canopy Posted November 15, 2015 Share Posted November 15, 2015 I have a new Schneider square d panel and installed the 3 phase to 1 phase conversion accessory (see photo). However, the store only sells 3 phase main circuit breakers for this box and they cost close to 4000 baht. Is there a single phase main offered that fits this box? If not, is it possible / advisable to use a 3 phase breaker? Link to comment Share on other sites More sharing options...
Crossy Posted November 15, 2015 Share Posted November 15, 2015 One wonders why you have a 3-phase box in the first place unless considering a later change to 3-phase. I'm not sure if there is a single-phase MCCB that will fit, no reason why you shouldn't use one phase of a 3-phase breaker apart from cost. How do you intend providing earth-leakage protection? Perhaps a front end Safe-T-Cut outside the box feeding the L and N of the box directly, blank off the switch plate where the incomer would normally fit. I don't like the Schneider / Square-D units anyway as it's very difficult to create even simple non-standard arrangements, for me it's DIN mount every time Link to comment Share on other sites More sharing options...
canopy Posted November 15, 2015 Author Share Posted November 15, 2015 Ok, that's good to know. If going with a 3 phase main, is the size in amps computed the same way? For single phase I would want to select a 63A mcb. I'll also check a bigger province electrical store for a single phase main. The reason for this panel is it is an upgrade from a smaller single phase square d panel. So the idea is staying with square d all the mcb's can be reused. After working in cramped space in the small panel, couldn't resist their beautiful and spacious panels. I had not considered an ELCB (?). Do I need one in this case? Here is a bit about the install. The ground is two 3/4" diameter x 2.5M solid copper rods spaced in a row away from the house connected using 25mm2 wire and also connected to the house slab rebar (UFER). In the panel I have a MOV and rcbo mcb's where advisable. Link to comment Share on other sites More sharing options...
Forkinhades Posted November 16, 2015 Share Posted November 16, 2015 First off get a safety-cut device installed upstream of your new box. If you are going to to keep it, then you can link out your main terminals on your 3 phase main, to make single phase. Even if you found a single phase to fit, you would have to buy 3 of them, otherwise your down to 1/3 of the capacity. If you have individual RCBOs for your circuits then that is good, but you do need to be protecting your whole installation. That said with MEN implented correctly, your earth values 'should' be low enough to give protection on your lighting circuits, but this is thailand and we should stick to their requirements, which is a front end safety cut. Link to comment Share on other sites More sharing options...
canopy Posted November 30, 2015 Author Share Posted November 30, 2015 Just one more thing. The instructions say to run neutral from the mains directly to the ground bar, then connect the ground bar to the neutral bar. For developed countries this sounds like a great idea, but it makes me slightly nervous that if some genius messes up something nearby I have no way of isolating from the neutral line coming in. Would it be plausible to address this concern to instead send neutral through the 2nd pole of the main circuit breaker and then connect the neutral bar to the ground bar? This way turning off the main breaker isolates the site from both line and neutral. Or maybe it's not a good idea? Thanks for any suggestions. Below is the instruction sheet and the top panel is the configuration I am working with (primary panel) and the 2nd picture doesn't apply (sub-panel). Link to comment Share on other sites More sharing options...
bankruatsteve Posted November 30, 2015 Share Posted November 30, 2015 You need to find out if "MEN" has been implemented in your neighborhood. If so, do it. If not, then don't: connect the N to E. Some PEA systems are doing that - others are not. Link to comment Share on other sites More sharing options...
canopy Posted November 30, 2015 Author Share Posted November 30, 2015 Yes, MEN is used in this area and I have implemented it in the past. There is no question that I will connect the incoming N to ground. My question is would sending N through the main breaker first be a good idea or not. Link to comment Share on other sites More sharing options...
bankruatsteve Posted November 30, 2015 Share Posted November 30, 2015 Yes. Link to comment Share on other sites More sharing options...
RichCor Posted November 30, 2015 Share Posted November 30, 2015 How/where you wire for neutral will depends on the type of circuits in your box. If you include Residual Current Detection (Safe-T-Cut style device) then Neutral should be bonded to Ground-Earth prior to the RCD, then flow through your 63A Main Breaker. With an RCD in place, no N-E connections should be made after the RCD. Link to comment Share on other sites More sharing options...
Forkinhades Posted November 30, 2015 Share Posted November 30, 2015 You would need to install a 4 pole isolator before you DB, and Safety-cut , to fully isolate. That's another box in your cupboard Link to comment Share on other sites More sharing options...
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