RCD at QTH tripping on transmit

Discussion in 'EMC Matters' started by M0TYB, Dec 11, 2018.

  1. M0TYB

    M0TYB New Member

    I am having frequent problems with nuisance tripping of my main house RCD when transmitting. This occurs both when I transmit from my base station rig (between approx. 25W to 100W), and when using a small VHF handheld. Occurs with two base station rigs (FT450D and IC7300) and Yaesu Handheld on SSB, and FM, respectively. Base rigs are powered by MyDel switched mode PSU; and earthed in accordance with instructions.

    Have experimented with different shack locations within QTH and makes no difference. Antenna is a HyEndFed long wire, fed by RG213, and earthed in accordance with instructions. Problem diminished (but not eliminated) as feed point moved away from house. Mains supply has TT earth - all tested and OK. Temporary dipole antena still causes the trip. No tripping with dummy load!

    Investigations so far suggest possible RF pickup by mains wiring, although not confirmed. Is it possible - and likely - that the RCD (100mA on main household consumer unit) is faulty? Could anyone please advise on how to resolve this?
  2. Ken G3SDW

    Ken G3SDW Moderator

    Well the very first and simple thing is to do is to replace the RCD, best policy is never initially go in too deep as sometimes it is staring you in the face.

    You say RF being picked up on the mains wiring, i am sure that the mains wiring see`s RF but other than you have to many RF voltages floating around then the mains wiring should not be a problem.

    If you can do this and then get back to me.
  3. SSP

    SSP New Member

    A few thoughts
    It may not be that simple to swap out an RCD and it's possibly something that should be done by a qualified electrician (OK most hams have a level of knowledge equivalent to or above those of your average Sparky) but if you are affecting Kitchen or bathroom circuits when you change the device you could be opening yourself to problems. (Schedule P and all that!)
    A 100 mA RCD is not intended for 'human protection'. The usual rating is 30mA. Ideally you should have the latter in your home on the power circuits.
    I do not have 'in depth' knowleddge pf the topic but I'd say that RF transmissions would induce voltages/currents of equal value in both the live and the neutral sides of your supply and therefor NOT throw and RCD out of balance.
    So something else seem adrift.
    Can you isolate ALL appliances both poles in your home so that just your PSU is connected? Then when you transmit, does the RCD still trip? If not switch/reconnect one appliance at a time until it trips. There could be something awry with that appliance.
    If it keeps happening, I'd get a qualified electrician to do a an in depth survey of the wiring and plan from there.
    (As of next year I believe it will be mandatory to have separate RCD's on lighting and power circuits (so you and you family are not plunged into darkness when the electric oven heater element fails - as happens to me on my crappy Hotpoint oven every 18 months or so) - new installations that is; not sure what happens if you rewire.
    Steve G4SDM
  4. gm3sek

    gm3sek New Member

    If even a VHF handheld is causing the RCD to trip, that isn't just an "RF problem" - it simply should not be happening. It seems to indicate a definite fault of some kind, which could have other safety implications as well.

    What happens if you bring the handheld close to the consumer unit? If it trips, then what happens if you reduce power and bring it even closer to the RCD itself?

    73 from Ian GM3SEK
  5. Ken G3SDW

    Ken G3SDW Moderator

    So Ian if it is not the RCD itself then what do you suggest it is??
  6. M0TYB

    M0TYB New Member

    Thanks everyone for your thoughts so far.

    Firstly - I would not contemplate changing the RCD myself! To me this is definitley a job for a qualified electrician, and once I have found one that is prepared to do it, I will let you know the outcome!

    I have tried isolating everything else in the house (by unplugging, switching off FCUs etc.), and it still trips. I have gone on to turn off all the MCBs to the individual circuits and the same thing happens, although I appreciate that the circuit MCBs in the CU presumably do not disconnect the neutral wires.

    I have experimented with the handheld VHF at varying distances from the consumer unit. It seems to trip when within say 10' of it, whether the circuits are switched on or off, and certainly happens when used within a couple of feet of it.

    It feels as if the RCD itself is the only plausible culprit. I guess the only other test I could do is to have all the house circuits disconnected in the CU (live and neutral) and see if it still happens.

    Any further thoughts please?

    Thanks again!
  7. Ken G3SDW

    Ken G3SDW Moderator

    Tony, so how long has this been going on?, did it coincide with anything at that time or just come out of the blue.
  8. M0TYB

    M0TYB New Member

    Thanks Ken, it has been happening intermittently ever since I moved into my present house, therefore for several months now. Consequently during this time I have done a lot of experimenting (location of rig within the house, antenna configuration etc.), although relatively little ongoing operating unfortunately! The VHF handheld is a more recent phenomenon, since I have had it only a few weeks. I discovered this by accident when I happened to be within a few feet of the CU. (I had no problems in my previous QTH, not that that helps us much!)

  9. Ken G3SDW

    Ken G3SDW Moderator

    Well Tony as you do not have any history of the house, assuming that it not a new build, wiring then it would be sensible to have the complete wiring installation checked out by a registered and qualified electrician.
  10. M6IQW

    M6IQW New Member

    I am experiencing something similar. I have had a new RDC fitted (manufactured by Proteus) to replace a failed MK one. Both are identical spec (30mA / 30 mS). On transmit on 15m it now trips when the power reaches ~50W (RTTY). No problem on 20m. I've tested my switch mode power supply and it's leaking a couple of mW at 40W so I don't think it's that unless there's a sudden increase in the leakage as I increase power above 40W.
  11. M6IQW

    M6IQW New Member

    PS, My user name is M6IQW; I'm now M0LDP hence my transmit power above 10W
  12. Ken G3SDW

    Ken G3SDW Moderator

    Well if they are both the same spec then it is most likely the new RCD, old one no problem, new one a problem, get it replaced.

    That is the only way forward.

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