"Settling in"?

[Chuck U Farley]

This is going to sound like a stupid question, but meh...

I have re-wired a local gym and one of the circuits which powers their treadmills has tripped a couple of times, for no apparent reason. Obviously, all was good on the installation test, although I did use budget CU and RCBOs, and the kit has passed PATs.

Now the "Wise Old Spark" has shrugged and said "The RCBO's just settling in, it'll be OK after a few days and the only time you'll see that breaker off is when you press the button to test it. It happens all the time with new RCD/RCBOs..."

Part of me thinks "Ah, OK, sounds reasonable" and another part of me says "MOOOOOOOOOOOOO, that smells like BS". Which is more likely? (And I realise already - "Don't use cheap cruddy Curve boards")

 

[NozSpark]

TBH I thnk you're right, I've never heard of "settling in" regarding RCBO's

Unfortunately though as it's a RCBO that's tripping you don't know wether it's tripping on overload or fault.

It could also be that the RCD portion is tripping due to cumulative "allowable" earth leakage

 

[SLIPSHOD & SLAPDASH]

Big BS, but i suppose you could say the livening up of equipment that has been powered down for some time may need 'settling down' ie drying out any damp.

 

[Technician]

I have heard of RCD disconnection time increasing

because of dirt on the contacts, which is only burned

off by a couple of operations when on test.

 

[ProDave]

Could be something loose inside the treadmill that only shorts while it's being pounded, which could explain why it passes a PAT test.

The RCD "settling in" is BS

I have a similar one to investigate. An electric boiler tripping it's MCB. The MCB is 50A and the rated current is 45A. I've replaced the MCB and measured the current, all within limits, but still it trips on average once a day.

I'm going back next week and have given the owner instructions to turn the boiler off overnight and leave it off until I get there, so it will have a prolonged period of maximum demand when I get there. Advice he ignored last time as it was on and running when I got there, that's when I swapped the MCB.

 

[NozSpark]

I have heard of RCD disconnection time increasing because of dirt on the contacts, which is only burned

off by a couple of operations when on test.

I and others have said this before,

NEVER NEVER NEVER excercise an RCD to get it to pass the tests, you or someone else will not get a second chance when it has to operate "in anger"

---------- Post Auto-Merged at 13:30 ---------- Previous post was made at 13:27 ----------

Could be something loose inside the treadmill that only shorts while it's being pounded, which could explain why it passes a PAT test.The RCD "settling in" is BS

I have a similar one to investigate. An electric boiler tripping it's MCB. The MCB is 50A and the rated current is 45A. I've replaced the MCB and measured the current, all within limits, but still it trips on average once a day.

I'm going back next week and have given the owner instructions to turn the boiler off overnight and leave it off until I get there, so it will have a prolonged period of maximum demand when I get there. Advice he ignored last time as it was on and running when I got there, that's when I swapped the MCB.

I've had an electric boiler do this to me,,, I found that it must have been tripping the thermal trip because of heat build up due to the amount of time that they are on for and adjacent devices. Luckily I'd supplied it from it's own CU and was able to move the MCB to allow full module gaps beside it.

 

[apprentice87]

Hi All,

"NEVER NEVER NEVER excercise an RCD to get it to pass the tests, you or someone else will not get a second chance when it has to operate "in anger"

Would agree with that 100%...... Bit pointless if you have to try it a few times to get it to "free off" or what ever.

As Nozspark quite rightly points out, someone receiving a shock will not have that luxury.... They are hardly going to electrocute themselves several times until they are satified that the shock was "not that bad" cos it switched off very quickly !!!!!

john...

 

[OnOff]

Do the treadmills have an inverter / VSD / aka a speed drive in them? Been through something similar. To comply with CE marking they (drives) have to have EMF filters thus inverters are known to be a bit leaky. Option to fit a drive WITHOUT filters but then it's not CE compliant. Or...fit a 100mA trip...but an obvious no-no! So, what to do. Well Merlin Gerin do their Multi-9 "Si" RCD for "sensitive installations". Not sure if they now do it in a RCBO version though! Worked for me, we used to have about a 25% tripping rate. Don't get the "Si" confused with an "S" type though.

http://www.precicon.com.sg/Portals/28/docs/Merlin%20Gerin/RCCB%20-%20Datasheet.pdf

(IMO it's either that or some big fat bird's sweating all over the machine and the RCD's only doing it's job! In that case it's an IP issue!)

 

[Technician]

"Exercising" an RCD is not something I have

done; I know a lot of people who do it, just to

get the disconnection time down.

 

[OnOff]

Not forgetting that lack of "exercise" can be just as bad for them!

Just thought I better clarify that! I meant as in testing regularly!

---------- Post Auto-Merged at 19:32 ---------- Previous post was made at 17:38 ----------

Out of interest did you do a ramp test to see what it's tripping at? The inverter issues I had - sometimes it would trip it, sometimes it wouldn't. This on more than one job BTW. They were SEW inverters.

 

[sellers]

Does the treadmill require a different type breaker? Due to startup current? Maybe a C or a D? If so change it but make sure your Zs is acceptable.

 

[OnOff]

Does the treadmill require a different type breaker? Due to startup current? Maybe a C or a D? If so change it but make sure your Zs is acceptable.

Pity the OP doesn't have a separate RCD and breaker!

 

[NozSpark]

Pity the OP doesn't have a separate RCD and breaker!

Then he'd at least know why it's tripping

 

[batty]

Well I would certainly think they should be on C types is it one RCBO per item?

 

[Chuck U Farley]

Thanks for the replies. I was actually mistaken, it wasn't the circuits with the CV equipment on, it was actually a circuit which powered up their TV screens, and true to form, there's not been the slightest hint of a problem since that one day...

 

[ProDave]

I had to do a minor alteration to a house which involved moving a couple of sockets a short distance.

Half an hour after I left, phone call, RCD is tripping.

Went back and checked, it was the circuit I had altered had high leakage. Oh bu99er.

Unplugged everything, IR and continuity fine. Started plugging things back in, plug in shiny new flat screen telly, RCD trips.

Customer was not amused.

 

[revjames]

are they C curve RCBO's or just 'run of the mill'.... sorry couldnt resist :coat

 

[Nicky Tesla]

You know how solar panels get their energy to credit the meter so to speak, would it be viable for a group of treadmills to be connected to the meter somehow. I think it could be a possibility if panels and hardware are already installed and the treadmills were just an addition.

 

[binky]

'Thanks for the replies. I was actually mistaken, it wasn't the circuits with the CV equipment on, it was actually a circuit which powered up their TV screens, and true to form, there's not been the slightest hint of a problem since that one day... '

so what happened to the circuit schedules then :^O