100A 3P SquareD load center on 100A meter 50mm NYY cable

[Me Panhar]

I recently bought a Schneider electric 100A 3 phase breaker load center 42 way that takes in 50mm cables from the 3 phase 100A meter in the soi.

 

The electrician says I need the 250A one. 

 

I find this confusing to need a 250A rated l.c. for a 100A meter.  Is the 100A meter not really 100A?

 

Cheers

[Crossy]

What is the marking on your meter? Or post a photo of it.

 

Your 100A load centre will be a maximum of 100A per phase which will be limited by the incoming MCCB, so even if you had a 500A supply it would limit to 100A per phase.

 

Your sparks is telling you you need a 250A load centre? What is your prospective load?

 

[Me Panhar]

Thanks Crossy. I need to do some calc but it is a house with 3 42k btu 3 phase cassette air con and 6 wall air con 18k btu as the main draw. I will go and get the numbers. 

Don't have the meter yet. 

[Crossy]

Aircon load max would be about 22kW! about 33A per phase.

 

Water heaters? Cooking? Man-cave!

 

Is it a house, mansion, hotel, factory, mall?

 

From the available data I would suggest a 3-phase 30/100 supply fused at 100A would be more than adequate.

[Me Panhar]

I just read that Inverter Air Con is more efficient on 1 phase due to the conversion to DC so that simplifies things. Here's the A/C.

Daikin FCF42CV2S 4,155W 220V (18.9A)

Daikin FCF42CV2S 4,155W 220V (18.9A)

Daikin FCF42CV2S 4,155W 220V (18.9A)

Daikin FTKC18TV2S 1,365 220V (6.2A)

Daikin FTKC18TV2S 1,365 220V (6.2A)

Daikin FTKC09TV2S 680 220V (3.1 A)

Daikin FTKC18TV2S 1,365 220V (6.2A)

Daikin FTKC18TV2S 1,365 220V (6.2A)

Daikin FTKC18TV2S 1,365 220V (6.2A)

Daikin FTKC18TV2S 1,365 220V (6.2A)

 

I realise that's not all going to be going full on at the same time (well definitely not all the time!)  but the numbers do come to 97A which can be spread over the 3 phases.

Then there's another 100A conservatively reserved for 3 water heaters, pump, cooking, several rooms A/V, 100 lights conservatively future proof at 60W.

It's a 4 bed 2 floor house.

 

The load center i have is QO3-100EZ42G/SN from Schneider:

https://www.se.com/th/en/product/QO3-100EZ42G%2FSN/square-d-classic-main-breaker-load-center---100a---surface-mounted---42-ways/

 

If it is 100A per phase then is it within rating to carry 240A if 80A are on each phase?

If so then would the PEA allow it? I am not sure what meter they would provide. A 30/100 would be over nominal with just 2 air cons on. There is a small apartment block down the soi with 3 phase power cables running overhead.

 

If it should be 250A LC then I will go for that instead and try flogging the one I have. I'll check with Schneider as well but pretty sure they will recommend talking to the sparky.

 

Cheers

 

[Crossy]

I was going to suggest looking at single-phase aircons, but for a different reason. A common supply failure here (at least where we are) is loss of a single phase, 3-phase kit doesn't like this a lot. With single-phase loads spread across the three phases you get at least some areas with lighting and aircon.

 

That Schneider Load Centre is rated at 100A per phase, I see no reason at all why it wouldn't be just fine on up to a 30/100 meter.

 

I think you are over-estimating your consumption, but going high is better than being under (unless it takes you over the line to a more expensive solution).

 

A 30/100 meter is 3-phase 100A per phase, the biggest "domestic" supply available from PEA. BUT you may run into issues actually getting that size supply, particularly if the local transformer is near capacity. The biggest normally available would be 15/45 at 45A per phase, that may still be enough when you consider diversity (not all the air or water heaters on at once). If that's not adequate then we are in to "own transformer" country = $$$

 

From your aircon capacities that's a 390m² home, about 12m x 12m on two floors. A 42k BTU unit will service a room of about 70m². Without a floor plan it's impossible to be sure, but you may wish to re-visit your aircon sizes (do you have a pet Polar Bear?).

 

You could also consider storage (tank) type water heaters, these are typically <3kW and put a lot less strain on the power supply (consider solar pre-heat too). 

 

Our place is slightly smaller when it comes to outside dimensions, but much of the space is "natural ventilation" (not walled) and we have lots of shade plants and fans, we only aircon the bedrooms and lounge. Only 3 bedrooms and 3 baths with water heaters but we manage very nicely on a 15/45 single-phase supply with a 50A incoming breaker. That breaker has never opened on overload.

 

 

 

 

 

[tjo o tjim]

You really should have someone look at what you can do for energy efficiency. The lighting assumption is way too high; 4kW should be sufficient for interior lighting.  Oversized air conditioners are nice for pulling down the interior temperature quickly, but are a mess after that. Spend the money on good windows, double Q-con walls with radiant barrier and long roof overhangs, and insulation in the ceiling. 

 

Instant water heaters can be fine; they are more efficient when you have seldom-used rooms. BUT, using a solar pre-heater and dropping the instant units down to the minimum will help your service size. (A circulation pump on the pre-heated water is a nice premium adder.)

 

Any pool, water pump, fountain or water feature?  Sauna or hot tub?

[Me Panhar]

Really appreciate the advice.

The LC being ok is great news, will see if Schneider can put that in thai for my sparky then.

Walls are 20cm thick q-con, 15cm stay cool on upstairs ceiling with aluminium sheet under tiles. Windows and doors are all German uPVC with laminated glass and shading is good.

Air cons, water pump and fridge all inverter.

Solar water interests me but the budget says no. I might get some ppr pipes in place for future now you mention it though. I could put panels on the car port roof.

Thank you!

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