batman88
Newbie
 Offline
Posts: 3
|
 |
« on: January 23, 2012, 03:57:25 PM » |
|
One of our customers has a 4kW system, feeding into a dedicated circuit on an outbuilding'sconsumer unit which in turn feeds into a dedicated 32A circuit on a larger consumer unit. It's started tripping the main switch every time it powers up in the morning (after which it's ok, apparently).
Any ideas what might cause this? If it's a short, then I wouldn't expect it to work once it has been reset. I wondered if it might be faulty wiring to the RCD on the main consumer unit (ie neutral to non-RCD side of a split consumer unit, and live to the RCD side)
Any suggestions?
|
|
|
|
|
Logged
|
|
|
|
|
GavinA
|
|
« Reply #1 on: January 23, 2012, 04:32:15 PM » |
|
sorry, what's it actually tripping - an RCD or MCB?
|
|
|
|
|
Logged
|
at home | 80 tubes, 2 tanks direct PV powered SWH + 5 x Yingli 185Wp solar PV panels.
|
|
|
|
Pat_
|
|
« Reply #2 on: January 23, 2012, 05:02:01 PM » |
|
and is it a TT supply?
|
|
|
|
|
Logged
|
|
|
|
|
Justme
|
|
« Reply #3 on: January 23, 2012, 05:19:55 PM » |
|
If its the RCD is it a 30mA or 100mA one?
|
|
|
|
|
Logged
|
Navitron solar thermal system
30 x 58mm panel 259L TS
1200watts solar 120vdc
FX80 Solar controller
Victron 12v 3000w 120a
200w (250w peak) 12v turbine as a tester
6kva genny
6 x 2v cells 1550amp/h 5C
24 x 2v cells 700amp/h 5C
Total bank 4350 amp/h @12v
|
|
|
batman88
Newbie
Offline
Posts: 3
|
|
« Reply #4 on: January 23, 2012, 07:20:07 PM » |
|
The property has an earth rod, as far as I remember. I'll need to check if it's a 30mA or 100mA - would the 30mA unit be likely to trip? I've never heard of this problem before. From what the customer has said, it's the RCD that trips - ie the whole house power goes down - NOT just the PV circuit.
|
|
|
|
|
Logged
|
|
|
|
|
BruceB
|
|
« Reply #5 on: January 23, 2012, 07:27:43 PM » |
|
A PV generator circuit should not be sharing an rcd with any other circuit. If it does then when the rcd trips, the PV can carry on generating for up to 5s, which rather negates the point of an rcd for ADS or additional protection.
Regards
Bruce
|
|
|
|
|
Logged
|
|
|
|
|
Justme
|
|
« Reply #6 on: January 23, 2012, 07:35:18 PM » |
|
A PV generator circuit should not be sharing an rcd with any other circuit. If it does then when the rcd trips, the PV can carry on generating for up to 5s, which rather negates the point of an rcd for ADS or additional protection.
Regards
Bruce
So on any install that has a main RCD the PV should be fitted using Henley blocks in the tails so that it is on the grid side of the RCD? Any other way & you could have the main RCD trip due to a house fault & the PV RCD does not trip. Why does the PV carry on for 5 seconds? Surely the G83 specs dont allow this to happen on a grid outage (which is what the inverter will see when the RCD trips). |
|
|
|
|
Logged
|
Navitron solar thermal system
30 x 58mm panel 259L TS
1200watts solar 120vdc
FX80 Solar controller
Victron 12v 3000w 120a
200w (250w peak) 12v turbine as a tester
6kva genny
6 x 2v cells 1550amp/h 5C
24 x 2v cells 700amp/h 5C
Total bank 4350 amp/h @12v
|
|
|
|
GavinA
|
|
« Reply #7 on: January 23, 2012, 07:37:26 PM » |
|
A PV generator circuit should not be sharing an rcd with any other circuit. If it does then when the rcd trips, the PV can carry on generating for up to 5s, which rather negates the point of an rcd for ADS or additional protection.
Regards
Bruce
also, it's likely to cause nuisance tripping such as this if there's already a low level of current going to earth in the house circuits, as there's usually something like 8-10mA current to earth from the inverter, so add that to a few mA from the house circuits, and a low rated nominally 30mA RCD (can be as low as 15mA IIRC), and you have a recipe for nuisance tripping. |
|
|
|
|
Logged
|
at home | 80 tubes, 2 tanks direct PV powered SWH + 5 x Yingli 185Wp solar PV panels.
|
|
|
|
GavinA
|
|
« Reply #8 on: January 23, 2012, 07:40:59 PM » |
|
A PV generator circuit should not be sharing an rcd with any other circuit. If it does then when the rcd trips, the PV can carry on generating for up to 5s, which rather negates the point of an rcd for ADS or additional protection.
Regards
Bruce
So on any install that has a main RCD the PV should be fitted using Henley blocks in the tails so that it is on the grid side of the RCD? correct IMO - though the regs do allow it the other way.
Why does the PV carry on for 5 seconds?
Surely the G83 specs dont allow this to happen on a grid outage (which is what the inverter will see when the RCD trips).
Chances of the DNO getting an engineer to a fault inside 5 seconds are probably considered too low to be worth worrying about;) |
|
|
|
|
Logged
|
at home | 80 tubes, 2 tanks direct PV powered SWH + 5 x Yingli 185Wp solar PV panels.
|
|
|
|
BruceB
|
|
« Reply #9 on: January 23, 2012, 07:49:10 PM » |
|
The G83 spec does allow 5s for the inverter to cut out on loss of mains.
Whether the regs allow PV to be connected through a shared rcd is moot. They do not discuss the point directly. But as doing so negates the effect of having an rcd providing ADS in a TT situation or additional protection for buried cables, then I would argue it is against the regs because you are then failing to meet those requirements of the regs. It is only in recent months that the point has become widely understood amongst the mass of solar installers out there - the ones who read the forums anyway.
Regards
Bruce
|
|
|
|
|
Logged
|
|
|
|
|
GavinA
|
|
« Reply #10 on: January 23, 2012, 07:52:25 PM » |
|
The G83 spec does allow 5s for the inverter to cut out on loss of mains.
Whether the regs allow PV to be connected through a shared rcd is moot. They do not discuss the point directly. But as doing so negates the effect of having an rcd providing ADS in a TT situation or additional protection for buried cables, then I would argue it is against the regs because you are then failing to meet those requirements of the regs. It is only in recent months that the point has become widely understood amongst the mass of solar installers out there - the ones who read the forums anyway.
Regards
Bruce
preaching to the choir here, though I had to admit a while back that technically I didn't think the regs disallowed it, though I agree that they ought to. We've been doing it since our 4th install, and in my defence, the first 3 didn't have any RCDs. eta - I'm sure you knew that already though. |
|
|
|
« Last Edit: January 23, 2012, 07:56:02 PM by GavinA »
|
Logged
|
at home | 80 tubes, 2 tanks direct PV powered SWH + 5 x Yingli 185Wp solar PV panels.
|
|
|
|
BruceB
|
|
« Reply #11 on: January 23, 2012, 07:54:12 PM » |
|
Here is the G83 spec for those interested  hopefully a small extract is considered educational rather than a breach of copyright! |
|
|
|
« Last Edit: January 23, 2012, 07:56:52 PM by BruceB »
|
Logged
|
|
|
|
|
GavinA
|
|
« Reply #12 on: January 23, 2012, 08:25:26 PM » |
|
The G83 spec does allow 5s for the inverter to cut out on loss of mains.
Whether the regs allow PV to be connected through a shared rcd is moot. They do not discuss the point directly. But as doing so negates the effect of having an rcd providing ADS in a TT situation or additional protection for buried cables, then I would argue it is against the regs because you are then failing to meet those requirements of the regs. It is only in recent months that the point has become widely understood amongst the mass of solar installers out there - the ones who read the forums anyway.
Regards
Bruce
hold up, I just realised it was you who was arguing that it was allowed by the regs last time we had this discussion, and me arguing the other way. FWIW you convinced me it was allowed, though still not something I'd recommend. Did I convince you it wasn't? |
|
|
|
|
Logged
|
at home | 80 tubes, 2 tanks direct PV powered SWH + 5 x Yingli 185Wp solar PV panels.
|
|
|
nowty
Jr. Member
Offline
Posts: 88
|
|
« Reply #13 on: January 23, 2012, 08:35:39 PM » |
|
The way I read the extract from Bruce is that the disconnection time would be 0.5 seconds in most cases, but that is still much longer than an RCD trip under a fault condition. I had an argument with the electrician who wired mine up, they insisted on connecting it to the RCD side of the consumer unit.  After they left, it soon was re-wired onto its own mini consumer unit on the supply side.  |
|
|
|
|
Logged
|
|
|
|
|
micko
|
|
« Reply #14 on: January 23, 2012, 08:37:18 PM » |
|
The property has an earth rod, as far as I remember. I'll need to check if it's a 30mA or 100mA - would the 30mA unit be likely to trip? I've never heard of this problem before. From what the customer has said, it's the RCD that trips - ie the whole house power goes down - NOT just the PV circuit.
There is a good chance it will, I have a sunny boy 4000 tl and the documentation asks for 100mA RCD |
|
|
|
|
Logged
|
|
|
|
|
