Mains filters aaarrrrgggghh!!!!

[kityuser]

Mrs KU blew up the dishwasher over the weekend, so a trip to B&Q saw us the new owners of a shiney new integrated dishwasher *fanfare*.

all plumbed in and ready for the off when *puff* turning the plug on causes the RCD to blow in my consumer unit. Reset everything, try again........ *puff*

good earths (checked all round), try again with the dishwasher left on this time (at the plug), tripping the RCD back on results in a working system *horah!*.

Now I had these problems on my old dishwasher, except it required a binning of the mains filter. I tried a replacement which was just as bad. I`ve a 6 month old consumer unit, brand new RCD all up to current regs.

shunt caps in the mains filter need VERY careful balancing to allow these mains filters to play nice with RCDs. Slight in-balance and one side charges slightly faster than 'tother, and *puff* the RCD thinks somebody is getting a belt (current in-balance in the live and neutral for a short amount of time).

I`m sick and tired of all this! buy a new bit of gear and I`m never sure when I plug it in if I`ll be going around and reseting all our clocks again when the RCD trips.

is a more tolerant RCD the way to go?

is anybody else plagued by this?

Steve

 

[RogerS]

I can understand your logic and I can feel the frustration all the way over here!

What I can't fathom out is what the difference is between having the dishwasher on and then effectively turning on the electricity via the RCD and the other way round. If it was a capacitor imbalance then surely it would trip the RCD in both cases? Could it be that the switch on the dishwasher closes one leg (L or N) a fraction of a second before the other?

Might be worth posting on AskTheTrades.

Roger

 

[kityuser]

I can understand your logic and I can feel the frustration all the way over here!

What I can't fathom out is what the difference is between having the dishwasher on and then effectively turning on the electricity via the RCD and the other way round. If it was a capacitor imbalance then surely it would trip the RCD in both cases? Could it be that the switch on the dishwasher closes one leg (L or N) a fraction of a second before the other?

Might be worth posting on AskTheTrades.

Roger

I think the logic is that its the current in-balance is the initial closing of the mains switch, if one of the shunt caps charges slightly faster than the other (in-balanced) then the RCD trips. If you trip the RCD back with the dishwasher on, then I believe the few micro seconds of in-balance (in the mains filter) are negated as you are "switching" the RCD back on again (probably several miliseconds of hold on the RCD switch). Also I believe the mains filters have both live-earth and neutral-earth leakage paths that would also require careful balancing.
These things are generally transient current spike which are only a problem when turning the machine on, when the caps in the mains filter are initially being charged.

Ironic that the mains filter, which is suppose to suppress EMC interference (both into and out of the machine) is causing the RCD "interference".

tut tut tut

Steve

 

[RogerS]

I feel a pair of snips, some wire and a couple of choc blocks are going to be featuring soon :wink:

 

[Racers]

Hi,

Been there had to go round a whole room of computers turning them all off before switching the power back on.

Pete

 

[DaveL]

Been there had to go round a whole room of computers turning them all off before switching the power back on.

You did well, I had rooms of machines at college like that.

At work, in our last building we had a floor were if the mains died we had to raise a call, the breakers were in a locked cabinet. We were 24*7 back then, the site guys did not like turning out at 2:30 on a Sunday morning. :roll: