Church Service Big Enough?

[mkgrady]

A church is looking to add AC. It has a 200 amp 120/240 service now. I'm trying to confirm the service is large enough. I looked at the electric demand over the last year from the POCO invoice and it peaked at 6KW (or 25 amps). That leaves 175 amps of head room. I'm thinking the load shouldn't exceed 80% of total. So I figure the total load at 240 should not be more than 160 amps. 160-25=135 amps. So the total additional load should not exceed 135 amps. Am I doing this calculation correctly?

 

[GoldDigger]

My first thought on reading the thread title was that you were worried about attendance.

 

[mkgrady]

My first thought on reading the thread title was that you were worried about attendance.

I try to make the thread title meaningful but it doesn't always work out.

 

[kwired]

I'm guessing from the amount of peak demand you currently have this is not all that large of a church to begin with - plus if it were a large church (member wise/attendance wise) it likely would have had AC a long time ago.

That said I doubt you will need enough cooling capacity that it would take anywhere near 135 amps to run it, so you are probably ok.

 

[mwm1752]

Service calcs are 100% of the continuous & non continuous loads -- 200 amp service can have a load calc of 200 amps. Not a bad practice to limit total load at 80% of service rating but not required. What is your conductor size & material ? you may have 4/0 al URD @ 180 amp rating.

 

[jglavin427]

A church is looking to add AC. It has a 200 amp 120/240 service now. I'm trying to confirm the service is large enough. I looked at the electric demand over the last year from the POCO invoice and it peaked at 6KW (or 25 amps). That leaves 175 amps of head room. I'm thinking the load shouldn't exceed 80% of total. So I figure the total load at 240 should not be more than 160 amps. 160-25=135 amps. So the total additional load should not exceed 135 amps. Am I doing this calculation correctly?

For a "worst case" load calculation I'd take 6kW at a 0.8 power factor for a load of 7.5kVA, or ~31A. Then I'd multiply that by 125% per NEC 220.87 for a total existing load of ~40A. Then I'd add the new AC at its nameplate rating, take 125% for the largest motor, add the numbers together and show it less than 200A or the rating of the service conductors.

 

[kwired]

For a "worst case" load calculation I'd take 6kW at a 0.8 power factor for a load of 7.5kVA, or ~31A. Then I'd multiply that by 125% per NEC 220.87 for a total existing load of ~40A. Then I'd add the new AC at its nameplate rating, take 125% for the largest motor, add the numbers together and show it less than 200A or the rating of the service conductors.

MCA on nameplate will have already included 125% of largest motor.

 

[jglavin427]

MCA on nameplate will have already included 125% of largest motor.

Good point.

 

[mkgrady]

Thanks for all the responses. Very helpfull. The church is small. The plan is to add two 5 ton units with each having an mca of 42 so that will put me way under the 200 amp main or the even a 180 amp service entrance conductor.

 

[kwired]

Thanks for all the responses. Very helpfull. The church is small. The plan is to add two 5 ton units with each having an mca of 42 so that will put me way under the 200 amp main or the even a 180 amp service entrance conductor.

And outside of NEC - I bet those units only draw a maximum 20-25 amps each, at least when in new/good condition. That nameplate rating is what they should draw if they are working to full rated capacity, I don't think it is normal to have an evaporator unit that is sized to absorb enough heat to work them that hard - I never see one pull it's max rating anyway even on the hottest days - they are loaded by the amount of heat the refrigerant is moving for the most part - take a heat pump on a cold day and that 5 ton unit may only be pulling 5 amps, but will pull 20-25 on hot summer day.

 

[acrwc10]

I would also run a load calc using article 220 as if it were a new church building, just incase the attendance and use goes up. Once word gets out that it nice and cool, more people may start going. :lol:

 

[kwired]

I would also run a load calc using article 220 as if it were a new church building, just incase the attendance and use goes up. Once word gets out that it nice and cool, more people may start going. :lol:

I kind of get what you are saying, yet unless other loads are added I still see no increase in demand. If you turn on same lights for Sunday service it doesn't matter if 10 people attend or 100 - the lights are still using same energy. The AC being added will work harder though, but we have already determined there is capacity for that.