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Old 04-17-2019, 08:40 AM   #1
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Default Demonstrated load calc

Has anyone here used the peak demand ampacity for a load calc based on this bulletin? https://s2.renewityrma.com/leg2/Fron...319_86-1-0.pdf
I have a client that sent me an excel spreadsheet for their hourly consumption for every hour of every day for an entire year.

I have no idea how to determine the peak demand ampacity from this information.
The first 24 columns are hourly usage. The last 3 columns on the sheet are Total On-Peak kWh Consumption
Total Off-Peak kWh Consumption Total Mid-Peak kWh Consumption
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Old 04-17-2019, 09:01 AM   #2
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The peak demand is the highest consumption they had on any given day in the past year.
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Old 04-17-2019, 09:07 AM   #3
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Down here in the states, that Excel spreadsheet they gave you would not work.

We calculate on an average taken over 15 minutes.

I can get the customer load three ways:

Manually do a load calc.

Put our Fluke logger on it with a 15 minute sample rate and leave it for a month.(Obviously this needs to be installed at the right time of year to get peak loading)

Call the utility and ask for peak demand for the previous 12 months.


With the spreadsheet they gave you with energy consumed in a given hour, who's to say there was minimal load for 55 minutes, and then the majority of load for 5 consecutive minutes?


That's what you need to find out.
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Old 04-17-2019, 10:12 AM   #4
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Originally Posted by Incognito View Post
The peak demand is the highest consumption they had on any given day in the past year.

The highest date for consumption was July 7th at 71.624kWh of consumption. How am I supposed to use this in a load calc?
Sorry if I'm not seeing this clearly as I probably should be.
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Old 04-17-2019, 01:53 PM   #5
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The highest date for consumption was July 7th at 71.624kWh of consumption. How am I supposed to use this in a load calc?
Sorry if I'm not seeing this clearly as I probably should be.
That is what they consumed that day over a 24 hour period. Sorry, my statement should have said the highest consumption at one instant, not any given day. You need to find out the highest consumption ever (in amps) at one instant in the past year.



For instance, on that day maybe they had a steady consumption which was the most in a day but it was not the highest amps drawn at one time, like using their AC unit all day with the windows open. Now on another day they may have used everything in the house all at once but only for a short period of time. That's what you need.
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Old 04-17-2019, 07:01 PM   #6
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That is what they consumed that day over a 24 hour period. Sorry, my statement should have said the highest consumption at one instant, not any given day. You need to find out the highest consumption ever (in amps) at one instant in the past year.



For instance, on that day maybe they had a steady consumption which was the most in a day but it was not the highest amps drawn at one time, like using their AC unit all day with the windows open. Now on another day they may have used everything in the house all at once but only for a short period of time. That's what you need.

I think I'm staring to understand. The spreadsheet is by the hour for 365 days. The highest usage hour was in July at 11pm at 8.68kWh. So 8680/240 is 36amps. This is the highest usage of any given hour for the year but you're saying that I need to show highest amount of current used at one specific instance? How do I get that info?
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Old 04-17-2019, 07:40 PM   #7
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I might be stating the obvious, but you should ignore any load data that refers to kWh as the unit. Your kWh is irrelevant to the peak demand and only talks about consumption over time. You are looking for either Amps, KW, or KVA. Anything else is useless. If all you have is kWh data and you don't have any data regarding peak demand, it is simply not possible to apply the data to a load calculation.

It is possible to do a measurement on site yourself, but CEC 8-106 states the minimum duration that the monitoring equipment should be connected. This is typically 12-24 months depending on application. Watching a clamp meter for 15 minutes will give you a good idea where to start but it likely isn't good enough for formal service calculations.

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Old 04-17-2019, 07:42 PM   #8
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Sorry, one last thing... the term, "Demonstrated Load" is actually formally defined in the CEC. See CEC 2018 8-000:

Demonstrated load — historical maximum demand watt information recorded over at least a 24-month period for the same type of facility as the one in question, equated to watts per m2.

Converting to watts per m2 is likely not helpful. The main point to note is the 24 month monitoring duration.

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Old 04-17-2019, 07:53 PM   #9
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Quote:
Originally Posted by NDC View Post
I think I'm staring to understand. The spreadsheet is by the hour for 365 days. The highest usage hour was in July at 11pm at 8.68kWh. So 8680/240 is 36amps. This is the highest usage of any given hour for the year but you're saying that I need to show highest amount of current used at one specific instance? How do I get that info?
You just gave yourself the answer. It doesn't go any lower than an hour.

We have similar sheets from grow ops that we have had to "make safe" before hydro would allow reconnection.
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Old 04-17-2019, 07:55 PM   #10
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Old 04-17-2019, 11:01 PM   #11
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The caveat is more for an APEGA / APEGS / APEGBC requirement. I'm supposed to charge fees for formal engineering advice. No fees = not advice!

That is the problem with kWh calculations...
8.68 kWh could have been:
  • 0.75A load for 2 days
  • 36A load for an hour
  • 72A load for a half hour
  • 144A load for 15 mins
  • 2170A load for 1 minute
  • 130,200A for 1 second

Yes, I realize that some of these are completely impossible but it is an illustrative example. Each of these loads would have resulted in 8.68kWh but each would require drastically different service sizes. kWh means nothing except for billing purposes and should be completely ignored when calculating service size.

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Old 04-17-2019, 11:17 PM   #12
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Originally Posted by 908Eng View Post
The caveat is more for an APEGA / APEGS / APEGBC requirement. I'm supposed to charge fees for formal engineering advice. No fees = not advice!

That is the problem with kWh calculations...
8.68 kWh could have been:
  • 0.75A load for 2 days
  • 36A load for an hour
  • 72A load for a half hour
  • 144A load for 15 mins
  • 2170A load for 1 minute
  • 130,200A for 1 second

Yes, I realize that some of these are completely impossible but it is an illustrative example. Each of these loads would have resulted in 8.68kWh but each would require drastically different service sizes. kWh means nothing except for billing purposes and should be completely ignored when calculating service size.

CAVEAT: Information presented in this post does not constitute professional engineering advice.

I did state that the highest usage hour was in July at 11pm at 8.68kWh. Thats for one hour.
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Old 04-17-2019, 11:21 PM   #13
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Originally Posted by NDC View Post
I did state that the highest usage hour was in July at 11pm at 8.68kWh. Thats for one hour.
Yes, but all you know for sure is that the amps may have been anywhere between 36A and the main breaker size (100A / 125A / 200A, etc.). It is not possible to determine actual amps from kWh except for perfectly constant loads.

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Old 04-18-2019, 09:41 AM   #14
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Quote:
Originally Posted by NDC View Post
Has anyone here used the peak demand ampacity for a load calc based on this bulletin? https://s2.renewityrma.com/leg2/Fron...319_86-1-0.pdf
I have a client that sent me an excel spreadsheet for their hourly consumption for every hour of every day for an entire year.

I have no idea how to determine the peak demand ampacity from this information.
The first 24 columns are hourly usage. The last 3 columns on the sheet are Total On-Peak kWh Consumption
Total Off-Peak kWh Consumption Total Mid-Peak kWh Consumption
Call Hydro. They should provide you with the peak demands for the year. It will be in Kw as well.

I agree with 908 on the KWh, but given over a 2 year period at hourly increments, I'd think it would be darn close to the 36A.

Either way, Inspector will want the graph from Hydro, not the billing.
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Old 04-18-2019, 09:55 AM   #15
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Call Hydro. They should provide you with the peak demands for the year. It will be in Kw as well.

I agree with 908 on the KWh, but given over a 2 year period at hourly increments, I'd think it would be darn close to the 36A.

Either way, Inspector will want the graph from Hydro, not the billing.

Have you used this type of data for a load calc in the past? I tried calling hydro one for the highest kw usage at a given point and the rep was lost.
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Old 04-18-2019, 10:01 AM   #16
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Have you used this type of data for a load calc in the past? I tried calling hydro one for the highest kw usage at a given point and the rep was lost.
Never for resi.

We used to do it for Industrial plants thou.
I'd try calling again, ask for 'engineering'
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Old 05-03-2019, 03:39 PM   #17
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You just gave yourself the answer. It doesn't go any lower than an hour.

We have similar sheets from grow ops that we have had to "make safe" before hydro would allow reconnection.

Hey so just to confirm, you have used this kwh usage spreadsheet to determine the demonstrated load to ESA? or did the inspector want to see it as a graph?
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Old 05-03-2019, 03:45 PM   #18
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Never for resi.

We used to do it for Industrial plants thou.
I'd try calling again, ask for 'engineering'

Tried that too and no luck. No luck getting this info in on a graph and in only kW.
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Old 05-03-2019, 08:52 PM   #19
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Hey so just to confirm, you have used this kwh usage spreadsheet to determine the demonstrated load to ESA? or did the inspector want to see it as a graph?
All our AHJ's only want to see the calc's on the spreadsheet- they're not too interested in the graph- although it is easier to visualize.
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Old 05-03-2019, 11:00 PM   #20
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Tried that too and no luck. No luck getting this info in on a graph and in only kW.
As Moddy said, that's probably all the inspector will need. Call him and ask.

At plants where I worked, the graph was available, but the meter's also measured peak and reactive power as well. This may not be available for resi meters.
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