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New load installed What solution can you advice?

#1
09-18-15, 06:23 PM
Member
Join Date: Aug 2015
Location: Philippines
Posts: 77
New load installed What solution can you advice?

There is an installed 8.0 sq.mm for the range outlet (8.9 KW) but the problem is a new load was proposed (microwave and oven, 1150 W and 2350 W respectively). The 8.0 sq. mm was already installed but unfortunately the load increased. After getting some computations, the wire is not suited for the ampacity. The question is what alternative solution can I do? Should I splice the 8.0 to the 2 new outlets (1 for oven and 1 for microwave) with 5.5 sq. mm?

Here is the computation:

Total (I) = (8900+1150+2350)/230
I = 53.91 Amps

The wire suited is 14 sq.mm as the 8.0 sq. mm ampacity already exceeds.

Note: Assume to operate theses 3 loads at the same time (for the worst case).

Thanks Guys.

#2
09-18-15, 06:52 PM
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Join Date: Nov 2007
Location: Twin Cities, MN
Posts: 12,277
Without knowing what the allowable ampacity is for your 8mm wire we really can't say. According to my NEC book (US) #12 THHN is 8.5 square mm so I know that is not right.

According to our code each appliance should have its own circuit. One exception might be the oven and cooktop (range) could be considered as one "range" and fed off a single 50 amp circuit.

#3
09-18-15, 07:36 PM
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Join Date: Jul 2002
Location: Maryland
Posts: 14,587
Does the Philippines have an electrical code ?

#4
09-18-15, 09:15 PM
Member
Join Date: Aug 2015
Location: Philippines
Posts: 77
Sorry forgot to list that:

5.5 sq. mm = 36 ampacity = #10 AWG
8.0 sq. mm = 48 ampacity = #8 AWG
14 sq. mm = 65 ampacity = #6 AWG

I know that each appliances should have one circuit each but in this case, it was a sudden addition of the load which is not on the plan. The panel was already installed as well as the wires so we are having some problems.

#5
09-19-15, 07:21 AM
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Join Date: Nov 2007
Location: Twin Cities, MN
Posts: 12,277
Like I said, cooktop and range could likely share the same circuit as they won't be running full power all the time. The Microwave will need a new circuit or find another circuit to tap off of. Again, we don't know what is allowed in the Philippians. One way or another you will need another circuit.

Just because something changes after the rough in does not mean it is your job to just slap stuff together. If it was my job I would tell the customer that because of the addition of appliances they will need another circuit or they risk overloading the existing circuit.

You did not say the wiring method. Cable? Conduit? What kind of construction is this place? Wood framed? Concrete?

#6
09-19-15, 07:37 AM
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Join Date: Aug 2000
Location: U.S.
Posts: 5,451
I would take the microwave out of the equation and recompute.
The microwave will be the easiest to feed from another, existing circuit. It would also be the easiest to run a new dedicated circuit.

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