Diversity for bungalows

[Led Lolly Yellow Lolly]

We're building some new bungalows for guests. Somewhere along the line room sizes and cable sizes got all mixed up (Thai style planning etc etc). The bungalows are supplied by 10mm sq NYY cable in conduit underground. There is no way in hell these cables are coming out for replacement. We originally planned for 12,000 BTU aircon but I've looked at the figures and realised this is woefully inadequate for the size of the room. 24,000 BTU is what's required.

 

Complicating the situation further is I've seen 8000 watts as the specs for the showers!

 

I've got 40 Amp RCBOs protecting the cables. I'm concerned. I could probably get the specs for the showers reduce to a 6000 watt model. It MAY be possible to get away with 18,000 BTU aircons. How am I looking here for the 10mm cable?

[Crossy]

Have a look here http://www.linzi.hu/Katalogus/2008-2009/eng/X031 Current ratings for NYY, NAYY, NYCY, NYCWY, NAYCWY 0,6_.pdf

 

Even worst-case (30C in air) puts the cable at 60A, better if underground.

 

8kW shower = about 36A

 

24,000 BTU aircon = about 10A

 

Your 40A breaker would probably be fine if the shower wasn't on too long, replace with 50A and it will be totally fine (I'd try it with the existing 40A units to save cost). The cable won't even start to get unhappy

 

[Led Lolly Yellow Lolly]

Hi, thanks again for chiming in. Indeed, at ~2400 Baht a pop, I'm not inclined to replace all of the RCBOs. Taking a closer look at my wife's handwriting, it's seems the showers are not 8000 watts, but actually 6000 watts, so based on your guidance, I think we should be OK, although there's still not much room for a kettle being plugged in, or similar.

 

10 amps for the aircon though, that sounds a little lean. I'd have guessed more like 15 amps, but I'm not sure. Cable is 4mm with a 20 amp breaker as it stands.

 

I'm actually surprised at the current carrying capacity of the NYY. According to the Bangkok Cable specs sheets, this appears better than THW cable of the same size, but I may have read this wrong.

 

On a semi-related note, my local electricals supplier insists I cannot use NYY cable for the drop from the overhead cables down the pole to the load centre mounted on the same pole. She insists I must use THW cable for that, according to PEA rules. This sounds odd to me, I'd have thought it would be the other way around. I plan on using NYY cable anyway.

Edited September 17, 2016 by NilSS

[bankruatsteve]

Just to comment that doing something the PEA doesn't like is not a good plan. 

 

And, how big are your bungalows - or are they poorly insulated that you want 24K BTU aircons?

[Led Lolly Yellow Lolly]

That's not what I said. I said I've been advised that's what the PEA want. I'm saying this is likely poor advice, as THW cable should never be used exposed to the elements, especially where it can come into human contact.

 

Rooms are around 46 Sqm, so 24,000 is still a little on the low side. In this price bracket, customers will expect rooms to cool well and cool fast.

[Crossy]

24,000 BTU is about 7kW of cooling. Any reasonably modern aircon will pump about 3 times what it consumes in power, 7/3 = 2.3kW == 10.5A @ 220V

 

PEA do like THW for their aerials (on insulators), the dropper to our meter is certainly insulated and sheathed al-la NYY although I don't see any markings to that effect.

 

Once the power is on your property, and you've passed the PEA inspection what you do is largely your business. I doubt they would be unhappy with NYY droppers.