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darren12

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Wanted to see what I am missing. I am sizing a ''subpanel'' that will power several Sunday school class rooms and HVAC systems. I started it and I believe I am missing something that would allow for me to take better advantage of some demand%. This building is a multipurpose building for a church below I started looking at some of the loading for it.
Service available is 120/240, I got 266.51 amps so far and that is just the lighting, receptacles, and HVACs. Take a look and let me know what yall think.
We are in Louisiana and we will probably run these heaters very little, sucks to have to size for them like this
 
Guess I have to type it out.
7 rooms with -- 180VA x 8 rec = 1440VA/120VAC=12amps + 16 LEDs @ 14VA x 16 224VA/120VAC = 1.86 amps = total 13.86 amps
1 room with --- 180VA x 10 rec = 1800VA/120VAC=15amps + 24 LEDs @ 14VA x 24 336VA/120VAC = 2.8 amps = total 17.8 amps
Rec 10kva=100% = 41.66 amps over 10kva=50% 18.8kva @ 50%= 3.91 amps total = 45.58 amps of rec load and Lighting table 220.42 says others = 100% demand LEDs = 7.93 amps of lighting load

HVACs
3 5-ton condenser units --compressor + fan FLA= 25.1amps x 1.25= 31.36 min ckt amps. Unit calls out MOLP 50amps-
220.50 says look in 440.6 and I don’t see demand % in 440.6 reguardless the compressor and the heater will never run at the same time since its not a heatpump so I will not use this in the load since the heater is more load I will use heater.
3 5-ton air handlers/heaters ( 2 2pole CKTs per unit) First CKT = min ckt amps 27 MOLP 30 2nd CKT = min ckt amps 44 MOLP 50.
220.51 says heaters @ 100%
 
darren12 said:
Guess I have to type it out.
7 rooms with -- 180VA x 8 rec = 1440VA/120VAC=12amps + 16 LEDs @ 14VA x 16 224VA/120VAC = 1.86 amps = total 13.86 amps
1 room with --- 180VA x 10 rec = 1800VA/120VAC=15amps + 24 LEDs @ 14VA x 24 336VA/120VAC = 2.8 amps = total 17.8 amps
Rec 10kva=100% = 41.66 amps over 10kva=50% 18.8kva @ 50%= 3.91 amps total = 45.58 amps of rec load and Lighting table 220.42 says others = 100% demand LEDs = 7.93 amps of lighting load

HVACs
3 5-ton condenser units --compressor + fan FLA= 25.1amps x 1.25= 31.36 min ckt amps. Unit calls out MOLP 50amps-
220.50 says look in 440.6 and I don’t see demand % in 440.6 reguardless the compressor and the heater will never run at the same time since its not a heatpump so I will not use this in the load since the heater is more load I will use heater.
3 5-ton air handlers/heaters ( 2 2pole CKTs per unit) First CKT = min ckt amps 27 MOLP 30 2nd CKT = min ckt amps 44 MOLP 50.
220.51 says heaters @ 100%
Click to expand...
I dont use excel but in my program you can "export" as a pdf or a png image file.
You should check the specs on the HVAC again. Most of them these days are a heatpump that can pull in the electric resistance heating strip when needed but the heatpump @ 27 seems high. Lighting seems low. Mike has good videos on calculations, he has a nice way of breaking it down into steps.
This is what I came up with
loads.jpg
 
darren12 said:
Guess I have to type it out.
7 rooms with -- 180VA x 8 rec = 1440VA/120VAC=12amps + 16 LEDs @ 14VA x 16 224VA/120VAC = 1.86 amps = total 13.86 amps
1 room with --- 180VA x 10 rec = 1800VA/120VAC=15amps + 24 LEDs @ 14VA x 24 336VA/120VAC = 2.8 amps = total 17.8 amps
Rec 10kva=100% = 41.66 amps over 10kva=50% 18.8kva @ 50%= 3.91 amps total = 45.58 amps of rec load and Lighting table 220.42 says others = 100% demand LEDs = 7.93 amps of lighting load

HVACs
3 5-ton condenser units --compressor + fan FLA= 25.1amps x 1.25= 31.36 min ckt amps. Unit calls out MOLP 50amps-
220.50 says look in 440.6 and I don’t see demand % in 440.6 reguardless the compressor and the heater will never run at the same time since its not a heatpump so I will not use this in the load since the heater is more load I will use heater.
3 5-ton air handlers/heaters ( 2 2pole CKTs per unit) First CKT = min ckt amps 27 MOLP 30 2nd CKT = min ckt amps 44 MOLP 50.
220.51 says heaters @ 100%
Click to expand...
Keep in mind that the min ckt amps of 27 and 44 should already have 125% of actual load factored into them. Still going to be a significant heat load though, and in a place like you have, if needed it will run, possibly all at one time. Building has been sitting idle, a cold Sunday morning first person to arrive turns all the heat up because the rooms will be occupied later and it all runs for maybe at least half an hour until they get up to temp. You likely can get away with marginal sized supply, in this situation, as the heat is only thing running for the most part.

If heat is oversized for the application (sound like one could get by with lesser kW in your location than maybe could farther north) then maybe one could disable some of the heat strips?

I have seen many electric heat strips (say 20 kw unit) that you only get service call because it can't keep up when it is extremely cold outside, otherwise it has been running for who knows how long on only one working element out of four, it just happens to run for longer periods in order to keep up with the need.
 
tortuga said:
I dont use excel but in my program you can "export" as a pdf or a png image file.
You should check the specs on the HVAC again. Most of them these days are a heatpump that can pull in the electric resistance heating strip when needed but the heatpump @ 27 seems high. Lighting seems low. Mike has good videos on calculations, he has a nice way of breaking it down into steps.
This is what I came up with
View attachment 21246
Click to expand...
thanks I have never searched for the videos, are they on this site?
these are not heat pumps. There is a outside condenser unit and a inside air handler unit with heat strips installed. The 27 amps is for the air handler and one of the heat strips the second circuit to the air handler is another heat strip.
On the lighting I did not do it per sq ft I did by the actual load of the led. I can see that at some point in the future if the light fixtures are replaced with a type of light that draws more load than leds it could potentially cause loading issues on the branch circuits.
 
kwired said:
Keep in mind that the min ckt amps of 27 and 44 should already have 125% of actual load factored into them. Still going to be a significant heat load though, and in a place like you have, if needed it will run, possibly all at one time. Building has been sitting idle, a cold Sunday morning first person to arrive turns all the heat up because the rooms will be occupied later and it all runs for maybe at least half an hour until they get up to temp. You likely can get away with marginal sized supply, in this situation, as the heat is only thing running for the most part.

If heat is oversized for the application (sound like one could get by with lesser kW in your location than maybe could farther north) then maybe one could disable some of the heat strips?

I have seen many electric heat strips (say 20 kw unit) that you only get service call because it can't keep up when it is extremely cold outside, otherwise it has been running for who knows how long on only one working element out of four, it just happens to run for longer periods in order to keep up with the need.
Click to expand...

Good point on the 125% on the min ckt amps. I will be able to deduct a little there.
I understand that at some point they could have burned open elements but I can’t really account for anything like that. The HVAC guy already purchased the these units.
 
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