apartment wiring

This page shows how an apartment is done. The one pictured here has 60 suites & 4 stories. It also gives an example of how the code sets demand factors to get the sizes of everything. A real life Example.

We'll start off with the Suites. 60 in total. Each has:
- An electric range
- A 5 kw air conditioner
- A gas Furnace
- A 4 kw Electric Clothes Dryer
The suites are as follows:
4 x 176.5 Sq.Mtr.        16 x 124.3 Sq.Mtr.
8 x 162.5 Sq.Mtr.        4 x 119.4 Sq. Mtr
3 x 160.2 Sq.Mtr.        4 x 117.7 Sq. Mtr.
2 x 136.7 Sq.Mtr.        4 x 100.8 Sq. Mtr.
3 x 136.5 Sq.Mtr.        4 x 98.1   Sq. Mtr.
4 x 125.2 Sq.Mtr.        4 x 98.0   Sq. Mtr.

Next, we will find the basic demand based on the size of the suites. First 45 Sq Mtr is 3500 Watts. Next 45 Sq Mtr is 1500 Watts, Next 90 Sq mtr is 1000 watts. Rule 8-202 (1) (a)

4 x 176.5 Sq.Mtr. = 6000 Watts        16 x 124.3 Sq.Mtr. = 6000 Watts
8 x 162.5 Sq.Mtr. = 6000 Watts        4 x 119.4 Sq. Mtr.   = 6000 Watts
3 x 160.2 Sq.Mtr. = 6000 Watts        4 x 117.7 Sq. Mtr.   = 6000 Watts
2 x 136.7 Sq.Mtr. = 6000 Watts        4 x 100.8 Sq. Mtr.   = 6000 Watts
3 x 136.5 Sq.Mtr. = 6000 Watts        4 x 98.1   Sq. Mtr.   = 6000 Watts
4 x 125.2 Sq.Mtr. = 6000 Watts        4 x 98.0   Sq. Mtr.   = 6000 Watts

Next we take any electric heating and air conditioning loads as per rule 8-202 (1) (a) (iv). There is no Electric Heat, but there is 5 Kw of Air Condioning, and it must be taken at 100%.
Air Conditioner = 5000 Watts

Next we need to determine if there is an Electric Range provided for. If there is, then it must be 6000 Watts for any range up to 12 kw. These Suites will Have a standard 12 kw range. It will be wired with #8 copper or #6 aluminum off a 40 amp Breaker into a Receptacle as shown here.
Range = 6000 Watts Rule 8-202 (1) (a) (v)

Next we need to determine if there are any other loads greater than 1500 Watts. We have a Microwave oven/ Range Fan plug, but it is not over 1500 watts so it is ignored. The Dryer on the Left is 4000 Watts so it is taken at 25% because an Electric range has been provided for as per 8-202 (1) (a) (vi) (A) Dryer = 1000 Watts.

O.K. We have the loads for the suites. Now we need to find the feeder size. We have
Basic Watts     = 6000 Watts
Air Condioner = 5000 Watts              Total = 18000 watts:     18000 ÷ 208   = 86.7 Amps
Range               = 6000 Watts              Therefore, we need a #3 copper or # 2 Aluminum cable
Dryer                 = 1000 Watts                      &100 amp service to The Suites.   8-104 (1)

Here we show the meter bank to 30 of the suites. Each Meter has a 100 amp Breaker beside it, installed to protect the # 3 copper conductors feeding the suites. Because this is such a large building, there are also some #2 cables used to feed the suites that are furthest away so as to compensate for voltage drop. This is a 60 suite apartment, and each of the 2 banks of 30 suites is fed by a 800 Amp Fused Disconnect.

30 finished and 30 unfinished Meters

Now it gets Tricky, and we have the step that usually screws us up on calculations. We now REMOVE any heat and Air Conditioning Loads. We'll put the heat & air conditioning back later.
Basic Watts     = 6000 Watts
Air Condioner = 5000 Watts          Total is now 13,000 Watts
Range               = 6000 Watts
Dryer                 = 1000 Watts

Now, take the largest suite at 100% (in this case, all the suites have the same demand), = 13,000 Watts
The next 2 suites at 65%. 13000 x 2 x .65 = 16,900 Watts
The next 2 suites at 40%   13000 x 2 x .40 = 10,400 Watts
The next 15 suites at 25% 13000 x 15 x .25= 48,750 Watts
Remaining 40 suites at 10% 13000 x 40 x .10 = 52,000 Watts
Total basic suite load is 141,050 Watts

Now we have to add the Air conditioning or electric heat. (There is no Electric Heat in this case)
Each suite has 5000 watts of Air conditioning x 60 suites = 300,000 watts at 100% 8-202 (3) (c)
Total demand is now 141,050 + 300,000 = 441,050 Watts

Feeders to the suites. These pictures don't do it justice during construction, but it was sure nice to see such good workmanship! The Electricians on this job have done a remarkable job. No matter where i looked it showed the result of true tradesmen. They should be proud!.

House Loads: Now add the house loads. This includes all the loads that are not contained in the suites.

208/120 volt 3 phase House panel. To the left are the hall lighting contactor and hvac shutdown contactor boxes.

HVAC Contactor. Tied in to the Fire Alarm Panel, it is used to shut down the rooftop hvac unit in the event of a fire

Elevator disconnect switch

These are not loads, but just show how the fire alarm wires are installed with FT4 cables (Red). Also the #12 (Yellow) is for Emergency lighting.

To the right, it shows how electrical cables penetrate a fire wall. Any gaps will be filled with an approved foam near the end of the construction..

Now....Back to the demand

House loads include: Hallway Heating and Air Conditioning; Sometimes Laundry; Parking lot lighting; Winter Car plugs; Common area and perimiter lights; Elevators; Games and Meeting rooms; hot water systems; and anything else that is common to all the tennants.

In this Apartment, there is a large Gas Hot water system with a small circulating pump that keeps the hot water circulating so the guys at the far end of the building get hot water right away. The pump is only 1/2 hp so it is negligable.

We have:

House Load:
Electric Heat in the Hallways at 75%   20,000 x 75%    =   15000 Watts
Incandescent lighting at 75% = 10,000 x 75% =    7500 watts
High pressure sodium (HID) Perimeter lighting @ 75%    =     6375 watts
Underground parking fluorescent Lighting at 75% = 10,000 watts
Elevator Motor @ 75% = 20 a x 208 v x 1.732 x 75% = 5398 watts
HVAC rooftop Air Conditioner at 100% = 40amps x 208 volts x 1.732 = 14,410 Watts
                                                                                                  Total   58,683 Watts

House panel Feeder size will be 58683 ÷ 208 ÷ 1.732 = 162 amps. (Remember it is a 3 phase panel!)
In this case they installed a 100% continuous rated 3 phase 200 amp house panel fed with a 2" conduit and a #3/0 wire. Remember also that the special rule in table 2 (++ notes) that allows #2 for 200 amp services does not apply here as it does in a house with 3 wire 120/240 volt services..

The 441,050 Watt Suite Load 441,050 ÷ 208 ÷ 1.732 = 1224 amps, but it is split into 2 groups of 30 meters. Since all suits are the same demand , 1224 ÷ 2 = 612 amps per 30 suits (feed size to each meter bank) 612 Amps in table 2 is 1000 kcm Copper (using rule 8-106 (1) for 5%) or 1750 kcm Aluminum.
Since we dont like that big wire, it would be done with parallel runs of 1/2 of 612 Amps or 306 Amps.
That would then require 350 kcm Copper or 500 kcm Aluminum.
On this service they used 2 parallel runs of 750 kcm aluminum which is good for 810 Amps.

This is the main service. There are 2 x 800 amp fused switches, one for each of the 30 suite meter banks. The smaller 200 Amp switch on top is for the 3 phase lighting panel. The total demand is 1224 Amps for the Suite loads, plus 162 Amps for the house load giving a grand total of 1386 Amps for the Building. 1224 + 162 = 1386 Amps Total.

They Chose to run 4 parallel runs of 750 kcm Aluminum giving the building a capacity of 1620 amps, and the main Breaker shown here is 1600 amps.
Table 17 shows that needed a 3/0 ground conductor
Table 6 shows they needed a 4" conduit for 4 750kcm conductors.

This is the Transformer that Hydro installed for this 60 suite apartment building. It is a 500 Kva 7200 volt primary with a 120/208 volt 3 phase secondary. 500 Kva ÷ 208 ÷ 1.732 = 1387 amps.

This Pic shows a meter bank waiting for the suite feeds. These meters come prewired to a breaker and connected to a buss bar. They are phased a-b, b-c, a-c
from top to bottom.

Here is another building with a 200 Amp 3 phase house panel fed from a 200 Amp switch.

Here, is a 28 unit Townhouse meter bank. The House panel is connected to one of the meters in the bank. The box beside the meter is for a perimiter lighting contactor.

This is in another apartment block. Makes me wonder if the phone and Cable guys have ever heard of workmanship! We do our part for a neat installation, and they come and finish it like this. Maybe we should put in panduit for them? I hope this wasn't YOU!

Note: Most of these pictures were taken during construction and have a lot of construction type of stuff all over the place. I have also had to reduce the quality of the pictrues so this page would load in a reasonable time. If something is intriguing to you, email me and i can send you the original high quality picture....Les