Interference on HF from central heating

Discussion in 'EMC Matters' started by G4CLY, Jan 30, 2020.

  1. G4CLY

    G4CLY New Member

    I experience intermittent interference on the upper HF spectrum including 18MHz, in the form of S5 signals spaced about 16kHz each with a comb of sidebands at n x 100Hz ish. I initially suspected television but soon confirmed that it is definitely my central heating system. With either hot water or central heating on this interference is present and it goes away when off. I have British Gas UP2 controller downstairs and Grunfos Super Selectric pump upstairs. I can "Sniff" with a Sony portable and the noise peaks to a similar level at both components but am unable to determine which end is the culprit. Has anyone else had experience either with these components or similar central heating EMC? Are central heating pumps powered by chopped AC?
  2. Bob Bennett

    Bob Bennett New Member

    Has this interference appeared recently or has it been there for some time did the appearance interference coincide with anything changing on your central heating installation ?.
    I am aware of a similar problem which started when a new boiler was installed and the problem was down to missing filter components in the boiler control unit.
    Bob G8BFF
  3. Ken G3SDW

    Ken G3SDW Moderator

    Yes Bob is right to ask those questions which are very important.

    If your boiler is under some sort of warranty then a call to them for help would not go a miss, as something is not right.

  4. Ken G3SDW

    Ken G3SDW Moderator

    Just been looking at the British Gas UP2 controller, which in fact is a re badged Drayton LP722, it is AC fed but my thoughts are that they may well have an internal PSU which i am, sure is a SMPS.

    As for your Grundfos Pump then that has an AC supply.

    Next question is what type of boiler are you using?

    Ken G3SDW
  5. G4CLY

    G4CLY New Member

    Thank you both. The boiler and, I think, the controller were replaced in 2009. So out of guarantee although covered by British Gas maintenance agreement. I haven't been active on HF since 2008. Up until then I used to use 28MHz only. I don't remember it being a problem then. Boiler is a Baxi Combo, described on the commissioning as "Conventional, Condensing". I would doubt it is the SMPS in the controller as with the CH on but below thermostat the controller is on (LED on) but there is no noise. The pump is a UPS 15-60 130, now obsolete. I agree that it looks like AC supply. I think my next move will be to put clip-on ferrites on the controller mains.
  6. Ken G3SDW

    Ken G3SDW Moderator

    Well Nigel you can do that but i think that it is a very good idea if your system has a maintenance agreement that you should contact British Gas fists.

    If you still feel you want to go down the ferrite route and there is nothing wrong with doing that then it is most important to use the correct grade of ferrite as any old clip on will not be good enough.

    To find out the information then go to this web site by Ian GM3SEK who gives you all the details of what to use and were to go to get them.

    Good luck and we are always here to help at all times.
  7. G4CLY

    G4CLY New Member

    Thanks for the ferrite reminder and yes, I agree about taking it back to the maintainers. I would like to gather as much information as I can first though to maximise the chance of them fixing the problem first time.
    Thank you again Ken and Bob. If/when it gets fixed I'll update this.
  8. Ken G3SDW

    Ken G3SDW Moderator

    OK Nigel, dont be surprised if who ever comes to see you has not a clue about EMC/EMI problems.

    He will have two choices, either the controller or the boiler its self, my bet is the boiler, so all they will be able to do is to replace the boilers control panel as they are not technical enough to repair to component level.

    Look forward to the outcome.
  9. Ken G3SDW

    Ken G3SDW Moderator

    Hi Nigel, how are things going with your RFI problem??

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