Heating kicks in = television picture freezes!

Volcano

Everytime my oil-fired boiler starts up, my tv picture freezes (though I have intermittant sound). It lasts for about 20-25 seconds, then stutters a bit before returning to normal. I get less disruptive 'jumps' in the picture that coincide with other appliances going on and off: freezer, washing machine, even the fridge light coming on! Though the kettle strangely does not affect it.

I have an LCD tv connected to a digital hardrive recorder. Signal strength is poor in my area so I have to use a booster. (I'm guessing that the current draw from the boiler igniter temporarily reduces the current available to the booster, resulting in not enough signal strength for the picture, which then temporarily 'messes up' the digital decoder.)

Recorded programmes are fine when played back and the heater kicks in, though if recording a programme when the heating starts then the recording will jam completely (i.e. just a single frame will be recorded for the entire programme length).

I've connected a surge protector to the signal booster, but with no difference.

Any ideas about what else I could try?

totalsolutions

Get an electrician in to check out the wiring arrangements and voltage at the sockets, a simple (but expensive Fuke DVM) will monitor the power line for noise/gliches/spikes.

isofa

totalsolutions wrote: »

Get an electrician in to check out the wiring arrangements and voltage at the sockets, a simple (but expensive Fuke DVM) will monitor the power line for noise/gliches/spikes.

Or Fluke?!

Often in new houses, anything taking a large current draw causes a voltage drop across the sockets, we get this to a tiny degree when the kettle is on.

I'd definitely get an electrician in as totalsolutions suggests, the power drop / spike is obviously significant and affecting the TV.

isofa

Or it could be a fault with the heating, drawing too much power when it starts... either way get it checked.

xenon2020

Switches are notorious for causing interference with digital TV reception. It is likely to be picked up by the aerial, or possibly a badly shielded aerial cable. The booster is only going to amplify the noise of the switching (in this case inside the boiler). Does the aerial booster have an adjustable gain? If so, then try decreasing the gain a little.

kev_min

I am guessing that this is digital TV rather than analogue? If so it could be related to the TVs aerial system, as playback of previously recorded material is ok. Digital TV is prone to "impulse" interference, that can manifest itself amongst, other ways, by pixelating or freezing of the picture. This could the boilers ignitor generates a series of electric arcs which can be picked up by poorly screened TV aerial cable, the aerial itself or even the "boosrter". If you are competent I suggest ensuring ALL tv coax is good quality double screened, and that the aerial is fitted with a balun, as these measures will help reduce any interference. if its not within your abilities look for a local CAI approved aerial installer, if you explaining exactly whats happening they should be able to help.

espresso

It's nothing to do with the house wiring/voltage/heating system drawing too much current etc. etc.

You simply have insufficient signal level and therefore your signal to noise ratio is very poor.

You say that the signal strength in your area is poor so you have to use a booster. This booster will amplify any noise/interference as well as the low received signal level.

What you need is an external roof mounted aerial with a good quality low loss double screened downlead, preferably straight into the Freeview receiver without any wall plate/patch lead etc. If an amplifier is to be used, it should be a low noise masthead amplifier fitted close to the aerial.

If your boiler is controlled by a room stat, the cable from the stat back to the boiler will be acting as an aerial radiating RF interference caused by sparking when the contacts close.

The surge protector that you have fitted, has no effect because it is radiated interference that is being picked up by the Freeview receiver, not on it's mains supply.

A suppressor across the stat may work but your problem would definitely be solved by providing a better signal from a properly installed aerial.

kwikbreaks

It's nothing to do with voltage drops. The kettle will take lots more current than the boiler pump and the kettle doesn't cause a problem.

There is no doubt in my mind that the boiler pump isn't properly suppressed and is creating a huge splash of RF noise each time it switches and because the TV signal is so marginal that interference is enough to scupper it.

It will be interfering with neighbours too I imagine and if you have ADSL broadband that will suffer too.

Mark_Hewitt

As others have said, it's a signal interference problem. We had a thermostat like that which was faulty and kept switching several times a second. It caused lines to appear on the TV and you could hear it clearly through the radio.

Fifer

What espresso and kwikbreaks said.

I'd start by making sure the aerial signal route (both sides of the booster) uses good quality (CT100 or better) coax and that the screen (and core) is properly terminated at all connections (including at the aerial itself and behind the aerial wallplate). If possible, a good aerial installation which eliminates the booster would probably help enormously.

Volcano

Many thanks, that's given me plenty of options to look at!

The interference definitely coincides with the boiler's igniter firing; the boiler's blower (a large electric fan) and heating water pump come on briefly before the igniters fire up with no interference at all.

Thanks again