Apartment panel sizing

[Polarcat]

correct me if i am wrong. a 60 unit apartment building with indivudually metered apartments
to calculte the size of feeder and overcurrent protection (at the meter stack) and the size of the load center rating (MLO's)

the details: typical apt,

1375 square'
stackable washer and dryer electric
electric range
dishwasher
disposal
Hot water heater (small) electric
furnace (gas)
Condensor

we are being told they require 150amp each

if i use the "optional calculation for computing feeder and service loads" for the above i come up with the following (first can we use this method of calculation?)

1375 sq' x 3va= 4122va
(2) small apliance = 3000va
washer/dryer = 5000va (guess)
range = 8000va
dishwasher = 1200va
disposal = .24va
HW heater = 6000va
furnace = 1000va
Condensor = 3500va

total 27.32 KVA 100% of 1st 10kva and 40% of remainder = 16.93 KVA + 100% of condensor = 20.43 @ 208v single phase = 100 amps (i did not include the furnace in calc because i took 100% of AC. correct??)

therfore there should be no reason for me to go with 150amp meterstacks/OCP and loadcenters. I should be able to use 125amp equipment, wire size, OCP etc.. any flaws in my calculations

there is no chance for expansion later. and keep in mind this is the largest unit type by far.

 

[Buck Parrish]

I agree 125 is enough...
I have not done (Optional) apt . for the range calcs in a while. For some reason I was thinking 6500 (please correct me, too)

 

[suemarkp]

Washer/dryer nameplate seems small unless its only the dryer. Where's the laundry small appliance circuit for another 1500 VA? I doubt the range is 8 KW -- most are at least 10 of not 12 KW or more. You have to use nameplate values in the optional calculation. Only in the standard one can you take a 12 KW range and treat it as 8KW.

Does the air conditioning uses the air handler to distribute the air? If the furnace is gas, you'd need to include all of the furnace nameplate into the HVAC load because that same load will be used in cooling mode. If this is just a window shaker air conditioner, then what you did is correct.

Water heater seems too large. Many are 4400W, some are 5500W. Never seen a 6 KW unit.

What is the VA of the disposal?? Won't be fractional. Would expect something like 700 VA.

 

[Dennis Alwon]

I believe you must use 1500 for the laundry cir. and 5000 for the dryer. Art. 220.52(B) & 250.54

 

[Npstewart]

Theres no such thing as a "hot water heater" its just a water heater. If the water was already hot you wouldnt need the heater.

 

[Dennis Alwon]

:grin:

Theres no such thing as a "hot water heater" its just a water heater. If the water was already hot you wouldnt need the heater.

You have to keep it hot. Suppose I have a solar system that preheats the water to my water heater. Now my water heater is a hot water heater. :grin: Got you.

 

[Npstewart]

I use 1500 watts for a laundry circuit but this is for the iron. The iron takes an entire circuit. Also, I would be surprised if the washer/dryer didn't have separate receptacles. I use 5KW for a dryer, 1.5KW for the iron., 1.5 KW for the washer, and 8KW for the range.

Not sure if you have gas or electric heat but I take my heat at 65% and count the fan as 1KW if its electric.

Water heaters are typically 9KW total but non-simaltaneous elements which means you can count them as 4.5 KW. Do yourself a favor and put 4.5KW @ 208V because a lot of people will buy 4.5KW heaters @ 240V but your voltage is 208 because its an apartment.

Don't forget that when you size your main you can take diversity based on the number of units your supplying, if your supplying 60 units I think you can take your load at somewhere in the low 40% range, I would give you a reference but I dont have my NEC.

PS. Why is your disposal rated for .24VA? Those also take up a whole circuit. I think they are counted as 1KW each.

 

[Npstewart]

:grin: You have to keep it hot. Suppose I have a solar system that preheats the water to my water heater. Now my water heater is a hot water heater. :grin: Got you.

Alright, I concede lol

 

[Polarcat]

been away for a while.

let me clearify this I am looking to fig out the apartment panel sizes and overcurrent protection at the load side of meter stacks to the individual apts.

i have received the Name plate data on all the euipment in redid it. this is what i have.

C1 Unit (electric dryer)

General loads:

(2) small appliance loads @ 1500VA each 3000VA
3 watts per square foot for gen lighting and gen-use recap 4122VA
Laundry Ckt 1500VA
Range 9500VA
WaterHeater 3500VA
Disposal/Dishwasher 1680VA
Refrigerator (is included in the small apl. load but added it anyway) 540VA
Range Hood 240VA
Wash/Dryer (electric) 5440VA (includes the two motors and the heater element) Stackable unit

Total VA 29,522 VA = 29.52VA 100% first 10KVA and 40% of remainder = 17.81 KVA

100% of the HVAC (largest of the section) 2.60 KVA
.70 KVA Furnace blower motor

Total 21.11 KVA @ 208v single phase = 101.49 amps

is this alll correct? I want to use 125amp MLO's with 125amp OVPD at the meter

Thanks

 

[Smart $]

been away for a while.

let me clearify this I am looking to fig out the apartment panel sizes and overcurrent protection at the load side of meter stacks to the individual apts.

i have received the Name plate data on all the euipment in redid it. this is what i have.

C1 Unit (electric dryer)

General loads:

(2) small appliance loads @ 1500VA each 3000VA
3 watts per square foot for gen lighting and gen-use recap 4122VA
Laundry Ckt 1500VA
Range 9500VA
WaterHeater 3500VA
Disposal/Dishwasher 1680VA
Refrigerator (is included in the small apl. load but added it anyway) 540VA
Range Hood 240VA
Wash/Dryer (electric) 5440VA (includes the two motors and the heater element) Stackable unit

Total VA 29,522 VA = 29.52VA 100% first 10KVA and 40% of remainder = 17.81 KVA

100% of the HVAC (largest of the section) 2.60 KVA
.70 KVA Furnace blower motor

Total 21.11 KVA @ 208v single phase = 101.49 amps

is this alll correct? I want to use 125amp MLO's with 125amp OVPD at the meter

Thanks

No, not correct. Your line-to-neutral loads need to be calculated at 120V/leg ? 2 legs (i.e. 240V). See Annex D Example D5(b). As a result, your calculated feeder amps should be less.

 

[Polarcat]

we have 120/208v 3 phase incoming service into these buildings (they have comercial spaces as well)

the meter stacks are feed with 120/208v 3 phase and the internal buss alternates the meters to single phase 102/208v A-B, B-C, C-A etc..

 

[Smart $]

we have 120/208v 3 phase incoming service into these buildings (they have comercial spaces as well)

the meter stacks are feed with 120/208v 3 phase and the internal buss alternates the meters to single phase 102/208v A-B, B-C, C-A etc..

Wherever the feeders are 120/208 single phase, you have to calculate line-to-neutral loads at 120V/leg ? 2 legs and line-to-line loads at 208V. Once the single-phase feeder loads are combined into 3-phase feeder or service loads, you can calculate as 3-phase.

 

[Polarcat]

so if I am understanding you

I would take the range and the AC (condensor) and calculate them seperatly at 208V
and the rest i would calculate at 240v (because they are line to neutral loads)

correct?

what about the demand factor (is the range still calculated in the 100% of 1st 10KVA and 40% on remainder or is it 100%)

what would you calculate the feeders at for this unit? the only 2 pole circuits are the range and the AC condensor.

 

[Smart $]

so if I am understanding you

I would take the range and the AC (condensor) and calculate them seperatly at 208V
and the rest i would calculate at 240v (because they are line to neutral loads)

correct?

Correct, for determining feeder size.

what about the demand factor (is the range still calculated in the 100% of 1st 10KVA and 40% on remainder or is it 100%)

Good question. I've always wondered about this. The Example leaves me perplexed in that they don't use the 100%/40% factoring. D5(b) shows the calculated load of 18,782, which is from D4(b)'s "Application of Demand Factor" result... but it only applies first 3000 VA at 100%, balance at 35%, and only to the General Lighting and SA loads... then it shows 6,400 VA for an 8kW Range...???

Can anyone make sense of it?

what would you calculate the feeders at for this unit? the only 2 pole circuits are the range and the AC condensor.

What about the water heater?

I'm going to wait to see if anyone can make sense of the Example(s) before I attempt a calculation...:roll:

 

[Polarcat]

Correct, for determining feeder size.



Good question. I've always wondered about this. The Example leaves me perplexed in that they don't use the 100%/40% factoring. D5(b) shows the calculated load of 18,782, which is from D4(b)'s "Application of Demand Factor" result... but it only applies first 3000 VA at 100%, balance at 35%, and only to the General Lighting and SA loads... then it shows 6,400 VA for an 8kW Range...???

Can anyone make sense of it?


What about the water heater?

I'm going to wait to see if anyone can make sense of the Example(s) before I attempt a calculation...:roll:

Yes the Water heater is 2 pole as well

anybody care to take a crack at doing the calc's with the info i provided?

 

[Dennis Alwon]

I would suggest trying Mike Holts residential calculator-- go here then click on residential calculator.

 

[Smart $]

Yes the Water heater is 2 pole as well

anybody care to take a crack at doing the calc's with the info i provided?

Here's what I get...