In reply to a post by billford:

Andrew said that it doesn't happen every time, so I'd guess that it's not the ignition per se, but whether it's the transformer or a fan there's an inductive load suddenly being switched in- do that at the wrong moment in the mains cycle and there'll be quite a spike.

A filter in the supply to the router might do it... I run mine from the UPS, but that might be an expensive cure if there isn't one already there!

I tried a filter in the router supply last night but it didn't make any difference. I already have a ring ferrite on the supply lead from the PSU to the router. That's been there for over a year just as a precaution and I had one in stock anyway

Yeah remember that, but forgotten all the ways of estimating what is the best size/type of ferrite core for suppressing noise.

As a note: It may not happen all the time, as while a spark is often very similar, sometimes it may just arc a little differently across the gap and this is when the noise occurs.

Could try just wearing lots of jumpers.

I can recommend these 'power conditioners': http://www.amazon.co.uk/LINDY-Mains-Conditioner-Powe...


NB. As others have said it does sound as if the boiler probably has a faulty component...

In reply to a post by MrSaffron:

Could try just wearing lots of jumpers.

And save on the cost of oil! We do have a wood-burning stove as well

Thanks but I'd have to put a 13 amp plug on the boiler!!

Or you could just plug your router into it!

In reply to a post by b4dger:

Or you could just plug your router into it!

I have a single 13A mains filter (looks like a two way adapter with only one socket) that I have already tried on the router mains feed. No difference

I've an inline supression device from RS on my boiler, seems get rid of the nasty stuff. Will have a look for the RS stock code when I get home.

Thanks, please let me know what it is!

Here you go, RS part no 3256543 Link hopefully that will work, always seem to have problems with links to RS. There is a higher current version.
Got rid of the rubbish on the mains from the fan and pump from my boiler, also stuck a cap on the room thermostat just for good measure .