work this one out

[happysteve]

(Trainee, so bear in mind that some of what follows may be utter cr@p)

You mention solid fuel - out in the sticks by any chance? Reason I ask, (my understanding is that) if you're a long way from the substation/transformer with a relatively low current capacity supply cable - larger resistance - then any extra loads will lead to a larger volt drop than usual. If the motor is pulling a large current at start-up, then this could cause a temporary voltage drop that affects your DVD player.

(EDIT: We had this where we lived when I were a lad. Long way from substation. Poor overhead lines. My poor Commodore 64 was forever glitching and resetting, and it took so long to load Horace Goes Skiing as well!)

That might be part of the problem, but you said that if plugged into the cooker socket it was ok.

Same principle also applies on the final circuit. 20m of 2.5mm on L and N is about 0.3 Ohms, if your pump is briefly pulling 30A that's 9V. If the DVD player is sensitive then this could cause it to throw a wobbly.

How to diagnose? I (naive trainee) would consider doing the following:

- measure r1 and rn on your RFC
- measue the voltage drop with a fast-reaction voltmeter when you switch the pump on/off (on the same cct)
- measure the current pulled by the pump as it's turned on: either use a plug-top power/voltage/current meter, make up a plug to socket extension lead in singles and stick a clamp meter around L or N
- see if the above 3 measurements follow Ohm's law
- see if you can get any specs on the pump (particularly start-up current) - it may be faulty, or there may be a problem with the installation

Whatever it is, hope you find it, please let us know how you fixed it

 

[Lagentium]

I've seen this happen before albeit in different circumstances and I will put my tin hat on incase Glenn wants to throw anything at me. Does the system have a wireless thermostat or anything along those lines?

 

[Resu]

Thanks Murdoch, if i was on the pc i would like your post but im on the tablet sorry mate!

You should still be able to (I'm presuming Tapatalk) by clicking on his reply to highlight it and it gives you a few options including quote, like, thank, etc.

 

[Marvo]

Ive made the (potentially foolish) assumption that we are talking about a circulating pump in a heating system, but await correction by the OP

I'm genuinely clueless as to what type of pump this is, you might be right with the circ pump assumption. Some more info from the OP would be good.

 

[Lucien Nunes]

All normal domestic size circulator pumps are either PSC or electronically commutated PM. I'd hazard a guess this one is a regular PSC motor and the switching transient (not starting current, the radio-frequency interference spike caused by the closing and opening of stat contacts) is being picked up by the DVD player via the circuit. If that is the case, you won't find any electrical fault, or excess voltage drop, or anything like that. The test would be to fit a transient suppression VDR across the pump.

I've had this in various guises - Plasma screen goes off when the electric blinds hit their lower limit, lighting presets erase themselves when the motorised screen retracts. It was always a switching transient and the VDR or other suitable suppression always cured it.

FWIW, DVD players often have global power supplies that will work all the way down to 90V, in which case voltage drop is unlikely to be the cause. Some home electronics are unreasonably touchy about interference, it would be interesting to know if the replacement DVD player was the same model as the original, in which case it could be a design fault with that model. They are not usually earthed nor are the power supplies very heavily filtered.

I am not sure about the phone charger. The current there is so incredibly tiny that I can't see any electrical factor being the cause unless there really is a loose connection nearby and dropping the phone on the base disturbs it. But RF, the phone or charger could be emitting a burst of interference at the moment the two connect.

E2A more thoughts about testing, if you don't have a scope or a meter with graphing function to log the voltage, plug a low wattage filament lamp into the same socket as the DVD and have a de-tuned AM radio nearby. When the pump starts, if the lamp flickers but there's no 'pop' from the radio, it's voltage drop, vice versa it's interference. I would think that a voltage sag bad enough to crash a DVD player would be visible on a 40w lamp but again it could be a faulty design that's hyper-sensitive. Any significant switching spike usually makes itself heard on a portable AM radio.

 

[Benjamiin]

sorry for the lack of replies, I fell asleep! it is just a run of the mill central heating pump! thanks for all the replies , I've got a lot more to go on now! I'd reached the stage where I was considering telling her she had ghosts haha!!