplifies what has been said